ACS Measurement Science Au最新文献

Acetylcholine (ACh) is a neurotransmitter that plays critical roles in human health and diseases. To better understand ACh signaling in the brain, developing analytical capabilities for its selective and quantitative measurement in real time is essential. While electrochemical amperometry offers exceptional temporal resolution, most in vivo electrochemical ACh sensors have limited selectivity, such as against choline (the product of ACh hydrolysis) and ascorbic acid. Here, we report a micropipet-supported ITIES (interface between two immiscible electrolyte solutions), which demonstrated the selective detection of ACh against choline, ascorbic acid, and other neurotransmitters using chronoamperometry. The detection of ACh is based on its ion transfer across a water/oil interface, which was formed between an aqueous solution and a 2-nitrophenyl octyl ether (NPOE) solution containing an ACh ionophore, termed water/NPOE-ionophore ITIES. The ionophore was heptakis-(2,6-di-O-methyl)-β-cyclodextrin (DM-β-CD). The addition of DM-β-CD in the NPOE phase resulted in an easier ACh transfer at the water/NPOE-ionophore ITIES compared with that at the ITIES without the ionophore, suggesting the presence of ionophore-facilitated ion transfer in addition to the direct ion transfer at the water/NPOE-ionophore ITIES. We observed a linear detection of ACh on the water/NPOE-ionophore ITIES. When implanted in the cortex of the brain of a live mouse, the water/NPOE-ionophore ITIES tracked the dynamic concentration changes of the injected ACh in the brain. The measuring techniques are broadly applicable to quantifying real-time ACh release in the brain with negligible interference, enabling a better understanding of neurological disorders and diseases.

The COVID-19 pandemic has presented significant challenges for the effectiveness of existing diagnostic tools in detecting and monitoring infections. Currently, there is an increased emphasis on the potential challenges faced by individuals during their postrecovery phase. The impact of post-COVID conditions (PCC) has substantially influenced perspectives on disease management, fostering a positive trend toward personal healthcare. Here, we report a ZnO-modified, non-Faradaic impedimetric biosensor for the rapid detection of TRAIL and D-dimer across clinically relevant ranges. The dual-analyte platform demonstrated great sensitivity (LOD: 3.4 pg/mL for TRAIL, 8.9 ng/mL for D-dimer), with high specificity in human plasma. Optimized surface chemistry and impedance analysis enabled reliable signal acquisition from 5 μL samples in 5 min. Beyond detection, we introduce the PCCODE (Post-COVID Co-dysregulation Evaluator) threshold-based classifier model using quantified concentration output values-TRAIL <50 pg/mL, D-dimer >1000 ng/mL-to encode biomarker signals in four binary states. This logic-driven system was constructed using exogenously spiked plasma samples and validated through signal-mapped heatmaps, allowing stratification of healthy, inflammation, immune dysregulation, and post-COVID categories. Together, the biosensor and classifier framework enable real-time, mechanism-informed stratification of PCC, marking a significant advance toward point-of-care diagnostics.

Post-translational modifications have emerged as a key biomolecular process in the onset of neurodegenerative disorders, such as the hyperphosphorylation of tau protein in Alzheimer's disease (AD). High levels of phosphorylation are related to tau malfunction, self-assembly into amyloids forming neurofibrillary tangles in the brain, and cellular toxicity. These molecular processes are also reflected in human biofluids, allowing us to use tau phosphorylation as a biomarker of the disease onset and progression. However, it is not yet clear what structural changes the tau protein undergoes upon phosphorylation and what the early self-assembly steps are that lead to the formation of the final amyloid species. This knowledge gap is related in large part to the experimental challenge in achieving a multiparametric physical-chemical characterization of nanoscale size and heterogeneous amyloid at the single-molecule level. Here, we employ high-resolution and advanced atomic force microscopy methods to study the effect of phosphorylation on the tau pathway of self-assembly and on the physical-chemical properties of the heterogeneous amyloid species formed, down to the single-oligomer level. We report the correlative analysis of single-oligomer structural and chemical properties and achieve, for the first time, the quantitative determination of their phosphorylation state. Our findings reveal that hyperphosphorylation results in the formation of smaller, stiffer, and more adhesive oligomers, which might be critical for their pathological role in AD. This nanoresolved information might be, in turn, useful to understand the early molecular mechanisms of disease, as well as to improve the detection of pathological tau species in biofluids as diagnostic biomarkers.

