Conformational Change Induced Reversible Assembly/Disassembly of Poly-<scp>l</scp>-lysine-Functionalized Gold Nanoparticles

Abstract

The poly-l-lysine-functionalized gold nanoparticle (PLL-GNP) was found to undergo reversible assembly/disassembly in the range of pH from 6.5 to 11.0 at room temperature. At a high pH value, the deprotonated lysine residues allow the formation of α-helix and β-sheet structures at the expense of a part of random coil and β-turn structures, thus inducing the assembly of GNPs. With a decrease of pH to 6.5, the assembly of GNPs is disrupted due to the conversion of the α-helix and β-sheet back into the random and β-turn. It is identified that the formation/collapse of an antiparallel β-sheet structure among PLL chains from adjacent GNPs is responsible for reversible pH-dependent assembly/disassembly of GNPs. Since the conformation-induced assembly/disassembly process of the PLL-GNP can be well recognized by a shift of the surface plasmon resonance band of the GNP and the color change of the solution, this study presents the possibility of following the conformation change of a peptide by monitoring the spectral change of the GNP.