Gelatin-glutaraldehyde supramolecular structures studied by laser light scattering

Static and Dynamic laser light scattering (SLS and DLS) measurements are reported on 0.5% (w/v) aqueous gelatin solutions with glutaraldehyde (GA) present as a third component with very small concentrations, varying from 1 x 10(-5) to 1 x 10(-3)% (w/v). The wavevector (ci) dependence of the average scattered intensity I-s(q) (SLS data) and the relaxation time distribution h(tau) (DLS data), clearly showed the existence of two distinctive supramolecular structures of gelatin-GA complexes in these solutions, identified as (i) GA bound gelatin complexes having random coil conformations and (ii) GA bridged gelatin molecular pairs having "double strand" conformations. The ratio of hydrodynamic radius R-h to radius of gyration R-g was found to be R-h/R-g = xi(1) similar or equal to (0.70 +/- 0.05) for the random coil complexes for all concentrations of GA. The ratio of the effective lengths of the "double strand" structures measured by DLS (L-d) and SLS (L-s) was also found to be independent of GA concentrations and showed a fixed value, L-d/L-s = xi(2) similar or equal to (0.63 +/- 0.02). (C) 2000 Elsevier Science Ltd. All rights reserved.