O (with the extent of decrease dependent on the relative efficiency of cleavage by "basal" versus "experimental" proteases) and thus lower the chance of cleavage fragment detection. This scenario is illustrated by examples of thrombospondin-2 and IGFBP-4 where several low ratio peptides were confirmed by Edman sequencing to be the products of true cleavage events (Figs. 4 and 6). The second limiti