Laurent Bigler

Steroid hormones and their metabolites orchestrate female reproductive physiology. Key analytes such as 17β-estradiol and progesterone are integral to standard clinical practice worldwide. For more advanced endocrine monitoring of female reproduction, current analytical approaches lack automated throughput, broad metabolite coverage, and sufficient sensitivity. Herein, we present an ultrahigh-performance liquid chromatography coupled with high-resolution mass spectrometry (UHPLC-HRMS) workflow that targets 56 selected steroids (estrogens, progestogens, androgens, glucocorticoids, and steroid conjugates) and 5 prostaglandin metabolites for quantitative profiling using 250 μL of plasma within a single pipeline. The workflow integrates optimized, automated protein precipitation-enhanced solid-phase extraction and two complementary chromatographic separations with tailored eluent additives and ionization modes to accommodate the chemical diversity of the broad target panel. A full method validation demonstrated excellent performance, with low limits of quantification (5–200 pg/mL) determined in charcoal-stripped plasma as a surrogate matrix. The workflow was applied to authentic cattle (n = 5) and human (n = 18) plasma samples from males and, particularly, females across the female reproductive cycle and selected pregnancy stages. Both well-established endocrine hormones and their metabolites, as well as analytes whose roles in reproduction remain insufficiently characterized, were among the 42 and 48 targets detected in cattle and human samples, respectively. Compound-specific, valley-split, and composite quantification were reported separately. This demonstrates extensive target coverage and robust quantitative performance across biological matrices with distinct physiological contexts. The workflow thus offers a robust tool for steroidomic studies and enables broad-spectrum monitoring of endocrine dynamics for basic, translational, and clinical research.

Open‐shell molecular graphene fragments represent versatile synthons of graphene‐based carbon nanostructures because of their ability to undergo multi‐step π‐radical cascades that enable the formation of multiple bonds and rings in a single step. However, the use of graphene‐based π‐radicals in synthesis remains limited due to our incomplete understanding of their reactivity. This limitation primarily arises from the inherent difficulty of controlling reactions involving multiple reactive centers, as is the case with π‐delocalized radicals. To address this challenge and advance research on π‐radical reactivity, we establish reaction control in a system that can formally feature multiple unpaired π‐electrons. Specifically, we examine oxidative peri ‐fusion of the dihydro‐precursor of the prototypic non‐Kekulé hydrocarbon triangulene. By investigating the reactive intermediates that dictate selectivity, we demonstrate that monoradical, rather than diradical, intermediates play a key role. Through the precise placement of steric bulk around the periphery, we modulate reactivity at specific positions, steering selectivity toward doubly or singly peri ‐fused dimeric products. Our study demonstrates that, when controlled, the reactivity of open‐shell molecular graphene fragments can serve as a step‐economic and synthetically valuable tool.

Open‐shell molecular graphene fragments represent versatile synthons of graphene‐based carbon nanostructures because of their ability to undergo multi‐step π‐radical cascades that enable the formation of multiple bonds and rings in a single step. However, the use of graphene‐based π‐radicals in synthesis remains limited due to our incomplete understanding of their reactivity. This limitation primarily arises from the inherent difficulty of controlling reactions involving multiple reactive centers, as is the case with π‐delocalized radicals. To address this challenge and advance research on π‐radical reactivity, we establish reaction control in a system that can formally feature multiple unpaired π‐electrons. Specifically, we examine oxidative peri ‐fusion of the dihydro‐precursor of the prototypic non‐Kekulé hydrocarbon triangulene. By investigating the reactive intermediates that dictate selectivity, we demonstrate that monoradical, rather than diradical, intermediates play a key role. Through the precise placement of steric bulk around the periphery, we modulate reactivity at specific positions, steering selectivity toward doubly or singly peri ‐fused dimeric products. Our study demonstrates that, when controlled, the reactivity of open‐shell molecular graphene fragments can serve as a step‐economic and synthetically valuable tool.

