Study of the thermodynamics and conformational changes of collagen molecules upon self-assembly

The emphasis on mechanism of collagen self-assembly shows great significance for development of collagen based materials with targeted attributes. Here, combination of isothermal titration calorimetry (ITC) dilution experiments, circular dichroism (CD) and FTIR measurements were employed to investigate the thermodynamic differences and corresponding mechanisms associated with self-assembly of acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC). Firstly, the microrheology measurements of ASC and PSC under the different temperatures (20 degrees C, 25 degrees C, 30 degrees C and 37 degrees C) had confirmed the temperature induced collagen aggregation. The several thermodynamic parameters (Gibbs free energy change, enthalpy change and entropy change) and the critical mass concentration (CMC) of ASC and PSC, obtained by ITC dilution experiments, decreased with the rising temperatures. The magnitudes of negative Gibbs free energy changes were always higher for ASC than that of PSC, indicating former was more energetically favorable. Besides, the self-assembly of both two collagens were driven by hydrophobic interactions, as evidenced by a negative heat capacity value (Delta C-p,C-mic<0). Specifically, the hydrophobic effects improved due to the transformation of PPII into 8-sheet conformations upon collagen selfassembly, as supported by differential CD spectra and FT-IR measurements. Overall, ASC had a higher PPII population than PSC at most temperatures, which may elaborate the thermodynamic differences of two collagens in terms of secondary structure.

Automated summary

The emphasis on the mechanism of collagen self-assembly has significance for developing collagen-based materials with targeted attributes. Through ITC dilution experiments, CD, and FTIR measurements, it was found that ASC exhibited higher thermodynamic preference and energetically favorable characteristics compared to PSC in driving the self-assembly process through hydrophobic interactions under different temperatures.