A Multispecific Investigation of the Metal Effect in Mammalian Odorant Receptors for Sulfur-Containing Compounds.

Metal-coordinating compounds are generally known to have strong smells, a phenomenon that can be attributed to the fact that odorant receptors for intense-smelling compounds, such as those containing sulfur, may be metalloproteins. We previously identified a mouse odorant receptor (OR), Olfr1509, that requires copper ions for sensitive detection of a series of metal-coordinating odorants, including (methylthio)methanethiol (MTMT), a strong-smelling component of male mouse urine that attracts female mice. By combining mutagenesis and quantum mechanics/molecular mechanics (QM/MM) modeling, we identified candidate binding sites in Olfr1509 that may bind to the copper-MTMT complex.

Molecular mechanism of activation of human musk receptors OR5AN1 and OR1A1 by ()-muscone and diverse other musk-smelling compounds.

Understanding olfaction at the molecular level is challenging due to the lack of crystallographic models of odorant receptors (ORs). To better understand the molecular mechanism of OR activation, we focused on chiral ()-muscone and other musk-smelling odorants due to their great importance and widespread use in perfumery and traditional medicine, as well as environmental concerns associated with bioaccumulation of musks with estrogenic/antiestrogenic properties. We experimentally and computationally examined the activation of human receptors OR5AN1 and OR1A1, recently identified as specifically responding to musk compounds.

Phenothiazine Radical Cation Excited States as Super-oxidants for Energy-Demanding Reactions.

We demonstrate that the 10-phenyl-10 H-phenothiazine radical cation (PTZ) has a manifold of excited doublet states accessible using visible and near-infrared light that can serve as super-photooxidants with excited-state potentials is excess of +2.1 V vs SCE to power energy demanding oxidation reactions. Photoexcitation of PTZ in CHCN with a 517 nm laser pulse populates a D electronically excited doublet state that decays first to the unrelaxed lowest electronic excited state, D' (τ < 0.

Carbon chain shape selectivity by the mouse olfactory receptor OR-I7.

The rodent OR-I7 is an olfactory receptor exemplar activated by aliphatic aldehydes such as octanal. Normal alkanals shorter than heptanal bind OR-I7 without activating it and hence function as antagonists in vitro. We report a series of aldehydes designed to probe the structural requirements for aliphatic ligand chains too short to meet the minimum approximate 6.

Stable iridium dinuclear heterogeneous catalysts supported on metal-oxide substrate for solar water oxidation.

Atomically dispersed catalysts refer to substrate-supported heterogeneous catalysts featuring one or a few active metal atoms that are separated from one another. They represent an important class of materials ranging from single-atom catalysts (SACs) and nanoparticles (NPs). While SACs and NPs have been extensively reported, catalysts featuring a few atoms with well-defined structures are poorly studied.

Nitrogen-doped tungsten carbide nanoarray as an efficient bifunctional electrocatalyst for water splitting in acid.

Tungsten carbide is one of the most promising electrocatalysts for the hydrogen evolution reaction, although it exhibits sluggish kinetics due to a strong tungsten-hydrogen bond. In addition, tungsten carbide's catalytic activity toward the oxygen evolution reaction has yet to be reported. Here, we introduce a superaerophobic nitrogen-doped tungsten carbide nanoarray electrode exhibiting high stability and activity toward hydrogen evolution reaction as well as driving oxygen evolution efficiently in acid.

Investigating the Role of Copper Oxide in Electrochemical CO Reduction in Real Time.

Copper oxides have been of considerable interest as electrocatalysts for CO reduction (CO2R) in aqueous electrolytes. However, their role as an active catalyst in reducing the required overpotential and improving the selectivity of reaction compared with that of polycrystalline copper remains controversial. Here, we introduce the use of selected-ion flow tube mass spectrometry, in concert with chronopotentiometry, in situ Raman spectroscopy, and computational modeling, to investigate CO2R on CuO nanoneedles, CuO nanocrystals, and CuO nanoparticles.

