FIGURE 1.

LC-MS/MS analysis of a peptide mixture for identification of GRP78 protein as a potential TDF-R. The TDF-P1 AP protein sample was separated on SDS-PAGE, and the gel bands were excised and digested by trypsin. The resulting peptide mixture was separated on a C18 reverse phase column over an acetonitrile gradient. A, TIC of the chromatogram; B, MS survey mass spectrum, in which one double charged peak at m/z of 614.88 (expanded in the inset) was fragmented by MS/MS and produced a MS/MS spectrum (C). The resulting peaks in the MS/MS spectrum correspond to a series of b and y ions that resulted from fragmentation of a peptide that was part of GRP78. Data analysis of these MS/MS peaks led to identification of the sequence shown in C. Data analysis of this MS/MS spectrum, combined with data analysis of other MS/MS spectra (data not shown), led to identification of GRP78 as a potential TDF-R.