The symbiotic interaction between rhizobia and host plants takes place inside root nodules. Besides reducing atmospheric nitrogen into ammonium, which is then used by the plant to grow in nitrogen-deficient soils, certain rhizobia produce siderophores which enable iron uptake from the soil. Siderophores are strong iron chelators due to their hydroxamate, catecholate or carboxylate functional groups. In this work, the siderophores of the beta-rhizobial genus Paraburkholderia were analyzed by ultra-high-performance liquid chromatography (UHPLC) coupled to high-resolution mass spectrometry (HRMS). In particular, the production of the novel siderophore phymabactin by Paraburkholderia phymatum was confirmed and the structures of eleven derivatives were elucidated by tandem mass spectrometry (MS/MS) and nuclear magnetic resonance (NMR) spectroscopy. Phymabactins, consisting of a linear tetrapeptide backbone with hydroxamate and hydroxy-carboxylate groups, are structurally closely related to an already described family of siderophores called ornibactins. The acyl chain found in phymabactin derivatives is made up of eight, ten or twelve carbon atoms, contrarily to the more hydrophilic ornibactin derivatives with shorter acyl chains. Interestingly, spontaneous metal complexation of phymabactin derivatives with aluminum was observed. To explore this complexation in more detail, the collision cross sections (CCS) of phymabactins, ornibactins and corresponding metal complexes were determined by trapped ion mobility spectrometry. The CCS values of aluminum-phymabactin complexes were smaller than those of iron-phymabactin complexes, while an inverse relationship was observed for ornibactin complexes. In summary, this study discloses the molecular structures of phymabactins and investigates their metal complex formation.

Open-shell molecular graphene fragments represent versatile synthons of graphene-based carbon nanostructures, because of their ability to undergo multi-step π-radical cascades that enable the formation of multiple bonds and rings in a single step. However, the use of graphene-based π-radicals in synthesis remains limited due to our incomplete understanding of their reactivity. This limitation primarily arises from the inherent difficulty of controlling reactions involving multiple reactive centers, as is the case of π-delocalized radicals. To address this challenge and advance research on π-radical reactivity, we establish reaction control in a system that can formally feature multiple unpaired π-electrons. Specifically, we examine oxidative peri-fusion of the dihydro-precursor of the prototypic non-Kekulé hydrocarbon triangulene. By investigating the reactive intermediates that dictate selectivity, we demonstrate that monoradical, rather than diradical, intermediates play a key role. Through the precise placement of steric bulk around the periphery, we modulate reactivity at specific positions, steering selectivity toward doubly or singly peri-fused dimeric products. Our study demonstrates that, when controlled, the reactivity of open-shell molecular graphene fragments can serve as a step-economic and synthetically valuable tool.

Beneficial interactions between nitrogen-fixing soil bacteria and legumes offer a solution to increase crop yield on Earth and potentially in future Martian colonies. Paraburkholderia phymatum is a nitrogen-fixing beta-rhizobium, which enters symbiosis with more than 50 legumes and can survive in acidic or aluminium-rich soils. In a previous RNA-sequencing study, we showed that the beta-rhizobium P. phymatum grows well in simulated microgravity and identified phymabactin as the only siderophore produced by this strain. Here, the growth of the beta-rhizobium P. phymatum was assessed in Martian simulant soil using Enhanced Mojave Mars Simulant 2 (MMS-2), which contains a high amount of iron (18.4 percent by weight) and aluminium (13.1 percent by weight). While P. phymatum wild-type’s growth was not affected by exposure to MMS-2, a mutant strain impaired in siderophore biosynthesis (ΔphmJK) grew less than P. phymatum wild-type on gradient plates in the presence of a high concentration of MMS-2 or aluminium. This result suggests that the P. phymatum siderophore phymabactin alleviates aluminium-induced heavy metal stress. Ultra-high performance liquid chromatography–mass spectrometry (UHPLC-MS) showed that phymabactin can bind to aluminium more efficiently than iron. These results not only deepen our understanding of the behaviour of rhizobia in simulated extraterrestrial environments but also provide new insights into the potential use of P. phymatum for bioremediation of aluminium-rich soils and the multiple roles of the siderophore phymabactin.

Beneficial interactions between nitrogen-fixing soil bacteria and legumes offer a solution to increase crop yield on Earth and potentially in future Martian colonies. In this study, we assessed the growth of the beta rhizobium Paraburkholderia phymatum in Martian simulant soil using Enhanced Mojave Mars Simulant 2 (MMS-2) that contains a high amount of iron (18.37 percent by weight) and aluminium (13.07 percent by weight). We observed that while P. phymatum wild-type’s growth was not affected by exposure to MMS-2, a mutant strain impaired in siderophore biosynthesis (ΔphmJK) grew less than P. phymatum wild-type on gradient plates prepared with increasing proportions of MMS-2 or aluminium concentration. This result suggests that the P. phymatum siderophore phymabactin alleviates aluminium-induced heavy metal stress. Using Ultra-high performance liquid chromatography-mass spectrometry (UHPLC MS), we showed that phymabactin can bind to aluminium more efficiently than iron. These results not only deepen our understanding of the behaviour of rhizobia in simulated extraterrestrial environments but also provide new insights into the potential use of P. phymatum for bioremediation and the multiple roles of the siderophore phymabactin.