Metal Stabilization of Collagen and de Novo Designed Mimetic Peptides

Cooperative Metal Ion Coordination to the Short Self-Assembling Peptide Promotes Hydrogelation and Cellular Proliferation

Non-covalent interactions among short peptides and proteins led to their molecular self-assembly into supramolecular packaging, which provides the fundamental basis of life. These biomolecular assemblies are highly susceptible to the environmental conditions, including temperature, light, pH, and ionic concentration, thus inspiring the fabrication of a new class of stimuli-responsive biomaterials. Here, we report for the first time the cooperative effect of the divalent metal ions to promote hydrogelation in the short collagen inspired self-assembling peptide for developing advanced biomaterials. Introduction of the biologically relevant metal ions (Ca²⁺ /Mg²⁺ ) to the peptide surpasses its limitation to self-assemble into a multi-scale structure at physiological pH. In particular, in presence of metal ions, the negatively charged peptide showed a distinct shift in its equilibrium point of gelation and demonstrated conversion from sol to gel and thus enabling the scope of fabricating an advanced biomaterial for controlling cellular behaviour. Interestingly, tunable mechanical strength and improved cellular response were observed within ion-coordinated peptide hydrogels compared to the peptide gelator. Microscopic analyses, rheological assessment, and biological studies established the importance of utilizing a novel strategy by simply using metal ions to modulate the physical and biological attributes of CIPs to construct next-generation biomaterials. This article is protected by copyright. All rights reserved.

Abnormal (Hydroxy)proline Deuterium Content Redefines Hydrogen Chemical Mass

Analyzing the δ²H values in individual amino acids of proteins extracted from vertebrates, we unexpectedly found in some samples, notably bone collagen from seals, more than twice as much deuterium in proline and hydroxyproline residues than in seawater. This corresponds to at least 4 times higher δ²H than in any previously reported biogenic sample. We ruled out diet as a plausible mechanism for such anomalous enrichment. This finding puts into question the old adage that “you are what you eat”.

Lysosomal protein thermal stability does not correlate with cellular half-life: global observations and a case study of tripeptidyl-peptidase 1

Late-infantile neuronal ceroid lipofuscinosis (LINCL) is a neurodegenerative lysosomal storage disorder caused by mutations in the gene encoding the protease tripeptidyl-peptidase 1 (TPP1). Progression of LINCL can be slowed or halted by enzyme replacement therapy, where recombinant human TPP1 is administered to patients. In this study, we utilized protein engineering techniques to increase the stability of recombinant TPP1 with the rationale that this may lengthen its lysosomal half-life, potentially increasing the potency of the therapeutic protein. Utilizing multiple structure-based methods that have been shown to increase the stability of other proteins, we have generated and evaluated over 70 TPP1 variants. The most effective mutation, R465G, increased the melting temperature of TPP1 from 55.6°C to 64.4°C and increased its enzymatic half-life at 60°C from 5.4 min to 21.9 min. However, the intracellular half-life of R465G and all other variants tested in cultured LINCL patient-derived lymphoblasts was similar to that of WT TPP1. These results provide structure/function insights into TPP1 and indicate that improving in vitro thermal stability alone is insufficient to generate TPP1 variants with improved physiological stability. This conclusion is supported by a proteome-wide analysis that indicates that lysosomal proteins have higher melting temperatures but also higher turnover rates than proteins of other organelles. These results have implications for similar efforts where protein engineering approaches, which are frequently evaluated in vitro, may be considered for improving the physiological properties of proteins, particularly those that function in the lysosomal environment.

Recent trends in protein and peptide-based biomaterials for advanced drug delivery

Engineering protein and peptide-based materials for drug delivery applications has gained momentum due to their biochemical and biophysical properties over synthetic materials, including biocompatibility, ease of synthesis and purification, tunability, scalability, and lack of toxicity. These biomolecules have been used to develop a host of drug delivery platforms, such as peptide- and protein-drug conjugates, injectable particles, and drug depots to deliver small molecule drugs, therapeutic proteins, and nucleic acids. In this review, we discuss progress in engineering the architecture and biological functions of peptide-based biomaterials -naturally derived, chemically synthesized and recombinant- with a focus on the molecular features that modulate their structure-function relationships for drug delivery.

