Disentangling Driving Force Effects, Polar Effects, /H Imbalance, and Other Influences on H-Atom Transfer Reactions.

Hydrogen atom transfer (HAT) reactions and their kinetic barriers Δ are important in organic and inorganic chemistry. This study examines factors that influence Δ, reporting the kinetics and thermodynamics of HAT from various ruthenium bis(acetylacetonate) pyridine-imidazole complexes to nitroxyl radicals. Across these 36 reactions, the Δ and Δ can be independently varied, with different sets of Ru complexes primarily tuning either their ps or their °s.

Characterizing Conical Intersections of Nucleobases on Quantum Computers.

Hybrid quantum-classical computing algorithms offer significant potential for accelerating the calculation of the electronic structure of strongly correlated molecules. In this work, we present the first quantum simulation of conical intersections (CIs) in a biomolecule, cytosine, using a superconducting quantum computer. We apply the contracted quantum eigensolver (CQE)─with comparisons to conventional variational quantum deflation (VQD)─to compute the near-degenerate ground and excited states associated with the conical intersection, a key feature governing the photostability of DNA and RNA.

Recurrent events modeling based on a reflected Brownian motion with application to hypoglycemia.

Patients with type 2 diabetes need to closely monitor blood sugar levels as their routine diabetes self-management. Although many treatment agents aim to tightly control blood sugar, hypoglycemia often stands as an adverse event. In practice, patients can observe hypoglycemic events more easily than hyperglycemic events due to the perception of neurogenic symptoms.

Enantiocontrolled Cyclization to Form Chiral 7- and 8-Membered Rings Unified by the Same Catalyst Operating with Different Mechanisms.

Chiral medium-sized rings, albeit displaying attractive properties for drug development, suffer from numerous synthetic challenges due to difficult cyclization steps that must take place to form these unusually strained, atropisomeric rings from sterically crowded precursors. In fact, catalytic enantioselective cyclization methods for the formation of chiral seven-membered rings are unknown, and the corresponding eight-membered variants are also sparse. In this work, we present a substrate preorganization-based, enantioselective, organocatalytic strategy to construct seven- and eight-membered rings featuring chirality that is intrinsic to the ring in the absence of singular stereogenic atoms or single bond axes of chirality.

A Stereoselective Oxidative Dimerization En Route to (-)-Lomaiviticin A.

We describe a stereoselective synthesis of the dimeric diazofluorene , a potential precursor to the cytotoxic -symmetric bacterial metabolite (-)-lomaiviticin A (). An efficient route was developed to convert the tetracyclic diol to the diketone (five steps, 30% overall). Oxidative dimerization of the enoxysilane provided the -symmetric dimeric diazofluorene in 56% yield and with 15:1:0 diastereoselectivity.

[2Fe-2S] model compounds.

This feature article reviews the synthesis, structural comparison, and physical properties of [2Fe-2S] model compounds, which serve as vital tools for understanding the structure and function of Fe-S clusters in biological systems. We explore various synthetic methods for constructing [2Fe-2S] cores, offering insights into their biomimetic relevance. A comprehensive analysis and comparison of Mössbauer spectroscopy data between model compounds and natural protein systems are provided, highlighting the structural and electronic parallels.

Hydrogen Tunneling and Conformational Motions in Nonadiabatic Proton-Coupled Electron Transfer between Interfacial Tyrosines in Ribonucleotide Reductase.

Ribonucleotide reductase (RNR) is essential for DNA synthesis and repair in all living organisms. The mechanism of RNR requires long-range radical transport through a proton-coupled electron transfer (PCET) pathway spanning two different protein subunits. Herein, the direct PCET reaction between the interfacial tyrosine residues, Y356 and Y731, is investigated with a vibronically nonadiabatic theory that treats the transferring proton and all electrons quantum mechanically.

Nav1.8, an analgesic target for nonpsychotomimetic phytocannabinoids.

