The identification of biologically important thiols

Abstract

A new mass spectral method has been developed and used to identify biologically important thiols. This method is based upon the use of C-14 labeled N-para-bromophenylmaleimide (BPM) to selectively derivatize thiols. The isotopic label facilitates the isolation and purification of trace quantities of the maleimide thiol adducts by high performance liquid chromatography (HPLC) with radioactivity detection. The use of the bromine atom in the thiol derivative greatly enhances the detectability of the parent and fragment ions containing the BPM moiety because of the generation of the characteristic N + 2 doublet ions. Several examples of the use of this method to identify non-volatile thiol peptides such as glutathione (GSH) and homoglutathione (hGSH) by fast atom bombardment mass spectrometry (FAB-MS) are described in this report.

Chloroacetanilide herbicide selectivity: analysis of glutathione and homoglutathione in tolerant, susceptible, and safened seedlings

“…The biochemical basis for the safening action is poorly understood at present (Hatzios, 1983;Stephenson and Ezra, 1983a). However, it has recently been reported that the safeners cause the chloroacetanilides to be metabolized more readily to the corresponding GSH conjugate (Gronwald et al, 1986; Ezra et al, 1986; Breaux et al, 1986b). The basis for the enhanced metabolism is not clear at present.…”

“…The biochemical mechanism responsible for enhanced GSH levels is uncertain. It has been proposed that the safeners may interfere with the regulation of glutathione biosynthesis in treated seedlings (Breaux et al, 1986b).…”

“…In this case it was found that the GSH conjugate of 2,4-dinitrochlorobenzene prevented the normal feedback inhibition of glutamylcysteine synthetase caused by GSH. We have recently reported that flurazole forms a GSH conjugate in corn and sorghum (Breaux, 1986b). It is possible that the GSH conjugate may interfere with GSH feedback regulation in safened seedlings.…”