Fibrinopeptide a

Kemptide, angiotensin I, angiotensin II, bradykinin, leucine Enkephalin, neurotensin, angiotensinogen (1–14), substance P, fibrinopeptide A, ammonium acetate, methanol, and acetic acid were purchased from Sigma-Aldrich (St. Louis, MO). BSA tryptic digest standard was purchased from Protea (Morgantown, WV). A special integrated fused silica capillary serving as both CE separation capillary and ESI emitter was purchased as a customized product from New Objective, Inc. (Woburn, MA). The capillary and the ESI emitter maintained a constant i.d. and had a tapered o.d. at the emitter end. The external surface, about 2 cm from the tip of the emitter, was coated with a thin layer of platinum.

1 mg/mL stock solutions of each peptide (human angiotensin I, human angiotensin II, bradykinin, fibrinopeptide A, kemptide, neurotensin, porcine angiotensinogen, and substance P, all purchased from Sigma-Aldrich) were prepared in 0.1% formic acid (FA, Sigma-Aldrich, St. Louis, MO) in 10% acetonitrile (ACN, Fisher Scientific, Pittsburgh, PA) and deionized water. (Barnstead Nanopure Infinity System, Dubuque, IA). A peptide mixture containing 10 μM of each peptide was prepared from the stock solution in the same solvent mixture. Prior to MS analysis the peptide mixture solutions with final concentrations of 1 μM and 100 nM for each peptide were prepared by further dilution.