Static time-of-flight secondary ion mass spectrometry and x-ray photoelectron spectroscopy characterization of adsorbed albumin and fibronectin films

Static time-of-flight secondary ion mass spectrometry (ToF-SIMS), monochrom atized x-ray photoelectron spectroscopy (XPS) and I-125 radiolabeling have been used to characterize albumin films adsorbed onto titanium, gold, polyt etrafluoroethylene and r.f. glow discharge-deposited tetrafluoroethylene (T FE) substrates. A comparison between albumin and fibronectin films also was made. The intensities of characteristic amino acid mass fragments (immoniu m ions) detected in the static ToF-SIMS experiments depended on the protein type, the substrate type and the adsorption conditions, demonstrating the sensitivity of static ToF-SIMS for probing the structure of adsorbed protei n films. Based on the results from albumin and fibronectin, static ToF-SIMS can provide information about the identity of adsorbed proteins and their conformation, orientation, denaturation, etc. X-ray photoelectron spectrosc opy can distinguish pure protein films, but the higher molecular specificit y of static ToF-SIMS is more useful than XPS for examining complex protein films. The I-125 radiolabeling experiments and the XPS atomic percentage of nitrogen were used to quantify the amount of adsorbed protein. Copyright ( C) 2001 John Wiley & Sons, Ltd.