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Vitharana S, Stillahn JM, Katayama DS, Henry CS, Manning MC. Application of Formulation Principles to Stability Issues Encountered During Processing, Manufacturing, and Storage of Drug Substance and Drug Product Protein Therapeutics. J Pharm Sci 2023; 112:2724-2751. [PMID: 37572779 DOI: 10.1016/j.xphs.2023.08.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Revised: 07/24/2023] [Accepted: 08/07/2023] [Indexed: 08/14/2023]
Abstract
The field of formulation and stabilization of protein therapeutics has become rather extensive. However, most of the focus has been on stabilization of the final drug product. Yet, proteins experience stress and degradation through the manufacturing process, starting with fermentaition. This review describes how formulation principles can be applied to stabilize biopharmaceutical proteins during bioprocessing and manufacturing, considering each unit operation involved in prepration of the drug substance. In addition, the impact of the container on stabilty is discussed as well.
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Affiliation(s)
| | - Joshua M Stillahn
- Legacy BioDesign LLC, Johnstown, CO 80534, USA; Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA
| | | | - Charles S Henry
- Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA
| | - Mark Cornell Manning
- Legacy BioDesign LLC, Johnstown, CO 80534, USA; Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA.
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Manning RR, Holcomb RE, Katayama DS, Pauletti GM, Grant SN, Rosenbaum JS, Manning MC. Characterization of Oligomer Formation of Surfactant Protein-D (SP-D) Using AF4-MALLS. Curr Protein Pept Sci 2023; 23:862-873. [PMID: 36330647 DOI: 10.2174/1389203724666221102111145] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Revised: 09/13/2022] [Accepted: 09/13/2022] [Indexed: 11/06/2022]
Abstract
BACKGROUND Surfactant protein-S (SP-D) is a naturally occurring lung protein with the potential to treat pulmonary infections. A recombinant surfactant protein-D (SP-D) has been produced and was previously found to exist in multiple oligomeric states. INTRODUCTION Separation and characterization of interconverting oligomeric states of a protein can be difficult using chromatographic methods, so an alternative separation technique was employed for SPD to characterize the different association states that exist. METHODS Samples of SP-D were analyzed using asymmetrical flow field-flow fractionation (AF4) using UV and multi-angle laser light scattering (MALLS) detection. The AF4 method appears to be able to separate species as small as the monomer up to the dodecamer (the dominant species) to much larger species with a molar mass greater than 5 MDa. RESULTS Consistent elution of four distinct peaks was observed after repeated injections. The largest species observed under the last peak (labeled as Peak 4) were termed "unstructured multimers" and were resolved fairly well from the other species. The AF4-MALLS data suggest that only a small fraction of Peak 4 truly corresponds to high molar mass unstructured multimers. All other peaks demonstrated significant molar mass homogeneity consistent with AFM results. CONCLUSION AF4-MALLS technology appears to be a powerful analytical approach to characterize the complex and dynamic interplay among different protein oligomeric species of SP-D in an aqueous solution.
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Affiliation(s)
| | - Ryan E Holcomb
- Legacy BioDesign, Johnstown, CO, USA.,Department of Chemistry, Colorado State University, Fort Collins, CO, USA
| | - Derrick S Katayama
- Legacy BioDesign, Johnstown, CO, USA.,Department of Chemistry, Colorado State University, Fort Collins, CO, USA
| | | | | | | | - Mark Cornell Manning
- Legacy BioDesign, Johnstown, CO, USA.,Department of Chemistry, Colorado State University, Fort Collins, CO, USA
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Zbacnik NJ, Manning MC, Henry CS. Chemometric Study of the Relative Aggregation Propensity of Position 19
Mutants of Aβ(1-42). Curr Protein Pept Sci 2022; 23:52-60. [DOI: 10.2174/1389203723666220128105334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Revised: 12/12/2021] [Accepted: 12/13/2021] [Indexed: 11/22/2022]
Abstract
Background:
The importance of aromaticity vs. hydrophobicity of the central hydrophobic
core (CHC, residues 17-20) in governing fibril formation in Aβ(1-42) has been the focus of an ongoing
debate in the literature.
Introduction:
Mutations in the CHC (especially at Phe19 and Phe20) have been used to examine the
relative impact of hydrophobicity and aromaticity on the degree of aggregation of Aβ(1-42). However,
the results have not been conclusive.
Methods:
Partial least squares (PLS) modeling of aggregation rates, using reduced properties of a series
of position 19 mutants, was employed to identify the physicochemical properties that had the
greatest impact on the extent of aggregation.
Results:
The PLS models indicate that hydrophobicity at position 19 of Aβ(1-42) appears to be the
primary and dominant factor in controlling Aβ(1-42) aggregation, with aromaticity having little effect.
Conclusions:
This study illustrates the value of using reduced properties of amino acids in conjunction
with PLS modeling to investigate mutational effects in peptides and proteins, as the reduced properties
can capture in a quantitative manner the different physicochemical properties of the amino acid side
chains. In this particular study, hydrophobicity at position 19 was determined to be the dominant property
controlling aggregation, while size, charge, and aromaticity had little impact.
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Affiliation(s)
| | - Mark Cornell Manning
- Legacy BioDesign LLC, Johnstown, CO 80534, USA
- Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA
| | - Charles S. Henry
- Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA
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Manning RR, Holcomb RE, Katayama DS, Payne RW, Stillahn JM, Henry CS, Manning MC. Analysis of Peptides using Asymmetrical Flow Field-flow Fractionation (AF4). J Pharm Sci 2021; 110:3969-3972. [PMID: 34619152 DOI: 10.1016/j.xphs.2021.09.036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 09/24/2021] [Accepted: 09/24/2021] [Indexed: 11/19/2022]
Abstract
While asymmetrical flow field-flow fractionation (AF4) has been widely used for separation of high molecular weight species and even particles, its ability to resolve lower molecular weight species has rarely been explored. Over the course of many projects, we have discovered that AF4 can be an effective analytical method for separating peptides from oligomers and higher molecular weight aggregates. The methodology can be used even for peptides as small as 2 kD in molecular weight. Using multi-angle laser light scattering (MALLS) detection, accurate masses of the parent peptide can be obtained, provided accurate extinction coefficients are provided. It was shown that AF4 can be stability-indicating, suggesting that AF4-MALLS may be a suitable alternative to the use of SEC to monitor the aggregation of peptides.
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Affiliation(s)
| | - Ryan E Holcomb
- Legacy BioDesign, Johnstown, CO, United States; Department of Chemistry, Colorado State University, Fort Collins, CO, United States
| | - Derrick S Katayama
- Legacy BioDesign, Johnstown, CO, United States; Department of Chemistry, Colorado State University, Fort Collins, CO, United States
| | - Robert W Payne
- Legacy BioDesign, Johnstown, CO, United States; Department of Chemistry, Colorado State University, Fort Collins, CO, United States
| | - Joshua M Stillahn
- Legacy BioDesign, Johnstown, CO, United States; Department of Chemistry, Colorado State University, Fort Collins, CO, United States
| | - Charles S Henry
- Department of Chemistry, Colorado State University, Fort Collins, CO, United States
| | - Mark Cornell Manning
- Legacy BioDesign, Johnstown, CO, United States; Department of Chemistry, Colorado State University, Fort Collins, CO, United States
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Zbacnik NJ, Henry CS, Manning MC. A Chemometric Approach Toward Predicting the Relative Aggregation Propensity: Aβ(1-42). J Pharm Sci 2019; 109:624-632. [PMID: 31606543 DOI: 10.1016/j.xphs.2019.10.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Revised: 10/04/2019] [Accepted: 10/08/2019] [Indexed: 01/19/2023]
Abstract
A number of algorithms have been developed to predict the aggregation propensity of peptides and proteins, but virtually none have the ability to provide sequence-specific information on what physicochemical properties are most important in altering aggregation propensity. In this study, a chemometric approach using reduced amino acid properties is used to examine the aggregation behavior of a highly amyloidogenic peptide, Aβ(1-42). Specific residues are identified as being critical to the aggregation process. At each of these positions, the important physicochemical properties are identified that would either accelerate or inhibit fibril formation.
