Figure 3.
MS spectra showing chlorpyrifos oxon-labeled and unlabeled tubulin tryptic peptides. A) control tubulin dimer without chlorpyrifos oxon (CPO); B) tubulin dimer treated with 0.5 mM CPO; C) polymerized microtubules treated with 0.5 mM CPO. Peaks at 1023.5 and 1039.6 amu correspond to unlabeled EDAANNYAR and YLTVAAVFR peptides from alpha and beta tubulin, respectively. Peaks at 1059.6 and 1075.6 amu correspond to CPO labeled (+136 amu added mass from CPO) EDAANNY*AR and Y*LTVAAVFR peptides. The labeled peak at 1059.5 amu is present in panels B and C. The labeled peak at 1075.6 amu is present only in panel B. The letter X in panels A and C indicates absent peaks.