Reversible Covalent End-Capping of Collagen Model Peptides

The combination of supramolecular aggregation of collagen model peptides with reversible covalent end‐capping of the formed triple helix in a single experimental set‐up yielded minicollagens, which were characterized by a single melting temperature. In spite of the numerous possible reaction intermediates, a specific synthetic collagen with a leading, middle and trailing strand is formed in a highly cooperative self‐assembly process.

A self-assembling collagen mimetic peptide system to simultaneously characterize the effects of osteogenesis imperfecta mutations on conformation, assembly and activity

We have created a self-assembling collagen mimetic peptide system which for the first time facilitates simultaneous characterization of the effects of osteogenesis imperfecta mutations on stability, conformation, assembly and activity.

Tricine as a convenient scaffold for the synthesis of C-terminally branched collagen-model peptides

A novel and convenient method for the synthesis of C-terminally branched collagen-model peptides has been achieved using tricine (N-[tris(hydroxymethyl)methyl]glycine) as a branching scaffold and 1,2-diaminoethane or 1,4-diaminobutane as a linker. The peptide sequence was incorporated directly onto the linker and scaffold during solid-phase synthesis without additional manipulations. The resulting branched triple-helical peptides exhibited comparable thermal stabilities to the parent, unbranched sequence, and served as substrates for matrix metalloproteinase-1 (MMP-1). The tricine-based branch reported herein represents the simplest synthetic scaffold for the convenient synthesis of covalently linked homomeric collagen-model triple-helical peptides.

Collagen-Like Peptide Bioconjugates

Collagen-like peptides (CLPs), also known as collagen-mimetic peptides (CMPs), are short synthetic peptides that mimic the triple helical conformation of native collagens. Traditionally, CLPs have been widely used in deciphering the chemical basis for collagen triple helix stabilization, mimicking collagen fibril formation and fabricating other higher-order supramolecular self-assemblies. While CLPs have been used extensively for elucidation of the assembly of native collagens, less work has been reported on the use of CLP-polymer and CLP-peptide conjugates in the production of responsive assemblies. CLP triple helices have been used as physical cross-links in CLP-polymer hydrogels with predesigned thermoresponsiveness. The more recently reported ability of CLP to target native collagens via triple helix hybridization has further inspired the production of CLP-polymer and CLP-peptide bioconjugates and the employment of these conjugates in generating well-defined nanostructures for targeting collagen substrates. This review summarizes the current progress and potential of using CLPs in biomedical arenas and is intended to serve as a general guide for designing CLP-containing biomaterials.

Observing Effects of Calcium/Magnesium Ions and pH Value on the Self-Assembly of Extracted Swine Tendon Collagen by Atomic Force Microscopy

Self-assembly of extracted collagen from swine trotter tendon under different conditions was firstly observed using atomic force microscopy; then the effects of collagen concentration, pH value, and metal ions to the topography of the collagen assembly were analyzed with the height images and section analysis data. Collagen assembly under 0.1 M, 0.2 M, 0.3 M CaCl2, and MgCl2 solutions in different pH values showed significant differences (P < 0.05) in the topographical properties including height, width, and roughness. With the concentration being increased, the width of collagen decreased significantly (P < 0.05). The width of collagen fibers was first increased significantly (P < 0.05) and then decreased with the increasing of pH. The collagen was assembled with network structure on the mica in solution with Ca2+ ions. However, it had shown uniformed fibrous structure with Mg2+ ions on the new cleaved mica sheet. In addition, the width of collagen fibrous was 31~58 nm in solution with Mg2+ but 21~50 nm in Ca2+ solution. The self-assembly collagen displayed various potential abilities to construct fibers or membrane on mica surfaces with Ca2+ ions and Mg2+ irons. Besides, the result of collagen self-assembly had shown more relations among solution pH value, metal ions, and collagen molecular concentration, which will provide useful information on the control of collagen self-assembly in tissue engineering and food packaging engineering.