Figure 2
Relative percent abundance (RPA) of cysteine sulfenic acid on albumin (solid markers) as reported by the A) CPPCHD and B) DCP-Bio1 Cys-SOH probes over a range of plasma concentrations of hydrogen peroxide. As shown for albumin, there is a significant difference in the percent of modified protein detected when samples are prepared by dilution vs. MSIA. This demonstrates relative antibody aversion for CPPCHD and DCP-Bio1-tagged forms of albumin. Additionally, the RPA values for cysteine sulfenic acid-modified albumin appear significantly lower when trapped by (higher concentrations of) DCP-Bio1--demonstrating an empirical discrepancy in Cys-SOH trapping efficiency between the two dimedone-based probes. Plasma from the same individual was used for collection of these datasets. Data on the RPA of dimedone-tagged TTR (hollow markers) are shown for reference. RPA values decrease at the highest concentrations of hydrogen peroxide due to overoxidation of Cys-SH to cysteine sulfinic acid (SO2H). Evidence to support this assertion can be seen as a +32 Da mass shift from the Cys-SH form (and only the Cys-SH form) of the hydrogen peroxide treated samples in Figure 1, panel B.