Analyzing TOF-SIMS spectra of biopolymer using multivariate curve resolution

Abstract

Fragment ion analysis of protein samples is crucial for structural evaluation of proteins. Interpretation of fragment ions from bioplolymers, however, is often difficult because fragmentation mechanisms in secondary ion mass spectrometry have not been clarified. Therefore employment of chemometrics is necessary to obtain detailed information from time-of-flight secondary ion mass spectrometry (TOF-SIMS) data of complex samples. In this study, multivariate curve resolution (MCR) was applied to extract a pure component spectrum from a TOF-SIMS spectrum which contains mixed materials information. The model biopolymer, chicken egg white lysozyme was immobilized on a gulutaraldehyde-activated aminosilanized indium-tin oxide (ITO) glass plate by covalent bonding. A reference sample such as substrates without the protein were prepared. All samples were measured with TOF-SIMS using Bi3 + , and then the TOF-SIMS spectra data were analyzed using MCR with and without data preprocessing. As a result, images and spectra related to each material in the sample were obtained by MCR. The fragment ions in the extracted spectra are consistence with chemical information of each material.