Analysis of the dynamics of assembly and structural impact for a histidine tagged FGF1-1.5 nm Au nanoparticle bioconjugate.

Whether assembling proteins onto nanoscale, mesoscopic, or macroscropic material surfaces, maintaining a protein's structure and function when conjugated to a surface is complicated by the high propensity for electrostatic or hydrophobic surface interactions and the possibility of direct metal coordination of protein functional groups. In this study, the assembly of a 1.5 nm CAAKA passivated gold nanoparticle (AuNP) onto FGF1 (human acidic fibroblast growth factor) using an amino terminal His(6) tag is analyzed. The impact of structure and time-dependent changes in the structural elements in FGF1and FGF1-heparin in the presence of the AuNP is probed by a molecular beacon fluorescence assay, circular dichroism, and NMR spectroscopy. Analysis of the results indicates that a time-dependent evolution of the protein structure without loss of FGF1 heparin binding occurs following the formation of the initial FGF1-AuNP complex. The time-dependent changes are believed to reflect protein sampling of the AuNP surface to minimize the free energy of the AuNP-FGF1 complex without impacting FGF1 function.