Floquet Study of Quantum Control of the Cis-Trans Photoisomerization of Rhodopsin.

Understanding how to control reaction dynamics of polyatomic systems by using ultrafast laser technology is a fundamental challenge of great technological interest. Here, we report a Floquet theoretical study of the effect of light-induced potentials on the ultrafast cis-trans photoisomerization dynamics of rhodopsin. The Floquet Hamiltonian involves an empirical 3-state 25-mode model with frequencies and excited-state gradients parametrized to reproduce the rhodopsin electronic vertical excitation energy, the resonance Raman spectrum, and the photoisomerization time and efficiency as probed by ultrafast spectroscopy.

Active sites of copper-complex catalytic materials for electrochemical carbon dioxide reduction.

Restructuring-induced catalytic activity is an intriguing phenomenon of fundamental importance to rational design of high-performance catalyst materials. We study three copper-complex materials for electrocatalytic carbon dioxide reduction. Among them, the copper(II) phthalocyanine exhibits by far the highest activity for yielding methane with a Faradaic efficiency of 66% and a partial current density of 13 mA cm at the potential of - 1.

Can TDDFT Describe Excited Electronic States of Naphthol Photoacids? A Closer Look with EOM-CCSD.

The L and L excited states of naphthols are characterized by using time-dependent density functional theory (TDDFT), configuration interaction with singles (CIS), and equation-of-motion coupled cluster singles and doubles (EOM-CCSD) methods. TDDFT fails dramatically at predicting the energy and ordering of the L and L excited states as observed experimentally, while EOM-CCSD accurately predicts the excited states as characterized by natural transition orbital analysis. The limitations of TDDFT are attributed to the absence of correlation from doubly excited configurations as well as the inconsistent description of excited electronic states of naphthol photoacids revealed by excitation analysis based on the one-electron transition density matrix.

Hydrophobic CuO Nanosheets Functionalized with Organic Adsorbates.

A new class of hydrophobic CuO nanosheets is introduced by functionalization of the cupric oxide surface with p-xylene, toluene, hexane, methylcyclohexane, and chlorobenzene. The resulting nanosheets exhibit a wide range of contact angles from 146° (p-xylene) to 27° (chlorobenzene) due to significant changes in surface composition induced by functionalization, as revealed by XPS and ATR-FTIR spectroscopies and computational modeling. Aromatic adsorbates are stable even up to 250-350 °C since they covalently bind to the surface as alkoxides, upon reaction with the surface as shown by DFT calculations and FTIR and H NMR spectroscopy.

Retention System and Splinting on Morse Taper Implants in the Posterior Maxilla by 3D Finite Element Analysis.

The purpose of this study was to evaluate different retention systems (cement- or screw-retained) and crown designs (non-splinted or splinted) of fixed implant-supported restorations, in terms of stress distributions in implants/components and bone tissue, by 3-dimensional (3D) finite element analysis. Four 3D models were simulated with the InVesalius, Rhinoceros 3D, and SolidWorks programs. Models were made of type III bone from the posterior maxillary area.

Corrigendum: Robust resistive memory devices using solution-processable metal-coordinated azo aromatics.

This corrects the article DOI: 10.1038/nmat5009.

Electron-Hole-Pair-Induced Vibrational Energy Relaxation of Rhenium Catalysts on Gold Surfaces.

A combination of time-resolved vibrational spectroscopy and density functional theory techniques have been applied to study the vibrational energy relaxation dynamics of the Re(4,4'-dicyano-2,2'-bipyridine)(CO)Cl (Re(CO)Cl) catalyst for CO to CO conversion bound to gold surfaces. The kinetics of vibrational relaxation exhibits a biexponential decay including an ultrafast initial relaxation and complete recovery of the ground vibrational state. Ab initio molecular dynamics simulations and time-dependent perturbation theory reveal the former to be due to vibrational population exchange between CO stretching modes and the latter to be a combination of intramolecular vibrational relaxation (IVR) and electron-hole pair (EHP)-induced energy transfer into the gold substrate.

