Sulfite reductase-mediated synthesis of gold nanoparticles capped with phytochelatin.

An enzymatic synthesis route to peptide-capped gold nanoparticles has been developed. Gold nanoparticles were synthesized using alpha-NADPH-dependent sulfite reductase and phytochelatin in vitro. The gold ions were reduced in the presence of the enzyme sulfite reductase, leading to the formation of a stable gold hydrosol of dimensions 7-20 nm and were stabilized by the capping peptide. The nanoparticles were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy and UV-visible optical absorption. These studies will help in designing a rational enzymatic strategy for the synthesis of nanomaterials of different chemical compositions, shapes and sizes as well as their separation.