Comprehensive two-dimensional gas chromatography–mass spectrometry
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Elucidating reactive sugar-intermediates by mass spectrometry
The stereoselective introduction of glycosidic bonds is one of the greatest challenges in carbohydrate chemistry. A key aspect of controlling glycan synthesis is the glycosylation reaction in which the glycosidic linkages are formed. The outcome is governed by a reactive sugar intermediate – the glycosyl cation. Glycosyl cations are highly unstable and short-lived, making them difficult to study using established analytical tools. However, mass-spectrometry-based techniques are perfectly suited to unravel the structure of glycosyl cations in the gas phase. The main approach involves isolating the reactive intermediate, free from external influences such as solvents and promoters. Isolation of the cations allows examining their structure by integrating orthogonal spectrometric and spectroscopic technologies. In this perspective, recent achievements in gas-phase research on glycosyl cations are highlighted. It provides an overview of the spectroscopic techniques used to probe the glycosyl cations and methods for interpreting their spectra. The connections between gas-phase data and mechanisms in solution synthesis are explored, given that glycosylation reactions are typically performed in solution.
Acoustic impedance-based surface acoustic wave chip for gas leak detection and respiratory monitoring
Acoustic impedance enables many interesting acoustic applications. However, acoustic impedance for gas sensing is rare and difficult. Here we introduce a micro-nano surface acoustic wave (SAW) chip based on the acoustic impedance effect to achieve ultra-fast and wide-range gas sensing. We theoretically established the relationship between surface load acoustic impedance and SAW attenuation, and analyzed the influence of acoustic impedance on acoustic propagation loss under different gas/humidity media. Experimental measurements reveal that the differences in acoustic impedance generated by different gases trigger different acoustic attenuation, and can achieve wide-range (0–100 v/v%) gas monitoring, with ultra-fast response and recovery speeds reaching sub-second levels (t90 < 1 s, t10 < 0.5 s) and detection limit of ~1 v/v%. This capability can also be perfectly utilized for human respiratory monitoring, accurately reflecting respiratory status, frequency, and intensity. Consequently, the SAW chip based on the acoustic impedance effect provides a new solution for in-situ detection of gas leaks and precise monitoring of human respiration.
Direct air capture of CO2 for solar fuel production in flow
Direct air capture is an emerging technology to decrease atmospheric CO2 levels, but it is currently costly and the long-term consequences of CO2 storage are uncertain. An alternative approach is to utilize atmospheric CO2 on-site to produce value-added renewable fuels, but current CO2 utilization technologies predominantly require a concentrated CO2 feed or high temperature. Here we report a gas-phase dual-bed direct air carbon capture and utilization flow reactor that produces syngas (CO + H2) through on-site utilization of air-captured CO2 using light without requiring high temperature or pressure. The reactor consists of a bed of solid silica-amine adsorbent to capture aerobic CO2 and produce CO2-free air; concentrated light is used to release the captured CO2 and convert it to syngas over a bed of a silica/alumina-titania-cobalt bis(terpyridine) molecular–semiconductor photocatalyst. We use the oxidation of depolymerized poly(ethylene terephthalate) plastics as the counter-reaction. We envision this technology to operate in a diurnal fashion where CO2 is captured during night-time and converted to syngas under concentrated sunlight during the day.
Power price stability and the insurance value of renewable technologies
To understand if renewables stabilize or destabilize electricity prices, we simulate European power markets as projected by the National Energy and Climate Plans for 2030 but replicating the historical variability in electricity demand, the prices of fossil fuels and weather. We propose a β-sensitivity metric, defined as the projected increase in the average annual price of electricity when the price of natural gas increases by 1 euro. We show that annual power prices spikes would be more moderate because the β-sensitivity would fall from 1.4 euros to 1 euro. Deployment of solar photovoltaic and wind technologies exceeding 30% of the 2030 target would lower it further, below 0.5 euros. Our framework shows that this stabilization of prices would produce social welfare gains, that is, we find an insurance value of renewables. Because market mechanisms do not internalize this value, we argue that it should be explicitly considered in energy policy decisions.
Kdm2a inhibition in skeletal muscle improves metabolic flexibility in obesity
Skeletal muscle is a critical organ in maintaining homoeostasis against metabolic stress, and histone post-translational modifications are pivotal in those processes. However, the intricate nature of histone methylation in skeletal muscle and its impact on metabolic homoeostasis have yet to be elucidated. Here, we report that mitochondria-rich slow-twitch myofibers are characterized by significantly higher levels of H3K36me2 along with repressed expression of Kdm2a, an enzyme that specifically catalyses H3K36me2 demethylation. Deletion or inhibition of Kdm2a shifts fuel use from glucose under cold challenge to lipids under obese conditions by increasing the proportion of mitochondria-rich slow-twitch myofibers. This protects mice against cold insults and high-fat-diet-induced obesity and insulin resistance. Mechanistically, Kdm2a deficiency leads to a marked increase in H3K36me2 levels, which then promotes the recruitment of Mrg15 to the Esrrg locus to process its precursor messenger RNA splicing, thereby reshaping skeletal muscle metabolic profiles to induce slow-twitch myofiber transition. Collectively, our data support the role of Kdm2a as a viable target against metabolic stress.
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