Figure 1: Extent of deprotection of Sec(Mob) using different deprotection cocktails at 40 °C for 4 hours as measured by analytical HPLC.
A) ~30% deprotection of Sec(Mob) was observed after incubation in neat TFA as seen by the appearance of the deprotected peptide peak at 10 min in the chromatogram. B) Nearly 100% deprotection of Sec(Mob) was observed after incubation in TFA/TES/H2O (96:2:2). C) ~90% deprotection of Sec(Mob) was observed after incubation in TFA/TES/phenol (96:2:2). An unidentified peak appears at 21 minutes. D) 100% deprotection of Sec(Mob) was observed after incubation in TFA/TES/thioanisole (96:2:2). E) ~98% deprotection of Sec(Mob) was observed after incubation in TFA/phenol/H2O (96:2:2). F) The diselenide peak near 13 minutes decreases substantially when the sample shown in E) was treated with 5-fold excess TCEP for 12 h. The extent of deprotection was determined by peak areas in all cases.