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Affiliation(s)
| | - Charles S Henry
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523
| | - Mark Cornell Manning
- Legacy BioDesign LLC, Johnstown, Colorado 80534; Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523.
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Mathaes R, Manning MC, Winter G, Engert J, Wilson GA. Shape Characterization of Subvisible Particles Using Dynamic Imaging Analysis. J Pharm Sci 2019; 109:375-379. [PMID: 31476311 DOI: 10.1016/j.xphs.2019.08.023] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2019] [Revised: 08/04/2019] [Accepted: 08/06/2019] [Indexed: 12/16/2022]
Abstract
Protein aggregates and subvisible particles (SbvP), inherently present in all marketed protein drug products, have received increasing attention by health authorities. Dynamic imaging analysis was introduced to visualize SbvP and facilitate understanding of their origin. The educational United States Pharmacopeia chapter <1787> emphasizes that dynamic imaging analysis could be used for morphology measurements in the size range of 4-100 μm. However, adequate morphology characterization, as suggested in the United States Pharmacopeia <1787> proposed size range, remains challenging as nonspherical size standards are not commercially available. In this study, a homogenous and well-defined nonspherical particle standard was fabricated and used to investigate the capabilities of 2 dynamic imaging analysis systems (microflow imaging (MFI) and FlowCAM) to characterize SbvP shape in the size range of 2-10 μm. The actual aspect ratio of the SbvP was measured by scanning electron microscopy and compared to the results obtained by dynamic imaging analysis. The test procedure was used to assess the accuracy in determining the shape characteristics of the nonspherical particles. In general, dynamic imaging analysis showed decreasing accuracy in morphology characterization for 5 μm and 2 μm particles. The test procedure was also capable to compare and evaluate differences between the 2 dynamic imaging methods. The present study should help to define ranges of operation for dynamic imaging analysis systems.
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Affiliation(s)
- Roman Mathaes
- Pharmaceutical Technology, Ludwig-Maximilian Universitaet, Munich, Germany.
| | | | - Gerhard Winter
- Pharmaceutical Technology, Ludwig-Maximilian Universitaet, Munich, Germany
| | - Julia Engert
- Pharmaceutical Technology, Ludwig-Maximilian Universitaet, Munich, Germany
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Zbacnik TJ, Holcomb RE, Katayama DS, Murphy BM, Payne RW, Coccaro RC, Evans GJ, Matsuura JE, Henry CS, Manning MC. Role of Buffers in Protein Formulations. J Pharm Sci 2016; 106:713-733. [PMID: 27894967 DOI: 10.1016/j.xphs.2016.11.014] [Citation(s) in RCA: 105] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Revised: 10/25/2016] [Accepted: 11/17/2016] [Indexed: 12/19/2022]
Abstract
Buffers comprise an integral component of protein formulations. Not only do they function to regulate shifts in pH, they also can stabilize proteins by a variety of mechanisms. The ability of buffers to stabilize therapeutic proteins whether in liquid formulations, frozen solutions, or the solid state is highlighted in this review. Addition of buffers can result in increased conformational stability of proteins, whether by ligand binding or by an excluded solute mechanism. In addition, they can alter the colloidal stability of proteins and modulate interfacial damage. Buffers can also lead to destabilization of proteins, and the stability of buffers themselves is presented. Furthermore, the potential safety and toxicity issues of buffers are discussed, with a special emphasis on the influence of buffers on the perceived pain upon injection. Finally, the interaction of buffers with other excipients is examined.
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Affiliation(s)
| | - Ryan E Holcomb
- LegacyBioDesign LLC, Johnstown, Colorado 80534; Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523
| | - Derrick S Katayama
- LegacyBioDesign LLC, Johnstown, Colorado 80534; Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523
| | - Brian M Murphy
- LegacyBioDesign LLC, Johnstown, Colorado 80534; Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523
| | - Robert W Payne
- LegacyBioDesign LLC, Johnstown, Colorado 80534; Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523
| | | | | | | | - Charles S Henry
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523
| | - Mark Cornell Manning
- LegacyBioDesign LLC, Johnstown, Colorado 80534; Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523.
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Merutka G, Murphy BM, Payne RW, Wilson GA, Matsuura JE, Henry CS, Manning MC. Stability of lyophilized teriparatide, PTH(1-34), after reconstitution. Eur J Pharm Biopharm 2016; 99:84-93. [DOI: 10.1016/j.ejpb.2015.11.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Revised: 11/17/2015] [Accepted: 11/18/2015] [Indexed: 01/01/2023]
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Stockdale G, Murphy BM, D'Antonio J, Manning MC, Al-Azzam W. Comparability of Higher Order Structure in Proteins: Chemometric Analysis of Second-Derivative Amide I Fourier Transform Infrared Spectra. J Pharm Sci 2015; 104:25-33. [DOI: 10.1002/jps.24218] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2013] [Revised: 09/02/2014] [Accepted: 09/08/2014] [Indexed: 11/11/2022]
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Abstract
One of the most versatile methods for monitoring the structure of proteins, either in solution or in the solid state, is Fourier transform infrared spectroscopy. Also known as mid-range infrared, which covers the frequency range from 4000 to 400 cm(-1), this wavelength region includes bands that arise from three conformationally sensitive vibrations within the peptide backbone (amide I, II and III). Of these vibrations, amide I is the most widely used and can provide information on secondary structure composition and structural stability. One of the advantages of infrared spectroscopy is that it can be used with proteins that are either in solution or in the solid state. The use of infrared to monitor protein structure and stability is summarized herein. In addition, specialized infrared methods are presented, such as techniques for the study of membrane proteins and oriented samples. In addition, there is a growing body of literature on the use of infrared to follow reaction kinetics and ligand binding in proteins, as well as a number of infrared studies on protein dynamics. Finally, the potential for using near-infrared spectroscopy to study protein structure is introduced.
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Nagarkar RP, Murphy BM, Yu X, Manning MC, Al-Azzam WA. Characterization of protein higher order structure using vibrational circular dichroism spectroscopy. Curr Pharm Biotechnol 2013; 14:199-208. [PMID: 23167760 DOI: 10.2174/1389201011314020010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2012] [Accepted: 09/30/2012] [Indexed: 11/22/2022]
Abstract
Better understanding of protein higher order structures (HOS) is of major interest to researchers in the field of biotechnology and biopharmaceutics. Monitoring a protein's HOS is crucial towards understanding the impact of molecular conformation on the biotechnological application. In addition, maintaining the HOS is critical for achieving robust processes and developing stable formulations of therapeutic proteins. Loss of HOS contributes to increased aggregation, enhanced immunogenicity and loss of function. Selecting the proper biophysical methods to monitor the secondary and tertiary structures of therapeutic proteins remains the central question in this field. In this study, both Fourier Transform Infrared (FTIR) and vibrational circular dichroism (VCD) spectroscopy are employed to characterize the secondary structures of various proteins as a function of temperature and pH. Three proteins with different secondary structures were examined, human serum albumin (HSA), myoglobin, and the monoclonal antibody, ofatumumab. This work demonstrates that VCD is useful technique for monitoring subtle secondary structure changes of protein therapeutics that may occur during processing or handling.
