The 6-protein mix consists of the 75pmol amount of each of the following proteins: Rabbit aldolase (gi 68184), Bovine carbonic anhydrase (gi 115453), Equine myoglobin (gi 70561), Human acid glycoprotein (gi 112877), Equine cytochrome C (gi 117995), and Chicken lysozyme (gi 126608). Individual trypsinized and carboxymethylated protein digests were purchased from Microsolv Tech. Tandem data were acquired via a continuous reverse phase elution off the BioBasic C18 column for 140min with the final acetonitrile concentration of 65%. The 6-protein, 75pmol dataset includes 3,775 MS/MS scans.