Figure 1.

(A). LC-MS total ion chromatogram of the crude duct venom extract of Red Sea C. pennaceus (pictured in (C)). The extracted ion chromatogram for m/z = 659.2 (shown in blue) has peaks corresponding to the [M+2H]²⁺ ions of the native PnID peptides. (B). The total ion chromatogram LC-MS after TCEP reduction. The extracted ion chromatogram for m/z = 661.2 (shown in blue) has only a single peak, corresponding to the [M+2H]²⁺ ion of fully reduced PnID. (D). Mass spectrum corresponding to a retention time of 34.1 min in the LC-MS data shown in (A). has an m/z value consistent with the expected value for the [M+2H]²⁺ ion of fully oxidized PnID. (E). Mass spectrum corresponding to a retention time of 36.4 min in the LC-MS data shown in (B). has an m/z value consistent with the expected value for the fully-reduced [M+2H]²⁺ ion of PnID.