101
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Abstract
The hydrodynamic radii of a series of genetically engineered monodisperse elastin like polypeptides (ELP) was determined by dynamic light scattering in aqueous solution as function of molar mass. Utilizing the known theoretical expression for the hydrodynamic radius of wormlike chains, the Kuhn statistical segment length was determined to be lk = 2.1 nm, assuming that the length of the peptide repeat unit was b = 0.365 nm, a value derived for a coiled conformation of ELP. The resulting chain stiffness is significantly larger than previously reported by force-distance curve analysis (lk < 0.4 nm). The possible occurrence of superstructures, such as hairpins or helices, would reduce the contour length of the ELP, further increasing lk . Accordingly, the value lk = 2.1 nm reported here represents a lower limit of the chain stiffness for ELP.
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Affiliation(s)
- Sabine Fluegel
- Institute of Physical Chemistry, University of Mainz, 55099 Mainz,.Germany
| | - Karl Fischer
- Institute of Physical Chemistry, University of Mainz, 55099 Mainz,.Germany
| | - Jonathan R. McDaniel
- Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708
| | - Ashutosh Chilkoti
- Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708
| | - Manfred Schmidt
- Institute of Physical Chemistry, University of Mainz, 55099 Mainz,.Germany
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102
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Muiznieks LD, Weiss AS, Keeley FW. Structural disorder and dynamics of elastin. Biochem Cell Biol 2010; 88:239-50. [PMID: 20453927 DOI: 10.1139/o09-161] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Elastin is a self-assembling, extracellular-matrix protein that is the major provider of tissue elasticity. Here we review structural studies of elastin from over four decades, and draw together evidence for solution flexibility and conformational disorder that is inherent in all levels of structural organization. The characterization of disorder is consistent with an entropy-driven mechanism of elastic recoil. We conclude that conformational disorder is a constitutive feature of elastin structure and function.
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Affiliation(s)
- Lisa D Muiznieks
- Research Institute, Hospital for Sick Children, 555 University Ave., Toronto, ON M5G 1X8, Canada.
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103
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Sun C, Boutis GS. Investigation of the dynamical properties of water in elastin by deuterium Double Quantum Filtered NMR. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2010; 205:86-92. [PMID: 20452263 PMCID: PMC2925226 DOI: 10.1016/j.jmr.2010.04.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 01/18/2010] [Accepted: 04/09/2010] [Indexed: 05/25/2023]
Abstract
The anisotropic motion of tightly bound waters of hydration in bovine nuchal ligament elastin has been studied by deuterium Double Quantum Filtered (DQF) NMR. The experiments have allowed for a direct measurement of the degree of anisotropy within pores of elastin over a time scale ranging from 100 micros to 30 ms, corresponding to a tortuous spatial displacement ranging from 0.2 to 7 microm. We studied the anisotropic motion of deuterium nuclei in D2O hydrated elastin over a temperature of -15 degrees C to 37 degrees C and in solvents with varying dielectric constants. Our experimental measurements of the residual quadrupolar interaction as a function of temperature are correlated to the existing notion of hydrophobic collapse near 20 degrees C.
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Affiliation(s)
- Cheng Sun
- Brooklyn College, Department of Physics, 2900 Bedford Avenue Brooklyn, NY 11210, United States
| | - Gregory S. Boutis
- Brooklyn College, Department of Physics, 2900 Bedford Avenue Brooklyn, NY 11210, United States
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104
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Banta S, Wheeldon IR, Blenner M. Protein Engineering in the Development of Functional Hydrogels. Annu Rev Biomed Eng 2010; 12:167-86. [PMID: 20420519 DOI: 10.1146/annurev-bioeng-070909-105334] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Scott Banta
- Department of Chemical Engineering, Columbia University, New York, New York 10027;
| | - Ian R. Wheeldon
- Department of Chemical Engineering, Columbia University, New York, New York 10027;
| | - Mark Blenner
- Current address: Department of Medicine, Center for Biomedical Engineering, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115;
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105
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Bilsel M, Arkin H. Residue length and solvation model dependency of elastinlike polypeptides. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2010; 81:051906. [PMID: 20866260 DOI: 10.1103/physreve.81.051906] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2010] [Indexed: 05/29/2023]
Abstract
We have performed exhaustive multicanonical Monte Carlo simulations of elastinlike polypeptides with a chain including amino acids (valine-proline-glycine-valine-glycine)n or in short (VPGVG)n, where n changes from 1 to 4, in order to investigate the thermodynamic and structural properties. To predict the characteristic secondary structure motifs of the molecules, Ramachandran plots were prepared and analyzed as well. In these studies, we utilized a realistic model where the interactions between all types of atoms were taken into account. Effects of solvation were also simulated by using an implicit-solvent model with two commonly used solvation parameter sets and compared with the vacuum case.
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Affiliation(s)
- Mustafa Bilsel
- Department of Physics Engineering, Ankara University, Tandoğan, Ankara 06100, Turkey.
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106
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Chen Y, Guan Z. Bioinspired Modular Synthesis of Elastin-Mimic Polymers To Probe the Mechanism of Elastin Elasticity. J Am Chem Soc 2010; 132:4577-9. [DOI: 10.1021/ja9104446] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Yulin Chen
- Department of Chemistry, University of California, 1102 Natural Sciences 2, Irvine, California 92697-2025
| | - Zhibin Guan
- Department of Chemistry, University of California, 1102 Natural Sciences 2, Irvine, California 92697-2025
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107
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Arkin H, Bilsel M. How conformational transition depends on hydrophobicity of elastin-like polypeptides. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2010; 31:327-332. [PMID: 20229015 DOI: 10.1140/epje/i2010-10573-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2009] [Revised: 01/19/2010] [Accepted: 01/27/2010] [Indexed: 05/28/2023]
Abstract
The three-dimensional structures of elastin-like polypeptides Val1-Pro2-Gly3-Xaa4-Gly5 were investigated by using the multicanonical Monte Carlo (MC) simulation procedure. By substituting different amino acids in the fourth position of the sequence, the thermodynamical variables are calculated in vacuo and in solvent to determine the hydrophobicity dependence of the conformational transition temperatures of the peptides. Resultant hydrophobicity scale is in good agreement with many hydrophobicity scales.
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Affiliation(s)
- H Arkin
- Department of Physics Engineering, Ankara University, Dögol Caddesi 06100 Tandoğan, Ankara, Turkey.