Characterization of ammonia binding to the second coordination shell of the oxygen-evolving complex of photosystem II.

The second-shell ammonia binding sites near the OEC (oxygen-evolving complex) of PSII are characterized by combined Continuum Electrostatic/Monte Carlo (MCCE), QM/MM and DFT calculations and compared with new and earlier experimental measurements. MCCE shows ammonia has significant affinity at 6 positions but only two significantly influence the OEC. Although the pK of ammonium ion is 9.

Electron Transfer Assisted by Vibronic Coupling from Multiple Modes.

Understanding the effect of vibronic coupling on electron transfer (ET) rates is a challenge common to a wide range of applications, from electrochemical synthesis and catalysis to biochemical reactions and solar energy conversion. The Marcus-Jortner-Levich (MJL) theory offers a model of ET rates based on a simple analytic expression with a few adjustable parameters. However, the MJL equation in conjunction with density functional theory (DFT) has yet to be established as a predictive first-principles methodology.

Thousandfold Enhancement of Photoreduction Lifetime in Re(bpy)(CO) via Spin-Dependent Electron Transfer from a Perylenediimide Radical Anion Donor.

Spin-dependent intramolecular electron transfer is revealed in the Re(CO)(py)(bpy-Ph)-perylenediimide radical anion (Re-bpy-PDI) dyad, a prototype model system for artificial photosynthesis. Quantum chemical calculations and ultrafast transient absorption spectroscopy experiments demonstrate that selective photoexcitation of Re-bpy results in electron transfer from PDI to Re-bpy, forming two distinct charge-shifted states. One is an overall doublet whose return to the ground state is spin-allowed.

Robust resistive memory devices using solution-processable metal-coordinated azo aromatics.

Non-volatile memories will play a decisive role in the next generation of digital technology. Flash memories are currently the key player in the field, yet they fail to meet the commercial demands of scalability and endurance. Resistive memory devices, and in particular memories based on low-cost, solution-processable and chemically tunable organic materials, are promising alternatives explored by the industry.

Crystallographic Data Support the Carousel Mechanism of Water Supply to the Oxygen-Evolving Complex of Photosystem II.

Photosystem II (PSII) oxidizes water to produce oxygen through a four-step photocatalytic cycle. Understanding PSII structure-function relations is important for the development of biomimetic photocatalytic systems. The quantum mechanics/molecular mechanics (QM/MM) analysis of substrate water binding to the oxygen-evolving complex (OEC) has suggested a rearrangement of water ligands in a carousel mechanism around a key Mn center.

On the relationship between cumulative correlation coefficients and the quality of crystallographic data sets.

In 2012, Karplus and Diederichs demonstrated that the Pearson correlation coefficient CC is a far better indicator of the quality and resolution of crystallographic data sets than more traditional measures like merging R-factor or signal-to-noise ratio. More specifically, they proposed that CC be computed for data sets in thin shells of increasing resolution so that the resolution dependence of that quantity can be examined. Recently, however, the CC values of entire data sets, i.

Erratum: Role of Tensorial Electronic Friction in Energy Transfer at Metal Surfaces [Phys. Rev. Lett. 116, 217601 (2016)].

This corrects the article DOI: 10.1103/PhysRevLett.116.

X-ray Free Electron Laser Radiation Damage through the S-State Cycle of the Oxygen-Evolving Complex of Photosystem II.

The oxygen-evolving complex (OEC) catalyzes water-splitting through a reaction mechanism that cycles the OEC through the "S-state" intermediates. Understanding structure/function relationsships of the S-states is crucial for elucidating the water-oxidation mechanism. Serial femtosecond X-ray crystallography has been used to obtain radiation damage-free structures.