Determination of Binding Constants of Lipopolysaccharides of Different Structure with Chitosan

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V. N. Davidova^*, G. A. Naberezhnykh, I. M. Yermak, V. I. Gorbach, and T. F. Solov'eva

Pacific Institute of Bioorganic Chemistry, Far-Eastern Division of the Russian Academy of Sciences, pr. 100-letiya Vladivostoka 159, 690022 Vladivostok, Russia; fax: (4232) 314-050; E-mail: viktoria@piboc.dvo.ru

^* To whom correspondence should be addressed.

Received April 20, 2005

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The interaction of endotoxins--lipopolysaccharides (LPS) different in degree of the O-specific chain polymerization--with 20- and 130-kD chitosan was studied using the competitive binding of LPS with the complex of chitosan-anionic dye (tropaeolin 000-2) and the direct binding of ¹²⁵I-labeled LPS with chitosan immobilized on Sepharose 4B. The interaction of 20-kD chitosan with LPS was non-cooperative, and immobilization of the polycation on Sepharose resulted in its binding to ¹²⁵I-labeled LPS with a positive cooperativity. The interaction of LPS possessing a long O-specific chain with 130-kD chitosan was characterized by negative cooperativity. Binding constants of LPS with the polycation and the number of binding sites per amino group of chitosan were determined. The interaction affinity and stoichiometry of the LPS-chitosan complexes significantly depend on the LPS structure and concentration in the reaction mixture. The increase in the length of carbohydrate chains of LPS results in increase in the binding constants and decrease in the bound endotoxin amount.

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KEY WORDS: lipopolysaccharide, chitosan, tropaeolin 000-2, binding constants, O-specific chain of LPS

DOI: 10.1134/S0006297906030151

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