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108
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Ma M, Kuang Y, Gao Y, Zhang Y, Gao P, Xu B. Aromatic−Aromatic Interactions Induce the Self-Assembly of Pentapeptidic Derivatives in Water To Form Nanofibers and Supramolecular Hydrogels. J Am Chem Soc 2010; 132:2719-28. [DOI: 10.1021/ja9088764] [Citation(s) in RCA: 294] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Manlung Ma
- Department of Chemistry, Brandeis University, Waltham, Massachusetts 02454, and Departments of Chemistry and of Chemical and Biomolecular Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
| | - Yi Kuang
- Department of Chemistry, Brandeis University, Waltham, Massachusetts 02454, and Departments of Chemistry and of Chemical and Biomolecular Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
| | - Yuan Gao
- Department of Chemistry, Brandeis University, Waltham, Massachusetts 02454, and Departments of Chemistry and of Chemical and Biomolecular Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
| | - Yan Zhang
- Department of Chemistry, Brandeis University, Waltham, Massachusetts 02454, and Departments of Chemistry and of Chemical and Biomolecular Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
| | - Ping Gao
- Department of Chemistry, Brandeis University, Waltham, Massachusetts 02454, and Departments of Chemistry and of Chemical and Biomolecular Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
| | - Bing Xu
- Department of Chemistry, Brandeis University, Waltham, Massachusetts 02454, and Departments of Chemistry and of Chemical and Biomolecular Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
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109
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Fujimoto M, Hara M, Hayashi T, Furuta M. Effect of heating process on the formation of nanoparticles of elastin model polypeptide, (GVGVP)251, by gamma-ray crosslinking. Polym Bull (Berl) 2009. [DOI: 10.1007/s00289-009-0220-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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110
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Floss DM, Sack M, Arcalis E, Stadlmann J, Quendler H, Rademacher T, Stoger E, Scheller J, Fischer R, Conrad U. Influence of elastin-like peptide fusions on the quantity and quality of a tobacco-derived human immunodeficiency virus-neutralizing antibody. PLANT BIOTECHNOLOGY JOURNAL 2009; 7:899-913. [PMID: 19843249 DOI: 10.1111/j.1467-7652.2009.00452.x] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The use of vaginal microbicides containing human immunodeficiency virus (HIV)-neutralizing antibodies (nAbs) is a promising strategy to prevent HIV-1 infection. Although antibodies are predominantly manufactured using mammalian cells, elastin-like peptide (ELP) fusion technology improves the stability of recombinant, plant-produced proteins and facilitates their purification, making plants an alternative platform for antibody production. We generated transgenic tobacco plants accumulating four different formats of the anti-HIV-1 antibody 2G12 in the endoplasmic reticulum (ER), i.e. with ELP on either the light or heavy chain, on both, or on neither. Detailed analysis of affinity-purified antibodies by surface plasmon resonance spectroscopy showed that the kinetic binding parameters of all formats were identical to 2G12 lacking ELP produced in Chinese hamster ovary (CHO) cells. Importantly, protein purification from seeds by inverse transition cycling (ITC) did not affect the binding kinetics. Analysis of heavy chain N-glycans from leaf-derived antibodies showed that retrieval to the ER was efficient for all formats. In seeds, however, N-glycans on the naked antibody were extensively trimmed compared with those on the ELP fusion formats, and were localized to a different subcellular compartment. The in vitro HIV-neutralization properties of the tobacco-derived 2G12 were equivalent to or better than those of the CHO counterpart.
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Affiliation(s)
- Doreen M Floss
- Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Gatersleben, Germany
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111
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Wei H, Fan Y, Gao YQ. Effects of Urea, Tetramethyl Urea, and Trimethylamine N-Oxide on Aqueous Solution Structure and Solvation of Protein Backbones: A Molecular Dynamics Simulation Study. J Phys Chem B 2009; 114:557-68. [DOI: 10.1021/jp9084926] [Citation(s) in RCA: 148] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- Haiyan Wei
- Department of Chemistry, P.O. Box 3012, Texas A&M University, College Station, Texas 77842
| | - Yubo Fan
- Department of Chemistry, P.O. Box 3012, Texas A&M University, College Station, Texas 77842
| | - Yi Qin Gao
- Department of Chemistry, P.O. Box 3012, Texas A&M University, College Station, Texas 77842
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112
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Ribeiro A, Arias FJ, Reguera J, Alonso M, Rodríguez-Cabello JC. Influence of the amino-acid sequence on the inverse temperature transition of elastin-like polymers. Biophys J 2009; 97:312-20. [PMID: 19580769 DOI: 10.1016/j.bpj.2009.03.030] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2009] [Revised: 03/20/2009] [Accepted: 03/26/2009] [Indexed: 11/17/2022] Open
Abstract
This work explores the dependence of the inverse temperature transition of elastin-like polymers (ELPs) on the amino-acid sequence, i.e., the amino-acid arrangement along the macromolecule and the resulting linear distribution of the physical properties (mainly polarity) derived from it. The hypothesis of this work is that, in addition to mean polarity and molecular mass, the given amino-acid sequence, or its equivalent--the way in which polarity is arranged along the molecule--is also relevant for determining the transition temperature and the latent heat of that transition. To test this hypothesis, a set of linear and di- and triblock ELP copolymers were designed and produced as recombinant proteins. The absolute sequence control provided by recombinant technologies allows the effect of the amino-acid arrangement to be isolated while keeping the molecular mass or mean polarity under strict control. The selected block copolymers were made of two different ELPs: one exhibiting temperature and pH responsiveness, and one exhibiting temperature responsiveness only. By changing the arrangement and length of the blocks while keeping other parameters, such as the molecular mass or mean polarity, constant, we were able to show that the sequence plays a key role in the smart behavior of ELPs.
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Affiliation(s)
- Artur Ribeiro
- G.I.R. Bioforge, Universidad de Valladolid, Centro de I+D, and Networking Research Center on Bioengineering, Biomaterials and Nanomedicine, Valladolid, Spain
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113
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Conrad R, Grubbs R. Tunable, Temperature-Responsive Polynorbornenes with Side Chains Based on an Elastin Peptide Sequence. Angew Chem Int Ed Engl 2009. [DOI: 10.1002/ange.200903888] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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114
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115
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Kyle S, Aggeli A, Ingham E, McPherson MJ. Production of self-assembling biomaterials for tissue engineering. Trends Biotechnol 2009; 27:423-33. [PMID: 19497631 PMCID: PMC2828541 DOI: 10.1016/j.tibtech.2009.04.002] [Citation(s) in RCA: 148] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2008] [Revised: 04/01/2009] [Accepted: 04/01/2009] [Indexed: 11/24/2022]
Abstract
Self-assembling peptide-based biomaterials are being developed for use as 3D tissue engineering scaffolds and for therapeutic drug-release applications. Chemical synthesis provides custom-made peptides in small quantities, but production approaches based upon transgenic organisms might be more cost-effective for large-scale peptide production. Long lead times for developing appropriate animal clones or plant lines and potential negative public opinion are obstacles to these routes. Microbes, particularly safe organisms used in the food industry, offer a more rapid route to the large-scale production of recombinant self-assembling biomaterials. In this review, recent advances and challenges in the recombinant production of collagen, elastin and de novo designed self-assembling peptides are discussed.
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Affiliation(s)
- Stuart Kyle
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK.