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Affiliation(s)
- Radhika P Nagarkar
- Bioanalytical Sciences, Biopharmaceutical Development R & D, GlaxoSmithKline, 709 Swedeland Rd, King of Prussia, PA 19406, USA
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Wilson GA, Manning MC. Flow Imaging: Moving Toward Best Practices for Subvisible Particle Quantitation in Protein Products. J Pharm Sci 2013; 102:1133-4. [DOI: 10.1002/jps.23445] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Accepted: 12/17/2012] [Indexed: 11/08/2022]
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Chou DK, Krishnamurthy R, Manning MC, Randolph TW, Carpenter JF. Effects of Solution Conditions on Methionine Oxidation in Albinterferon Alfa-2b and the Role of Oxidation in its Conformation and Aggregation. J Pharm Sci 2013. [DOI: 10.1002/jps.23401] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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P. Nagarkar R, M. Murphy B, Yu X, Cornell Manning M, A. Al-Azzam W. Characterization of Protein Higher Order Structure Using Vibrational Circular Dichroism Spectroscopy. Curr Pharm Biotechnol 2013. [DOI: 10.2174/138920113805219368] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Chou DK, Krishnamurthy R, Manning MC, Randolph TW, Carpenter JF. Physical Stability of Albinterferon-α2b in Aqueous Solution: Effects of Conformational Stability and Colloidal Stability on Aggregation. J Pharm Sci 2012; 101:2702-19. [DOI: 10.1002/jps.23215] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2012] [Revised: 03/28/2012] [Accepted: 05/08/2012] [Indexed: 11/12/2022]
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Davis JM, Zhang N, Payne RW, Murphy BM, Abdul-Fattah AM, Matsuura JE, Herman AC, Manning MC. Stability of lyophilized sucrose formulations of an IgG1: subvisible particle formation. Pharm Dev Technol 2012; 18:883-96. [DOI: 10.3109/10837450.2012.705295] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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D'antonio J, Murphy BM, Manning MC, Al-azzam WA. Comparability of Protein Therapeutics: Quantitative Comparison of Second-Derivative Amide I Infrared Spectra. J Pharm Sci 2012; 101:2025-33. [DOI: 10.1002/jps.23133] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2011] [Revised: 02/27/2012] [Accepted: 03/07/2012] [Indexed: 11/12/2022]
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Murphy BM, Zhang N, Payne RW, Davis JM, Abdul-Fattah AM, Matsuura JE, Herman AC, Manning MC. Murphy B, Zhang N, Payne R, Davis J, Abdul-Fattah A, Matsuura J, Herman A, Manning M. 2012. Structure, Stability, and Mobility of a Lyophilized IgG1 Monoclonal Antibody as Determined using Second-Derivative Infrared Spectroscopy. J Pharm Sci 101:81–91. J Pharm Sci 2012. [DOI: 10.1002/jps.23095] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Murphy BM, Zhang N, Payne RW, Davis JM, Abdul-Fattah AM, Matsuura JE, Herman AC, Manning MC. Structure, stability, and mobility of a lyophilized IgG1 monoclonal antibody as determined using second-derivative infrared spectroscopy. J Pharm Sci 2011; 101:81-91. [PMID: 21918984 DOI: 10.1002/jps.22753] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2011] [Revised: 06/13/2011] [Accepted: 08/18/2011] [Indexed: 12/11/2022]
Abstract
There are many aspects of stabilization of lyophilized proteins. Of these various factors, retention of native structure, having sufficient amount of stabilizer to embed the protein within an amorphous matrix, and dampening β-relaxations have been shown to be critical in optimizing protein stability during storage. In this study, an IgG1 was lyophilized with varying amounts of sucrose. In some formulations, a small amount of sorbitol was added as a plasticizer. The structure of the protein in dried state was monitored using infrared (IR) spectroscopy. The IR spectra indicated increasing retention of the native structure, which correlated with stability as indicated by size-exclusion chromatography as well as micro-flow imaging. Maximal stability was achieved with a 2:1 mass ratio of sucrose to protein, which is more than that would be expected based on earlier studies. Analysis of both high and low frequency bands associated with intramolecular β-sheet structure provides additional information on the structure of antibodies in the solid state. Finally, there is a correlation between the bandwidth of the β-sheet bands and the enthalpy of relaxation, suggesting that amide I bands can provide some indication of the degree of coupling to the sugar matrix, as well as structural heterogeneity of the protein.
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Bai S, Manning MC, Randolph TW, Carpenter JF. BIOTECHNOLOGY: Aggregation of Recombinant Human Botulinum Protein Antigen Serotype C in Varying Solution Conditions: Implications of Conformational Stability for Aggregation Kinetics. J Pharm Sci 2011; 100:836-48. [DOI: 10.1002/jps.22345] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2010] [Revised: 07/19/2010] [Accepted: 08/13/2010] [Indexed: 11/10/2022]
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Manning MC, Chou DK, Murphy BM, Payne RW, Katayama DS. Stability of protein pharmaceuticals: an update. Pharm Res 2010; 27:544-75. [PMID: 20143256 DOI: 10.1007/s11095-009-0045-6] [Citation(s) in RCA: 732] [Impact Index Per Article: 52.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2009] [Accepted: 12/27/2009] [Indexed: 12/16/2022]
Abstract
In 1989, Manning, Patel, and Borchardt wrote a review of protein stability (Manning et al., Pharm. Res. 6:903-918, 1989), which has been widely referenced ever since. At the time, recombinant protein therapy was still in its infancy. This review summarizes the advances that have been made since then regarding protein stabilization and formulation. In addition to a discussion of the current understanding of chemical and physical instability, sections are included on stabilization in aqueous solution and the dried state, the use of chemical modification and mutagenesis to improve stability, and the interrelationship between chemical and physical instability.
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Dolan MC, Jordan RA, Schulze TL, Schulze CJ, Manning MC, Ruffolo D, Schmidt JP, Piesman J, Karchesy JJ. Ability of two natural products, nootkatone and carvacrol, to suppress Ixodes scapularis and Amblyomma americanum (Acari: Ixodidae) in a Lyme disease endemic area of New Jersey. J Econ Entomol 2009; 102:2316-24. [PMID: 20069863 DOI: 10.1603/029.102.0638] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We evaluated the ability of the natural, plant-derived acaricides nootkatone and carvacrol to suppress Ixodes scapularis Say and Amblyomma americanum (L.) (Acari: Ixodidae). Aqueous formulations of 1 and 5% nootkatone applied by backpack sprayer to the forest litter layer completely suppressed I. scapularis nymphs through 2 d. Thereafter, the level of reduction gradually declined to < or =50% at 28 d postapplication. Against A. americanum nymphs, 1% nootkatone was less effective, but at a 5% concentration, the level of control was similar or greater to that observed with I. scapularis through 21 d postapplication. Initial applications of 0.05% carvacrol were ineffective, but a 5% carvacrol formulation completely suppressed nymphs of both species through 2 d and resulted in significant reduction in I. scapularis and A. americanum nymphs through 28 and 14 d postapplication, respectively. Backpack sprayer applications of 5% nootkatone to the shrub and litter layers resulted in 100% control of I. scapularis adults through 6 d, but the level of reduction declined to 71.5% at 28 d postapplication. By contrast, high-pressure applications of 2% nootkatone to the litter layer resulted in 96.2-100% suppression of both I. scapularis and A. americanum nymphs through 42 d, whereas much lower control was obtained from the same formulation applied by backpack sprayer. Backpack sprayer application of a 3.1% nootkatone nanoemulsion resulted in 97.5-98.9 and 99.3-100% reduction in I. scapularis and A. americanum nymphs, respectively, at 1 d postapplication. Between 7 d and 35 d postapplication, the level of control varied between 57.1% and 92.5% for I. scapularis and between 78.5 and 97.1% for A. americanum nymphs. The ability of natural products to quickly suppress and maintain significant control of populations of these medically important ticks at relatively low concentrations may represent a future alternative to the use of conventional synthetic acaricides.
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Affiliation(s)
- Marc C Dolan
- Division of Vector-Borne Infectious Diseases, National Center for Zoonotic, Vector-Borne and Enteric Diseases, Centers for Disease Control and Prevention, Fort Collins, CO 80521, USA.
