Several extremely low volatility organic compounds (ELVOCs) formed in the ozonolysis of endocyclic alkenes have recently been detected in laboratory and field studies. These experiments have been carried out with chemical ionization atmospheric pressure interface time-of-flight mass spectrometers (CI-APi-TOF) with nitrate ions as reagent ions. The nitrate ion binds to the detected species through hydrogen bonds, but it also binds very strongly to one or two neutral nitric acid molecules. This makes the measurement highly selective when there is an excess amount of neutral nitric acid in the instrument. In this work, we used quantum-chemical methods to calculate the binding energies between a nitrate ion and several highly oxidized ozonolysis products of cyclohexene. These were then compared with the binding energies of nitrate ion-nitric acid clusters. Systematic configurational sampling of the molecules and clusters was carried out at the B3LYP/6-31+G* and ωB97xD/aug-cc-pVTZ levels, and the final single-point energies were calculated with DLPNO-CCSD(T)/def2-QZVPP. The binding energies were used in a kinetic simulation of the measurement system to determine the relative ratios of the detected signals. Our results indicate that at least two hydrogen bond donor functional groups (in this case, hydroperoxide, OOH) are needed for an ELVOC molecule to be detected in a nitrate ion CI-APi-TOF. Also, a double bond in the carbon backbone makes the nitrate cluster formation less favorable.

The discovery of functional RNAs critical for normal and disease physiology continues to expand at a break-neck pace. Many RNA functions are controlled by the formation of specific structures; an understanding of each structural component is necessary to elucidate its function. Measuring solvent accessibility intracellularly with experimental ease is an unmet need in the field. Here, we present a novel method for probing nucleobase solvent accessibility, Light Activated Structural Examination of RNA (LASER). LASER depends on light activation of a small molecule, nicotinoyl azide (NAz), to measure solvent accessibility of purine nucleobases. In vitro, this technique accurately monitors solvent accessibility and identifies rapid structural changes due to ligand binding in a metabolite-responsive RNA. LASER probing can further identify cellular RNA-protein interactions and unique intracellular RNA structures. Our photo-activation technique provides an adaptable framework to structurally characterize solvent accessibility of RNA in a myriad of environments.

Nonadiabatic molecular dynamics simulations suggest an excited state electron proton transfer mechanism and explain the observation of mobile hydroxyl radicals.

Dissolution of elemental gold in organic solutions is ac ontemporary approach to lower the environmental burden associated with gold recycling.Herein, we describe fundamental studies on ah ighly efficient method for the dissolution of elemental Au that is based on DMF solutions containing pyridine-4-thiol (4-PSH) as ar eactive ligand and hydrogen peroxidea sa no xidant. Dissolution of Au proceeds through several elementary steps:i somerization of 4-PSH to pyridine-4-thione (4-PS), coordination with Au 0 ,and then oxidation of the Au 0 thione species to Au I simultaneously with oxidation of free pyridine thione to elemental sulfur and further to sulfuric acid. The final dissolution product is aA u I complex bearing two 4-PS ligands and SO 4 2À as ac ounterion. The ligand is crucial as it assists the oxidation process and stabilizes and solubilizes the formed Au cations.