HSA-interaction studies of uranyl complexes of alkyl substituted isothiosemicarbazone

Interaction between Human Serum Albumine (HSA) and six related uranyl complexes of alkyl substituted (methyl, ethyl, allyl, butyl, pentyl and benzyl) isothiosemicarbazone with general formula [UO2L(sovent)] are examined experimentally and theoretically. In order to determine the effects of changing the length of alkyl groups and their consequent differences in hydrophobicity in HSA interaction, UV-Vis, fluorescence and circular dichroism spectroscopies are utilized as probes. The results show that the complexes quench the fluorescence emission of HSA significantly and induce unfolding of the polypeptide of HSA through converting part of the alpha-helical content to beta-structures and random coil. Docking results obtained from Autodock Vina software indicates that the complexes enter the cleft between three domains of HSA during their interaction. Experimental and theoretical data show that hydrophobic forces play an important role in the interaction of the complexes with HSA. It also appears that some hydrogen bonds between some residues of polypeptide with the complexes could be formed. Finally, it becomes clarified that changing alkyl groups does not represent significant alteration in the interaction of uranyl complexes with HSA and the other structural parameters of complexes have more decisive role in HSA-interaction. (C) 2019 Elsevier B.V. All rights reserved.