Conformational changes of adsorbed and free proteins on magnetic nanoclusters.

Conformational changes of proteins have an influence on their biological activity, so as to affect their use efficiency. However, the conformation of proteins is typically measured in a mixture containing the adsorbed protein, free protein and adsorbing material, which does not truly reflect the influence of the material on protein conformation. In this study, FeO/carboxymethylated chitosan (FeO/CMCS) nanoclusters with unique superparamagnetism were utilized as the separation carrier to study the conformational changes of the adsorbed and the free proteins. Four representative proteins with different molecular weights and isoelectric points, lysozyme (LYZ, 13.4 kDa; pI 10.8), bovine hemoglobin (BHB, 64.5 kDa; pI 6.9), apo-transferrin (TRT, 80 kDa; pI 5.9) and bovine serum albumin (BSA, 68 kDa; pI 4.8), were selected as model proteins to investigate the influences of material coating with/without metal ions and environmental factors including pH and ion strength, on the conformational behaviors of the adsorbed or free proteins. This study was aimed at providing a platform for an improved reflection of the conformational changes of proteins and has a potential to guide immobilization and separation of proteins.