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116
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Araújo R, Silva C, Machado R, Casal M, Cunha AM, Rodriguez-Cabello JC, Cavaco-Paulo A. Proteolytic Enzyme Engineering: A Tool for Wool. Biomacromolecules 2009; 10:1655-61. [DOI: 10.1021/bm9002943] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Rita Araújo
- CBMA (Centre of Molecular and Environmental Biology), Department of Biology, University of Minho, Campus of Gualtar 4710-057 Braga, Portugal, 2C2T (Centre of Science and Textile Engineering), Department of Textile Engineering, University of Minho, Campus of Azurém, 4800-058 Guimarães, Portugal, Department of Polymer Engineering, University of Minho, Campus de Azurém, 4800-058 Guimarães, Portugal, and BIOFORGE Research Group, Dpto. Física de la Materia Condensada, E.T.S.I.I., Universidad de Valladolid,
| | - Carla Silva
- CBMA (Centre of Molecular and Environmental Biology), Department of Biology, University of Minho, Campus of Gualtar 4710-057 Braga, Portugal, 2C2T (Centre of Science and Textile Engineering), Department of Textile Engineering, University of Minho, Campus of Azurém, 4800-058 Guimarães, Portugal, Department of Polymer Engineering, University of Minho, Campus de Azurém, 4800-058 Guimarães, Portugal, and BIOFORGE Research Group, Dpto. Física de la Materia Condensada, E.T.S.I.I., Universidad de Valladolid,
| | - Raul Machado
- CBMA (Centre of Molecular and Environmental Biology), Department of Biology, University of Minho, Campus of Gualtar 4710-057 Braga, Portugal, 2C2T (Centre of Science and Textile Engineering), Department of Textile Engineering, University of Minho, Campus of Azurém, 4800-058 Guimarães, Portugal, Department of Polymer Engineering, University of Minho, Campus de Azurém, 4800-058 Guimarães, Portugal, and BIOFORGE Research Group, Dpto. Física de la Materia Condensada, E.T.S.I.I., Universidad de Valladolid,
| | - Margarida Casal
- CBMA (Centre of Molecular and Environmental Biology), Department of Biology, University of Minho, Campus of Gualtar 4710-057 Braga, Portugal, 2C2T (Centre of Science and Textile Engineering), Department of Textile Engineering, University of Minho, Campus of Azurém, 4800-058 Guimarães, Portugal, Department of Polymer Engineering, University of Minho, Campus de Azurém, 4800-058 Guimarães, Portugal, and BIOFORGE Research Group, Dpto. Física de la Materia Condensada, E.T.S.I.I., Universidad de Valladolid,
| | - António M. Cunha
- CBMA (Centre of Molecular and Environmental Biology), Department of Biology, University of Minho, Campus of Gualtar 4710-057 Braga, Portugal, 2C2T (Centre of Science and Textile Engineering), Department of Textile Engineering, University of Minho, Campus of Azurém, 4800-058 Guimarães, Portugal, Department of Polymer Engineering, University of Minho, Campus de Azurém, 4800-058 Guimarães, Portugal, and BIOFORGE Research Group, Dpto. Física de la Materia Condensada, E.T.S.I.I., Universidad de Valladolid,
| | - José Carlos Rodriguez-Cabello
- CBMA (Centre of Molecular and Environmental Biology), Department of Biology, University of Minho, Campus of Gualtar 4710-057 Braga, Portugal, 2C2T (Centre of Science and Textile Engineering), Department of Textile Engineering, University of Minho, Campus of Azurém, 4800-058 Guimarães, Portugal, Department of Polymer Engineering, University of Minho, Campus de Azurém, 4800-058 Guimarães, Portugal, and BIOFORGE Research Group, Dpto. Física de la Materia Condensada, E.T.S.I.I., Universidad de Valladolid,
| | - Artur Cavaco-Paulo
- CBMA (Centre of Molecular and Environmental Biology), Department of Biology, University of Minho, Campus of Gualtar 4710-057 Braga, Portugal, 2C2T (Centre of Science and Textile Engineering), Department of Textile Engineering, University of Minho, Campus of Azurém, 4800-058 Guimarães, Portugal, Department of Polymer Engineering, University of Minho, Campus de Azurém, 4800-058 Guimarães, Portugal, and BIOFORGE Research Group, Dpto. Física de la Materia Condensada, E.T.S.I.I., Universidad de Valladolid,
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117
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Insights into a putative hinge region in elastin using molecular dynamics simulations. Matrix Biol 2009; 28:92-100. [DOI: 10.1016/j.matbio.2008.12.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2008] [Revised: 12/04/2008] [Accepted: 12/05/2008] [Indexed: 11/17/2022]
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118
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Bermudez H, Hathorne AP. Incorporating stimulus-responsive character into filamentous virus assemblies. Faraday Discuss 2009; 139:327-35; discussion 399-417, 419-20. [PMID: 19049004 DOI: 10.1039/b800675j] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Controlling interactions between building blocks, in either guided- or self-assemblies, is becoming increasingly important for the creation of functional materials. We have focused our attention on the well-known model assembly, the filamentous bacteriophage, where our strategy is to selectively alter surface features by focusing on spatially distinct capsid proteins. Towards introducing stimulus-responsive behavior in these flexible, rod-like particles, we have introduced elastin-like polypeptide (ELP) motifs of isoleucine and tyrosine "guest" residues by recombinant DNA methods. Our hypothesis is that modification of the major coat capsid protein would be greatly amplified by the 2700 copies per particle. Characterization of ELP-phage particles was carried out by microbiological assays, zeta potential, dynamic light scattering, and calorimetry. Bacteria producing ELP-phage particles grow more slowly and surprisingly, ELP-modified phages display a significant reduction in viral infectivity. For the lengths of ELP inserts studied, modified phages do not aggregate from solution as monitored by DLS. However, the hydrodynamic size of the phages depends on the details of the ELP motif. Zeta potential measurements reveal the particles are electrostatically stabilized, and this contributes in part to the energetic barrier against aggregation. Preliminary calorimetric data indicate subtle thermal transitions in the range 35-45 degrees C, suggesting that the ELP motif may collapse without triggering macroscopic aggregation. The results are consistent with the classical picture of critical solution phenomena at low concentrations, where to drive phase separation, solvent quality must be increasingly poor. Apart from being model systems to study basic questions of self-assembly, extending these modular systems is likely to result in improved understanding and control over self-assembly in various applications.
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Affiliation(s)
- Harry Bermudez
- Department of Polymer Science & Engineering, University of Massachusetts. Amherst, MA 01003, USA.
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119
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Conrad RM, Grubbs RH. Tunable, temperature-responsive polynorbornenes with side chains based on an elastin peptide sequence. Angew Chem Int Ed Engl 2009; 48:8328-30. [PMID: 19784987 PMCID: PMC3517114 DOI: 10.1002/anie.200903888] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Rosemary M. Conrad
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, Fax: (+1) 626-564-9297
| | - Robert H. Grubbs
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, Fax: (+1) 626-564-9297
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120
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Ahmed Z, Scaffidi J, Asher SA. Circular dichroism and UV-resonance Raman investigation of the temperature dependence of the conformations of linear and cyclic elastin. Biopolymers 2009; 91:52-60. [PMID: 18932268 PMCID: PMC5325690 DOI: 10.1002/bip.21081] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
We used electronic circular dichroism (CD) and UV resonance Raman (UVRR) spectroscopy at 204 nm excitation to examine the temperature dependence of conformational changes in cyclic and linear elastin peptides. We utilize CD spectroscopy to study global conformation changes in elastin peptides, while UVRR is utilized to probe the local conformation and hydrogen bonding of Val and Pro peptide bonds. Our results indicate that at 20 degrees C cyclic elastin predominantly populates distorted beta-strand, beta-type II and beta-type III turn conformations. At 60 degrees C, the beta-type II turn population increases, while the distorted beta-strand population decreases. Linear elastin predominantly adopts distorted beta-strand and beta-type III turn conformations with some beta-type II turn population at 20 degrees C. Increasing temperature to 60 degrees C results in a small increase in the turn population.
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Affiliation(s)
- Zeeshan Ahmed
- Department of Chemistry, University of Pittsburgh, PA 15260
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121
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Kim B, Chilkoti A. Allosteric actuation of inverse phase transition of a stimulus-responsive fusion polypeptide by ligand binding. J Am Chem Soc 2008; 130:17867-73. [PMID: 19055326 PMCID: PMC2648868 DOI: 10.1021/ja8059057] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report herein a biopolymer actuator with a modular design that allosterically transduces ligand binding into an aqueous demixing phase transition. The biopolymer actuator consists of two modular domains: a ligand binding protein domain, calmodulin (CaM), that is fused to a transducer domain, a stimulus-responsive elastin-like polypeptide (ELP) that exhibits a reversible lower critical solution temperature (LCST) phase transition. We demonstrate that binding of calcium to CaM spontaneously triggers the phase transition of the attached ELP, leading to formation of meso-microscale particles depending on the chain length of the ELP. This behavior is reversible as chelation of the bound calcium results in dissolution of the assembled particles, is selective for calcium as opposed to magnesium, and is abolished by the binding of a peptide ligand that is specific to calcium-bound CaM. These results are, to our knowledge, the first demonstration of biomolecular recognition-triggered, allosteric regulation of the LCST phase transition of a polymer and are significant because they expand the available triggers of the LCST transition of stimulus-responsive polymers to biochemical ligand binding. The ability to allosterically trigger the LCST transition of ELPs by biomolecular recognition will be useful for developing "smart" polymer actuators that capitalize upon the myriad ligand-protein pairs that are available from biology and for application in the design of selective pull-down assays in proteomics, drug delivery, and nanoscale biomolecular devices.