Pain impacts billions of people worldwide, but treatment options are limited and have a spectrum of adverse effects. The search for safe and nonaddictive pain treatments has led to a focus on key mediators of nociceptor excitability. Voltage-gated sodium (Nav) channels in the peripheral nervous system-Nav1.

Spontaneous Formation of Single-Crystalline Spherulites in a Chiral 2D Hybrid Perovskite.

In two-dimensional (2D) chiral metal-halide perovskites (MHPs), chiral organic spacers induce structural chirality and chiroptical properties in the metal-halide sublattice. This structural chirality enables reversible crystalline-glass phase transitions in (-NEA)PbBr, a prototypical chiral 2D MHP where NEA represents 1-(1-naphthyl)ethylammonium. Here, we investigate two distinct spherulite states of (-NEA)PbBr, exhibiting either radial-like or stripe-like banded patterns depending on the annealing conditions of the amorphous film.

Novel Quinazoline Derivatives Inhibit Splicing of Fungal Group II Introns.

We report the discovery of small molecules that target the RNA tertiary structure of self-splicing group II introns and display potent antifungal activity against yeasts, including the major public health threat . High-throughput screening efforts against a yeast group II intron resulted in an inhibitor class which was then synthetically optimized for enhanced inhibitory activity and antifungal efficacy. The most highly refined compounds in this series display strong, gene-specific antifungal activity against .

Engineering mechanisms of proton-coupled electron transfer to a titanium-substituted polyoxovanadate-alkoxide.

Metal oxides are promising catalysts for small molecule hydrogen chemistries, mediated by interfacial proton-coupled electron transfer (PCET) processes. Engineering the mechanism of PCET has been shown to control the selectivity of reduced products, providing an additional route for improving reductive catalysis with metal oxides. In this work, we present kinetic resolution of the rate determining proton-transfer step of PCET to a titanium-doped POV, TiVO(OCH) with 9,10-dihydrophenazine by monitoring the loss of the cationic radical intermediate using stopped-flow analysis.

The Impact of Electric Fields on Processes at Electrode Interfaces.

The application of external electric fields to influence chemical reactions at electrode interfaces has attracted considerable interest in recent years. However, the design of electric fields to achieve highly efficient and selective catalytic systems, akin to the optimized fields found at enzyme active sites, remains a significant challenge. Consequently, there has been substantial effort in probing and understanding the interfacial electric fields at electrode/electrolyte interfaces and their effect on adsorbates.

Contextualizing the Upper Paleolithic of the Armenian Highlands: New data from Solak-1, central Armenia.

As a potential corridor connecting Southwest Asia with western and northern Europe, the Armenian Highlands and southern Caucasus hold great potential for increasing our understanding of Upper Paleolithic behavioral and cultural variability. However, given the dearth of Upper Paleolithic sites, we lack the data necessary to answer basic questions regarding the timing and nature of the Upper Paleolithic in this region. Solak-1 is an open-air site located along the upper Hrazdan Valley (1635 m above sea level) in central Armenia.

Photoemission Study of GaN Passivation Layers and Band Alignment at GaInP(100) Heterointerfaces.

To date, III-V semiconductor-based tandem devices with GaInP top photoabsorbers show the highest solar-to-electricity or solar-to-fuel conversion efficiencies. In photoelectrochemical (PEC) cells, however, III-V semiconductors are sensitive, in terms of photochemical stability and, therefore, require suitable functional layers for electronic and chemical passivation. GaN films are discussed as promising options for this purpose.

Digital and Tunable Genetically Encoded Tension Sensors Based on Engineered Coiled-Coils.

Genetically encoded tension sensors (GETSs) allow for quantifying forces experienced by intracellular proteins involved in mechanotransduction. The vast majority of GETSs are comprised of a FRET pair flanking an elastic "spring-like" domain that gradually extends in response to force. Because of ensemble averaging, the FRET signal generated by such analog sensors conceals forces that deviate from the average, and hence it is unknown if a subset of proteins experience greater magnitudes of force.

