Figure 2: Percent reduction of total Cys in vitro in HT-29 cells and in vivo in mouse liver. A. HT-29 cells were extracted and protein thiol content was measured with DTNB with and without treatment by TCEP. Results showed similar percent reduction to the average found for the ICAT method (see Figure 1). B. Mouse liver was extracted and treated similarly to determine average protein thiol oxidation in vivo. Values in A are mean SEM: untreated, 86.0 1.5; TCEP-treated, 100 0.9, n = 3-5. Values in B are untreated, 91.7 ± 1.5 and TCEPtreated, 100 ± 4.0, n = 3. *p < 0.05.