The team found that organic nitrogen was highly concentrated in all of the zinc-sulfide aggregates, indicating a high protein or polypeptide content relative to inorganic zinc-sulfide minerals. In combination with the other techniques and experiments, the team concluded that the protein caused the zinc-sulfide nanoparticle aggregation.
The researchers conducted experiments guided by known bacterial metal-binding proteins that bind zinc and other potentially toxic metals at cysteine locales. Cysteine is a sulfur-containing amino acid. Amino acids are the building blocks of proteins.
The researchers found that inorganic aggregation of zinc-sulfide initially occurred rapidly to 100-nanometer diameter aggregates but then slowed or ceased after one week. However, zinc-sulfide nanoparticles in the presence of cysteine displayed more extensive and prolonged aggregation, accumulating up to 1-10 micron (1/1000th of a millimeter)-sized structures.
“Potentially we can use cysteine or cysteine-rich polypeptides or proteins for nanoparticle clean up,” Weber said. “With the boom in nanoscience, people are naturally asking questions about the potential environmental impacts. Here, we see that naturally produced nanoparticles can be naturally controlled.”
Source:DOE/Lawrence Livermore National Laboratory