Sulfilimines from a Medicinal Chemist's Perspective: Physicochemical and in Vitro Parameters Relevant for Drug Discovery.

While sulfoximines are nowadays a well established functional group for medicinal chemistry, the properties of sulfilimines are significantly less well studied, and no sulfilimine has progressed to the clinic to date. In this account, the physicochemical and in vitro properties of sulfilimines are reported and compared to those of sulfoximines and other more traditional functional groups. Furthermore, the impact on the physicochemical and in vitro properties of real drug scaffolds is studied in two series of sulfilimine-containing analogs of imatinib and hNE inhibitors.

Articulatory correlates of consonantal length contrasts: The case of Japanese mimetic geminates.

This study investigates the articulatory correlates of consonantal length contrasts in Japanese mimetic words using electromagnetic articulography data. Regression and dynamic time warping analyses applied to intragestural timing, kinematic properties, and intergestural timing reveal that Japanese geminates are characterized by longer closure phases, longer gestural plateaus, higher tongue tip positions, larger movements, and lower stiffness. Geminates also exhibit distinct timing relationships with adjacent vowels, specifically, longer times to target that allow for longer preceding vowels.

pH-Dependent Electrocatalytic Aqueous Ammonia Oxidation to Nitrite and Nitrate by a Copper(II) Complex with an Oxidation-Resistant Ligand.

The electrocatalytic aqueous ammonia oxidation (AO) represents a more sustainable alternative to accessing nitrite (NO) and nitrate (NO). We now report that Cu(pyalk) {pyalk = 2-(pyridin-2-yl)propan-2-oate}, previously employed as a homogeneous water oxidation (WO) catalyst, is also active for selective AO in aqueous environments. The traditional Griess analytical test for NO/NO was modified to permit the operation in the presence of the otherwise interfering Cu ion.

Resisting High-Energy Impact Events through Gap Engineering in Superconducting Qubit Arrays.

Quantum error correction (QEC) provides a practical path to fault-tolerant quantum computing through scaling to large qubit numbers, assuming that physical errors are sufficiently uncorrelated in time and space. In superconducting qubit arrays, high-energy impact events can produce correlated errors, violating this key assumption. Following such an event, phonons with energy above the superconducting gap propagate throughout the device substrate, which in turn generate a temporary surge in quasiparticle (QP) density throughout the array.

Two-Dimensional Transition Metal Dichalcogenides: A Theory and Simulation Perspective.

Two-dimensional transition metal dichalcogenides (2D TMDs) are a promising class of functional materials for fundamental physics explorations and applications in next-generation electronics, catalysis, quantum technologies, and energy-related fields. Theory and simulations have played a pivotal role in recent advancements, from understanding physical properties and discovering new materials to elucidating synthesis processes and designing novel devices. The key has been developments in theory, deep learning, molecular dynamics, high-throughput computations, and multiscale methods.

C-H Activation and Sequential Addition to Dienes and Imines: Synthesis of Amines with -Quaternary Centers and Mechanistic Studies on the Complex Interplay Between the Catalyst and Three Reactants.

A Rh(III)-catalyzed sequential C-H bond addition to dienes and in situ formed aldimines was developed, allowing for the preparation of otherwise challenging to access amines with quaternary centers at the -position. A broad range of dienes were effective inputs and installed a variety of aryl and alkyl substituents at the quaternary carbon site. Aryl and alkyl sulfonamide and carbamate nitrogen substituents were incorporated by using different formaldimine precursors.

Trap States in Reduced Colloidal Titanium Dioxide Nanoparticles Have Different Proton Stoichiometries.

Added electrons and holes in semiconducting (nano)materials typically occupy "trap states," which often determine their photophysical properties and chemical reactivity. However, trap states are usually ill-defined, with few insights into their stoichiometry or structure. Our laboratory previously reported that aqueous colloidal TiO nanoparticles prepared from TiCl + HO have two classes of electron trap states, termed and .