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Affiliation(s)
- Bumjoon Kim
- Department of Biomedical Engineering, Duke University, Durham, NC 27708-0281 (USA)
| | - Ashutosh Chilkoti
- Department of Biomedical Engineering, Duke University, Durham, NC 27708-0281 (USA)
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122
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Valiaev A, Lim DW, Schmidler S, Clark RL, Chilkoti A, Zauscher S. Hydration and conformational mechanics of single, end-tethered elastin-like polypeptides. J Am Chem Soc 2008; 130:10939-46. [PMID: 18646848 PMCID: PMC2736882 DOI: 10.1021/ja800502h] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We investigated the effect of temperature, ionic strength, solvent polarity, and type of guest residue on the force-extension behavior of single, end-tethered elastin-like polypeptides (ELPs), using single molecule force spectroscopy (SMFS). ELPs are stimulus-responsive polypeptides that contain repeats of the five amino acids Val-Pro-Gly-Xaa-Gly (VPGXG), where Xaa is a guest residue that can be any amino acid with the exception of proline. We fitted the force-extension data with a freely jointed chain (FJC) model which allowed us to resolve small differences in the effective Kuhn segment length distributions that largely arise from differences in the hydrophobic hydration behavior of ELP. Our results agree qualitatively with predictions from recent molecular dynamics simulations and demonstrate that hydrophobic hydration modulates the molecular elasticity for ELPs. Furthermore, our results show that SMFS, when combined with our approach for data analysis, can be used to study the subtleties of polypeptide-water interactions and thus provides a basis for the study of hydrophobic hydration in intrinsically unstructured biomacromolecules.
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Affiliation(s)
- Alexei Valiaev
- Department of Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina 27708
- Center for Biologically Inspired Materials and Materials Systems, Duke University, Durham, North Carolina 27708
| | - Dong Woo Lim
- Center for Biologically Inspired Materials and Materials Systems, Duke University, Durham, North Carolina 27708
- Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708
| | - Scott Schmidler
- Institute of Statistics and Decision Sciences, Duke University, Durham, North Carolina 27708
| | - Robert L. Clark
- Department of Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina 27708
- Center for Biologically Inspired Materials and Materials Systems, Duke University, Durham, North Carolina 27708
| | - Ashutosh Chilkoti
- Center for Biologically Inspired Materials and Materials Systems, Duke University, Durham, North Carolina 27708
- Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708
| | - Stefan Zauscher
- Department of Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina 27708
- Center for Biologically Inspired Materials and Materials Systems, Duke University, Durham, North Carolina 27708
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123
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Floss DM, Sack M, Stadlmann J, Rademacher T, Scheller J, Stöger E, Fischer R, Conrad U. Biochemical and functional characterization of anti-HIV antibody-ELP fusion proteins from transgenic plants. PLANT BIOTECHNOLOGY JOURNAL 2008; 6:379-91. [PMID: 18312505 DOI: 10.1111/j.1467-7652.2008.00326.x] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The stability and recovery of recombinant proteins expressed in plants are improved by fusion to elastin-like peptides (ELPs). In order to test the suitability of ELP for the production of pharmaceutical proteins, transgenic plants were created that individually expressed the light and heavy chains of the broadly neutralizing anti-human immunodeficiency virus type 1 (anti-HIV-1) monoclonal antibody 2F5, which is being evaluated as a microbicide component. The antibody chains were expressed both with and without a C-terminal ELP fusion. Crossing these plants in all combinations resulted in transgenic lines producing the full antibody in four formats, with ELP on either the light or heavy chains, on both or on neither. Characterization of the affinity-purified antibodies by surface plasmon resonance spectroscopy showed that the kinetic binding parameters were identical to those of a Chinese hamster ovary (CHO) cell counterpart lacking ELP. N-Glycan analysis showed that all four derivatives contained predominantly oligo-mannose-type N-glycans and that the ELP fusions had no significant effect on N-glycan structure. It was concluded that ELP fusion to the light chain, heavy chain or both chains of a plant-derived antibody had no adverse affects on protein quality, but had a positive impact on the yield. ELP fusions do not interfere with folding, assembly, trafficking in the secretory pathway or post-translational modification, but enhance stability whilst at the same time simplifying recovery.
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Affiliation(s)
- Doreen M Floss
- Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstrasse 3, D-06466 Gatersleben, Germany
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124
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Porter D, Vollrath F. The role of kinetics of and amide bonding in protein stability. SOFT MATTER 2008; 4:328-336. [PMID: 32907247 DOI: 10.1039/b713972a] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The physical properties and function of biological tissues depend critically upon the hydration of proteins; in particular, their thermal, mechanical, and chemical stability. Here, we show quantitatively how thermal, mechanical, and chemical conditions can denature a protein. An elastic instability criterion is applied to localised ab initio quantum mechanics simulations of water and amide bond energies to predict both denaturing conditions and the effect of water on the glass transition temperature of a protein. The kinetics of bond instability for denaturation over a wide range of time scales is quantified by an expression for a second order phase change using parameters derived directly from the quantum simulations. We also show how the zero point energy of vibrations in a potential energy well of intermolecular bonding can differentiate between crystal and amorphous states of matter and their corresponding transition temperatures; this is illustrated by calculating the crystal melt and glass transition temperatures of water.
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Affiliation(s)
- D Porter
- Department of Zoology, University of Oxford, South Parks Road, Oxford, UKOX1 3PS.
| | - F Vollrath
- Department of Zoology, University of Oxford, South Parks Road, Oxford, UKOX1 3PS.
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125
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Lim DW, Nettles DL, Setton LA, Chilkoti A. In situ cross-linking of elastin-like polypeptide block copolymers for tissue repair. Biomacromolecules 2008; 9:222-30. [PMID: 18163573 PMCID: PMC3075888 DOI: 10.1021/bm7007982] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Rapid cross-linking of elastin-like polypeptides (ELPs) with hydroxymethylphosphines (HMPs) in aqueous solution is attractive for minimally invasive in vivo implantation of biomaterials and tissue engineering scaffolds. In order to examine the independent effect of the location and number of reactive sites on the chemical cross-linking kinetics of ELPs and the mechanical properties of the resulting hydrogels, we have designed ELP block copolymers comprised of cross-linkable, hydrophobic ELP blocks with periodic Lys residues (A block) and aliphatic, hydrophilic ELP blocks with no cross-linking sites (B block); three different block architectures, A, ABA, and BABA were synthesized in this study. All ELP block copolymers were rapidly cross-linked with HMPs within several minutes under physiological conditions. The inclusion of the un-cross-linked hydrophilic block, its length relative to the cross-linkable hydrophobic block, and the block copolymer architecture all had a significant effect on swelling ratios of the cross-linked hydrogels, their microstructure, and mechanical properties. Fibroblasts embedded in the ELP hydrogels survived the cross-linking process and remained viable for at least 3 days in vitro when the gels were formed from an equimolar ratio of HMPs and Lys residues of ELPs. DNA quantification of the embedded cells indicated that the cell viability within triblock ELP hydrogels was statistically greater than that in the monoblock gels at day 3. These results suggest that the mechanical properties of ELP hydrogels and the microenvironment that they present to cells can be tuned by the design of the block copolymer architecture.
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Affiliation(s)
- Dong Woo Lim
- Department of Biomedical Engineering, Box 90281, Duke University, Durham, North Carolina 27708-0281
| | - Dana L. Nettles
- Department of Biomedical Engineering, Box 90281, Duke University, Durham, North Carolina 27708-0281
| | - Lori A. Setton
- Department of Biomedical Engineering, Box 90281, Duke University, Durham, North Carolina 27708-0281
| | - Ashutosh Chilkoti
- Department of Biomedical Engineering, Box 90281, Duke University, Durham, North Carolina 27708-0281
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126
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Rodríguez-Cabello JC, Prieto S, Arias FJ, Reguera J, Ribeiro A. Nanobiotechnological approach to engineered biomaterial design: the example of elastin-like polymers. Nanomedicine (Lond) 2007; 1:267-80. [PMID: 17716158 DOI: 10.2217/17435889.1.3.267] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Today, the development of advanced biomaterials is still lacking an appropriate tailored engineering approach. Most of the biomaterials currently used have their origin in materials developed for other technological applications. This lack of adequate biomaterial design is probably due to the peculiar environment where those materials must operate. On the one hand, this environment is dominated by the immune rejection system. On the other hand, the functionality of natural biomolecules is based on complex topological physical-chemical function distributions at the nanometer level. This review presents arguments concerning the role of biotechnology and nanotechnology in the future development of new advanced biomaterials and the potential of these biomaterials as a way to achieve highly biofunctional and truly biocompatible biomaterials for hot areas, such as regenerative medicine and controlled release. Recombinant protein-polymers will be presented as an example of candidates for this new paradigm in biomaterial design and production.
