Mass spectrometry imaging (MSI) enables the spatial distributions of molecules possessing different mass‐to‐charge ratios to be mapped within complex environments revealing regional changes at the molecular level. Even at high mass resolving power, however, these images often reflect the summed distribution of multiple isomeric molecules, each potentially possessing a unique distribution coinciding with distinct biological function(s) and metabolic origin. Herein, this chemical ambiguity is addressed through an innovative combination of ozone‐induced dissociation reactions with MSI, enabling the differential imaging of isomeric lipid molecules directly from biological tissues. For the first time, we demonstrate both double bond‐ and sn‐positional isomeric lipids exhibit distinct spatial locations within tissue. This MSI approach enables researchers to unravel local lipid molecular complexity based on both exact elemental composition and isomeric structure directly from tissues.

In most radicals the singly occupied molecular orbital (SOMO) is the highest-energy occupied molecular orbital (HOMO); however, in a small number of reported compounds this is not the case. In the present work we expand significantly the scope of this phenomenon, known as SOMO-HOMO energy-level conversion, by showing that it occurs in virtually any distonic radical anion that contains a sufficiently stabilized radical (aminoxyl, peroxyl, aminyl) non-π-conjugated with a negative charge (carboxylate, phosphate, sulfate). Moreover, regular orbital order is restored on protonation of the anionic fragment, and hence the orbital configuration can be switched by pH. Most importantly, our theoretical and experimental results reveal a dramatically higher radical stability and proton acidity of such distonic radical anions. Changing radical stability by 3-4 orders of magnitude using pH-induced orbital conversion opens a variety of attractive industrial applications, including pH-switchable nitroxide-mediated polymerization, and it might be exploited in nature. AbstractIn most radicals the singly-occupied molecular orbital (SOMO) is the highest-energy occupied one

The modulation of dopamine release by presynaptic nicotinic receptors in vitro is well established, but the significance of this effect in vivo is unclear. We have characterised the effect of nicotine, locally applied via a microdialysis probe, on dopamine release from the terminal regions of three ascending dopaminergic pathways in conscious, freely moving rats. Nicotine caused a dose-dependent increase in dopamine release in the striatum, the nucleus accumbens, and, to a lesser extent, the frontal cortex. Metabolite levels were unaltered by any concentration of nicotine. Prior administration of mecamylamine via the probe abolished the nicotineevoked increase in dopamine release, confirming the mediation of nicotinic receptors. The dose dependence of mecamylamine-sensitive, nicotine-evoked dopamine release was similar in all three brain regions. However, io-M tetrodotoxin totally blocked nicotine-stimulated dopamine release in the striatum and the accumbens but not the cortex. Daily subcutaneous injections of nicotine (0.4 mg kg 1 for 7 days) increased the response to a subsequent local application of nicotine in the striatum, and a similar trend was found in the other brain areas. The same daily dose of nicotine given as a continuous infusion had no effect, whereas infusion of 4mg kg1 day1 increased the response to a subsequent nicotine challenge. The localisation and regulation of nicotinic receptors in the terminal fields of dopaminergic pathways are discussed.

Highlights d FADS2 promiscuity yields unreported families of fatty acids (i.e., n-8, n-10, and n-12) d n-5 and n-13 fatty acids indicate apocryphal activities of SCD-1 and FADS1 d Unusual fatty acids display selective incorporation into phospholipid subclasses d Distinctive enzyme-substrate interactions revealed in tumor tissue regions