Quantum Phase Transition as a Promising Route to Enhance the Critical Current in Kagome Superconductor CsVSb.

Developing strategies to systematically increase the critical current, the threshold current below which the superconductivity exists, is an important goal of materials science. Here, the concept of quantum phase transition is employed to enhance the critical current of a kagome superconductor CsVSb, which exhibits a charge density wave (CDW) and superconductivity that are both affected by hydrostatic pressure. As the CDW phase is rapidly suppressed under pressure, a large enhancement in the self-field critical current (I) is recorded.

Large Fermi surface in pristine kagome metal CsVSb and enhanced quasiparticle effective masses.

The kagome metal CsV[Formula: see text]Sb[Formula: see text] is an ideal platform to study the interplay between topology and electron correlation. To understand the fermiology of CsV[Formula: see text]Sb[Formula: see text], intensive quantum oscillation (QO) studies at ambient pressure have been conducted. However, due to the Fermi surface reconstruction by the complicated charge density wave (CDW) order, the QO spectrum is exceedingly complex, hindering a complete understanding of the fermiology.

Nodeless Superconductivity in Kagome Metal CsVSb with and without Time Reversal Symmetry Breaking.

The kagome metal CsVSb features an unusual competition between the charge-density-wave (CDW) order and superconductivity. Evidence for time reversal symmetry breaking (TRSB) inside the CDW phase has been accumulating. Hence, the superconductivity in CsVSb emerges from a TRSB normal state, potentially resulting in an exotic superconducting state.

Catalytically impaired fluorescent class C β-lactamase enables rapid and sensitive cephalosporin detection by stabilizing fluorescence signals: implications for biosensor design.

Biosensors have found applications in many sectors including the food industry, where cephalosporin detection has played an important role in reducing the incidence of cephalosporin contamination, ensuring food safety, and reducing the spread of antibiotic resistance. Taking advantage of the specific interaction between β-lactamase and its cephalosporin substrates/inhibitors, we previously constructed a biosensor based on a fluorescein-labeled class C β-lactamase mutant, V211Cf, for specific and reagentless detection of cephalosporins and class C β-lactamase inhibitors (Anal. Chem.

Engineered Amp C β-lactamase as a fluorescent screening tool for class C β-lactamase inhibitors.

Class C β-lactamases mediate antibiotic resistance in bacteria by efficiently hydrolyzing a broad range of β-lactam antibiotics. With their clinical significance and the lack of commercially available effective inhibitors, development of class C β-lactamase inhibitors has become one of the recent hot issues in the pharmaceutical industry. In this paper, we report the protein engineering of a fluorescent Amp C β-lactamase mutant designated as V211Cf for the in vitro screening of class C β-lactamase inhibitors.

Fluorophore-labeled beta-lactamase as a biosensor for beta-lactam antibiotics: a study of the biosensing process.

The fluorescein-labeled E166C mutant of the PenPC beta-lactamase (E166Cf) represents a successful model in the construction of "switch-on" fluorescent biosensors from nonallosteric proteins (Chan P.-H. et al.

Dissociation of alkaliated alanine in the gas phase: the role of the metal cation.

The dissociation of prototypical metal-cationized amino acid complexes, namely, alkaliated alanine ([Ala+M]+, M+ = Li+, Na+, K+), was studied by energy-resolved tandem mass spectrometry with an ion-trap mass analyzer and by density functional theory. Dissociation leads to formation of fragment ions arising from the loss of small neutrals, such as H2O, CO, NH3, (CO+NH3), and the formation of Na+/K+. The order of appearance threshold voltages for different dissociation pathways determined experimentally is consistent with the order of critical energies (energy barriers) obtained theoretically, and this provides the necessary confidence in both experimental and theoretical results.

Competition between pi and non-pi cation-binding sites in aromatic amino acids: a theoretical study of alkali metal cation (Li+, Na+, K+)-phenylalanine complexes.

To understand the cation-pi interaction in aromatic amino acids and peptides, the binding of M(+) (where M(+) = Li(+), Na(+), and K(+)) to phenylalanine (Phe) is studied at the best level of density functional theory reported so far. The different modes of M(+) binding show the same order of binding affinity (Li(+)>Na(+)>K(+)), in the approximate ratio of 2.2:1.

Rational design of a novel fluorescent biosensor for beta-lactam antibiotics from a class A beta-lactamase.

A rational design strategy was used to construct a sensitive "turn-on" biosensor for beta-lactam antibiotics and beta-lactamase inhibitors from a class A beta-lactamase mutant with suppressed hydrolytic activity. A fluorescein molecule was attached to the 166 position on the Omega-loop of the E166C mutant close to the active site of the beta-lactamase. Upon binding with antibiotics or inhibitors, the flexibility of the Omega-loop allows the fluorescein molecule to move out from the active site and be more exposed to solvent.

