The constraint in synthesis of ß-lactams by penicillin acylase is the hydrolysis of the activated acyl donor and the synthetic product. The thermodynamically controlled synthesis of ß-lactams deals with direct acylation of a nucleophile (6APA, 7-ACA or 7-ADCA) by free acids in acidic pH and high concentration of solvent to achieve good yield. On the other hand, the kinetically controlled synthe...

The mechanism of the argininosuccinate lyase reaction has been probed by the measurement of the effects of isotopic substitution at the reaction centers. A primary deuterium isotope effect of 1.0 on both V and V/K is obtained with (2S,3R)-argininosuccinate-3-d, while a primary 15N isotope effect on V/K of 0.9964 +/- 0.0003 is observed. The 15N isotope effect on the equilibrium constant is 1.018...

Recent work has shown that the nature of hydration of pure hydrophobic surfaces changes with the length scale considered: water hydrogen-bonding networks adapt to small exposed hydrophobic species, hydrating or "wetting" them at relatively high densities, whereas larger hydrophobic areas are "dewetted" [Chandler D (2005), Nature 29:640-647]. Here we determine whether this effect is also present...

Enantiomeric excess (ee) in asymmetric catalysis may be strongly dependent on the solvent. The reaction product may range from an almost racemic mixture to an ee of over 90% for different solvents. We study this phenomenon for the C-C coupling reaction between nitromethane and benzaldehyde (the Henry reaction) with cinchona thiourea as the catalyst, where solvents that are strong Lewis bases in...

In this work, two types of solvents ethanol or water were used in preparation of the LaFeO3 catalysts by citrate sol gel method. The obtained samples were subjected to various calcination temperatures in order to study the catalytic activity and stability for methanol electro-oxidation by XRD, cyclic voltammetry and chronoamperometry. The crystallinity of the LaFeO3 ph...

The time-dependent fluorescence of a model diatomic molecule with a charge-transfer electronic transition in confined solvents has been simulated. The effect of confining the solvent is examined by comparing results for solutions contained within hydrophobic spherical cavities of varying size (radii of 10-20 angstroms). In previous work [J. Chem. Phys. 118, 6618 (2002)] it was found that the so...

Electron transfer reactions between thiopyronine triplet (acceptor 3A+) and the electron donors (D), aniline, p-Br-aniline and p-I-aniline, are investigated by flash spectroscopy in solvents of different viscosity and polarity. Due to the heavy-atom effect the radical yield becomes very ~ensitive to the solvent influence, which can be explained by the dynamic properties of a triplet exciplex (3...

Most of the recent organic solar cells (OSCs) with top-of-the-line efficiencies are processed from solvents a high vapor pressure such as CF in nitrogen-filled glovebox, which is not feasible for large-area manufacturing. Herein, we cast active layers both aromatic hydrocarbon and halogenated without any solvent additive or post-treatment, well interlayers water methanol air (35% relative humid...