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Affiliation(s)
- J Carlos Rodríguez-Cabello
- Bioforge group, Dpto. Física de la Materia Condensada, ETSII, Universidad de Valladolid, Valladolid, Spain.
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127
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Lim DW, Trabbic-Carlson K, Mackay JA, Chilkoti A. Improved non-chromatographic purification of a recombinant protein by cationic elastin-like polypeptides. Biomacromolecules 2007; 8:1417-24. [PMID: 17407348 PMCID: PMC2562536 DOI: 10.1021/bm060849t] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
This paper reports an improvement in the purification of thioredoxin (Trx) expressed from E. coli by inverse transition cycling (ITC) using cationic elastin-like polypeptides (ELPs). Two ELP libraries having 2% and 5% lysine residues and molecular weights ranging from 4 to 61.1 kDa showed greater salt sensitivity in their inverse transition behavior than purely aliphatic ELPs. Expression yield of Trx-ELP fusions was an unpredictable function of guest residue composition, but reducing the molecular weight of the ELP tag generally increased Trx yield. A cationic 4.3 kDa ELP is the shortest ELP used to purify any protein by ITC to date. A 15.9 kDa ELP with a guest residue composition of K:V:F of 1:7:1 was found to be the optimal cationic tag to purify Trx, as it provided 50% greater Trx yield and only required one-fifth the added NaCl for purification of Trx as compared to previously used aliphatic ELP tags.
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Affiliation(s)
- Dong Woo Lim
- Department of Biomedical Engineering, Box 90281, Duke University, Durham, North Carolina 27708-0281, USA
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128
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Pechar M, Brus J, Kostka L, Konák C, Urbanová M, Slouf M. Thermoresponsive self-assembly of short elastin-like polypentapeptides and their poly(ethylene glycol) derivatives. Macromol Biosci 2007; 7:56-69. [PMID: 17238231 DOI: 10.1002/mabi.200600196] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Short polypeptides with four pentad repeats, (VPGVG)(4) and (VPAVG)(4), were synthesised by manual fluorenylmethoxycarbonyl/tert-butyl (Fmoc/t-Bu) solid phase peptide synthesis using a convergent approach. In the next step, the peptides were coupled via their N-terminus with activated semi-telechelic poly(ethylene glycol) O-(N-Fmoc-2-aminoethyl)-O'-(2-carboxyethyl)undeca(ethylene glycol) (Fmoc-PEG-COOH) to yield monodisperse Fmoc-PEG-peptide diblock copolymer. Both the presence of the terminal hydrophobic Fmoc group and the hydrophilic PEG chain in the copolymers were shown to play a crucial role in their self-associative behaviour, leading to reversible formation of supramolecular thermoresponsive assemblies. The peptides and their PEG derivatives were characterised by HPLC, NMR and MALDI-TOF MS. The associative behaviour of the peptides and their PEG derivatives was studied by dynamic light scattering, MAS NMR and phase contrast microscopy. [image: see text]
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Affiliation(s)
- Michal Pechar
- Institute of Macromolecular Chemistry, Academy of Sciences of Czech Republic, 162 06 Prague 6, Czech Republic.
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129
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Kim W, Conticello VP. Protein Engineering Methods for Investigation of Structure-Function Relationships in Protein-Based Elastomeric Materials. POLYM REV 2007. [DOI: 10.1080/15583720601109586] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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130
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Dyksterhuis LB, Baldock C, Lammie D, Wess TJ, Weiss AS. Domains 17–27 of tropoelastin contain key regions of contact for coacervation and contain an unusual turn-containing crosslinking domain. Matrix Biol 2007; 26:125-35. [PMID: 17129717 DOI: 10.1016/j.matbio.2006.10.002] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2006] [Revised: 09/19/2006] [Accepted: 10/11/2006] [Indexed: 11/27/2022]
Abstract
The central region of tropoelastin including domains 19-25 of human tropoelastin forms a hot-spot for contacts during the inter-molecular association of tropoelastin by coacervation [Wise, S.G., Mithieux, S.M., Raftery, M.J. and Weiss, A.S (2005). "Specificity in the coacervation of tropoelastin: solvent exposed lysines." Journal of Structural Biology 149: 273-81.]. We explored the physical properties of this central region using a sub-fragment bordered by domains 17-27 of human tropoelastin (SHEL 17-27) and identified the intra- and inter-molecular contacts it forms during coacervation. A homobifunctional amine reactive crosslinker (with a maximum reach of 11 A, corresponding to approximately 7 residues in an extended polypeptide chain) was used to capture these contacts and crosslinked regions were identified after protease cleavage and mass spectrometry (MS) with MS/MS verification. An intermolecular crosslink formed between the lysines at positions 353 of each strand of tropoelastin at the lowest of crosslinker concentrations and was observed in all samples tested, suggesting that this residue forms an important initial contact during coacervation. At higher crosslinker concentrations, residues K425 and K437 showed the highest levels of involvement in crosslinks. An intramolecular crosslink between these K425 and K437, separated by 11 residues, indicated that a structural bend must serve to bring these residues into close proximity. These studies were complemented by small angle X-ray scattering studies that confirmed a bend in this important subfragment of the tropoelastin molecule.
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Affiliation(s)
- L B Dyksterhuis
- School of Molecular and Microbial Biosciences, University of Sydney, NSW, Australia
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131
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Kim W, Hardcastle KI, Conticello VP. Fluoroproline Flip-Flop: Regiochemical Reversal of a Stereoelectronic Effect on Peptide and Protein Structures. Angew Chem Int Ed Engl 2006. [DOI: 10.1002/ange.200603227] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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132
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Kim W, Hardcastle KI, Conticello VP. Fluoroproline Flip-Flop: Regiochemical Reversal of a Stereoelectronic Effect on Peptide and Protein Structures. Angew Chem Int Ed Engl 2006; 45:8141-5. [PMID: 17109457 DOI: 10.1002/anie.200603227] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Wookhyun Kim
- Department of Chemistry, Emory University, 1515 Dickey Drive, Atlanta, GA 30322, USA
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133
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Chilkoti A, Christensen T, MacKay JA. Stimulus responsive elastin biopolymers: Applications in medicine and biotechnology. Curr Opin Chem Biol 2006; 10:652-7. [PMID: 17055770 PMCID: PMC3732176 DOI: 10.1016/j.cbpa.2006.10.010] [Citation(s) in RCA: 135] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2006] [Accepted: 10/06/2006] [Indexed: 11/29/2022]
Abstract
Elastin-like polypeptides (ELPs) are artificial polypeptides, derived from Val-Pro-Gly-Xaa-Gly (VPGXG) pentapeptide repeats found in human tropoelastin, that reversibly coacervate above a critical temperature. Genetically encodable ELPs are monodisperse, stimuli responsive, and biocompatible, properties that make them attractive for drug delivery and tissue engineering. The potential of ELPs to self-assemble into nanostructures in response to environmental triggers is another interesting feature of these polypeptides that promises to lead to a host of new applications.
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Affiliation(s)
- Ashutosh Chilkoti
- Department of Biomedical Engineering, Duke University, Durham, NC 27708-0281, USA.