The global burden of multidrug-resistant tuberculosis (MDR-TB) underscores the urgent need for novel therapeutics with distinct mechanisms of action. Here, we report a comparative evaluation of four antimicrobial peptides (AMPs) derived from the amphibian peptide B1CTcu5, integrating experimental validation with molecular modeling to elucidate structure-activity relationships. Among them, W-B1CTcu5, featuring a single N-terminal tryptophan substitution, exhibited the most potent antimycobacterial activity (MIC = 3.2 μg/mL) against Mycobacterium tuberculosis (MTB) combined with high structural stability, persistent membrane interaction, and multitarget affinity against key MTB proteins, including the porin MspA, the transporter CpnT, and the cell wall enzyme Ag85B. In contrast, analogs with reduced hydrophobic anchoring or dynamic instability demonstrated diminished efficacy despite partial membrane insertion or surface affinity. Molecular dynamics simulations revealed that peptides with low root-mean-square deviation and minimal residue fluctuation retained compact, α-helical conformations and maintained productive bilayer engagement, which are traits correlated with antimicrobial performance. However, the hemolytic properties of W-B1CTcu5 highlight a therapeutic trade-off between potency and host toxicity. Together, these findings emphasize the predictive power of dynamic structural descriptors in AMP design, and identify W-B1CTcu5 as a promising, yet optimization-requiring, scaffold for future design of anti-TB AMPs.

Accurate evaluation and comparison of site-normalized catalytic activity (turnover frequency, TOF) in heterogeneous catalysis require consideration of catalyst nanoparticle (NP) size and geometry. In this study, we systematically quantify the impact of NP geometry on the fraction of surface atoms across FCC, BCC, and HCP crystal structures with various geometries and evaluate the absolute and relative errors introduced by assuming spherical NPs. Using catalytic H₂ combustion (CHC) over an octahedron Ni catalyst supported on γAl₂O₃ as a model experiment, we demonstrate that assuming spherical single-crystal Ni NPs underestimates the fraction of the surface atoms and overestimates TOF by 86%. This discrepancy arises from the miscalculation of surface site availability in spherical approximations. These findings emphasize the need for geometry-specific models to ensure reliable TOF calculations and accurate catalyst performance comparisons in heterogeneous catalysis. We work provide a framework for geometry-dependent TOF calculations, offering new insights into morphology-controlled catalyst design and facet-specific reactivity optimization.

Ammonia is a critical impurity in hydrogen fuel due to its irreversible poisoning effect on proton exchange membrane fuel cells. Therefore, international standards (e.g., ISO 14687) set a stringent threshold of 100 nmol/mol. Furthermore, with the growing potential use of ammonia as a hydrogen carrier, its accurate quantification is becoming increasingly important. However, the presence of trace humidity poses analytical challenges, as ammonia may interact with water or interfaces, thereby affecting its detectability. Therefore, the goal of this work is to enable accurate trace ammonia quantification for hydrogen purity measurements through fundamental studies of the methodological challenges. Here, low-pressure sampling (ultra)-long-path Optical-Feedback Cavity-Enhanced Absorption Spectroscopy (OF-CEAS) was applied with an effective optical path length of approximately 6.17 km. We studied three average amounts of ammonia: (38.2 ± 0.8) nmol/mol, (74.8 ± 0.7) nmol/mol, and (112.1 ± 1.2) nmol/mol. Furthermore, these amounts were investigated at trace-humidity levels ranging from 0.8 to 8.5 ppm_V. We observed a systematic, nonlinear, and humidity-dependent positive measurement bias of up to + (1.0 ± 0.2) nmol/mol at the maximum investigated trace-humidity volume fraction of 8.5 ppm_V. This bias was not caused by spectral interference but rather by water-induced accumulation of ammonia within the optical cavity. Moreover, time-resolved measurements in the presence of trace ammonia showed that water desorption follows first-order kinetics, whereas water adsorption followed mixed-order kinetics with an apparent reaction order of 1.57 ± 0.03. Distinct hydration states of surface-bound ammonia were identified, whereas under dry conditions and with increasing amounts of ammonia, enhanced surface adhesion through intermolecular clustering was observed. In addition, the presence of ammonium species within the sorption layer was indirectly confirmed by our experiments. In conclusion, we provide a deeper insight into trace-level ammonia-water interactions and establish a framework for optimizing methodologies, particularly for (ultra)-long-path optical gas measurement systems.

