DigitalCommons@Linfield

Determination of the Optimal Conditions for Bovine Serum Albumin Using Surface Enhanced Raman Scattering on Silver Colloids and Nanoparticle Films

Jereld R. Nicholson Library

Bovine serum albumin (BSA) was analyzed using surface enhanced Raman scattering (SERS) to find the optimal conditions to observe BSA with SERS on colloids and nanoparticles films. The optimal conditions were determined by varying the concentrations of colloidal silver, Na₂SO₄, and BSA. The most favorable conditions using SERS for BSA were 500ug/mL, pH 4, and 0.1 M Na₂SO₄. Under these conditions, peaks due to an alpha helical secondary structure by the amide 3 vibrations at 1297 cm^-1 were most distinct. The peaks appearing in the spectrum are the parts of the BSA molecule which are interacting with the silver colloids. Colloidal metal films were made and soaked in varying pH of 500 µg/mL BSA solutions, the spectrum at pH 4 showed tyrosine peaks at 1566 and 1339 cm^-1 and tryptophan peaks at 1158 and 1038 cm^-1. The peaks on colloidal films only appear when the amino acid residue is perpendicular to the colloidal surface; therefore, one could deduce that the tyrosine molecules at 1566 and 1339 cm^-1 and tryptophan molecules at 1158 and 1038 cm^-1 are perpendicular to the film. SERS can be used for label-free detection of proteins, thus finding the best conditions to obtain spectra using this technique may be very beneficial to proteomic research.