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134
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Rauscher S, Baud S, Miao M, Keeley FW, Pomès R. Proline and Glycine Control Protein Self-Organization into Elastomeric or Amyloid Fibrils. Structure 2006; 14:1667-76. [PMID: 17098192 DOI: 10.1016/j.str.2006.09.008] [Citation(s) in RCA: 272] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2006] [Revised: 09/08/2006] [Accepted: 09/12/2006] [Indexed: 11/28/2022]
Abstract
Elastin provides extensible tissues, including arteries and skin, with the propensity for elastic recoil, whereas amyloid fibrils are associated with tissue-degenerative diseases, such as Alzheimer's. Although both elastin-like and amyloid-like materials result from the self-organization of proteins into fibrils, the molecular basis of their differing physical properties is poorly understood. Using molecular simulations of monomeric and aggregated states, we demonstrate that elastin-like and amyloid-like peptides are separable on the basis of backbone hydration and peptide-peptide hydrogen bonding. The analysis of diverse sequences, including those of elastin, amyloids, spider silks, wheat gluten, and insect resilin, reveals a threshold in proline and glycine composition above which amyloid formation is impeded and elastomeric properties become apparent. The predictive capacity of this threshold is confirmed by the self-assembly of recombinant peptides into either amyloid or elastin-like fibrils. Our findings support a unified model of protein aggregation in which hydration and conformational disorder are fundamental requirements for elastomeric function.
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Affiliation(s)
- Sarah Rauscher
- Molecular Structure and Function Programme, Hospital for Sick Children, 555 University Avenue, Toronto, Ontario M5G 1X8, Canada
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135
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Hantash BM, Bedi VP, Sudireddy V, Struck SK, Herron GS, Chan KF. Laser-induced transepidermal elimination of dermal content by fractional photothermolysis. JOURNAL OF BIOMEDICAL OPTICS 2006; 11:041115. [PMID: 16965143 DOI: 10.1117/1.2241745] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
The wound healing process in skin is studied in human subjects treated with fractional photothermolysis. In-vivo histological evaluation of vacuoles formed over microthermal zones (MTZs) and their content is undertaken. A 30-W, 1550-nm single-mode fiber laser system delivers an array of 60 microm or 140 microm 1e2 incidence microbeam spot size at variable pulse energy and density. Treatments span from 6 to 20 mJ with skin excisions performed 1-day post-treatment. Staining with hematoxylin and eosin demonstrates an intact stratum corneum with vacuolar formation within the epidermis. The re-epithelialization process with repopulation of melanocytes and keratinocytes at the basal layer is apparent by 1-day post-treatment. The dermal-epidermal (DE) junction is weakened and separated just above zones of dermal coagulation. Complete loss of dermal cell viability is noted within the confines of the MTZs 1-day post-treatment, as assessed by lactate dehydrogenase. All cells falling outside the irradiation field remain viable. Content within the epidermal vacuoles stain positively with Gomori trichrome, suggesting a dermal origin. However, the positive staining could be due to loss of specificity after thermal alteration. Nevertheless, this dermal extrusion hypothesis is supported by very specific positive staining with an antihuman elastin antibody. Fractional photothermolysis creates microthermal lesions that allow transport and extrusion of dermal content through a compromised DE junction. Some dermal material is incorporated into the microepidermal necrotic debris and shuttled up the epidermis to eventually be exfoliated through the stratum corneum. This is the first report of a nonablative laser-induced transport mechanism by which dermal content can be predictably extruded biologically through the epidermis. Thus, treatment with the 1550-nm fiber laser may provide the first therapeutic option for clinical indications, including pigmentary disorders such as medically recalcitrant melasma, solar elastosis, as well as depositional diseases such as mucinosis and amyloidosis.
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Affiliation(s)
- Basil M Hantash
- Reliant Technologies, Incorporated, Mountain View, California 94043, USA
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136
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Liu W, Dreher MR, Chow DC, Zalutsky MR, Chilkoti A. Tracking the in vivo fate of recombinant polypeptides by isotopic labeling. J Control Release 2006; 114:184-92. [PMID: 16904221 DOI: 10.1016/j.jconrel.2006.06.001] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
We report a method to incorporate a stable isotope (13C) and a radioactive isotope (14C) into a recombinant polypeptide during Escherichia coli culture in M9 minimal medium supplemented with universally labeled 13C- or 14C-labeled glucose. We chose a thermally responsive elastin-like polypeptide (ELP) as a model polypeptide for this study because of its utility in various biotechnology applications such as drug delivery and tissue engineering. High cell densities were obtained by step-wise adaptation of E. coli to M9 medium in addition to supplementing the medium with trace elements that facilitated growth of E. coli. Furthermore, an optimal concentration of isopropyl-beta-d-thiogalactopyranoside was determined for induction of ELP expression to achieve high yield (mg/L culture) of the ELP. The incorporation of carbon isotopes was stoichiometrically related to the ratio of labeled glucose to unlabeled glucose in the culture medium. The isotope-labeled variants retained the physicochemical properties of the unlabeled ELP, specifically its temperature dependent aggregation behavior. As an example of the utility of this method, the in vitro stability of 14C-labeled ELP in PBS and mouse serum was conveniently quantified by SDS-PAGE and autoradiography. In addition, the in vivo stability of the 14C-labeled ELP in plasma was determined along with its plasma pharmacokinetics.
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Affiliation(s)
- Wenge Liu
- Department of Biomedical Engineering, Campus Box 90281 Duke University, Durham, NC 27708, USA
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137
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Buttafoco L, Kolkman NG, Engbers-Buijtenhuijs P, Poot AA, Dijkstra PJ, Vermes I, Feijen J. Electrospinning of collagen and elastin for tissue engineering applications. Biomaterials 2006; 27:724-34. [PMID: 16111744 DOI: 10.1016/j.biomaterials.2005.06.024] [Citation(s) in RCA: 362] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2005] [Accepted: 06/24/2005] [Indexed: 11/19/2022]
Abstract
Meshes of collagen and/or elastin were successfully prepared by means of electrospinning from aqueous solutions. Flow rate, applied electric field, collecting distance and composition of the starting solutions determined the morphology of the obtained fibres. Addition of PEO (M(w)=8 x 10(6)) and NaCl was always necessary to spin continuous and homogeneous fibres. Spinning a mixture of collagen and elastin resulted in fibres in which the single components could not be distinguished by SEM. Increasing the elastin content determined an increase in fibres diameters from 220 to 600 nm. The voltage necessary for a continuous production of fibres was dependent on the composition of the starting solution, but always between 10 and 25 kV. Under these conditions, non-woven meshes could be formed and a partial orientation of the fibres constituting the mesh was obtained by using a rotating tubular mandrel as collector. Collagen/elastin (1:1) meshes were stabilized by crosslinking with N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS). This treatment afforded materials with a high thermal stability (T(d)=79 degrees C) without altering their original morphology. Upon crosslinking PEO and NaCl were fully leached out. Smooth muscle cells grew as a confluent layer on top of the crosslinked meshes after 14 d of culture.
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Affiliation(s)
- L Buttafoco
- Department of Polymer Chemistry and Biomaterials, Faculty of Science and Technology and Institute of Biomedical Technology BMTI, University of Twente, Enschede, P.O. Box 217, 7500 AE, The Netherlands
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138
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Kurková D, Kříž J, Rodríguez-Cabello JC, Arias FJ. NMR study of the cooperative behavior of thermotropic model polypeptides. POLYM INT 2006. [DOI: 10.1002/pi.2117] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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139
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Tamburro AM, Bochicchio B, Pepe A. The dissection of human tropoelastin: from the molecular structure to the self-assembly to the elasticity mechanism. ACTA ACUST UNITED AC 2005; 53:383-9. [PMID: 16085114 DOI: 10.1016/j.patbio.2004.12.014] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2004] [Accepted: 12/07/2004] [Indexed: 10/25/2022]
Abstract
After a historical introduction the authors describe their most recent results on the structure, assembly and elasticity of elastin. Recent results obtained by analyzing the conformation of polypeptide sequences encoded by the single exons of human tropoelastin demonstrated the presence of labile conformations such as poly-proline II helix (PPII) and beta-turns whose stability is strongly dependent on the microenvironment. Stable, periodic structures, such as alpha-helices, are only present in the poly-alanine cross-linking domains. These findings give a strong experimental basis to the understanding of the molecular mechanism of elasticity of elastin. In particular, they strongly support the description of the native relaxed state of the protein in terms of trans-conformational equilibria between extended and folded structures as previously proposed [Int. J. Biochem. Cell. Biol. 31 (1999) 261]. The same polypeptide sequences have been analyzed for their ability to coacervate and to self-assembly. Although the great majority of them were shown to be able to adopt more or less organized structures, only a few were indeed able to coacervate. Studies carried out by transmission electron microscopy showed the polypeptides to adopt a variety of supramolecular structures going from a filamentous organization (typical of elastin) to amyloid-like fibers. On the whole, the results obtained gave significant insight to the roles played by specific polypeptide sequences in self-assembly and possibly in elasticity.
