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Chitosan (CTS), a linear binary copolymer of (1-->8)-linked 2-acetamido-2-deoxy-beta-D-glucopyranose (GlcNAc unit) and 2-amino-2-deoxy-beta-D-glucopyranose (GlcNH2 unit), is derived from chitin by alkaline deacetylation. In the present work, the narrow molecular weight distribution chitooligosaccharides were prepared by degraded CTS with a microwave-assisted-cleavage method of metal-coordinating template-absorption catalytic oxidation. Under physiological pH conditions, the interaction of CTS and the narrow distribution chitooligosaccharides with Human serum albumin (HSA) was preliminarily explored by fluorescence spectra. Low molecular weight CTS in different concentration was added into HSA solution respectively, the absorptivity of the HSA solution decreased considerably. This phenomenon indicated that there was an interaction between these six different low molecular weight CTS with HSA, and the smaller the DP of the narrow distribution chitooligosaccharides, the stronger the interaction with HSA. However, the interaction gradually failed in as the DP was less than eight. The interaction almost disappeared when using glucosamine, the final product of degraded CTS, which revealed that there was a scale effect between chain-like CTS molecule and protein biomacromolecule. The results suggest that the strongest interaction binding occurs in CTS with DP approximately =8. Whether the DP increases or decreases, the interaction will weaken.

Four sulfur-contained D(+)-glucosamine metal complexes were synthesized (M-GLUS, M = Co, Cu, Ni and Zn)and characterized by elementary analysis, molar conductance, and proton nuclear magnetic resonance. The yield of the complex was about 70%, and it dissolved easily in water. The ligand coordinates with metalions mainly between sulphur and metalions, the coordination molar ratio of the ligand to metalion was 2 : 1, and the molar conductivity indicated that all the complexes are nonelectrolyte. The mechanism of the interaction between metal complexes and calf thymus (ct) DNA in Tris buffer (pH = 7. 08), was studied by ultraviolet absorption and fluorescence spectroscopy. The results from varied experiments showed that the intensity of the maximal absorption peaks increased with gradual addition of metal complexes, but the metalions can decrease the maximal absorption and the ligand has no effect on it. Meanwhile, metal complexes could remarkably quench the emission intensity of the DNA-EB system, and the metal complexes could be bound to ct DNA. The quenching mechanism was discussed by Stern-Volmer's equation, the figure showed that it is influenced by static quenching and dynamic quenching, so the partial interaction of the complexes and ct DNA was the major mode. Under physiological pH condition, this study was designed to examine the effect of complexes on human serum albumin and bovine serum albumin by fluorescence. The binding constants and sites of the interaction with SA were analyzed by the Scatchard's equation, the results indicated that there was a strong interaction between the four metal complexes and serum albumin and the binding force was Co-GLUS > Zn-GLUS > Cu-GLUS > Cu-GLUS, and the binding site is only one.