Quantitative characterization of the complexation between proteins and electroneutral polymers

Abstract

Quantitative characterization of the complexation between proteins and electroneutral polymers is of great importance in biology and medicine science. However, the investigation of it has long been hindered due to the difficulties in characterization. And the few existing analysis models have various problems. In view of this, we focused on the complexation between proteins and electroneutral polymers in this work, and came up with a novel model analysis method to quantitatively characterize it. The mathematical model, based on the reversible complexing equilibrium among free proteins, free polymers and complexes of proteins with polymers, successfully associates the primary complexing parameters with the variation of the fluorescence intensities of the complexing system, so that one can quantitatively characterize the complexation of proteins with electroneutral water-soluble polymers in aqueous systems in situ, without destroying the dynamic equilibrium, which is more accurate. In this study, the complexation of bovine serum albumin (BSA) with poly(N-iso-propylacrylamide) (PNIPAM) is investigated as an example, and with the help of this method, numerous complexing parameters can be calculated accurately and rapidly. And by examining their variation with the increase of the mixing ratio (r_mixing, molar ratio of PNIPAM to BSA), the complex interaction of proteins with electroneutral water-soluble polymers is further illuminated. Compared with traditional analysis methods, this method has the advantages of simplicity, accuracy and extensive application.