Knowing concentrations of lipids is essential for understanding their physiological functions and discovering new disease biomarkers. However, it is highly challenging to accurately quantify lipids due to structural diversity and multiple isomeric forms of lipids.To address these critical gaps, we have developed a novel aziridine-based isobaric tag labelling strategy that allows (i) determination of lipid double-bond positional isomers, (ii) accurate relative quantification of unsaturated lipids, and (iii) improvement of ionization efficiencies of nonpolar lipids. The power of this method is demonstrated in characterization and quantification of various categories of lipids such as fatty acids, phosphoglycerol lipids, cholesteryl esters (CE), and glycerides. 17 CE lipid isomers were identified and quantified simultaneously from Alzheimer's disease (AD) mouse serum without using lipid standards. Among them, 6 CE isomers showed significant changes in concentrations in AD serum.

Development of new transition-metal-catalyzed electrochemistry promises to improve overall synthetic efficiency.Here, we describe the first integrated platform for online screening of electrochemical transition-metal catalysis. It utilizes the intrinsic electrochemical capabilities of nanoelectrospray ionization mass spectrometry (nano-ESI-MS) and picomole-scale anodic corrosion of a Pd electrode to generate and evaluate highly efficient cationic catalysts for mild electrocatalysis. We demonstrate the power of the novel electrocatalysis platform by (1) identifying electrolytic Pdcatalyzed Suzuki coupling at room temperature, (2) discovering Pd-catalyzed electrochemical C−H arylation in the absence of external oxidant or additive, (3) developing electrolyzed Suzuki coupling/C−H arylation cascades, and (4) achieving late-stage functionalization of two drug molecules by the newly developed mild electrocatalytic C−H arylation. More importantly, the scale-up reactions confirm that new electrochemical pathways discovered by nano-ESI can be implemented under the conventional electrolytic reaction conditions. This approach enables in situ mechanistic studies by capturing various intermediates including transient transition metal species by MS, and thus uncovering the critical role of anodically generated cationic Pd catalyst in promoting otherwise sluggish transmetalation in C−H arylation. The anodically generated cationic Pd with superior catalytic efficiency and novel online electrochemical screening platform hold great potential for discovering mild transition-metal-catalyzed reactions.

Researchers have emphasized the detrimental effects of COVID-19 on mental health, but less attention has been given to personal strengths promoting resilience during the pandemic. One strength might be gratitude, which supports wellbeing amidst adversity. A two-wave examination of 201 college students revealed anxiety symptom severity increased to a lesser extent from pre-COVID (January–March 2020) to onset-COVID (April 2020) among those who reported greater pre-COVID gratitude. A similar trend appeared for depression symptom severity. Gratitude was also correlated with less negative changes in outlook, greater positive changes in outlook, and endorsement of positive experiences resulting from COVID-19. Thematic analysis showed “strengthened interpersonal connections” and “more time” were the most commonly reported positive experiences. Overall findings suggest gratitude lessened mental health difficulties and fostered positivity at the onset of the pandemic, but more research is needed to determine whether gratitude and other strengths promote resilience as COVID-19 continues.

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Extracellular vesicles (EVs) convey information used in cell‐to‐cell interactions. Lipid analysis of EVs remains challenging because of small sample amounts available. Lipid discovery using traditional mass spectrometry platforms based on liquid chromatography and high mass resolution typically employs milligram sample amounts. We report a simple workflow for lipid profiling of EVs based on multiple reaction monitoring (MRM) profiling that uses microgram amounts of sample. After liquid–liquid extraction, individual EV samples were injected directly into the electrospray ionization (ESI) ion source at low flow rates (10 μl/min) and screened for 197 MRM transitions chosen to be a characteristic of several classes of lipids. This choice was based on a discovery experiment, which applied 1,419 MRMs associated with multiple lipid classes to a representative pooled sample. EVs isolated from 12 samples of human lymphocytes and 16 replicates from six different rat cells lines contained an estimated amount of total lipids of 326 to 805 μg. Samples showed profiles that included phosphatidylcholine (PC), sphingomyelin (SM), cholesteryl ester (CE), and ceramide (Cer) lipids, as well as acylcarnitines. The lipid profiles of human lymphocyte EVs were distinguishable using principal component and cluster analysis in terms of prior antibody and drug exposure. Lipid profiles of rat cell lines EV's were distinguishable by their tissue of origin.

Despite the versatility of semiconductor nanocrystals (NCs) in photoinduced chemical processes, the generation of stable radicals has been more challenging due to reverse charge transfer or charge recombination even in the presence of sacrificial charge acceptors. Here, we show that cesium lead halide (CsPbX3) NCs can selectively photogenerate either aminium or aminyl radicals from amines, taking advantage of the controllable imbalance of the electron and hole populations achieved by varying the solvent composition. Using dihalomethane as the solvent, irreversible removal of the electrons from CsPbX3 NCs enabled by the photoinduced halide exchange between the NCs and the dihalomethane resulted in efficient oxidative generation of the aminium radical. In the absence of dihalomethane in solvent, the availability of both electrons and holes resulted in the production of an aminyl radical via sequential hole transfer and reductive N–H bond dissociation. The negative charge of the halide ions on the NC’s lattice surface appears to facilitate the aminyl radical production, competing favorably with the reversible charge transfer reverting to the reactant.

Knowing concentrations of lipids is essential for understanding their physiological functions and discovering new disease biomarkers. However, it is highly challenging to accurately quantify lipids due to structural diversity and multiple isomeric forms of lipids. To address these critical gaps, we have developed a novel aziridine‐based isobaric tag labelling strategy that allows (i) determination of lipid double‐bond positional isomers, (ii) accurate relative quantification of unsaturated lipids, and (iii) improvement of ionization efficiencies of nonpolar lipids. The power of this method is demonstrated in characterization and quantification of various categories of lipids such as fatty acids, phosphoglycerol lipids, cholesteryl esters (CE), and glycerides. 17 CE lipid isomers were identified and quantified simultaneously from Alzheimer's disease (AD) mouse serum without using lipid standards. Among them, 6 CE isomers showed significant changes in concentrations in AD serum.

Characterization of nonpolar lipids is of significance, as they serve a variety of key biological functions and can naturally exist in isomeric forms. Electrospray ionization mass spectrometry (ESI-MS) is a powerful tool for most lipid analysis, but nonpolar lipids do not easily ionize in electrospray, complicating their analyses. In this work, we use the Du Bois catalyst (Rh2(esp)2) for aziridina-tion of carbon-carbon double bonds (C=C bond) of six nonpolar sterol lipids, simultaneously increasing ionization efficiency of nonpolar lipids and facilitating C=C bond identification. The incorporation of nitrogen expands the lipid categories detected by MS, and higher-energy C-trap dissociation of the aziridines generates diagnostic ions that can be used to locate C=C bond positions.