Strategies for gathering structural information on unknown peaks in the GC/MS analysis of Corynebacterium glutamicum cell extracts

Abstract

A comprehensive analysis of low molecular weight compounds in biological samples by the hyphenated method of GC/MS in general detects a large number of peaks which can not be identified by searching of commercially available mass spectral libraries. Therefore, more information is required for a successful identification of these compounds. Some structural features like molecular weight and number of derivatization groups present in the molecule can be determined by variation of the derivatization prior to GC/MS. The use of deuterated derivatizing reagents and the newly developed N-methyl-N-ethyldimethylsilyl-trifluoracetamide for this purpose is described. The knowledge of these structural properties alone undoubtedly will not lead to the structure elucidation of novel metabolites. However, it may be helpful in identifying derivatives of known metabolites or artifacts. Thus, by use of the molecular weight as search criterion it is possible to find plausible candidates in metabolic pathway databases. It is shown that the application of this method to a hydrophilic extract of C. glutamicum lead to the identification of 31 in previous analyses unidentified peaks, in their majority representing minor derivatives of common metabolites.

Mass spectral fragmentation of trimethylsilylated small molecules

“…Reducing sugars (such as maltose) have one monosaccharide with an open aldehyde group which can be distinguished from non‐reducing sugars (such as sucrose) by forming methoxyamine syn ‐ and anti ‐isomeric derivatives (Fiehn, ). Hence, the presence of aldehydes in these reducing sugars can be tested by using ethoxyamine hydrochloride in contrast to methoxyamine hydrochloride reagent, which leads to a slight retention time shift and an increase of 14 mass units (Herebian, Hanisch, & Marner, ; Fiehn, ; Huang & Regnier, ). Another function of sugar MO‐TMS derivatives is the specificity of their syn / anti isomer ratios.…”

In‐depth gas chromatography/tandem mass spectrometry fragmentation analysis of formestane and evaluation of mass spectral discrimination of isomeric 3‐keto‐4‐ene hydroxy steroids

“…With the use of labelled derivatization agents such as N,O ‐bis(trimethyl‐[ 2 H 9 ]‐silyl)acetamide ([ 2 H 18 ]‐BSA) 10–12 or [ 2 H 9 ]‐MSTFA 13–15 the structure and origin of diagnostically important (TMS) fragment ions can be further elucidated in gas chromatography/(tandem) mass spectrometry (GC/MS(/MS)) analysis. Combined with H 2 18 O for selective labelling of oxo functions and modern high‐resolution mass spectrometers, a better understanding of fragmentation behavior can be expected.…”

Metabolite Variation between Nematode and Bacterial Seed Galls in Comparison to Healthy Seeds of Ryegrass Using Direct Immersion Solid-Phase Microextraction (DI-SPME) Coupled with GC-MS

“…Fatty acids play an important role in bacterial lipid membranes, and it has previously been reported that the presence of C-15 saturated branched chain acid, pentadecanoic acid, C-17 saturated branched chain acids and normal saturated fatty acids, such as lauric, myristic, stearic and arachidic, are major components of cell membranes in Rathayibacter species. [ 34 , 35 , 36 ]. Here, the closely related fatty acids tetradecanoic acid (myristic), hexadecenoic acid, and hexacosanoic acid were identified in bacterial galls.…”