Formation of nitrogen‐containing heterocycles using di(imidazole‐1‐yl)methanimine

A mild and efficient synthesis of five‐ and six‐membered nitrogen containing heterocyclic compounds, in which di(imidazole‐1‐yl)methanimine serves as a one‐carbon source, is reported.     

The effect of pressure on the raman spectrum of ice at low temperature

Extensive experimental studies of the Raman spectra of H₂O and D₂O ice in the lattice translational and OH (OD) stretching regions are reported for the first time at 88 K and from 0→6 kbar. An unambiguous transformation from ice I_h to ice IX has been observed, although previous studies suggest that a transition to ice II would have occurred. The ice I_h data are analysed in terms of various coefficients.     

Cooperative hydrogen-bonding effects in a water square: a single-crystal neutron and partial atomic charges and hardness analysis study

Four isomorphous complexes of formula [M(L)(4)(H(2)O)(2)]SO(4).2H(2)O (M = Co, 1a; Ni, 1b; Cu, 1c; Zn, 1d) have been isolated and characterized by single-crystal X-ray diffraction and neutron diffraction using the quasi-Laue diffractometer VIVALDI at the Institut Laue-Langevin as well as by thermogravimetric analysis. The structures contain a discrete, strongly hydrogen-bonded water tetramer which causes a significant distortion of the metal coordination sphere in each case. Partial atomic charges and hardness analysis (PACHA) calculations reveal that the shortest hydrogen bonds are not the strongest in this constrained, cyclic solid-state structure and show that the distortion at the metal center is caused by the drive to maintain the integrity of the water tetramer. The system undergoes a disorder-order transition on slow cooling that provides insight into the nature of communication between water squares.     

Single-molecule nanopore sensing of actin dynamics and drug binding

Actin is a key protein in the dynamic processes within the eukaryotic cell. To date, methods exploring the molecular state of actin are limited to insights gained from structural approaches, providing a snapshot of protein folding, or methods that require chemical modifications compromising actin monomer thermostability. Nanopore sensing permits label-free investigation of native proteins and is ideally suited to study proteins such as actin that require specialised buffers and cofactors. Using nanopores, we determined the state of actin at the macromolecular level (filamentous or globular) and in its monomeric form bound to inhibitors. We revealed urea-dependent and voltage-dependent transitional states and observed the unfolding process within which sub-populations of transient actin oligomers are visible. We detected, in real-time, filament-growth, and drug-binding at the single-molecule level demonstrating the promise of nanopore sensing for in-depth understanding of protein folding landscapes and for drug discovery.

Nanopipettes were used for real-time investigation into actin dynamics and drug binding at single-molecule resolution, showing promise for a better understanding of the mechanism of protein–protein interactions and drug discovery.     

Novel methods for the synthesis of 5-substituted-3-carboxy-2,5- and 4,5-dihydrothiophenes and 5-substituted 2- and 3-sulfolenes

Various approaches to the syntheses of 5-substituted-3-carbomethoxy-2,5-dihydrothiophenes and their product sulfolenes, required as synthetic precursors for tangutorine, are described. An efficient route to 3,5-disubstituted-4,5-dihydrothiophenes and hence 3,5-disubstituted-2-sulfolenes by radical chemistry is also described.     

Quenching of triplet states by molecular oxygen and the role of charge-transfer interactions

The rate constants for oxygen quenching in benzene solution of the triplet states of several organic compounds with relatively high triplet energies have been measured in laser photolysis and pulse radiolysis experiments. The previously observed trend for aromatic hydrocarbons where the quenching rate constants decrease from a limiting value of about one ninth of that expected for a diffusion controlled reaction to lower values for triplet states with increasing triplet energy was not observed for the triplet states of certain aromatic ketones and amines. The higher rate constants observed, e.g. oxygen quenching of triplet N-methyl indole has k_Q = 1.4 × 10¹⁰ dm³ mol^?1 s^?1, are interpreted as being due to the presence of low lying triplet charge-transfer states which enhance the efficiency of quenching.     

THE MECHANISM OF ENERGY TRANSFER FROM POLY-p-BENZOYLPHENYLACETIMIDO-BOVINE SERUM ALBUMIN TO SMALL-MOLECULE QUENCHERS

Abstract— Results of a quantitative photochemical study of poly- p -benzoylphenylacetimido-bovine serum albumin in the presence of small-molecule triplet quenchers are reported. The efficiency of quenching by organic salts containing low triplet energy chromophores is shown to be qualitatively dependent on their predicted association constants to the modified protein. In addition, quenching is inhibited by salts of organic acids which possess high binding affinities for the protein but do not contain chromophores of low triplet energy. Quantitative treatment of the quenching and inhibition data yields results which strongly support the operation of an 'affinity controlled' mechanism for triplet energy transfer from the benzophenone moieties of the modified-bovine serum albumin to quenchers such as α-naphthylacetate and trans -cinnamate.