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Katayama DS, Carpenter JF, Menard KP, Manning MC, Randolph TW. Mixing properties of lyophilized protein systems: a spectroscopic and calorimetric study. J Pharm Sci 2009; 98:2954-69. [PMID: 18623211 DOI: 10.1002/jps.21467] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The purpose of this study was to investigate the solid-state properties of lyophilized formulations of protein (ribonuclease A) containing sucrose or trehalose across a wide range of compositions, both in the presence or absence of hydroxyethylstarch (HES). Infrared spectroscopy reveals that the protein forms hydrogen bonds to sugars (sucrose or trehalose) as water is removed from the sample. The strength and/or number of hydrogen bonds in dried samples increase as the weight fraction of sugar increases. Significant deviations of glass transition temperatures (T(g)'s) from those predicted by free volume theory are seen in both protein-sugar systems. The behavior can be explained by formation of protein-sugar hydrogen bonds at the expense of self-interactions between the sugars. Attractive interactions between lyophilized ribonuclease A and HES were detected spectroscopically and from thermodynamic analysis of T(g) values, contrary to the view that HES is sterically hindered from interacting with the protein surface. Sucrose-HES interactions were much less favorable than trehalose-HES interactions, suggesting that phase separation in sugar/HES/protein mixtures would be more likely in the presence of sucrose than trehalose. Finally, the thermodynamics of mixing were investigated using differential scanning calorimetry (DSC) providing some of the first data for such solid protein sugar formulations with and without HES. In nearly all samples, positive excess enthalpy, excess entropy and excess free energy were observed, with the excess free energy being greater for samples containing sucrose rather than trehalose. Analysis of Flory-Huggins chi parameters suggests that phase separation between protein and excipients may be thermodynamically favored in these dried solid preparations.
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Affiliation(s)
- Derrick S Katayama
- Department of Pharmaceutical Sciences, Center for Pharmaceutical Biotechnology, University of Colorado, Denver Health Sciences Center, Denver, Colorado, USA
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Meyer JD, Nayar R, Manning MC. Impact of bulking agents on the stability of a lyophilized monoclonal antibody. Eur J Pharm Sci 2009; 38:29-38. [DOI: 10.1016/j.ejps.2009.05.008] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2009] [Revised: 04/09/2009] [Accepted: 05/16/2009] [Indexed: 10/20/2022]
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Lin JJ, Meyer JD, Carpenter JF, Manning MC. Aggregation of human serum albumin during a thermal viral inactivation step. Int J Biol Macromol 2009; 45:91-6. [DOI: 10.1016/j.ijbiomac.2009.04.017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2009] [Revised: 04/10/2009] [Accepted: 04/13/2009] [Indexed: 10/20/2022]
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Katayama DS, Carpenter JF, Manning MC, Randolph TW, Setlow P, Menard KP. Characterization of Amorphous Solids with Weak Glass Transitions Using High Ramp Rate Differential Scanning Calorimetry. J Pharm Sci 2008; 97:1013-24. [PMID: 17724657 DOI: 10.1002/jps.20991] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Measurement of the glass transition temperature (T(g)) of proteins and other high molecular weight polymers in the amorphous state is often difficult, since the transition is extremely weak, that is, the DeltaC(p) at the glass transition temperature is small. For example, little is known about the solid-state properties of hydroxyethyl starch (HES), which is beginning to become more commonly evaluated as a bulking agent in pharmaceutical products. For weak thermal events, such as the change in heat capacity at the T(g) of a pure protein or large synthetic polymer, increased heating rate should produce greater sensitivity in terms of heat flow. Recent innovations in rapid scanning technology for differential scanning calorimetry (DSC) allow measurements on materials where the thermal events are difficult to detect by conventional DSC. In the current study, measurements of the T(g) of proteins in the solid state, amorphous pharmaceutical excipients which have small DeltaC(p) at the glass transition temperature, and bacterial spores, have all been made using high ramp rate DSC, providing information on materials that was inaccessible using conventional DSC methods.
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Affiliation(s)
- Derrick S Katayama
- Department of Pharmaceutical Sciences, Center for Pharmaceutical Biotechnology, University of Colorado Health Sciences Center, Denver, Colorado, USA
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Abstract
There is little known about the solution structure and stability of peptide-protein conjugates, which comprise a new class of potential biopharmaceutical agents. This study describes the solution behavior of gonadotropins-releasing hormone (GnRH) chemically conjugated to pokeweed antiviral protein (PAP). The conjugate adopts a well-defined conformation across a pH range of 4 to 8. Even after heating to 80 degrees C, the conjugate retains a significant amount of secondary and tertiary structure. Heating for 1 h at 60 degrees C does lead to chemical damage, as determined by cation exchange chromatography. Using an experimental design approach, the optimal pH and salt concentration for limiting chemical damage was determined.
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Affiliation(s)
- Derrick S Katayama
- Department of Pharmaceutical Sciences, University of Colorado Health Sciences Center, Denver, CO 80262, USA
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Katayama DS, Nayar R, Chou DK, Valente JJ, Cooper J, Henry CS, Vander Velde DG, Villarete L, Liu CP, Manning MC. Effect of buffer species on the thermally induced aggregation of interferon-tau. J Pharm Sci 2006; 95:1212-26. [PMID: 16637050 DOI: 10.1002/jps.20471] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
It is now becoming apparent that a common pathway of protein aggregation involves the unimolecular structural rearrangement from the native state to a slightly expanded aggregation-competent species. It is the goal of this study to understand the aggregation and the effects of buffer on the stability of IFN-tau. In this study, the thermally-induced aggregation of interferon-tau (IFN-tau) is described. By monitoring the aggregation rate in the presence of increasing amounts of sucrose, the relative change in surface area (Deltas) for conversion to the aggregation-competent state can be determined. Under conditions of pH 7 and in 20 mM buffer, the protein displays different aggregation rates depending on the nature of the buffer species. The protein aggregates mostly quickly in phosphate buffer, slower in the presence of Tris and slowest in the presence of histidine. The largest value for Deltas occurs for the histidine-containing samples, where aggregation proceeds via a slightly expanded aggregation competent state with a surface area increase of 7.6%. Furthermore, it appears that histidine binds to the native state of IFN-tau, thereby stabilizing the native state and retarding aggregation. Measurement of the second virial coefficient, B(22), for different formulations indicates that inclusion of histidine has only a small effect on repulsion between protein molecules, suggesting that colloidal stabilization is not the dominant mechanism for stabilization of IFN-tau. This study represents the first detailed biophysical study of specific buffer-induced stabilization, resulting in shifting the equilibrium towards the native state and away form the expanded aggregation-competent species.
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Affiliation(s)
- Derrick S Katayama
- Center for Pharmaceutical Biotechnology, University of Colorado Health Sciences Center, Denver, CO, USA
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Valente JJ, Payne RW, Manning MC, Wilson WW, Henry CS. Colloidal behavior of proteins: effects of the second virial coefficient on solubility, crystallization and aggregation of proteins in aqueous solution. Curr Pharm Biotechnol 2006; 6:427-36. [PMID: 16375727 DOI: 10.2174/138920105775159313] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
There has been an increasing awareness that proteins, like other biopolymers, are large enough to exhibit colloidal behavior in aqueous solution. Net attractive or repulsive forces have been found to govern important physical properties, such as solubility and aggregation. The extent of intermolecular interactions, usually expressed in terms of the osmotic second virial coefficient, B, is most often measured using static light scattering. More recently, self-interaction chromatography (SIC) has emerged as a method for rapid determination of B in actual formulations, as it uses much less protein and has higher throughput. This review will summarize the relationship of B to crystallization, solubility, and aggregation of proteins in aqueous solution. Moreover, the capability of SIC to obtain B values in a rapid and reproducible fashion will be described in detail. Finally, the use of miniaturized devices to measure B is presented.
