An acetone precipitation of an E. coli cellular lysate Computer Analysis of Tandem Mass
was obtained from Sigma Chemical Co. (St. Louis, MO; Spectrometru Data
cat. no. E-0125, lot ni. 42C6900, strain ATCC 11246). ’
I
Proteins from the E. coli lysate (1 mg) were digested in
All computer algorithms were written in the C pro
500 PL of 50-n&I ammonium bicarbonate that congramming
language under the UNIX operating systamed
lo-mM Ca++, pH 8.6. The peptides produced tern. The Genpept database was obtained as an ASCII
from this digest were analyzed directly by liquid chro- text file in the FASTA format from the National Center
matography-mass spectroscopy (LC-MS) and liquid
for Biotechnology Information by anonymous ftp
chromatography-tandem mass spectrometry (LC- (NCBI-Genbank Release 77.0; release date 06/15/93;
MS/MS) without further purification. Approximately 74,938 proteins containing 29,127,050 amino acids). This
l/500 of the mixture was used for each analysis by database contains protein sequences translated from
mass spectrometry.