| Popis: |
The phenomenon of the homochirality of life, its origin and implications remains one of the most enigmatic fields of science. It has been shown that homochirality provides necessary control for proper protein dynamics (folding) and is a fundamental basis of selectivity in all biochemical processes. Little is known, though, about the implications of the structural phenomenon of homochirality on the strength, elasticity, and other relevant mechanical characteristics of biopolymers. However, these effects could be profound and lead to significant morphological differences of the resulting biomaterial which is relevant to a number of severe human pathologies. Here, we present the detailed study of the peptide hydrogels assembled from a pair of self-repulsive but mutually attractive oppositely-charged oligopeptides with identical (homochiral) or mirror (heterochiral) chirality. Nanoscale structural and morphological characteristics derived from the SANS data demonstrate the distinctions between homochiral and heterochiral hydrogels as seen from the 2D cross-sections of the fibers, pair-wise distance distribution functions and the mass-fractal and correlation length analysis. 1H NMR was used to monitor faster gelation kinetics for heterochiral gels as compared to the homochiral ones, and to observe the differences in the diffusion coefficients and T1 and T2 relaxation times. Studies at the nanoscale and molecular level have allowed us to suggest how these differences translate into the distinctive mechanical strength and elasticity of such homochiral and heterochiral hydrogels observed by means of dynamic rheometry. Our findings show that homochiral biomaterials are characterized by much better visco-elastic properties, thus possessing evident stability advantages over the heterochiral ones. |
