Time-of-flight accurate mass spectrometry identification of quinoline alkaloids in honey

Odorant receptors for floral- and plant-derived volatiles in the yellow fever mosquito, Aedes aegypti (Diptera: Culicidae)

Adult mosquitoes require regular sugar meals, including nectar, to survive in natural habitats. Both males and females locate potential sugar sources using sensory proteins called odorant receptors (ORs) activated by plant volatiles to orient toward flowers or honeydew. The yellow fever mosquito, Aedes aegypti (Linnaeus, 1762), possesses a large gene family of ORs, many of which are likely to detect floral odors. In this study, we have uncovered ligand-receptor pairings for a suite of Aedes aegypti ORs using a panel of environmentally relevant, plant-derived volatile chemicals and a heterologous expression system. Our results support the hypothesis that these odors mediate sensory responses to floral odors in the mosquito's central nervous system, thereby influencing appetitive or aversive behaviors. Further, these ORs are well conserved in other mosquitoes, suggesting they function similarly in diverse species. This information can be used to assess mosquito foraging behavior and develop novel control strategies, especially those that incorporate mosquito bait-and-kill technologies.

Odorant receptors for floral- and plant-derived volatiles in the yellow fever mosquito, Aedes aegypti (Diptera: Culicidae)

Adult mosquitoes require regular sugar meals, usually floral nectar, to survive and flourish in natural habitats. Both males and females locate potential sugar sources using sensory proteins called odorant receptors activated by plant volatiles that facilitate orientation toward flowers or honeydew. The Yellow Fever mosquito, Aedes aegypti (Linnaeus, 1762), possesses a large repertoire of odorant receptors, many of which are likely to support floral odor detection and nectar-seeking. In this study, we have employed a heterologous expression system and the two-electrode voltage clamping technique to identify environmentally relevant chemical compounds that activate specific odorant receptors. Importantly, we have uncovered ligand-receptor pairings for a suite of Aedes aegypti odorant receptors likely to mediate appetitive or aversive behavioral responses, thus shaping a critical aspect of the life history of a medically important mosquito. Moreover, the high degree of conservation of these receptors in other disease-transmitting species suggests common mechanisms of floral odor detection. This knowledge can be used to further investigate mosquito foraging behavior to either enhance existing, or develop novel, control strategies, especially those that incorporate mosquito bait-and-kill or attractive toxic sugar bait technologies.

Time resolved growth of (N)-polycyclic aromatic hydrocarbons in engine deposits uncovered with OrbiSIMS depth profiling

Insoluble carbonaceous deposits were grown in internal combustion engine components and interrogated by OrbiSIMS depth profiling, and we uncovered the composition and proposed time resolved growth mechanisms of these materials.

Comprehensive tropane alkaloids analysis and retrospective screening of contaminants in honey samples using liquid chromatography-high resolution mass spectrometry (Orbitrap)

A wide-scope analytical method was developed and validated for the determination of tropane alkaloids (TAs) in honey samples. A simple and fast extraction procedure, using a mixture of methanol/water/formic acid (75/25/0.4, v/v/v) as extraction solvent, followed by a clean-up with graphitized black carbon (GBC) and magnesium sulphate was optimized, and compounds were analysed by liquid chromatography coupled to high resolution mass spectrometry (LC-HRMS-Orbitrap). Validation of the proposed method provided adequate linearity (R² > 0.99), trueness (recoveries 71-120%) and precision (relative standard deviation, RSD ≤ 20.1%), with limits of quantitation (LOQs) at 20 µg/kg (except anisodamine and scopolamine at 40 µg/kg) and a significant matrix effect (≤-50%). Nineteen honey samples were analysed, but only one was positive, containing 27 µg/kg of scopolamine. Additionally, a post-targeted screening was performed, and 47% of samples were contaminated with different herbicides, insecticides and veterinary drugs. Therefore, the proposed analytical method is a powerful tool for both targeted TAs and post-targeted contaminant analyses.

VUV Dissociative Photoionization of Quinoline in the 7–26 eV Photon Energy Range

The dissociative photoionization of quinoline was studied by photoionization mass spectrometry and ion yield measurements over a synchrotron photon excitation energy range 7–26 eV. The ionic and neutral products were identified with the aid of thermochemical calculations that, in some cases, led to deeper understanding of photodissociation pathways and the determination of upper limits of heats of formation of ionic and neutral dissociation products. A detailed comparison between the 20 eV photon excitation and 70 eV electron impact mass spectra, coupled with estimation of thermochemical appearance energies, leads to assignment of the dissociative ionization cation and neutral products for each detected ion. Reaction schemes for formation of these products are proposed in a number of cases. Ion intensities in the photon and electron impact mass spectra were used to consider extending a rule of charge retention in simple bond cleavage to more complex cases of dissociative ionization.