Xie Jianping, Lee Jim Yang, Wang Daniel I C, Ting Yen Peng
Singapore-MIT Alliance, 4 Engineering Drive 3, National University of Singapore, Singapore 117576.
ACS Nano. 2007 Dec;1(5):429-39. doi: 10.1021/nn7000883.
This paper describes the synthesis of single-crystalline Ag nanoplates using the extract of unicellular green alga Chlorella vulgaris at room temperature. Proteins in the extract were involved in the biological synthesis, providing the dual function of Ag ion reduction and shape-controlled synthesis of nanosilver. Hydroxyl groups in Tyr residues and carboxyl groups in Asp and/or Glu residues were further identified as the most active functional groups for Ag ion reduction and for directing the anisotropic growth of Ag nanoplates, respectively. The kinetics of Ag ion reduction in biological systems was discussed and probed by using custom-designed peptides. The results showed the Tyr content (the reduction source) and the content of Ag complexers (the reaction inhibitors, e.g., His and Cys) in the protein molecules as important factors affecting the reduction kinetics. The comprehensive system identification effort has led to the design of a simple bifunctional tripeptide (DDY-OMe) with one Tyr residue as the reduction source and two carboxyl groups in the Asp residues as shape-directors, which could produce small Ag nanoplates with low polydispersivity in good yield (>55%). The roles of the carboxyl groups in the formation of Ag nanoplates were also discussed.
本文描述了在室温下使用单细胞绿藻普通小球藻的提取物合成单晶银纳米片的过程。提取物中的蛋白质参与了生物合成，发挥了还原银离子和控制纳米银形状合成的双重功能。进一步确定，酪氨酸残基中的羟基以及天冬氨酸和/或谷氨酸残基中的羧基分别是还原银离子和引导银纳米片各向异性生长的最具活性的官能团。通过使用定制设计的肽对生物系统中银离子还原的动力学进行了讨论和探究。结果表明，蛋白质分子中的酪氨酸含量（还原源）和银络合剂含量（反应抑制剂，如组氨酸和半胱氨酸）是影响还原动力学的重要因素。通过全面的系统鉴定工作，设计出了一种简单的双功能三肽（DDY-OMe），其中一个酪氨酸残基作为还原源，天冬氨酸残基中的两个羧基作为形状导向基团，该三肽能够以较高产率（>55%）制备出多分散性低的小尺寸银纳米片。还讨论了羧基在银纳米片形成过程中的作用。
