Observation of fluorescence-labeled protein A on a biosensor surface by means of TOF-SIMS

The ability to carry out evaluations of proteins on biomaterial surfaces such as the distribution of each protein and the orientation of immobilized proteins are required for the development of high performance materials. Since proteins all have the same basic chemical structure it is difficult to distinguish one from the others by means of spectroscopy, even though such techniques do provide useful chemical information. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) provides an avenue into the submicron-scale distribution of specific chemicals and enables investigation of chemical conditions on materials surfaces. Though TOF-SIMS also has problems with the characterization of the mass spectra of protein samples, the mass spectra can be interpreted using data analysis techniques such as are provided by information theory. s study, the distribution of fluorescence-labeled protein A immobilized on glass plates was chemically visualized by means of TOF-SIMS and a spectra analysis technique making use of mutual information. With this analysis technique, TOF-SIMS spectra can be interpreted such that it allows one to select specific peaks for chemical imaging of proteins. In addition, fragment ions from protein A labeled with different fluorescence substances, FITC and quantum dots, are characterizable by means of the mutual information, and their chemical conditions are investigated.