Title
Synthesis and capping of water-dispersed gold nanoparticles by an amino acid: Bioconjugation and binding studies
Author
Nishima Wangoo, K.K. Bhasin, S.K. Mehta, C. Raman Suria
Year
2008
Journal
Journal of Colloid and Interface Science
Abstract
We report a novel strategy for the synthesis of aqueous stable, carboxylated gold nanoparticles (GNPs) by using glutamic acid as the reducing agent. The ratio of chloroaurate ions, AuCl−4 to glutamic acid was optimized in the reaction medium to obtain monodispersed GNPs. Glutamic acid reduced gold nanoparticles were characterized by UV–visible, FTIR, dynamic light scattering and transmission electron microscopy, which demonstrated high stability in aqueous solution over a period of time indicating stabilization via surface-bound amino acid. Functionalized nanoparticles were conjugated with protein molecules through electrostatic attraction between the surface-terminated negatively charged carboxylate groups (single bondCOO−) of glutamic acid and the positively charged amino groups (single bondNH+3) of the protein. The conjugation efficiency of the GNP:protein conjugates was confirmed qualitatively and quantitatively through gel electrophoresis and critical flocculation concentration analysis. The interaction between functionalized GNPs with protein molecules was investigated using fluorescence spectroscopy showing the fluorescence quenching of the tryptophan residues of protein molecules after conjugation. Circular dichroism (CD) studies of the conjugates confirmed that the protein undergoes a more flexible conformational state on the boundary surface of GNPs after conjugation. There was substantial conformational transition from α-helix to β-sheet structure after conjugation of protein to GNPs.
Instrument
J-???
Keywords
Circular dichroism, Secondary structure, Nanostructures, Biochemistry, Materials