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140
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Pepe A, Guerra D, Bochicchio B, Quaglino D, Gheduzzi D, Pasquali Ronchetti I, Tamburro AM. Dissection of human tropoelastin: supramolecular organization of polypeptide sequences coded by particular exons. Matrix Biol 2005; 24:96-109. [PMID: 15890261 DOI: 10.1016/j.matbio.2005.01.004] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2004] [Revised: 01/29/2005] [Accepted: 01/31/2005] [Indexed: 10/25/2022]
Abstract
Polypeptide sequences encoded by some exons of the human tropoelastin gene (EDP, elastin-derived peptide) have been analysed for their ability to coacervate and to self-assembly. The great majority of them were shown to form organized structures, but only a few were indeed able to coacervate. Negative staining and rotary shadowing transmission electron microscopy showed the polypeptides to adopt a variety of supramolecular organization, from filaments, as those typical of tropoelastin, to amyloid-like fibers. The results obtained gave significant insight to the possible roles played by specific polypeptide sequences of tropoelastin.
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Affiliation(s)
- Antonietta Pepe
- Department of Chemistry, Università della Basilicata, Via N. Sauro 85, 85100 Potenza, Italy
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141
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Trabbic-Carlson K, Liu L, Kim B, Chilkoti A. Expression and purification of recombinant proteins from Escherichia coli: Comparison of an elastin-like polypeptide fusion with an oligohistidine fusion. Protein Sci 2005; 13:3274-84. [PMID: 15557268 PMCID: PMC2287301 DOI: 10.1110/ps.04931604] [Citation(s) in RCA: 131] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Thermally responsive elastin like polypeptides (ELPs) can be used to purify proteins from Escherichia coli culture when proteins are expressed as a fusion with an ELP. Nonchromatographic purification of ELP fusion proteins, termed inverse transition cycling (ITC), exploits the reversible soluble-insoluble phase transition behavior imparted by the ELP tag. Here, we quantitatively compare the expression and purification of ELP and oligohistidine fusions of chloramphenicol acetyltransferase (CAT), blue fluorescent protein (BFP), thioredoxin (Trx), and calmodulin (CalM) from both a 4-h culture with chemical induction of the plasmid-borne fusion protein gene and a 24-h culture without chemical induction. The total protein content and functional activity were quantified at each ITC purification step. For CAT, BFP, and Trx, the 24-h noninduction culture of ELP fusion proteins results in a sevenfold increase in the yield of each fusion protein compared to that obtained by the 4-h-induced culture, and the calculated target protein yield is similar to that of their equivalent oligohistidine fusion. For these proteins, ITC purification of fusion proteins also results in approximately 75% recovery of active fusion protein, similar to affinity chromatography. Compared to chromatographic purification, however, ITC is inexpensive, requires no specialized equipment or reagents, and because ITC is a batch purification process, it is easily scaled up to accommodate larger culture volumes or scaled down and multiplexed for high-throughput, microscale purification; thus, potentially impacting both high-throughput protein expression and purification for proteomics and large scale, cost-effective industrial bioprocessing of pharmaceutically relevant proteins.
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142
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Nicolini C, Ravindra R, Ludolph B, Winter R. Characterization of the temperature- and pressure-induced inverse and reentrant transition of the minimum elastin-like polypeptide GVG(VPGVG) by DSC, PPC, CD, and FT-IR spectroscopy. Biophys J 2004; 86:1385-92. [PMID: 14990468 PMCID: PMC1303976 DOI: 10.1016/s0006-3495(04)74209-5] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
We investigated the temperature- and pressure-dependent structure and phase behavior of a solvated oligopeptide, GVG(VPGVG), which serves as a minimalistic elastin-like model system, over a large region of the thermodynamic phase field, ranging from 2 to 120 degrees C and from ambient pressure up to approximately 10 kbar, applying various spectroscopic (CD, FT-IR) and thermodynamic (DSC, PPC) measurements. We find that this octapeptide behaves as a two-state system which undergoes the well-known inverse-temperature folding transition occurring at T approximately 36 degrees C, and, in addition, a slow trend reversal at higher temperatures, finally leading to a reentrant unfolding close to the boiling point of water. Furthermore, the pressure-dependence of the folding/unfolding transition was studied to yield a more complete picture of the p, T-stability diagram of the system. A molecular-level picture of these processes, in particular on the role of water for the folding and unfolding events of the peptide, presented with the help of molecular-dynamics simulations, is presented in a companion article in this issue.
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Affiliation(s)
- C Nicolini
- Department of Chemistry, University of Dortmund, Dortmund, Germany
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143
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Haider M, Megeed Z, Ghandehari H. Genetically engineered polymers: status and prospects for controlled release. J Control Release 2004; 95:1-26. [PMID: 15013229 DOI: 10.1016/j.jconrel.2003.11.011] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2003] [Accepted: 11/11/2003] [Indexed: 10/26/2022]
Abstract
Genetic engineering methodology has enabled the synthesis of protein-based polymers with precisely controlled structures. Protein-based polymers have well-defined molecular weights, monomer compositions, sequences and stereochemistries. The incorporation of tailor-made motifs at specified locations by recombinant techniques allows the formation of hydrogels, sensitivity to environmental stimuli, complexation with drugs and nucleic acids, biorecognition and biodegradation. Accordingly, a special interest has emerged for the use of protein-based polymers for controlled drug and gene delivery, tissue engineering and other biomedical applications. This article is a review of genetically engineered polymers, their physicochemical characteristics, synthetic strategies used to produce them and their biomedical applications with emphasis on controlled release.
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Affiliation(s)
- Mohamed Haider
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD 21201, USA
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144
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Dreher MR, Elas M, Ichikawa K, Barth ED, Chilkoti A, Rosen GM, Halpern HJ, Dewhirst M. Nitroxide conjugate of a thermally responsive elastin-like polypeptide for noninvasive thermometry. Med Phys 2004; 31:2755-62. [PMID: 15543780 DOI: 10.1118/1.1782677] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Hyperthermia, as an adjuvant with radiation and chemotherapy, has shown promise in the treatment of cancer. The relevant biological effects of a hyperthermia treatment are both time and temperature-dependent, creating a need for accurate thermometry. We present a novel noninvasive thermometry modality that combines a temperature responsive biopolymer, the elastin-like polypeptide (ELP), and nitroxide to produce an ELP-nitroxide conjugate. When examined with electron paramagnetic resonance (EPR) spectroscopy, the ELP-nitroxide conjugate has temperature-dependent spectral line widths whose predictive accuracy is approximately 0.3 degrees C (80 microM). We believe that the temperature-dependent changes observed in the EPR spectrum are due to the combined effect of temperature, viscosity and effective radius on the rotational correlation time of the ELP-nitroxide conjugate.
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Affiliation(s)
- Matthew R Dreher
- Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708, USA
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145
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Kim W, George A, Evans M, Conticello VP. Cotranslational Incorporation of a Structurally Diverse Series of Proline Analogues in an Escherichia coli Expression System. Chembiochem 2004; 5:928-36. [PMID: 15239049 DOI: 10.1002/cbic.200400052] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
A set of Escherichia coli expression strains have been defined that are competent for the incorporation of a structurally diverse series of proline analogues under culture conditions that are compatible with high levels of analogue substitution within a proline-rich protein substrate. These bacterial strains have been employed to assay the efficacy of incorporation of noncanonical amino acids into a recombinant-protein test substrate and to create variant polypeptides in which native protein sequences have been globally substituted with imino acid analogues in response to proline codons. We envision that these methods may be used to interrogate the effect of imino acid substitution on protein structure and function and may be particularly informative in the context of structural comparison of a series of modified proteins with respect to the stereoelectronic differences between the incorporated proline analogues.
