Concentration-mediated Folding and Unfolding of Collagen Triple Helix

Background: Collagen has been widely utilized in tissue engineering, regenerative medicine and cosmetics. Collagen of low concentrations is frequently applied to reduce the production cost, while it may result in the loss of triple helical structure and bioactivity. CD and NMR techniques have enhanced our understanding of collagen triple helix, while they require high concentrations of collagen samples. Objective: We have systematically investigated the folding and unfolding features of collagen mimetic peptides at a broad variety of concentrations in order to decipher the role of the concentration in the triple helical stability. Methods: Peptide FAM-G(POG)10 was synthesized by the solid phase synthesis method. Fluorescence spectra of peptide FAM-G(POG)10 at different concentrations were recorded. The unfolding and folding profiles of peptide FAM-G(POG)10 with concentrations varying from 1 nM to 100 μM were examined. The effect of concentration on the folding and unfolding capability of peptide FAMG( POG)10 was investigated. Results: Fluorescence characterization of peptide FAM-G(POG)10 under widely varying concentrations from 1 nM to 100 μM has revealed that concentration played a critical role in the stability of collagen peptides. The two-phase pattern of the concentration-dependent folding and unfolding curves has for the first time demonstrated the presence of a critical concentration for the collagen peptide to trigger the complete folding of the triple helix and to maintain the triple helix structure. It is noteworthy that the triple helix structure of collagen peptides was very stable at μM-level concentrations from both the folding and unfolding perspectives. Conclusion: It has significantly contributed to our understanding of collagen triple helix stability at low and ultra-low concentrations, and provided valuable and practical guidelines for the preparation of collagen-based products.