Conformational structure of binary polypeptide complexes on the surface of a charged gold nanoparticle with changing pH

Abstract

Using molecular dynamics simulation, pH-sensitive conformations of binary complexes of homogeneous polypeptides located on the surface of a charged spherical gold nanoparticle were studied. A mathematical model of conformations has been developed taking into account interactions in a complex of two homogeneous polymers on the surface of a charged spherical nanoobject. When two polypeptides were adsorbed on a nanoparticle, the structure of the macromolecular corona depended significantly on the polypeptide combinations in the binary complex. Two identical homogeneous polypeptides shifted away from each other along the neutral surface when their pH deviated from the isoelectric point, while on the surface of a similarly charged nanoparticle, the macrochain corona became strongly loosened. On the charged nanoparticle, the polymer shell of the two polypeptides of opposite polarities delaminated, and the shell itself swelled significantly. When one of the polypeptides in this binary complex reached the isoelectric point, the second charged polypeptide unfolded and disengaged from the first macrochain, shifting away from the surface of the similarly charged nanoparticle.