94 - De novo mass spectral data analysis of sulfur speciation in the reaction between GSNO and H2S: A sulfomic study using a Kendrick mass deficient approach

Abstract

An efficient method for mass spectral data analyses and visualization of sulfur speciation in the reaction between S- nitroso glutathione (GSNO) and hydrogen sulfide (H2S) based on Kendrick mass defect (KMD) methodology is described. KMD is defined as the difference in exact mass and Kendrick mass of any species detected by the mass spectrometry study. GSNO + H2S → GSSxG + GSSx H + GSNSxH2 + GSSxOH + GSSxO3H + HSxOyH The mass spectral data of modified terminal thiol in glutathione, containing persulfane and polysulfides and as well small oxoacids of sulfur products, generated in the reaction between GSNO and H2S recorded using Orbitrap high resolution liquid chromatography (LC/MS) were used to perform the KMD analysis. The traditional KMD method utilizing the mass scale of the methylene unit (CH2) set to 14.000 u for rapid graphical identification of members of a homologous series for species like GSSxG, GSSH, GSNSxH, GSSxOH and GSSxO3H produced a cumbersome plot for visual recognition. We present here an effective methodology for mass spectral data visualization by simply substituting the mass scale of methylene unit to sulfur (32 u) in Kendrick mass significantly enhancing the graphical representation of the S- modified glutathione and SOS species. The broad applicability of this new method is demonstrated by a range electrophilic and nucleophilic trapping reagent like dimedone, 1-trimethylsiloxycyclohexene, monobromobimane, phenyl acetylene, t-butyl styrene, benzyl bromide, iodoacetamide, N-ethylmaleimide, 4-Chloro-7-nitrobenzofurazan, and 3-Bromo-1,1,1-trifluoroacetone in the trapping of reactive species generated in the reaction between GSNO and H2S. We also show that the inclusion of mass spectral intensity in the KMD analysis allows to quantify and differentiate concentration of species generated within and across various other homologous series.