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Affiliation(s)
- Joseph J Valente
- Department of Chemistry, Colorado State University, Fort Collins, CO, USA
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Payne RW, Nayar R, Tarantino R, Del Terzo S, Moschera J, Di J, Heilman D, Bray B, Manning MC, Henry CS. Second virial coefficient determination of a therapeutic peptide by self-interaction chromatography. Biopolymers 2006; 84:527-33. [PMID: 16767741 DOI: 10.1002/bip.20554] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Self-interaction of macromolecules has been shown to play an important role in a number of physical processes, including crystallization, solubility, viscosity, and aggregation. Peptide self-interaction is not as well studied as for larger proteins, but should play an equally important role. The osmotic second virial coefficient, B, can be used to quantify peptide and protein self-interaction. B values are typically measured using static light scattering (SLS). Peptides, however, do not scatter enough light to allow such measurements. This study describes the first use of self-interaction chromatography (SIC) for the measurement of peptide B values because SIC does not have the molecular size limitations of SLS. In the present work, SIC was used to measure B for enfuvirtide, a 36-amino acid therapeutic peptide, as a function of salt concentration, salt type, and pH. B was found to correlate strongly with solubility and apparent molecular weight. In general, the solubility of enfuvirtide increases with pH from 6 to 10 and decreases as the salt concentration increases from 0 to 0.5M for three different salts. The effect of peptide concentration on B was also investigated and shown to have a significant effect, but only at high concentrations (>80 mg/mL).
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Affiliation(s)
- Robert W Payne
- Department of Chemistry, Colorado State University, Fort Collins, CO
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Katayama DS, Nayar R, Chou DK, Campos J, Cooper J, Vander Velde DG, Villarete L, Liu CP, Cornell Manning M. Solution behavior of a novel type 1 interferon, interferon-τ. J Pharm Sci 2005; 94:2703-15. [PMID: 16258985 DOI: 10.1002/jps.20461] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Interferon-tau (IFN-tau) is a novel cytokine that appears during fetal development of mammals. It is currently being investigated for treatment of viral infections and autoimmune diseases. In order to develop a commercial product, a stable formulation will need to be identified. In this study, the solution behavior of IFN-tau was studied using a variety of biophysical methods. The overall structure of IFN-tau is well defined, with the polypeptide chain folding into a four-helix bundle structure, much like other type 1 interferons. However, its solution behavior has not been characterized. The globular structure has a free energy of unfolding of approximately 4 kcal/mole at room temperature. IFN-tau was found to remain monomeric upon increasing the protein concentration, even up to 60 mg/mL. The overall structure of IFN-tau is maintained across a pH range of 2-8, but is significantly altered in the presence of nonaqueous solvents. However, IFN-tau appears to refold efficiently when diluted into an aqueous medium from a nonaqueous solution. This behavior allows the protein to be formulated in low water content formulations suitable for use in capsules.
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Affiliation(s)
- Derrick S Katayama
- Center for Pharmaceutical Biotechnology, University of Colorado Health Sciences Center, Denver, Colorado, USA
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Abstract
Protein self-interaction is important in protein crystal growth, solubilization, and aggregation, both in vitro and in vivo, as with protein misfolding diseases, such as Alzheimer's. Although second virial coefficient studies can supply invaluable quantitative information, their emergence as a systematic approach to evaluating protein self-interaction has been slowed by the limitations of traditional measurement methods, such as static light scattering. Comparatively, self-interaction chromatography is an inexpensive, high-throughput method of evaluating the osmotic second virial coefficient (B) of proteins in solution. In this work, we used self-interaction chromatography to measure B of lysozyme in the presence of various cosolvents, including sucrose, trehalose, mannitol, glycine, arginine, and combinations of arginine and glutamic acid and arginine and sucrose in an effort to develop a better fundamental understanding of protein self-interaction in complex cosolvent systems. All of these cosolvents, alone or in combination, increased B, indicating a reduction in intermolecular attraction. However, the magnitude of cosolvent-induced changes in B was found to be largely dependent on the ability to control long-range electrostatic repulsion. To the best of our knowledge, this work represents the most comprehensive virial coefficient study to date focusing on complex cosolvent-induced effects on the self-interaction of lysozyme.
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Affiliation(s)
- Joseph J Valente
- Department of Chemistry, Colorado State University, Fort Collins, Colorado, USA
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Dunn JS, Nayar R, Campos J, Hybertson BM, Zhou Y, Manning MC, Repine JE, Stringer KA. Feasibility of tissue plasminogen activator formulated for pulmonary delivery. Pharm Res 2005; 22:1700-7. [PMID: 16180128 PMCID: PMC2040297 DOI: 10.1007/s11095-005-6335-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2005] [Accepted: 06/06/2005] [Indexed: 10/25/2022]
Abstract
PURPOSE This study was conducted to assess the feasibility of a pulmonary formulation of tissue plasminogen activator (tPA) for nebulization into the airway by measuring protein stability, biologic activity, particle size, and estimating human lung distribution. METHODS Formulations were derived by varying the surfactant and protein concentrations. Protein stability and recovery of each nebulized tPA formulation were assessed by ultraviolet spectroscopy. Formulations that met protein stability feasibility criteria were assessed for biologic and fibrinolytic activities. Biologic activity was determined by their ability to inhibit superoxide anion production by human neutrophils. Fibrinolytic activity was assessed by the cleavage of plasminogen to plasmin. Aerodynamic properties were assessed using a cascade impactor, and an estimation of human airway deposition was made via a human lung replica. RESULTS Twenty-seven tPA formulations were initially assessed, 15 of which met protein stability criteria. Subsequently, three of these formulations maintained biologic and fibrinolytic activities. These formulations exhibited particle sizes of 2.4-3.1 microm, and had respirable doses > or =65%. A formulation of 1mg mL(-1) tPA and 0.1% Tween 80 exhibited a 45% deposition in the lower airways of a human lung replica. CONCLUSIONS A suitable pulmonary tPA formulation was identified that, following nebulization, maintained protein stability as well as biologic and fibrinolytic activities, and resulted in an optimal respirable dose and human airway deposition. This formulation may be applicable in the treatment of lung diseases, such as acute respiratory distress syndrome by permitting targeted pulmonary delivery of a therapeutic protein to the lungs.
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Affiliation(s)
- John S. Dunn
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Colorado Health Sciences Center, Denver, Colorado, USA
| | - Rajiv Nayar
- HTD Biosystems, Inc., Hercules, California, USA
| | | | - Brooks M. Hybertson
- Webb Waring Institute for Antioxidant Research, University of Colorado Health Sciences Center, Denver, Colorado, USA
| | - Yue Zhou
- Lovelace Respiratory Research Institute, Albuquerque, New Mexico, USA
| | | | - John E. Repine
- Webb Waring Institute for Antioxidant Research, University of Colorado Health Sciences Center, Denver, Colorado, USA
| | - Kathleen A. Stringer
- Department of Clinical Pharmacy, School of Pharmacy, University of Colorado Health Sciences Center, C238, 4200 East Ninth Avenue, Denver, Colorado 80262, USA
- To whom correspondence should be addressed. (e-mail: )
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Bai S, Nayar R, Carpenter JF, Manning MC. Noninvasive Determination of Protein Conformation in the Solid State Using Near Infrared (NIR) Spectroscopy. J Pharm Sci 2005; 94:2030-8. [PMID: 16052558 DOI: 10.1002/jps.20416] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Fourier transform infrared (FTIR) spectroscopy is a powerful tool for monitoring structural changes in lyophilized protein formulations. However, direct measurement of IR spectra requires significant handling time and effort. The possibility of using near infrared (NIR) spectroscopy as a rapid and noninvasive alternative to FTIR is explored in this study. NIR and conventional FTIR spectra were collected for two model proteins, alpha-chymotrypsinogen A and cytochrome c, under conditions of varying stability and structural perturbation. NIR was then compared to FTIR and whereby calibration model was generated by partial least square (PLS) regression to correlate NIR data with FTIR spectra. There is a strong correlation of certain NIR bands with the amide I region of FTIR spectra. It appears that NIR can distinguish damage caused by elevated temperatures and freeze-drying stresses. The ability of sucrose to stabilize the structure of these two proteins can be detected by both methods. It appears that NIR spectroscopy has the potential to provide detailed information on the secondary structure of proteins in the solid state. However, many more examples will be needed to demonstrate fully the ability of NIR to replace FTIR as the standard tool for characterizing lyophilized protein formulations.
