ACS Measurement Science Au最新文献

G protein-coupled receptors (GPCRs) serve critical physiological roles as the most abundant family of receptors. Here, we describe the design of a generalizable and cell lysate-based method that leverages the interaction between an agonist-activated GPCR and a conformation-specific binder to reconstitute split nanoluciferase (NanoLuc) in vitro. This tool, In vitro GPCR split NanoLuc ligand Triggered Reporter (IGNiTR), has broad applications. We have demonstrated IGNiTR’s use with three G_s-coupled GPCRs, two G_i-coupled GPCRs and three classes of conformation-specific binders: nanobodies, miniG proteins, and G protein peptidomimetics. As an in vitro method, IGNiTR enables the use of synthetic G protein peptidomimetics and provides easily scalable and portable reagents for characterizing GPCRs and ligands. We tested three diverse applications of IGNiTR: (1) proof-of-concept GPCR ligand screening using dopamine receptor D1 IGNiTR; (2) detection of opioids for point-of-care testing; and (3) characterizing GPCR functionality during Nanodisc-based reconstitution processes. Due to IGNiTR’s unique advantages and the convenience of its cell lysate-based format, this tool will find extensive applications in GPCR ligand detection, screening, and GPCR characterization.

High-resolution X-ray computed tomography (CT) has become an invaluable tool in battery research for its ability to probe phase distributions in sealed samples. The Cartesian coordinates used in describing the CT image stack are not appropriate for understanding radial dependencies, like that seen in bobbin-type batteries. The most prominent of these bobbin-type batteries is alkaline Zn–MnO₂, which dominates the primary battery market. To understand material radial dependencies within these batteries, a method is presented to approximate the Cartesian coordinates of CT data into pseudo-cylindrical coordinates. This is important because radial volume fractions are the output of computational battery models, and this will allow the correlation of a battery model to CT data. A selection of 10 anodes inside Zn–MnO₂ AA batteries are used to demonstrate the method. For these, the pseudo-radius is defined as the relative distance in the anode between the central current collecting pin and the separator. Using these anodes, we validate that this method results in averaged one-dimensional material profiles that, when compared to other methods, show a better quantitative match to individual local slices of the anodes in the polar θ-direction. The other methods tested are methods that average to an absolute center point based on either the pin or the separator. The pseudo-cylindrical method also corrects for slight asymmetries observed in bobbin-type batteries because the pin is often slightly off-center and the separator often has a noncircular shape.

Due to the increasing demand for clinical testing of infectious diseases at the point-of-care, the global market claims alternatives for rapid diagnosis tools such as disposable biosensors, avoiding the need for specialized laboratories and skilled personnel. Bacterial vaginosis (BV) is an infectious disease that commonly affects reproductive-age women and predisposes the infection of sexually transmitted diseases. Especially in asymptomatic cases, BV can lead to pelvic inflammatory conditions, postpartum endometritis, and preterm labor. Conventionally, BV diagnosis involves the microscopic analysis of vaginal swab samples; it thus requires highly trained personnel. In response, we report a novel microfluidic paper-based analytical device for BV diagnosis. Sialidase, a biomarker overexpressed in BV, was detected by exploiting an immunosensing mechanism previously discovered by our team. This technology employs a graphene oxide-coated surface as a quencher of fluorescence; the fluorescence of the immunoprobes that do not experiment immunoreactions (antibody–antigen) are deactivated by graphene oxide via non-radiative energy transfer, whereas those immunoprobes undergoing immunoreactions preserve their photoluminescence due to the distance and the low affinity between the immunocomplex and the graphene oxide-coated surface. Our paper-based test was typically carried out within 20 min, and the sample volume was 6 μL. Besides, it was tested with 14 vaginal swabs specimens to discriminate clinical samples of women with normal microbiota from those with BV. Our disposable device represents a new tool to prevent the consequences of BV.

Despite the ubiquitous absorption of mid-infrared (IR) radiation by virtually all molecules that belong to the major biomolecules groups (proteins, lipids, carbohydrates, nucleic acids), the application of conventional IR microscopy to the life sciences remained somewhat limited, due to the restrictions on spatial resolution imposed by the diffraction limit (in the order of several micrometers). This issue is addressed by AFM-IR, a scanning probe-based technique that allows for chemical analysis at the nanoscale with resolutions down to 10 nm and thus has the potential to contribute to the investigation of nano and microscale biological processes. In this perspective, in addition to a concise description of the working principles and operating modes of AFM-IR, we present and evaluate the latest key applications of AFM-IR to the life sciences, summarizing what the technique has to offer to this field. Furthermore, we discuss the most relevant current limitations and point out potential future developments and areas for further application for fruitful interdisciplinary collaboration.

