| 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 deprotonatedlysine residues allow the formation of α-helix and β-sheet structures at the expense of a part of random coiland β-turn structures, thus inducing the assembly of GNPs. With a decrease of pH to 6.5, the assembly ofGNPs is disrupted due to the conversion of the α-helix and β-sheet back into the random and β-turn. It isidentified that the formation/collapse of an antiparallel β-sheet structure among PLL chains from adjacentGNPs 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 surfaceplasmon resonance band of the GNP and the color change of the solution, this study presents the possibilityof following the conformation change of a peptide by monitoring the spectral change of the GNP.
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