Skip to main content
. Author manuscript; available in PMC: 2014 Jan 22.
Published in final edited form as: Biochemistry. 2013 Jan 11;52(3):466–476. doi: 10.1021/bi301341r

Table 2.

Cys436 containing peptides and their modifications detected by Sequest analysis of tandem mass spectraa

Peptide sequence MH+ z P (pep) XC ΔCn
AAPLSRDPTEVTAIGAVEAAFKC@CAAAIIVLTT 3323.82 3 1.01E-05 3.72 0.36
AAPLSRDPTEVTAIGAVEAAFKC#C#AAAIIVLTTTGR 3704.27 3 2.81E-12 8.21 0.58
C@C@AAAIIVLTTTGR 1489.70 2 7.17E-05 2.68 0.35
C#C#AAAIIVLTTTGR 1507.80 2 1.24E-06 3.93 0.42
a

L-PYK was subjected to iodoamide alkylation previously to its overnight treatment with trypsin at 37°C. The resulting peptides were analyzed by HPLC-MS/MS on an LTQ-FT mass spectrometer. C# stands for carboxymethylcysteine; C@ stands for Cysteine sulfonic acid. Tandem mass spectra were searched against a human protein database using the Sequest algorithm and the following parameters for protein ID: peptide probability of random match <10-3, XC ≥ 1.9, 2.5 or 3.5 for z=1, 2 or 3 respectively and ΔCn ≥ 0.1. Peptides containing oxydized Cys are highlited in boldface. Since C# denoted cysteines were reactive modified by alkylation, they were not irreversibly oxidized.