Peptide mapping of apoA-I by MALDI mass spectrometry. (A) MS and MS/MS analysis of a trypsin-digested gel splice resulted in matching of most of the major peaks as either apoA-I (peaks indicated by nos. 1-21), immunoglobulin kappa light chain (IgK, *), or trypsin autolysis products (•). No other proteins were identified as significant matches. (B) A total of 21 different peaks matched to apoA-I with MS/MS sequencing of 3 of these matching 19, 12, and 11 fragment ion peaks. (C) Matching peptides indicated in bold represent 66% of the sequence and are distributed throughout the sequence.