The 6-protein gradient mix consists of the following proteins and their amounts: Rabbit aldolase (gi 68184) - 100pmol, Bovine carbonic anhydrase (gi 115453) - 1pmol, Equine myoglobin (gi 70561) - 50pmol, Human acid glycoprotein (gi 112877) - 2.5pmol, Equine cytochrome C (gi 117995) - 5pmol, and Chicken lysozyme (gi 126608) - 10pmol. Individual trypsinized and carboxymethylated protein digests were purchased from Microsolv Tech. Tandem mass spec data were acquired via a continuous reverse phase elution off the BioBasic C18 column for 140min with the final acetonitrile concentration of 50%. The 6-protein, 75pmol dataset includes 3,788 MS/MS scans.