(725f) Thermoresponsive Properties and Mechanical Response of Highly Concentrated Aqueous Poly(L-proline) Solutions

The gelation behavior of the left helical N-substituted homopolypeptide poly(L-proline) (PLP) in water was explored, employing rheological and small-angle scattering studies at different temperatures and concentrations in order to investigate the network structure and its mechanical properties. Stiff gels were obtained at 10 wt. % or higher at 5^oC, the first time gelation has been observed for homopolypeptides. It was found that, with temperature, the network transitions in D₂O from a homogenous to a two-phase network, with broad scattering features of similar correlation length for all the examined high concentration PLP samples. A thermoresponsive transition was also achieved between 5 and 35^oC, with moduli higher than gelatin, collagen and collagen-mimetic peptide gels, and higher/comparable to β-sheets gels. The brittle gels could tolerate strains of 1 % before yielding, and the linear properties were also independent of angular frequency over the range 0.001-100 rad/s, similar to proline-rich proteins, showing that the gel structure is not dynamic. The secondary structure and helical rigidity of PLP has large structural similarities to collagen, but in gels, the two materials show a different trend with temperature