电荷密度和疏水性对疏水改性聚丙烯酰胺与牛血清蛋白相互作用的影响

Abstract

Interactions between bovine serum albumin (BSA) and 10% hydrolyzed poly(acrylamide) (PAM-AA(10%)) or several hydrophobically modified poly(acrylamide)s without and with acrylic acid (AA) segments (PAM-C12(1%), PAM-C12(2%)-AA( x %)) have been studied. The enthalpy changes associated with the polymer/BSA interaction process are exothermic except for PAM-C12(1%)/BSA system, and the binding enthalpy (Δ H bind) becomes much more exothermic in the order of PAM-AA(10%) ≈ PAM-C12(2%)-AA(5%) H bind of BSA with the polymers containing AA segments may be attributed to the electrostatic binding of negative AA segments on the polymers with the positive charged patches of BSA. Additionally, compared with PAM-AA(10%) and PAM-C12(1%), PAM-C12(2%)-AA( x %) induce remarkable changes in both secondary structure and microenvironment of BSA. This proves that both charge density and hydrophobicity have important effects on the interactions between the polymers and BSA. Moreover, PAM-C12(2%)-AA( x %) show different interaction modes with BSA at the different polymer concentrations. When the polymer concentration is slightly higher than CMC, the electrostatic attraction force between AA segments on polymer chains and positive charged patches of BSA molecules is more favorable for un-aggregated polymer monomers due to its flexible chain, which leads to the unfolding of BSA molecules in some extent. When the polymer concentration is much higher than CMC, the micelle-like self-aggregates of PAM-C12(2%)-AA( x %) play a dominant role, thus the secondary structure of BSA is stabilized instead of being destroyed due to the small proportion of polymer monomer molecules.