In this paper, we report on a printable glass-based manufacturing method and a new proof-of-concept colorimetric signal readout scheme for a dielectric barrier discharge (DBD)-type helium plasma photoionization detector. The sensor consists of a millimeter-sized glass chamber manufactured using a printable glass suspension. Plasma inside the chip is generated using a custom-built power supply (900 V and 83.6 kHz), and the detector uses ∼5 W of power. Our new detection scheme is based on detecting the change in the color of plasma after the introduction of target gases. The change in color is first captured by a smartphone camera as a video output. The recorded video is then processed and converted to an image light intensity vs retention time plot (gas chromatogram) using three standard color space models (red, green, blue (RGB), hue, saturation, lightness (HSL), and hue, saturation, value (HSV)) with RGB performing the best among the three models. We successfully detected three different categories of volatile organic compounds using our new detection scheme and a 30-m-long gas chromatography column: (1) straight-chain alkanes (n-pentane, n-hexane, n-heptane, n-octane, and n-nonane), (2) aromatics (benzene, toluene, and ethylbenzene), and (3) polar compounds (acetone, ethanol, and dichloromethane). The best limit of detection of 10 ng was achieved for benzene at room temperature. Additionally, the device showed excellent performance for different types of sample mixtures consisting of three and five compounds. Our new detector readout method combined with our ability to print complex glass structures provides a new research avenue to analyze complex gas mixtures and their components.

Online techniques for the quantitative analysis of reaction products have many advantages over offline methods. However, owing to the low product formation rates in electrochemical reactions, few of these techniques can be coupled to electrochemistry. An exception is differential electrochemical mass spectrometry (DEMS), which gains increasing popularity not least because of its high time resolution in the sub-second regime. DEMS is often combined with a dual thin-layer cell (a two-compartment flow cell), which helps to mitigate a number of problems that arise due to the existence of a vacuum|electrolyte interface. However, the efficiency with which this cell transfers volatile reaction products into the vacuum of the mass spectrometer is far below 100%. Therefore, a calibration constant that considers not only the sensitivity of the DEMS setup but also the transfer efficiency of the dual thin-layer cell is needed to translate the signals observed in the mass spectrometer into electrochemical product formation rates. However, it can be challenging or impossible to design an experiment that yields such a calibration constant. Here, we show that the transfer efficiency of the dual thin-layer cell depends on the diffusion coefficient of the analyte. Based on this observation, we suggest a two-point calibration method. That is, a plot of the logarithm of the transfer efficiencies determined for H₂ and O₂ versus the logarithm of their diffusion coefficients defines a straight line. Extrapolation of this line to the diffusion coefficient of another analyte yields a good estimate of its transfer efficiency. This is a versatile and easy calibration method, because the transfer efficiencies of H₂ and O₂ are readily accessible for a large range of electrode–electrolyte combinations.

Fluorescence-based single-molecule approaches have helped revolutionize our understanding of chemical and biological mechanisms. Unfortunately, these methods are only suitable at low concentrations of fluorescent molecules so that single fluorescent species of interest can be successfully resolved beyond background signal. The application of these techniques has therefore been limited to high-affinity interactions despite most biological and chemical processes occurring at much higher reactant concentrations. Fortunately, recent methodological advances have demonstrated that this concentration barrier can indeed be broken, with techniques reaching concentrations as high as 1 mM. The goal of this Review is to discuss the challenges in performing single-molecule fluorescence techniques at high-concentration, offer applications in both biology and chemistry, and highlight the major milestones that shatter the concentration barrier. We also hope to inspire the widespread use of these techniques so we can begin exploring the new physical phenomena lying beyond this barrier.

In this article, we present a toolset to fully leverage a previously developed transcutaneous oxygenation monitor (TCOM) wearable technology to accurately measure skin oxygenation values. We describe numerical models and experimental characterization techniques that allow for the extraction of precise tissue oxygenation measurements. The numerical model is based on an inverse boundary problem of the parabolic equation with Dirichlet boundary conditions. To validate this model and characterize the diffusion of oxygen through the oxygen sensing materials, we designed a series of control/calibration experiments modeled after the device’s clinical application using oxygenation values in the physiological range expected for healthy tissue. Our results demonstrate that it is possible to obtain accurate tissue pO₂ measurements without the need for long equilibration times with a small wearable device.