DEFECTION AND IDENTIFICATION OF CARCINOGEN-PEPTIDE ADDUCTS BY NANOELECTROSPRAY TANDEM MASS-SPECTROMETRY

Nanoelectrospray (nanoES) tandem mass spectrometry was used to examine covalently modified peptides in crude enzymatic digests of human seru m albumin (HSA) that had been exposed to either benzo[a]pyrene diol ep oxide (B[a]PDE, 1), chrysene diol epoxide (CDE, 2), 5-methylchrysene d iol epoxide (5MeCDE, 3), or benzo[g]chrysene diol epoxide (B[g]CDE, 4) . The low flow rates of nanoES (similar to 20 nL/min) allowed several MS/MS experiments to be optimized and performed on a single sample wit h very little sample consumption (similar to 30 min analysis time/mu L sample). Initially, nanoES was compared with conventional LC/MS/MS an alysis of carcinogen-peptide adducts. For example, nanoES analysis of an unseparated digest of B[a]PDE-treated serum albumin revealed the sa me peptides (RRHPY and RRHPY-FYAPE) that were preciously shown, by LC/ MS/MS, to be adducted with B[a]PDE. In addition, nanoES could detect u nstable peptide adducts that might not otherwise have been directly ob servable. Finally, nanoES was shown to be an effective way to screen m ixtures of modified and unmodified peptides for which no chromatograph ic Information is available. (C) 1998 American Society for Mass Spectr ometry.