Isomerizations of free enzyme can be detected in kinetic patterns of product inhibition when the isomerization is partially rate-limiting. The kinetic pattern is non-competitive, owing to binding of substrate and product to different forms of free enzyme. This adds an additional term to the rate equation, sometimes represented as KSP. Several kineticists have noted that, as the rate of isomeriz...

Fragmentation and isomerization of methylamine (CH3NH2(+)), methanol (CH3OH(+)), and methyl fluoride (CH3F(+)) cations by short, intense laser pulses have been studied by ab initio classical trajectory calculations. Born-Oppenheimer molecular dynamics (BOMD) on the ground-state potential energy surface were calculated with the CAM-B3LYP/6-31G(d,p) level of theory for the cations in a four-cycle...

We report the first measurements of the activation barrier for ground state trans-cis isomerization of secondary amides. We measured activation barriers of Ea ) 13.8 ( 0.8 kcal/mol for aqueous solutions of N-methylacetamide (NMA) and Ea ) 11.0 ( 0.7 kcal/mol for glycylglycine (Gly-Gly). These activation barriers were determined from the temperature dependence of the ground state isomerization r...

Kinematic effects associated with movements of molecular frames, which specify instantaneous orientation of molecules, is investigated in structural isomerization dynamics of a triatomic cluster whose total angular momentum is zero. The principal-axis frame is employed to introduce the so-called principal-axis hyperspherical coordinates, with which the mechanism of structural isomerization dyna...

The excited state reactivity of Ru(ii) complexes continues to be a topic of intense investigation because of their widespread use in applications related to solar energy conversion, such as in photoswitches and for medicinal chemistry. In an effort to gain further understanding of photoinduced ligand exchange and isomerization in Ru(ii) complexes, various isomers of the formula [Ru(PTPI)2(CH3CN...

Proteorhodopsin (pR) is a membrane-embedded proton pump from the microbial rhodopsin family. Light absorption by its retinal chromophore initiates a photocycle, driven by trans/cis isomerization on the femtosecond to picosecond time scales. Here, we report a study on the photoisomerization dynamics of the retinal chromophore of pR, using dispersed ultrafast pump-dump-probe spectroscopy. The app...

The chaperonin GroEL and the peptidyl-prolyl cis-trans isomerase cyclophilin are major representatives of two distinct cellular systems that help proteins to adopt their native three-dimensional structure: molecular chaperones and folding catalysts. Little is known about whether and how these proteins cooperate in protein folding. In this study, we have examined the action of GroEL and cyclophi...

Several previous studies reported that sn-2 acyl lysophosphatidylcholines (LPCs) undergo rapid isomerization due to acyl migration, especially at physiological pH and temperature. However, these studies have been carried out using mostly sn-2 palmitoyl LPC, whereas the naturally occurring sn-2 LPCs are predominantly unsaturated. In this study, we investigated the acyl migration in four naturall...

Zirconia-supported tungsten oxide (WO(x)/ZrO(2)) is considered an important supported metal oxide model acid catalyst, for which structure-property relationships have been studied for numerous acid-catalyzed reactions. The catalytic activity for xylene isomerization, alcohol dehydration, and aromatic acylation follows a volcano-shape dependence on tungsten surface density. However, WO(x)/ZrO(2)...

The isomerization of glucose into fructose is a large-scale reaction for the production of high-fructose corn syrup (HFCS; reaction performed by enzyme catalysts) and recently is being considered as an intermediate step in the possible route of biomass to fuels and chemicals. Here, it is shown that a large-pore zeolite that contains tin (Sn-Beta) is able to isomerize glucose to fructose in aque...