USE OF FOURIER-TRANSFORM INFRARED ATTENUATED TOTAL REFLECTANCE SPECTROSCOPY FOR THE STUDY OF SURFACE-ADSORPTION OF PROTEINS

The adsorption behavior of lysozyme and immunoglobulin G (IgG) onto a ZnSe crystal surface has been detected by the FT-IR/ATR technique. With this technique we are able to detect the protein adsorption process at a very low concentration (0.0005 mg/mL). The equation of Sperline et al. [Langmuir 3, 198 (1987)] was successfully applied to calculate the adsorption density of protein from an aqueous solution on a real-time basis. The monolayer formation of lysozyme was observed at a concentration range of 10(-7) M to 10(-5) M. A monolayer-to-multilayer adsorption transition of lysozyme was clearly observed from the adsorption isotherm plot at 35 muM. A differential adsorption density was observed for IgG that could be explained on the basis of its differential size and surface charge.