High-Pressure Ozone-Induced Dissociation for Lipid Structure Elucidation on Fast Chromatographic Timescales.

Ozone-induced dissociation (OzID) is a novel ion activation technology that exploits the gas-phase reaction between mass-selected ions and ozone inside a mass spectrometer to assign sites of unsaturation in complex lipids. Since it was first demonstrated [ Thomas et al. Anal. Chem. 2008 , 80 , 303 ], the method has been widely deployed for targeted lipid structure elucidation but its application to high throughput and liquid chromatography-based workflows has been limited due to the relatively slow nature of the requisite ion-molecule reactions that result in long ion-trapping times and consequently low instrument duty cycle. Here, the implementation of OzID in a high-pressure region, the ion-mobility spectrometry cell, of a contemporary quadrupole time-of-flight mass spectrometer is described. In this configuration, a high number density of ozone was achieved and thus abundant and diagnostic OzID product ions could be observed even on the timescale of transmission through the reaction region (ca. 20-200 ms), representing a 50-1000-fold improvement in performance over prior OzID implementations. Collisional activation applied prereaction was found to yield complementary and structurally informative product ions arising from ozone- and collision-induced dissociation. Ultimately, the compatibility of this implementation with contemporary ultrahigh performance liquid chromatography is demonstrated with the resulting hyphenated approach showing the ability to separate and uniquely identify isomeric phosphatidylcholines that differ only in their position(s) of unsaturation.

Functional characterisation of a SNP in the ABCC11 allele - effects on axillary skin metabolism, odour generation and associated behaviours.

BACKGROUND: A single nucleotide polymorphism (SNP), 538G→A, leading to a G180R substitution in the ABCC11 gene results in reduced concentrations of apocrine derived axillary odour precursors. OBJECTIVE: Determine the axillary odour levels in the SNP ABCC11 genotype variants and to investigate if other parameters associated with odour production are affected. METHODS: Axillary odour was assessed by subjective quantification and gas chromatography headspace analysis. Metabolite profiles, microbiome diversity and personal hygiene habits were also assessed. RESULTS: Axillary odour in the A/A homozygotes was significantly lower compared to the G/A and G/G genotypes. However, the perception-based measures still detected appreciable levels of axillary odour in the A/A subjects. Metabolomic analysis highlighted significant differences in axillary skin metabolites between A/A subjects compared to those carrying the G allele. These differences resulted in A/A subjects lacking specific volatile odourants in the axillary headspace, but all genotypes produced odoriferous short chain fatty acids. Microbiomic analysis revealed differences in the relative abundance of key bacterial genera associated with odour generation between the different genotypes. Deodorant usage indicated a high level of self awareness of axillary odour levels with A/A individuals less likely to adopt personal hygiene habits designed to eradicate/mask its presence. CONCLUSIONS: The SNP in the ABCC11 gene results in lower levels of axillary odour in the A/A homozygotes compared to those carrying the G allele, but A/A subjects still produce noticeable amounts of axillary odour. Differences in axillary skin metabolites, bacterial genera and personal hygiene behaviours also appear to be influenced by this SNP.

Analysis of androgenic steroid Girard P hydrazones using multistage tandem mass spectrometry.

Seven androgenic steroids have been converted into steroid hydrazones using Girard P hydrazine and analysed by electrospray ionisation multistage tandem mass spectrometry. The cationic derivatives 17alpha-testosterone hydrazone, 17beta-nortestosterone hydrazone, 17beta-bolasterone hydrazone, 17alpha-boldenone hydrazone, 17beta-fluoxymesterone hydrazone, 17alpha-trenbolone hydrazone and 4-chloroandrosten-3,17-dione hydrazone show good response in positive ion mode with enhancements for the method of up to 33 times relative to the native species. Detailed characterisation of fragmentation pathways reveals structurally specific ions formed by fragmentation of the hydrazine moiety. Comparison of structural similarities among the androgenic steroids allows recognition of common ions/fragmentation processes as well as analyte-specific transitions. The suitability of the derivatisation approach in the screening of heifer urine for the presence of administered hormones has been demonstrated using partially purified urine spiked with a mixture of androgenic steroids.