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Affiliation(s)
- Wookhyun Kim
- Department of Chemistry, Emory University, 1515 Dickey Drive, Atlanta, GA 30322, USA
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146
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Schreiner E, Nicolini C, Ludolph B, Ravindra R, Otte N, Kohlmeyer A, Rousseau R, Winter R, Marx D. Folding and unfolding of an elastinlike oligopeptide: "inverse temperature transition," reentrance, and hydrogen-bond dynamics. PHYSICAL REVIEW LETTERS 2004; 92:148101. [PMID: 15089575 DOI: 10.1103/physrevlett.92.148101] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2003] [Indexed: 05/24/2023]
Abstract
The temperature-dependent behavior of a solvated oligopeptide, GVG(VPGVG), is investigated. Spectroscopic measurements, thermodynamic measurements, and molecular dynamics simulations find that this elastinlike octapeptide behaves as a two-state system that undergoes an "inverse temperature" folding transition and reentrant unfolding close to the boiling point of water. A molecular picture of these processes is presented, emphasizing changes in the dynamics of hydrogen bonding at the protein/water interface and peptide backbone librational entropy.
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Affiliation(s)
- Eduard Schreiner
- Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, 44780 Bochum, Germany
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147
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Paschek D. Temperature dependence of the hydrophobic hydration and interaction of simple solutes: An examination of five popular water models. J Chem Phys 2004; 120:6674-90. [PMID: 15267560 DOI: 10.1063/1.1652015] [Citation(s) in RCA: 221] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We examine five different popular rigid water models (SPC, SPCE, TIP3P, TIP4P, and TIP5P) using molecular dynamics simulations in order to investigate the hydrophobic hydration and interaction of apolar Lennard-Jones solutes as a function of temperature in the range between 275 and 375 K along the 0.1 MPa isobar. For all investigated models and state points we calculate the excess chemical potential for the noble gases and methane employing the Widom particle insertion technique. All water models exhibit too small hydration entropies, but show a clear hierarchy. TIP3P shows poorest agreement with experiment, whereas TIP5P is closest to the experimental data at lower temperatures and SPCE is closest at higher temperatures. As a first approximation, this behavior can be rationalized as a temperature shift with respect to the solvation behavior found in real water. A rescaling procedure inspired by the information theory model of Hummer et al. [Chem. Phys. 258, 349 (2000)] suggests that the different solubility curves for the different models and real water can be largely explained on the basis of the different density curves at constant pressure. In addition, the models that give a good representation of the water structure at ambient conditions (TIP5P, SPCE, and TIP4P) show considerably better agreement with the experimental data than the ones which exhibit less structured O-O correlation functions (SPC and TIP3P). In the second part of the paper we calculate the hydrophobic interaction between xenon particles directly from a series of 60 ns simulation runs. We find that the temperature dependence of the association is to a large extent related to the strength of the solvation entropy. Nevertheless, differences between the models seem to require a more detailed molecular picture. The TIP5P model shows by far the strongest temperature dependence. The suggested density rescaling is also applied to the chemical potential in the xenon-xenon contact-pair configuration, indicating the presence of a temperature where the hydrophobic interaction turns into purely repulsive. The predicted association for xenon in real water suggests the presence of a strong variation with temperature, comparable to the behavior found for TIP5P water. Comparing different water models and experimental data we conclude that a proper description of density effects is an important requirement for a water model to account correctly for the correct description of the hydrophobic effects. A water model exhibiting a density maximum at the correct temperature is desirable.
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Affiliation(s)
- Dietmar Paschek
- Department of Physical Chemistry, Otto-Hahn Strasse 6, University of Dortmund, D-44221 Dortmund, Germany.
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148
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Rousseau R, Schreiner E, Kohlmeyer A, Marx D. Temperature-dependent conformational transitions and hydrogen-bond dynamics of the elastin-like octapeptide GVG(VPGVG): a molecular-dynamics study. Biophys J 2004; 86:1393-407. [PMID: 14990469 PMCID: PMC1303977 DOI: 10.1016/s0006-3495(04)74210-1] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2003] [Accepted: 12/12/2003] [Indexed: 11/24/2022] Open
Abstract
A joint experimental/theoretical investigation of the elastin-like octapeptide GVG(VPGVG) was carried out. In this article a comprehensive molecular-dynamics study of the temperature-dependent folding and unfolding of the octapeptide is presented. The current study, as well as its experimental counterpart (see companion article in this issue) find that this peptide undergoes an inverse temperature transition (ITT), leading to a folding at approximately 40-60 degrees C. In addition, an unfolding transition is identified at unusually high temperatures approaching the normal boiling point of water. Due to the small size of the system, two broad temperature regimes are found: the ITT regime at approximately 10-60 degrees C and the unfolding regime at approximately T > 60 degrees C, where the peptide has a maximum probability of being folded at T approximately 60 degrees C. A detailed molecular picture involving a thermodynamic order parameter, or reaction coordinate, for this process is presented along with a time-correlation function analysis of the hydrogen-bond dynamics within the peptide as well as between the peptide and solvating water molecules. Correlation with experimental evidence and ramifications on the properties of elastin are discussed.
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Affiliation(s)
- Roger Rousseau
- Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, Bochum, Germany
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149
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Nowatzki PJ, Tirrell DA. Physical properties of artificial extracellular matrix protein films prepared by isocyanate crosslinking. Biomaterials 2004; 25:1261-7. [PMID: 14643600 DOI: 10.1016/s0142-9612(03)00635-5] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Artificial extracellular matrix proteins, genetically engineered from elastin- and fibronectin-derived repeating units, were crosslinked with hexamethylene diisocyanate in dimethylsulfoxide. The resulting hydrogel films were transparent, uniform, and highly extensible. Their tensile moduli depended on crosslinker concentration and spanned the range characteristic of native elastin. The water content of the films was low ( approximately 27%), but the temperature-dependent swelling behavior of the crosslinked materials was reminiscent of the lower critical solution temperature property of the soluble polymers.
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Affiliation(s)
- Paul J Nowatzki
- Division of Chemistry and Chemical Engineering, 210-41, California Institute of Technology, Pasadena, CA 91125, USA
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150
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Pometun MS, Chekmenev EY, Wittebort RJ. Quantitative Observation of Backbone Disorder in Native Elastin. J Biol Chem 2004; 279:7982-7. [PMID: 14625282 DOI: 10.1074/jbc.m310948200] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Elastin is a key protein in soft tissue function and pathology. Establishing a structural basis for understanding its reversible elasticity has proven to be difficult. Complementary to structure is the important aspect of flexibility and disorder in elastin. We have used solid-state NMR methods to examine polypeptide and hydrate ordering in both elastic (hydrated) and brittle (dry) elastin fibers and conclude (i) that tightly bound waters are absent in both dry and hydrated elastin and (ii) that the backbone in the hydrated protein is highly disordered with large amplitude motions. The hydrate was studied by (2)H and (17)O NMR, and the polypeptide by (13)C and (2)H NMR. Using a two-dimensional (13)C MAS method, an upper limit of S < 0.1 was determined for the backbone carbonyl group order parameter in hydrated elastin. For comparison, S approximately approximately 0.9 in most proteins. The former result is substantiated by two additional observations: the absence of the characteristic (2)H spectrum for stationary amides and "solution-like" (13)C magic angle spinning spectra at 75 degrees C, at which the material retains elasticity. Comparison of the observed shifts with accepted values for alpha-helices, beta-sheets, or random coils indicates a random coil structure at all carbons. These conclusions are discussed in the context of known thermodynamic properties of elastin and, more generally, protein folding. Because coacervation is an entropy-driven process, it is enhanced by the observed backbone disorder, which, we suggest, is the result of high proline content. This view is supported by recent studies of recombinant elastin polypeptides with systematic proline substitutions.
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Affiliation(s)
- Maxim S Pometun
- Department of Chemistry, University of Louisville, Louisville, Kentucky 40208, USA
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