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Affiliation(s)
- Shujun Bai
- Center for Pharmaceutical Biotechnology, University of Colorado Health Sciences Center, Denver, Colorado, USA
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Chou DK, Krishnamurthy R, Randolph TW, Carpenter JF, Manning MC. Effects of Tween 20® and Tween 80® on the Stability of Albutropin During Agitation. J Pharm Sci 2005; 94:1368-81. [PMID: 15858848 DOI: 10.1002/jps.20365] [Citation(s) in RCA: 215] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The objectives of this work were to determine the effects of nonionic surfactants (Tween 20 and Tween 80) on agitation-induced aggregation of the recombinant fusion protein, Albutropintrade mark (human growth hormone genetically fused to human albumin), and to characterize the binding interactions between the surfactants and the protein. Knowing the binding stoichiometry would allow a rational choice of surfactant concentration to protect the protein from surface-induced aggregation. Fluorescence spectroscopy and isothermal titration calorimetry (ITC) were employed to study Albutropin surfactant binding. Albutropin was agitated at 25 +/- 2 degrees C to induce aggregation, and samples were taken during a 96-h incubation. Size-exclusion chromatography (SEC-HPLC) (HPLC, high-performance liquid chromatography) was used to detect and quantify the extent of protein aggregation. The effect of surfactants on the protein's free energy of unfolding was determined using guanidine HCl as a denaturant. Tween 20 and Tween 80 had saturable binding to Albutropin with a molar binding stoichiometry of 10:1 and 9:1 (surfactant:protein), respectively. Binding of the surfactants to Albutropin increased the free energy of unfolding by over 1 and 0.6 kcal/mol, respectively. In protein samples that were agitated in the absence of surfactant, soluble aggregates were detected within 24 h, and there was almost complete loss of monomer to soluble aggregates by the end of the 96-h experiment. At the molar binding stoichiometry, Tween 20 and Tween 80 prevented the formation of soluble aggregates, even though the concentrations of surfactants were well below their critical micelle concentrations (CMC). Tween 20 and Tween 80 protected Albutropin against agitation-induced aggregation, even at concentrations below the CMC. Equilibrium unfolding data indicate that Tween confer protection by increasing the free energy of unfolding of Albutropin.
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Affiliation(s)
- Danny K Chou
- Department of Pharmaceutical Sciences, School of Pharmacy, Center for Pharmaceutical Biotechnology, University of Colorado Health Sciences Center, Denver, CO 80262, USA
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Abstract
Leuprolide acetate (pGlu-His-Trp-Ser-Tyr-d-Leu-Leu-Arg-Pro-NHEt), a potent LHRH agonist in wide clinical use, was characterized conformationally by NMR and circular dichroism. It displayed quite different preferred conformations under different solution conditions: two low population beta-turns in water, a nascent helix in TFE/water at low pH, and a high population beta-turn in TFE/water at slightly acidic pH. The pH-related conformational change in TFE/water is attributed to the pK(a) of the acetate counterion, not to ionizable groups on the peptide. None of these conformations are in exact agreement with previous computational predictions.
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Affiliation(s)
- J D Meyer
- Center for Pharmaceutical Biotechnology, University of Colorado Health Sciences Center, Denver, USA
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Stratton LP, Kelly RM, Rowe J, Shively JE, Smith DD, Carpenter JF, Manning MC. Controlling deamidation rates in a model peptide: effects of temperature, peptide concentration, and additives. J Pharm Sci 2001; 90:2141-8. [PMID: 11745773 DOI: 10.1002/jps.1165] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The rate of deamidation of the Asn residue in Val-Tyr-Pro-Asn-Gly-Ala (VYPNGA), a model peptide, was determined at pH 9 (400 mM Tris buffer) as a function of temperature and peptide concentration. Over the temperature range 5-65 degrees C, deamidation followed Arrhenius behavior, with an apparent activation energy of 13.3 kcal/mol. Furthermore, increasing the peptide concentration slows the rate of deamidation. Self-stabilization with respect to deamidation has not been reported previously. The rate of deamidation was also determined in the presence of sucrose and poloxamer 407 (Pluronic F127). In both cases, the rate of deamidation was retarded by up to 40% at 35 degrees C. In aqueous solutions containing poloxamer 407, the degree of stabilization is independent of formation of a reversible thermosetting gel. With sucrose, maximum reduction in the deamidation rate was attained with as little as 5% (w/v). Addition of sucrose results in a greater conformational preference for a type II beta-turn structure, which presumably is less prone to intramolecular cyclization and subsequent deamidation.
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Affiliation(s)
- L P Stratton
- Center for Pharmaceutical Biotechnology and Department of Pharmaceutical Sciences, School of Pharmacy, Campus Box C238, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA
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Jones LS, Randolph TW, Kohnert U, Papadimitriou A, Winter G, Hagmann ML, Manning MC, Carpenter JF. The effects of Tween 20 and sucrose on the stability of anti-L-selectin during lyophilization and reconstitution. J Pharm Sci 2001; 90:1466-77. [PMID: 11745706 DOI: 10.1002/jps.1098] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
We have chosen an anti-L-selectin antibody as a model protein to investigate the effects of sucrose and/or Tween 20 on protein stability during lyophilization and reconstitution. Native anti-L-selectin secondary structure is substantially retained during lyophilization in the presence of sucrose (1 or 0.125%). However, aggregation of the protein during reconstitution of lyophilized protein powders prepared without sucrose is not reduced by the presence of sucrose in the reconstitution medium. Aggregate formation upon reconstitution is completely inhibited by freeze drying the protein with sucrose and reconstituting with a 0.1% Tween 20 solution. Tween 20 (0.1%) also partially inhibits loss of native anti-L-selectin secondary structure during lyophilization. However, upon reconstitution the formulations lyophilized with Tween 20 contain the highest levels of aggregates. The presence of Tween in only the reconstitution solution appears to inhibit the transition from dimers to higher order oligomers. Potential mechanism(s) for the Tween 20 effects were investigated. However, no evidence of thermodynamic stabilization of anti-L-selectin conformation (e.g., by Tween 20 binding) could be detected.
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Affiliation(s)
- L S Jones
- School of Pharmacy, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA
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Kim YS, Cape SP, Chi E, Raffen R, Wilkins-Stevens P, Stevens FJ, Manning MC, Randolph TW, Solomon A, Carpenter JF. Counteracting effects of renal solutes on amyloid fibril formation by immunoglobulin light chains. J Biol Chem 2001; 276:1626-33. [PMID: 11050093 DOI: 10.1074/jbc.m007766200] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In primary (light chain-associated) amyloidosis, immunoglobulin light chains deposit as amyloid fibrils in vital organs, especially the kidney. Because the kidney contains high concentrations of urea that can destabilize light chains as well as solutes such as betaine and sorbitol that serve as protein stabilizers, we investigated the effects of these solutes on in vitro amyloid fibril formation and thermodynamic stability of light chains. Two recombinant light chain proteins, one amyloidogenic and the other nonamyloidogenic, were used as models. For both light chains, urea enhanced fibril formation by reducing the nucleation lag time and diminished protein thermodynamic stability. Conversely, betaine or sorbitol increased thermodynamic stability of the proteins and partially inhibited fibril formation. These solutes also counteracted urea-induced reduction in protein thermodynamic stability and accelerated fibril formation. Betaine was more effective than sorbitol. A model is presented to explain how the thermodynamic effects of the solutes on protein state equilibria can alter nucleation lag time and, hence, fibril formation kinetics. Our results provide evidence that renal solutes control thermodynamic and kinetic stability of light chains and thus may modulate amyloid fibril formation in the kidney.
