title: Analysis of Flexibility of Proteins by means of Positive and Negative Ion MALDI In-Source Decay Mass Spectrometry.
abstract: The amino acid residues susceptible to in-source decay (ISD) in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry have been identified from both positive and negative ion ISD spectra of cytochrome c, myoglobin, thioredoxin and bovine serum albumin. Backbone cleavages at the N-Cα bonds of Xxx-Asp, Xxx-Asn, Xxx-Cys, and Gly-Xxx residues gave discontinuous intense peaks of c-ions, independent of positive and negative ion mode. The intensity values for c-ions, Int(c), were defined to allow estimation of the discontinuous intense peaks of c-ions. The identities of the high intensity value residues Asp, Asn, Cys, and Gly were compared with those identified using other measures of flexibility such as the B-factor, turn preferential factor and protection factor. The comparison indicates that Asp, Asn, and Gly residues are common to all measures. Thus, the intensity values of c-ions can be adopted as a measure of protein flexibility.
authors.affiliation: Graduate School of Nanobioscience, Mass Spectrometry Laboratory, Yokohama City University.
authors.forename: Ryunosuke
authors.initials: R
authors.lastname: Iimuro
authors.affiliation: Graduate School of Nanobioscience, Mass Spectrometry Laboratory, Yokohama City University.
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Takayama
keywords: flexibility; in-source decay; matrix-assisted laser desorption/ionization; protein
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