TABLE 3.

Cadmium-Modified Peptides in Human HSP90 Identified by NanoUPLC-MS

Position	Peptide Sequence	Calculated Mass	Observed Mass	Cys	Increase in Mass
411–423	KCLELFSELAEDK + Cd	1635.65	1635.61	Cys412	111.90
560–568	FENLCKLMK + Cd	1237.47	1237.45	Cys564	112.90

Recombinant human HSP90 beta (2.5 µM) was reacted with 10 µM cadmium chloride for 30 min. The native or cadmium-treated HSP90 was digested with trypsin and analyzed by nanoUPLC-MS^E, as described in the experimental procedures section. A mass number of 111.90 or 112.90 was used to calculate the effect of the modification of a cysteine residue by cadmium. The MS^E data are shown in Table 4.