Figure 7.

Theoretical curve defining the range of useful pK_a (αk_RS⁻ ≥ 5%) for a reacting thiolate group. The figure shows the pK_a range that allows a sufficient rate of reaction of a protein cysteine with different reagents (green area) at pH = 7.4. Values with αk_RS⁻ < 5% are reported in red. The continuous line represents an average of the experimental curves reported in Figure 1.