Mesoscale structures and gels of biological macromolecules

The project is directed to providing a molecular understanding of the function of biological macromolecules and their assemblies at the length scales embracing the atomic up to macroscopic lengths; i.e. from the isolated macromolecule and their segments t o the form of a biomaterial. One of the examples studied is the underlying principles of formation of the macrocyclic topology of the triple-helical polysaccharides macrocyclic <.beta.>(1,3)-D-glucans. This will be elucidated using statistical thermodynamic theory, combined with time-lapsed studies of the macromolecular assembly process using AFM. The other example is the detailed molecular design of a hydrogel based on scleroglucan and chitosans, including the charge densities of a modified scleroglucan, sclerox and chitosan as experimental parameters. The project include determination of gelation kinetics, determination of fractal dimensionality of the critical gel by rheological methods and the structure of the pregel clusters by ultramicroscopy-Correlation between microelastic mapping using AFM and t hat determined by conventional rheological methods are intended to address macromolecular mechanisms for volume transitions in gels made of "stiff" polymers, and distribution of frozen-in structures. Structural heterogeneities are intended to be further characterized by scattering experiments.