Targeted SRM-MS analyses of SNAP-25 in human brain. Individual values for the SRM-MS measured ratios (endogenous peptide/labeled peptide standard) of immunoprecipitated [antibodies SP12 (A-B) and SMI81 (C) SNAP-25, in biochemically fractionated membrane-bound (A) and membrane-raft associated (B) and soluble (C), extract of superior parietal gyrus from controls (N = 15) and patients with Alzheimer’s disease (N = 15). The lower, upper and middle lines of the error bars correspond to the 25th and 75th percentiles and medians, respectively. SMI81 recognizes the extreme N-terminus of SNAP-25, especially when it’s N-terminal acetylated. The exact epitope of SP12 is unknown.