An efficient heat-inducible Bacillus subtilis bacteriophage 105 expression and secretion system for the production of the Streptomyces clavuligerus beta-lactamase inhibitory protein (BLIP).

The Streptomyces clavuligerus beta-lactamase inhibitory protein (BLIP) has been shown to be a potent inhibitor of class A beta-lactamases including the Escherichia coli TEM-1 beta-lactamase (Ki = 0.6 nM). A heat-inducible BLIP expression system was constructed based on a derivative of Bacillus subtilis phage phi105.

Experimental validation of theoretical potassium and sodium cation affinities of amides by mass spectrometric kinetic method measurements.

In this study the theoretical Gaussian-2 K(+)/Na(+) binding affinities (enthalpies) at 0 K (in kJ mol(-1)) for six amides in the order: formamide (109.2/138.5) < N-methylformamide (117.

Interaction between pyridoxal kinase and pyridoxal-5-phosphate-dependent enzymes.

The interactions of two pyridoxal-5-phosphate (PLP)-dependent enzymes, alanine aminotransferase (ALT) and glutamate decarboxylase (GAD), with pyridoxal kinase (PK) were studied by fluorescence polarization as well as surface plasmon resonance techniques. The results demonstrated that PK can specifically bind to ALT and GAD. Moreover, binding profiles of both enzymes to immobilized PK were altered by excess amount of PLP.

Differentiation of isomeric polyaromatic hydrocarbons by electrospray Ag(I) cationization mass spectrometry.

Abundant Ag(I)-cationized complexes of 13 polyaromatic hydrocarbons (PAHs), [Ag+PAH](+) and [Ag+2(PAH)](+), were readily generated by electrospray ionization (ESI). In-source collision-induced dissociation (CID) of the [Ag+2(PAH)](+) complex yielded the monomer complex [Ag+PAH](+), which fragmented further to yield the radical molecular ion [PAH](+.).

Absolute potassium cation affinities (PCAs) in the gas phase.

The potassium cation affinities (PCAs) of 136 ligands (20 classes) in the gas phase were established by hybrid density functional theory calculations (B3-LYP with the 6-311+G(3df,2p) basis set). For these 136 ligands, 70 experimental values are available for comparison. Except for five specific PCA values-those of phenylalanine, cytosine, guanine, adenine (kinetic-method measurement), and Me(2)SO (by high-pressure mass spectrometric equilibrium measurement)-our theoretical estimates and the experimental affinities are in excellent agreement (mean absolute deviation (MAD) of 4.

A theoretical study of potassium cation binding to glycylglycine (GG) and alanylalanine (AA) dipeptides.

By combining Monte Carlo conformational search technique with high-level density functional calculations, the geometry and energetics of K(+) interaction with glycylglycine (GG) and alanylalanine (AA) were obtained for the first time. The most stable K(+)-GG and K(+)-AA complexes are in the charge-solvated (CS) form with K(+) bound to the carbonyl oxygens of the peptide backbone, and the estimated 0 K binding affinities (DeltaH(0)) are 152 and 157 kJ mol(-1), respectively. The K(+) ion is in close alignment with the molecular dipole moment vector of the bound ligand, that is, electrostatic ion-dipole interaction is the key stabilizing factor in these complexes.

Electron impact mass spectral fragmentation of chiral bisbenzoxazole, bisbenzothiazole and biscarbamide derivatives of 2,2-dimethyl-1,3-dioxolane.

The mass spectrometric fragmentation behaviour of five pairs of (R,R)- and (S,S)-4,5-bis(benzoxazol-2-yl)-2,2-dimethyl-1,3-dioxolane derivatives, one pair of (R,R)- and (S,S)-4,5-bis(benzothiazol-2-yl)-2,2-dimethyl-1,3-dioxolanes, and three pairs of (R,R)- and (S,S)-N,N'-bis(2-hydroxyaryl)-2,2-dimethyl-1,3-dioxolane-4,5-dicarbamides, all important compounds for asymmetric catalysis (P. Jiao et al., Tetrahedron Asymmetry 2001; 12: 3081), has been studied with the aid of mass-analyzed ion kinetic energy spectrometry and accurate mass measurements under electron impact ionization conditions.

Experimental validation of Gaussian-3 lithium cation affinities of amides: implications for the gas-phase lithium cation basicity scale.

Using a refined Gaussian-3 (G3) protocol, the highest level of ab initio calculations reported so far, we have established the Li+ cation binding enthalpy (affinity) at 0 K (in kJ mol-1) for formamide (195.7), N-methylformamide (209.2), N,N'-dimethylformamide (220.