[Study on adsorption of nonpolar R-side amino acids on silver nanoparticles by FT-SERS]

The adsorption orientation and adsorption characteristics of aliphatic-nonpolar amino acids represented by L-methionine on silver nanoparticles were studied by FT-surface-enhanced Raman spectroscopy (FT-SERS) method with different pH and concentrations. According to the experiments, in order to get the best FT-SERS effects, the optimal concentration range of the L-methionine on silver sol is between 10(-3) mol x L(-1)-10(-4)(mol x L(-1). The FT-SERS effects and adsorption model change with pH; The SERS are poor when pH is near the isoelectric point or over 11 or 3. The interaction of L-methionine with Ag nanoparticles is the physical and chemical adsorption by NH3, COO-, S, which could also be effected by pH. From the results and previous reports on this aspect, the general rules of the adsorption model and the orientation of the aliphatic-nonpolar amino acids on silver nanoparticles were speculated, which would be useful for the study of amino acids, protein, peptide, enzyme etc.