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Affiliation(s)
- Y S Kim
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Colorado Health Science Center, Denver, Colorado 80262, USA
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Yang TH, Cleland JL, Lam X, Meyer JD, Jones LS, Randolph TW, Manning MC, Carpenter JF. Effect of zinc binding and precipitation on structures of recombinant human growth hormone and nerve growth factor. J Pharm Sci 2000; 89:1480-5. [PMID: 11015692 DOI: 10.1002/1520-6017(200011)89:11<1480::aid-jps10>3.0.co;2-m] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Metal-induced precipitation of protein therapeutics is being used and further developed as a processing step in protein formulation and may have utility in protein purification and bulk storage. In such processes, it is imperative that native protein structure is maintained and the metal complexation is reversible. In the current study, we investigated the effects of zinc-induced precipitation on recombinant human growth hormone (rhGH) and recombinant human nerve growth factor (rhNGF). On the addition of ethylenediaminetetraacetic acid (EDTA), the precipitates were dissolved, yielding complete recovery of native protein in both cases. Both proteins have specific metal binding sites and require specific molar ratios of zinc to protein to initiate precipitation (zinc:rhGH > 2:1; zinc:rhNGF > 18:1). Furthermore, the secondary structures of both proteins were unperturbed in soluble zinc complexes and zinc-induced precipitates, as measured by infrared and circular dichroism spectroscopies. The soluble zinc complex of rhGH had minor tertiary structural alterations, whereas zinc binding did not alter the tertiary structure of rhNGF. These studies indicated that metal-induced precipitation provides a method to maintain proteins in their native state in precipitates, which may be useful for purification, storage, and formulation.
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Affiliation(s)
- T H Yang
- Department of Pharmaceutical Sciences, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA
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Dong A, Meyer JD, Brown JL, Manning MC, Carpenter JF. Comparative fourier transform infrared and circular dichroism spectroscopic analysis of alpha1-proteinase inhibitor and ovalbumin in aqueous solution. Arch Biochem Biophys 2000; 383:148-55. [PMID: 11097188 DOI: 10.1006/abbi.2000.2054] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Alpha1-proteinase inhibitor (alpha1Pi) and ovalbumin are both members of the serpin superfamily. They share about a 30% sequence identity and exhibit great similarity in their three-dimensional structures. However, no apparent functional relationship has been found between the two proteins. Unlike alpha1Pi, ovalbumin shows no inhibitory effect to serine proteases. To see whether or not a conformational factor(s) may contribute to the functional difference, we carried out comparative analysis of the two proteins' secondary structure, thermal stability, and H-D exchange using FT-IR and CD spectroscopy. FT-IR analysis reveals significant differences in the amide I spectral patterns of the two proteins. Upon thermal denaturation, both proteins exhibit a strong low-wavenumber beta-sheet band at 1624 cm(-1) and a weak high-wavenumber beta-sheet band at 1694 cm(-1), indicative of intermolecular aggregate formation. However, the midpoint of the thermal-induced transition of alpha1Pi (approximately 55 degrees C) is 18 degrees C lower than that of ovalbumin (approximately 73 degrees C). The thermal stability analysis provides new insight into the structural changes associated with denaturation. The result of H-D exchange explains some puzzling spectral differences between the two proteins in D2O reported previously.
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Affiliation(s)
- A Dong
- Department of Chemistry and Biochemistry, University of Northern Colorado, Greeley 80639, USA.
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Claffey DJ, Meyer JD, Beauvais R, Brandt T, Shefter E, Kroll DJ, Ruth JA, Manning MC. Long chain arginine esters: a new class of cationic detergents for preparation of hydrophobic ion-paired complexes. Biochem Cell Biol 2000; 78:59-65. [PMID: 10735564] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023] Open
Abstract
The ability of stoichiometric amounts (based on charged groups) of ionic detergents to bind to oppositely charged ionic compounds has been recently reviewed. These hydrophobic ion-paired (HIP) complexes display altered solubility properties. Most of the work to date on HIP compelxes has focused on basic drugs and anionic detergents. It would be extremely useful to extend this approach to acidic compounds, including DNA and RNA. However, most cationic detergents are relatively toxic. It is hypothesized that detergents constructed from naturally occurring or well tolerated components, coupled by labile linkages, will be less toxic and still able to form strong HIP complexes. This study describes the synthesis and characterization of long chain alkyl esters of arginine. This class of cationic detergents, which have not been reported previously, are less cytotoxic than alkyltrimethylammonium detergents, possibly making them more acceptable in drug delivery applications. These arginine esters exhibit detergent-like properties. For example, the dodecyl ester of arginine has a critical micelle concentration of 0.07 mM, while being approximately 5-10 fold less toxic than tetradecyltrimethylammonium bromide. The arginine dodecyl ester forms stable HIP complexes with plasmid DNA. The complex is sufficiently stable to allow some modest level of transfection with Cos-7 cells in a time- and concentration-dependent fashion. This work demonstrates that arginine-based cationic detergents are effective ion-pairing agents, appear to be less toxic than alkyltrimethylammonium compounds, and form stable complexes with DNA.
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Affiliation(s)
- D J Claffey
- Center for Pharmaceutical Biotechnology and Department of Pharmaceutical Sciences, School of Pharmacy, University of Colorado Health Sciences Center, Denver 80262, USA
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Lin JJ, Meyer JD, Carpenter JF, Manning MC. Stability of human serum albumin during bioprocessing: denaturation and aggregation during processing of albumin paste. Pharm Res 2000; 17:391-6. [PMID: 10870981 DOI: 10.1023/a:1007564601210] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
PURPOSE To assess the impact of various bioprocessing steps on the stability of freshly precipitated human serum albumin (HSA) obtained from pooled human plasma. METHODS After initial precipitation of HSA from plasma, the resultant paste is either (a) lyophilized or (b) washed with acetone and then air-dried in order to obtain a dry powder. The structure of HSA was examined using Fourier transform infrared (IR) spectroscopy. The extent of aggregation of redissolved HSA was measured using both dynamic light scattering and SDS-polyacrylamide gel electrophoresis (SDS-PAGE). RESULTS Both lyophilization and air-drying perturb the secondary structural composition of HSA, as detected by infrared (IR) spectroscopy. Upon dissolution of dried paste, most of the protein refolds to a native-like conformation. However, a small fraction of the protein molecules form soluble aggregates that can be detected by both dynamic light scattering and SDS-PAGE. The level of aggregation is so low that it could not be detected in the bulk by either circular dichroism or IR spectroscopy. The lyophilized protein, which appears to be more unfolded in the solid state than the acetone washed/air-dried material, exhibits a higher level of aggregation upon dissolution. CONCLUSIONS There is a direct correlation between the extent of unfolding in the solid state and the amount of soluble aggregate present after dissolution. Moreover, the presence of the aggregates persists throughout the remainder of the purification process, which includes dissolution, chromatography, sterile filtration and viral inactivation steps. Analytical methods used to monitor the stability of biopharmaceuticals in the final product can be used to assess damage inflicted during processing of protein pharmaceuticals.
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Affiliation(s)
- J J Lin
- Center for Pharmaceutivcal Biotechnology and Department of Pharmaceutical Sciences, School of Pharmacy, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA
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Cornelius LJ, Okundaye JN, Manning MC. Human immunodeficiency virus-related risk behavior among African-American females. J Natl Med Assoc 2000; 92:183-95. [PMID: 10976175 PMCID: PMC2640603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
This study draws attention to the demographic shift in the population of HIV-infected African Americans from young, low-income, unmarried homosexual, and injecting drug users to female, heterosexual, higher income, and older persons. We used data from the 1995 Survey of Family Growth, sponsored by the National Center for Health Statistics, to examine the patterns of HIV-related risk behavior (consistent condom use, number of sexual partners, sex education in birth control methods) among African-American females. We found that only 33.3% of the African-American females had indicated that their partners always used condoms; 23.8% had seven or more lifetime sexual partners; and nearly 30% did not have any sex education in birth control methods, sexually transmitted diseases, or abstinence. In addition, African-American females who had partners who had not used condoms in the last 12 months were less likely than those who reported occasional condom use to perceive that they were infected with HIV (21.1% vs. 33.1%). These risk factors were prevalent among low-income African-American females with low socioeconomic status (SES) as well as black women with higher SES who lived in smaller cities and suburbs. These results highlight the need for HIV prevention strategies that cut across socioeconomic class, gender, sexual orientation, and place of residence.
