Rationale
The development of miniaturized and field portable mass spectrometers could not succeed without a simple, compact, and robust ionization source. Here we present a voltage‐free ionization ...method, Vibrating Sharp‐edge Spray Ionization (VSSI), which can generate a spray of liquid samples using only one standard microscope glass slide to which a piezoelectric transducer is attached. Compared with existing ambient ionization methods, VSSI eliminates the need for a high electric field (~5000 V·cm−1) for spray generation, while sharing a similar level of simplicity and flexibility with the simplest direct ionization techniques currently available such as paper spray ionization (PSI) and other solid substrate‐based electrospray ionization methods.
Methods
The VSSI device was fabricated by attaching a piezoelectric transducer onto a standard glass microscope slide using epoxy glue. Liquid sample was aerosolized by either placing a droplet onto the vibrating edge of the glass slide or touching a wet surface with the glass edge. Mass spectrometric detection was achieved by placing the VSSI device 0.5–1 cm from the inlet of the mass spectrometer (Q‐Exactive, ThermoScientific).
Results
VSSI is demonstrated to ionize a diverse array of chemical species, including small organic molecules, carbohydrates, peptides, proteins, and nucleic acids. Preliminary sensitivity experiments show that high‐quality mass spectra of acetaminophen can be obtained by consuming 100 femtomoles of the target. The dual spray of VSSI was also demonstrated by performing in‐droplet denaturation of ubiquitin. Finally, due to the voltage‐free nature and the direct‐contact working mode of VSSI, it has been successfully applied for the detection of chemicals directly from human fingertips.
Conclusions
Overall, we report a compact ionization method based on vibrating sharp‐edges. The simplicity and voltage‐free nature of VSSI make it an attractive option for field portable applications or analyzing biological samples that are sensitive to high voltage or difficult to access by conventional ionization methods.
The diversity of glycerophospholipid species in cellular membranes is immense and affects various biological functions. Glycerol-3-phosphate acyltransferases (GPATs) and lysophospholipid ...acyltransferases (LPLATs), in concert with phospholipase A1/2s enzymes, contribute to this diversity via selective esterification of fatty acyl chains at the sn-1 or sn-2 positions of membrane phospholipids. These enzymes are conserved across all kingdoms, and in mammals four GPATs of the 1-acylglycerol-3-phosphate O-acyltransferase (AGPAT) family and at least 14 LPLATs, either of the AGPAT or the membrane-bound O-acyltransferase (MBOAT) families, have been identified. Here we provide an overview of the biochemical and biological activities of these mammalian enzymes, including their predicted structures, involvements in human diseases, and essential physiological roles as revealed by gene-deficient mice. Recently, the nomenclature used to refer to these enzymes has generated some confusion due to the use of multiple names to refer to the same enzyme and instances of the same name being used to refer to completely different enzymes. Thus, this review proposes a more uniform LPLAT enzyme nomenclature, as well as providing an update of recent advances made in the study of LPLATs, continuing from our JBC mini review in 2009.
Omega‐3 (ω‐3) fatty acids (FAs) such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are known to have important roles in human health and disease. Besides being utilized as fuel, ω‐3 ...FAs have specific functions based on their structural characteristics. These functions include serving as ligands for several receptors, precursors of lipid mediators, and components of membrane glycerophospholipids (GPLs). Since ω‐3 FAs (especially DHA) are highly flexible, the levels of DHA in GPLs may affect membrane biophysical properties such as fluidity, flexibility, and thickness. Here, we summarize some of the cellular mechanisms for incorporating DHA into membrane GPLs and propose biological effects and functions of DHA‐containing membranes of several cell and tissue types.
More than 100 different mutations in the gene encoding copper-zinc superoxide dismutase (SOD1) cause familial forms of amyotrophic lateral sclerosis (ALS) – a fatal neurodegenerative disease in which ...aggregation of the SOD1 protein is considered to be the primary mode of pathogenesis. Recent results show that these mutations have remarkably diverse and unexpected effects on the structure, activity and native state stability of SOD1. Intriguingly, many mutations seem to have no measurable effect on the biophysical and biochemical properties of SOD1, except for decreasing the net charge of the protein. Thus, it seems likely that different ALS-associated mutations promote SOD1 aggregation by fundamentally distinct mechanisms. Understanding this complexity has implications for drug development and treatment of the disease.
Impaired perfusion indices signal potential microvascular dysfunction preceding atherosclerosis and other cardiometabolic pathologies. Post-occlusive reactive hyperemia (PORH), a vasodilatory ...response following a mechanically induced ischemia, is a transient increase in perfusion and can assess microvascular function. The greatest blood flow change corresponding to the first minute of hyperemia (represented by time-to-peak, hyperemic velocity, AUC within 1st min) has been shown to indicate microvascular dysfunction. However, the reproducibility of these temporal kinetic indices of the PORH response is unknown. Our aim was to examine the inter- and intra-day reproducibility and standardization of reactive hyperemia, with emphasis on the kinetic indices of PORH, using laser speckle contrast imaging (LSCI) technique.
Seventeen healthy adults (age = 24 ± 3 years) completed three PORH bouts over two lab visits. LSCI region of interest was a standardized 10 cm region on the dominant ventral forearm. A 5-min brachial artery occlusion period induced by inflating an arm cuff to 200 mmHg, preceded a 4-min hyperemic period. Inter- and intra-day reliability and reproducibility of cutaneous vascular conductance (LSCI flux / mean arterial pressure) were determined using intraclass correlation (ICC) and coefficient of variation (CV%). Maximal flow and area under the curve standardized to zero perfusion showed intra- and inter-day reliability (ICC > 0.70). Time to maximal flow (TMF) was not reproducible (inter-day CV = 18%). However, alternative kinetic indices such as 1-min AUC and overshoot rate-of-change (ORC), represented as a piecewise function (at 5s, 10s, 15s, and 20s into hyperemia), were reproducible (CV< 11%). Biological zero was a reliable normalization point.
PORH measured with LSCI is a reliable assessment of microvascular function. However, TMF or its derived hyperemic velocity are not recommended for longitudinal assessment. Piecewise ORC and 1-min AUC are reliable alternatives to assess the kinetic response of PORH.
Intersystem crossing (ISC), a vital component of the electronic and nuclear transitions that compose photophysics, has been successfully simulated in light elements and transition metal complexes. ...Derived from the
-dependent spin-orbit coupling (SOC), ISC is expected to be of greater importance in heavier elements, but few attempts have been made at the simulation of ISC in lanthanides or actinides. In this work, we explore several of the challenges that will need to be overcome in order to treat ISC in late-row elements, including the loss of spin as a good quantum number, the need to include SOC variationally via two- or four-component electronic structure, and the high density of states present in late-row complexes. Density functional theory (DFT) calculations are used to illustrate several of these effects, while a model Hamiltonian is used to illustrate the importance of momentum rescaling in surface hopping simulations of strongly coupled states.
Mass spectrometry (MS) is an information rich analytical technique and plays a key role in various ‘omics studies. Standard mass spectrometers are bulky and operate at high vacuum, which hinder their ...adoption by the broader community and utility in field applications. Developing portable mass spectrometers can significantly expand the application scope and user groups of MS analysis. This review discusses the basics and recent advancements in the development of key components of portable mass spectrometers including ionization source, mass analyzer, detector, and vacuum system. Further, major areas where portable mass spectrometers are applied are also discussed. Finally, a perspective on the further development of portable mass spectrometers including the potential benefits for ‘omics analysis is provided.
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