Insight into the Selectivity and Mechanism of Surfactin Containing Multiple Dissociated Carboxyls with 1-Bromoacetylpyrene in Fluorescent Derivatization.

Fluorescent derivatization of the carboxyls in surfactin peptide rings is an effective way to improve the sensitivity of trace detection of surfactin, but very little is known about the reaction selectivity of surfactin containing multiple carboxyls in derivatization. In this paper, the reaction selectivity in fluorescent derivatization of a surfactin containing two carboxyls in its peptide ring with 1-bromoacetylpyrene and the catalysis role in the reactions were investigated using electrospray ionization mass spectrometry and tandem mass spectrometry. It showed that only one carboxyl was labeled with 1-bromoacetylpyrene in derivatization reactions, and the connection of the Asp residue with 1-bromoacetylpyrene was confirmed. It also showed that triethylamine as a catalyst was connected with surfactin to liberate more nucleophilic groups beneficial to promote the derivatization rate. This would contribute to better understanding the mechanism of derivatization of surfactin and its analogues with 1-bromoacetylpyrene, and with other fluorescent labeling reagents.