STRUCTURE-FUNCTIONAL PROPERTIES OF PROTEIN CONJUGATES WITH POLYALKYLENE OXIDES - A FLUORESCENT STUDY

A fluorescent study of some structural and functional properties of co njugates of a number of proteins (bovine serum albumin, pyruvate kinas e from rabbit skeletal muscles, alpha-chymotrypsin, and two toxic prot eins of plant origin - ricin and viscumin) with polyalkylene oxides (p olyethylene glycol and block copolymers of ethylene oxide and propylen e oxide - proxanols, pluronics) has been carried out. Analysis of the intrinsic protein fluorescence showed that the structure and stability of various protein conjugates to denaturing agents change only slight ly: the conformational mobility of tryptophan residues accessible to t he solvent decreases, whereas that of tryptophan residues localized in the protein regions of low polarity remains unchanged In addition, th e conjugates display higher thermal stability than the native proteins . The fluorescent properties of 1-anilinonaphthalene-8-sulfonic acid a nd water-insoluble 2',3',4',5'-tetrabenzoylriboflavin bound to the nat ive and modified proteins indicated that the polarity and viscosity of the medium near the protein globules are diminished in the conjugates . Thus, modification of the proteins by polyalkylene oxides allows the properties of proteins to be changed without markedly changing their structure.