Conjugation of BSA Protein and VP/AA Copolymers

Abstract

Macromolecular complex and water-soluble covalent conjugate formation of poly(N-vinylpyrrolidone-2-coacrylicacid) (VP/AA 2:1) with bovine serum albumin (BSA) was studied at different pH and investigated by spectrofluorometric method. Conjugates of VP/AA-BSA were synthesized by cross-linking the carboxyl groups of anionic VP/AA copolymer to the amino groups of bovine serum albumin by using 1-ethyl -3-(3-dimethylaminopropyl) carbodiimide
hydrochloride (EDC) as a coupling reagent. Water-soluble complexes of VP/AA with BSA were formed by mixing copolymer and protein solutions at different molar ratio (nVP/AA/nBSA) and different pH. When the pH is higher than the isoelectric pH of BSA (pI) the stability of the VP/AA-BSA complexes was weak, however when pH is approximately equal to pI of BSA (pH 5.0), VP/AA-BSA complexes were stable. The fluorescence spectroscopy results of VP/AA-BSA
complexes and water-soluble covalent conjugates showed decreased fluorescence intensities and a distinct blue shift on maximum wavelength (λmax.). This indicates that tryptophanyls of BSA were completely isolated from water when the complex or conjugates are formed between VP/AA and BSA.