One of the ways to improve the performance of electrospray ionization (ESI) mass spectrometry (MS) is to introduce additives to the sample solution. Alternatively, such additives can be introduced in the gaseous form directly into the electrospray plume. Normally, only one additive can be introduced via one method. Here, we present a flexible automated system that enables dynamic switching among several gas-phase additives, which can alternately be introduced to the ion source compartment over a short period of time. These additives include vapors of acids and solvents. We show that different gaseous additives enhance the signals of different analytes to a varied extent. The enhancement factors were in the range ∼ 2-15. We applied the gas-phase additive switching in real sample analysis, where it enhanced signal intensities and broadened the detection range. The automated system also enables the dosing of vapors at different concentrations. Unlike conventional approaches that saturate the electrospray plume with a fixed vapor level, controlled dosing of acid or solvent vapor levels enables optimization of the protein signal intensity and facilitates structural probing. Overall, it is possible to systematically vary both the type and the concentration of vapor additives using a single setup, improving the analytical performance and versatility of ESI-MS. The proposed setup is compatible with liquid chromatography.

Chiral amines are fundamental building blocks in pharmaceuticals and bioactive molecules, necessitating fast and reliable enantiomeric analysis. However, developing a single probe capable of effectively distinguishing primary, secondary, and particularly tertiary amines remains challenging due to their diverse steric and electronic characteristics. Herein, we report a novel ¹⁹F-labeled palladium-based probe bearing a strategically positioned trifluoromethyl group away from the coordination site to minimize steric hindrance. This structural design enables broad applicability across all three classes of amines, producing well-resolved ¹⁹F NMR signals that directly correlate with their absolute configurations. The method allows rapid, derivatization-free determination of enantiomeric excess and demonstrates a strong potential for application in pharmaceutical analysis and high-throughput screening.

Nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) suffer from inherently low sensitivity due to the weak thermal polarization of nuclear spins. Parahydrogen-induced polarization (PHIP) offers a powerful route to enhance NMR signals by several orders of magnitude, enabling real-time metabolic imaging. However, PHIP implementations are often constrained by small sample volumes, limited automation, and complex high-pressure requirements. In this work, we present an upgraded, automated PHIP system capable of hyperpolarizing sample volumes up to 2.2 mL, which is suitable for preclinical MRI applications. We developed several high-pressure reactors and multiport NMR tube caps compatible with standard commercial 5, 10, and 16 mm glass tubes. Reactor designs were simulated and fabricated from chemically resistant polymers, ensuring mechanical safety at more than 30 bar. Using FLASH MRI, nutation, and CPMG sequences, we characterized magnetic field homogeneity and stability, establishing optimal sample dimensions (12.5/16 mm ID/OD glass tube, 20 mm height) with a B ₀ inhomogeneity below 2.5 ppm and a B ₁ inhomogeneity around 1%. A high level of injection reproducibility was confirmed (volume precision ∼ 0.6%). Optimization of experimental parameters, including the hydrogenation pressure, pH₂ flow rate, and sample temperature, enabled rapid and efficient polarization transfer. At optimized conditions (20 bar pH₂, 2 L/min flow, 55 °C, 4 s bubbling time), up to 31.3% ¹H polarization of two protons was achieved for deuterated ethyl acetate in acetone with the theoretical maximum of 50%. This level of polarization was achieved with a duty cycle of 80 s, and the coefficient of variation of the mean was below 6.8%. This system lays the groundwork for the broader adoption of PHIP in preclinical imaging and metabolic research, providing practical sample volumes and facilitating the rapid production of hyperpolarization. Future work includes automating the purification process and further maximization of the polarization yield.

Flunixin, a nonsteroidal anti-inflammatory drug widely used in veterinary therapy, presents a risk of residues entering both the food supply and the environment. Therefore, developing sensitive methods for the treatment of flunixin is of great importance. Herein, we report a highly sensitive and selective CRISPR-Cas12a based fluorescent assay for flunixin measurement. By employing functionalized magnetic beads which carry double-stranded DNA (dsDNA) formed by a flunixin binding aptamer and its short partially complementary single-stranded DNA (ssDNA) hybridization probe and taking advantage of two split ssDNA strands to synergistically trigger the trans-cleavage activity of Cas12a, flunixin can be detected with a limit of detection (LOD) reaching as low as 0.35 nM. Furthermore, our sensor was highly selective: other commonly used veterinary drugs such as ciprofloxacin, neomycin, sulfanilamide, sulfamethoxazole, ketoprofen, meloxicam, and mefenamic acid would not interfere with the detection of flunixin. In addition, the simulated water samples were successfully analyzed. The cooperative split DNA activation of the CRISPR-Cas12a sensing strategy developed in this work should find useful application in the development of CRISPR sensors for various non-nucleic acid species, including large biomolecules such as proteins and small molecules and ionic species like metals.