Elizabeth Crew - Homocysteine-Mediated Reactivity and Assembly of Gold Nanoparticles

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      Publication Details (including relevant citation   information):

      I-I. S. Lim, W. Ip, E.   Crew, P. Njoki, D. Mott, Y. Pan, S. Zhou, C. J. Zhong,   Langmuir,  2007, 23, 826-833.

      Abstract:

      This paper reports the findings of an investigation of the   reactivity and assembly of gold nanoparticles mediated

      by homocysteine (Hcys), a thiol-containing amino acid found in   plasma. The aim is to gain insight into the interparticle

      interaction and reactivity, which has potential application for   the detection of thiol-containing amino acids. By monitoring

      the evolution of the surface plasmon resonance absorption and the   dynamic light scattering of gold nanoparticles in

      the presence of Hcys, the assembly was shown to be dependent on   the nature and concentration of the electrolytes,

      reflecting an effective screening of the diffuse layer around the   initial citrate-capped nanoparticles that decreases the

      barrier to the Hcys adsorption onto the surface, and around the   subsequent Hcys-capped nanoparticles that facilitate

      the zwitterion-type electrostatic interactions between amino acid   groups of Hcys bound to different nanoparticles. A

      key element of the finding is that the interparticle zwitterion   interaction of the Hcys-Au system is much stronger

      than the expectation for a simple Hcys or Au solution, a new   phenomenon originating from the unique nanoscale

      interparticle interaction. The strength and reversibility of the   interparticle zwitterion-type electrostatic interactions

      between amino acid groups are evidenced by the slow disassembly   upon increasing pH at ambient temperatures and

      its acceleration at elevated temperature. These findings provide   new insight into the precise control of interfacial

      interactions and reactivities between amino acids anchored to   nanoparticles and have broad implications in the development

      of colorimetric nanoprobes for amino acids.

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