On the fluorescence of methyl salicylate in hydrogen bonding solvents

Two fluorescence bands have been observed in methanolic solutions of methyl salicylate whose relative intensity depends on excitation wavelength. This effect which is not observed in methylcyclohexane is explained by the existence of a small fraction of ester molecules, each with a broken hydrogen bond.     

Hydroxylase activity of Met471Cys tyramine beta-monooxygenase

A series of mutations was targeted at the methionine residue, Met471, coordinating the Cu(M) site of tyramine beta-monooxygenase (TbetaM). The methionine ligand at Cu(M) is believed to be key to dioxygen activation and the hydroxylation chemistry of the copper monooxygenases. The reactivity and copper binding properties of three TbetaM mutants, Met471Asp, Met471Cys, and Met471His, were examined. All three mutants show similar metal binding affinities to wild type TbetaM in the oxidized enzyme forms. EPR spectroscopy suggests that the Cu(II) coordination geometry is identical to that of the WT enzyme. However, substrate hydroxylation was observed for the reaction of tyramine solely with Met471Cys TbetaM. Met471Cys TbetaM provides the first example of an active mutant directed at the Cu(M) site of this class of hydroxylases. The reactivity and altered kinetics of the Met471Cys mutant further highlight the central role of the methionine residue in the enzyme mechanism. The sole ability of the cysteine residue to support activity among the series of alternate amino acids investigated is relevant to theoretical and biomimetic investigations of dioxygen activation at mononuclear copper centers.     

Kinetically Controlled Sequential Growth of Surface‐Grafted Chiral Supramolecular Copolymers

We report a facile strategy to grow supramolecular copolymers on Au surfaces by successively exposing a surface‐anchored monomer to solutions of oppositely charged peptide comonomers. Charge regulation on the active chain end of the polymer sufficiently slows down the kinetics of the self‐assembly process to produce kinetically trapped copolymers at near‐neutral pH. We thereby achieve architectural control at three levels: The β‐sheet sequences direct the polymerization away from the surface, the height of the supramolecular copolymer brushes is well‐controlled by the stepwise nature of the alternating copolymer growth, and 2D spatial resolution is realized by using micropatterned initiating monomers. The programmable nature of the resulting architectures renders this concept attractive for the development of customized biomaterials or chiral interfaces for optoelectronics and sensor applications.     

Phosphorus-bearing axially chiral biaryls by catalytic asymmetric cross-cyclotrimerization and a first application in asymmetric hydrosilylation

A novel and efficient, two-step route to axially chiral biaryls is demonstrated. In a direct asymmetric cross-cyclotrimerization in the presence of a chiral cobalt(I) catalyst, axially chiral biaryls bearing phosphoryl moieties have been prepared, and through indirect evidence the authors have been able to clarify the origin of the stereochemical induction and the nature of the central intermediate in the catalytic cycle. By subsequent reduction of the phosphoryl moiety to the corresponding phosphine, a very efficient and atom-economical approach to chiral systems has been developed. These chiral systems clearly have great potential use as axially chiral monodentate P- or bidentate P,O-ligands, as has been demonstrated by the employment of the novel NAPHEP as a new monodentate acting ligand in an asymmetric hydrosilylation reaction.     

(C3H4N2)2Au]Cl--a bis protic gold(I)-NHC

The gold(I) bis-NHC (NHC = imidazol-2-ylidene) parent compound was synthesised in high yield by a three step reaction starting from imidazole. The compound is highly water soluble and stable in concentrated hydrochloric acid.     

ChemInform Abstract: Synthesis of [(SnSe)1.15]m(TaSe2)n Ferecrystals: Structurally Tunable Metallic Compounds.

The title ferecrystals (fere: Latin, almost) with 1 ≤ n,m ≤ 6 and n and m varied independently are prepared by physical vapor deposition of the elements followed by annealing at 400 °C for 30 min.