Surface-enhanced Raman spectroscopy (SERS) is an important tool in the characterization of proteins, which can lead to vital information pertaining to biological functions. Spectra of lysozyme, bovine serum albumin (BSA), catalase, and hemoglobin were obtained using SERS on silver colloids with sodium sulfate as the aggregating agent. Optimization of the SERS was attempted through adjustment of the acidity of sulfate aggregating agent. A link was investigated between the pI (pH at which there is no net charge on the molecule) of the proteins and the pH of the solutions needed for optimum SERS. It was found that any pH higher than the pI of the protein would not result in readable Raman bands. SERS of each protein were obtainable at any pH below the protein’s pI and was enhanced until reaching a pH of approximately two. At any pH lower than two, SERS were not possible because of inability of the aggregating agent to work in extreme pH conditions
