ADSORPTION TO SILICA NANOPARTICLES OF HUMAN CARBONIC-ANHYDRASE-II ANDTRUNCATED FORMS INDUCE A MOLTEN-GLOBULE-LIKE STRUCTURE

Human carbonic anhydrase II pseudo-wild type (HCAII(pwt)) and two trun cated variants were adsorbed to approximate to 9 nm silica nanoparticl es. Ellipsometry was used as an indirect measure of protein adsorption . The structural changes of adsorbed proteins were investigated with t he use of circular dichroism (CD), intrinsic fluorescence, ANS binding ability and inhibitor binding capacity, It was found that the variant s that were truncated at positions 5 and 17 in the N-terminal end atta in a molten-globule-like state after interaction with the silica nanop articles. In contrast, the more stable HCAII(pwt) retained most of its native structure after 24 h adsorption to silica nanoparticles. The r esult suggests that surface induced unfolding may give rise to interme diates similar to those for unfolding induced by, for example GuHCl, T hus, the intermediate observed has some features of the molten globule .