Liq. sepn. methods in combination with electrospray mass spectrometry as well as the recently introduced fragmentation method electron capture dissocn. (ECD) have become powerful tools in proteomics research. This paper presents the results of the first successful attempts to combine liq. chromatog. (LC) and Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS) with ECD in the anal. of a mixt. of std. peptides and of a bovine serum albumin tryptic digest. A novel electron injection system provided conditions for ECD sufficient to yield extensive sequence information for the most abundant peptides in the mixts. on the time-scale of the chromatog. sepn. The results suggest that LC/ECD-FTICRMS can be employed in the characterization of peptides in enzymic digests of proteins or protein mixts. and identify and localize posttranslational modifications. [on SciFinder (R)]