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Affiliation(s)
- L J Cornelius
- School of Social Work, University of Maryland, Baltimore 21201, USA
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Abstract
The storage stability of a dry protein depends on the structure of the dried protein, as well as on the storage temperature relative to the glass transition temperature of the dried preparation. Disaccharides are known to preserve the native conformation of a dried protein; however, the resulting T(g) of the sample may be too low ensure adequate storage stability. On the other hand, formulations dried with high molecular weight carbohydrates, such as dextran, have higher glass transition temperatures, but fail to preserve native protein conformation. We tested the hypothesis that optimizing both protein structure and T(g) by freeze-drying actin with mixtures of disaccharides and dextran would result in increased storage stability compared to actin dried with either disaccharide or dextran alone. Protein structure in the dried solid was analyzed immediately after lyophilization and after storage at elevated temperatures with infrared spectroscopy, and after rehydration by infrared and circular dichroism spectroscopy. Structural results were related to the polymerization activity recovered after rehydration. Degradation was noted with storage for formulations containing either sucrose, trehalose, or dextran alone. Slight increases in T(g) observed in trehalose formulations compared to sucrose formulations did not result in appreciable increases in storage stability. Addition of dextran to sucrose or trehalose increased formulation T(g) without affecting the capacity of the sugar to inhibit protein unfolding during lyophilization and resulted in improved storage stability. Also, dextran provides an excellent amorphous bulking agent, which can be lyophilized rapidly with formation of strong, elegant cake structure. These results suggest that the strategy of using a mixture of disaccharide and polymeric carbohydrates can optimize protein storage stability.
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Affiliation(s)
- S D Allison
- University of Colorado Center for Pharmaceutical Biotechnology, Denver, Colorado 80262, USA
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Kim Y, Wall JS, Meyer J, Murphy C, Randolph TW, Manning MC, Solomon A, Carpenter JF. Thermodynamic modulation of light chain amyloid fibril formation. J Biol Chem 2000; 275:1570-4. [PMID: 10636846 DOI: 10.1074/jbc.275.3.1570] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
To obtain further insight into the pathogenesis of amyloidosis and develop therapeutic strategies to inhibit fibril formation we investigated: 1) the relationship between intrinsic physical properties (thermodynamic stability and hydrogen-deuterium (H-D) exchange rates) and the propensity of human immunoglobulin light chains to form amyloid fibrils in vitro; and 2) the effects of extrinsically modulating these properties on fibril formation. An amyloid-associated protein readily formed amyloid fibrils in vitro and had a lower free energy of unfolding than a homologous nonpathological protein, which did not form fibrils in vitro. H-D exchange was much faster for the pathological protein, suggesting it had a greater fraction of partially folded molecules. The thermodynamic stabilizer sucrose completely inhibited fibril formation by the pathological protein and shifted the values for its physical parameters to those measured for the nonpathological protein in buffer alone. Conversely, urea sufficiently destabilized the nonpathological protein such that its measured physical properties were equivalent to those of the pathological protein in buffer, and it formed fibrils. Thus, fibril formation by light chains is predominantly controlled by thermodynamic stability; and a rational strategy to inhibit amyloidosis is to design high affinity ligands that specifically increase the stability of the native protein.
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Affiliation(s)
- Y Kim
- Department of Pharmaceutical Sciences, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA
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Abstract
The terminase enzyme from bacteriophage lambda is responsible for the insertion of a dsDNA genome into the confines of the viral capsid. The holoenzyme is composed of gpA and gpNu1 subunits in a gpA(1) x gpNu1(2) stoichiometry. While genetic studies have described regions within the two proteins responsible for DNA binding, capsid binding, and subunit interactions in the holoenzyme complex, biochemical characterization of these domains is limited. We have previously described the cloning, expression, and biochemical characterization of a soluble DNA binding domain of the terminase gpNu1 subunit (Met1 to Lys100) and suggested that the hydrophobic region spanning Lys100 to Pro141 defines a domain responsible for self-association interactions, and that is important for cooperative DNA binding [Yang et al. (1999) Biochemistry 38, 465-477]. We further suggested that the genetically defined gpA-interactive domain in the C-terminal half of the protein is limited to the C-terminal approximately 40 amino acids of gpNu1. Here we describe the cloning, expression, and biochemical characterization of gpNu1DeltaP141, a deletion mutant of gpNu1 that comprises the DNA binding domain and the putative hydrophobic self-assembly domain of the full-length protein. Purified gpNu1DeltaP141 shows a strong tendency to aggregate in solution; However, the protein remains soluble in 0.4 M guanidine hydrochloride, and circular dichroism (CD) and fluorescence spectroscopic studies demonstrate that the protein is folded under these conditions. Moreover, CD spectroscopy and thermally induced unfolding studies suggest that the DNA binding domain and the self-association domain represent independent folding domains of gpNu1DeltaP141. The mutant protein interacts weakly with the gpA subunit, but does not form a catalytically competent holoenzyme complex, suggesting that the C-terminal 40 residues are important for appropriate subunit interactions. Importantly, gpNu1DeltaP141 binds DNA tightly, but with less specificity than does full-length protein, and the data suggest that the C-terminal residues are further required for specific DNA binding activity. The implications of these results in the assembly of a functional holoenzyme complex are discussed.
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Affiliation(s)
- Q Yang
- Department of Pharmaceutical Sciences, Molecular Biology Program, University of Colorado Health Sciences Center, Denver 80262, USA
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Affiliation(s)
- J F Carpenter
- Department of Pharmaceutical Sciences, University of Colorado Health Sciences Center, Denver 80262, USA
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Sreerama N, Manning MC, Powers ME, Zhang JX, Goldenberg DP, Woody RW. Tyrosine, phenylalanine, and disulfide contributions to the circular dichroism of proteins: circular dichroism spectra of wild-type and mutant bovine pancreatic trypsin inhibitor. Biochemistry 1999; 38:10814-22. [PMID: 10451378 DOI: 10.1021/bi990516z] [Citation(s) in RCA: 147] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Improved descriptions of the lowest energy excited states of tyrosine and phenylalanine side chains have been developed in order to extend the capabilities of calculating the circular dichroism (CD) spectra of proteins. Four transitions (Lb, La, Bb, and Ba) for each of the side-chain chromophores were considered, and the transition monopole charges were obtained from a CNDO/S calculation on models representing the individual groups. Monopole charges at midpoints of the bonds, corresponding to the maximum transition charge densities in the Lb band, and monopole charges representing the vibronic coupling with the B transitions for the La transition were also included. The aromatic transitions were combined with the peptide transitions (npi, pi0pi n'pi, and pi+pi) and disulfide transitions (n1sigma and n4sigma) in the framework of the origin-independent matrix method to compute the CD spectra of different crystal forms and Y --> L and F --> L mutants of bovine pancreatic trypsin inhibitor (BPTI). The structures of the mutants were obtained by replacing the appropriate tyrosine or phenylalanine residue by leucine in the wild-type crystal structure. The CD calculations were performed on the energy-minimized structures. The CD spectrum calculated for the form II crystal structure of BPTI showed the best agreement with experiment. In the far UV, the calculated and experimental CD spectra agree to various extents for the wild-type and mutant BPTI. Among the mutants, the calculated CD spectra of Y4L, Y10L, Y23L, and F45L showed reasonable agreement with experiment, while those of Y21L and F22L, the two residues interacting with most aromatic groups, showed poor agreement. In the near UV, the negative bands predicted for the wild-type and mutant BPTI have much less intensity than observed experimentally.
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Affiliation(s)
- N Sreerama
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins 80523, USA
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