Figure 3.

Schematic of the general approaches for measuring different reversible thiol-based redox PTMs. The free thiols are typically blocked by alkylation with NEM as the initial step. (A) In the indirect methods, the different types of modified cysteines are selectively reduced to free thiols by using individual sets of reagents. (B) In the direct methods, dimendone probe is often used to react with SOH, and organomercury resin for SNO. The reduced or labeled protein samples are then subjected to enrichment and measurement by either gel-based or MS-based proteomic approaches.