Dispersion Function of a Protein, DP-1, Identified in Collimonas sp. D-25, for the Synthesis of Gold Nanoparticles

Collimonas sp. (D-25), found in the soil of Akita Prefecture, is a gram-negative bacterium with the ability to synthesize gold nanoparticles (AuNPs). During the synthesis of AuNPs, one specific protein (DP-1) was found to have disappeared in the sonicated solution of the bacterium. Recombinant DP-1 (rDP-1) from Escherichia coli BL21 (DE3) was used to study the effect of DP-1 on the synthesis of AuNPs. AuNPs synthesized with rDP-1 result in small, stabilized nanoparticles. AuNPs synthesized by DP-1 retained the stability of both the dispersion and nano-size particles under high salt concentrations. Isothermal titration calorimetry was employed to investigate the bonding ratio of rDP-1 to AuNPs. Several thousand rDP-1 proteins are attached to the surface of an AuNP to form a protein corona containing multiple layers. These results suggest that DP-1 obtained from D-25 has a size and stability control function during AuNP synthesis.