Effect of marimastat on the platelet N-terminome during storage. Heatmap overview of time-dependent changes in relative abundance of peptides from platelets stored in the absence (3 columns on the left) or presence (3 columns in the middle) of marimastat. iTRAQ values for 1111 quantifiable and positionally annotated high-confidence peptides were normalized for the starting value on day 1. Only the peptides that were significantly regulated up (ratios ≥2, yellow) or down (ratios ≤0.5, blue) in at least 1 condition (when compared with day 1) are shown. Black indicates intermediate iTRAQ ratios (0.5 ≥ ratios ≤ 2) that did not reach our statistical significance cutoff. Last three columns on the right show marimastat response of the same peptides on specific days (ie, DMSO/marimastat ratios on days 3, 5, and 7). Original and internal N-terminal peptides were sorted based on their ratios and presented separately. Generalized responses of the main peptide clusters are described on the left-hand side of the heatmap. *Denotes natural N termini of proteins where expression is affected by metalloproteinases/marimastat via an indirect mechanism (ie, through control of protein synthesis or uptake and not by direct cleavage of these proteins). Gene symbols of the corresponding proteins are shown.