HPLC elution profiles obtained with known bimane derivatives or observed for a tissue extract derivatized with monobromobimane. A) sulfite bimane; B) glutathione bimane; C) cysteine bimane; D) heart extract. Similar results for bimane standards are obtained when the derivatives are prepared by reaction of monobromobimane with a mixture of sulfite, cysteine, and glutathione (Figure S1). RFU, relative fluorescence units; x, reagent-derived peaks. The red trace in panel D is plotted according to a 17-fold less sensitive RFU scale compared with the black trace which shows the elution profile from 0 to 7.35 min, a region that includes a reagent-derived peak at 4.30 min due to the presence of SDS in the tissue extraction buffer. SDS does not otherwise affect the elution profile, as judged by control studies with bimane standards (data not shown).