Comprehensive Omics Profiling for Volatiles and Uncommon Fatty Acids: from Bees to Microbes

Gas Chromatography Mass Spectrometry (GC-MS) has held a constant ratio of annually published metabolomics articles. A steady increase in the number of metabolomic reports for LC-MS was accompanied by a decrease of NMR-based metabolic phenotyping over the past 10 years. What is the reason for this success in GC-MS?

First, GC can analyze both compounds that are volatile at room temperature, in addition to those that remain stable up to their boiling point. While classic volatiles such as terpenes continue to be the exclusive domain of GC-MS, a surprisingly high number of compounds show high thermal stability to be analyzed by this technique without any additional derivatization. UC Davis continues its use of GC-TOF MS for profiling primary metabolism with two-step derivatizations, now with the latest innovation, the Pegasus BTX instrument. However, we have also expanded our portfolio by measuring a range of volatiles that can be broadly classified into room-temperature volatiles (requiring trapping techniques) and volatiles that have higher boiling points than hexane (enabling liquid injections).

Here, we focus on an additional advantage of GC-techniques over LC-MS, the superior total chromatographic resolution owed to the total number of theoretical plates (either with or without 2D separations). With very long columns, a large number of isomers can be separated prior to MS detection. For example, human gut microbes have the ability to produce a vast array of uncommon lipids, from sulfonolipids and FAHFAs to cyclopropane-containing fatty acids. These compounds have identical formulas to isomers, requiring 60 m columns to distinguish complex mixtures in human diet studies such as with almonds. Secondly, we will showcase how LECO’s benchtop GC-TOF MS instrument enables studying the social interactions within the honeybee hives, distinguishing chemical signaling panels between queens, drones, nurses and foragers. As many of these types of compounds cannot be ionized by electrospray ionization, GC-MS techniques are here to stay, and thriving in the analysis of complex mixtures!

Presenter: Oliver Fiehn (University of California, Davis)