Chromosomal dihydrofolate reductase (DHFR) enzymatically reduces dihydrofolate (DHF) to tetrahydrofolate (THF) using NADPH as a cofactor. R67 DHFR is an R-plasmid encoded enzyme that confers resistance to trimethoprim (TMP), an antibacterial drug. It shares no structural homology with TMP targeted, chromosomal DHFRs. Previous osmolyte studies in our lab have indicated that DHF binding to R67 DH...

The enthalpy relaxation behavior of Ti41.5Cu37.5Ni7.5Zr2.5Hf5Sn5Si1 bulk metallic glass (BMG) was investigated in this study. It is found that relaxation behavior follows the general characteristics for amorphous materials: the annealing time dependence of recovery enthalpy follows a stretched exponential function with the mean relaxation time obeying an Arrhenius law. In addition, the equilibr...

On the basis of the thermokinetics of the hydrogen (deuterium) evolution reaction and the thermodynamics of Pd+H(D) system, we analytically and numerically discuss effects of temperature on the loading ratio of hydrogen (deuterium) absorption into electrodes of β-phase PdHx (PdDx) under the galvanostatic charging condition. It is found that the change of the loading ratio with temperature depen...

Kinetic studies on solvolysis of cinnamoyl chloride in aqueous acetone and acetonitrile with lesser water content shows an order 2.6 with respect to water and it is comparable to that of benzoyl chloride. The relatively greater enthalpy and lesser negative entropy of activation compared to benzoyl chloride favours an SN2 mechanism for cinnamoyl chloride rather than addition elimination mechanis...

The mobility of the inert gases argon and xenon in pure and doped single crystals of KBr was studied. The gases were introduced by ion bombardment. The recently established system of stages was used to interpret the results. Normal volume diffusion was found for xenon at low gas concentration, the activation enthalpy being 1.4 + 0.2 eV. This release was independent of doping, thus favoring a tr...

BACKGROUND Thermophilic enzymes are often less active than their mesophilic homologues at low temperatures. One hypothesis to explain this observation is that the extra stabilizing interactions increase the rigidity of thermophilic enzymes and hence reduce their activity. Here we employed a thermophilic acylphosphatase from Pyrococcus horikoshii and its homologous mesophilic acylphosphatase fro...

A series of ionic liquids containing anions of differing coordination strength were investigated as solvents for the condensation reaction of an alkyl amine and an aromatic aldehyde. As predicted, the rate constant of the process was found to increase with the proportion of the ionic liquid in the reaction mixture. Temperature-dependent kinetic analyses demonstrated that by varying the ability ...

Current Isothermal Titration Calorimetry (ITC) data in the literature have relatively high errors in the measured enthalpies of protein-ligand binding reactions. There is a need for universal validation standards for titration calorimeters. Several inorganic salt co-precipitation and buffer protonation reactions have been suggested as possible enthalpy standards. The performances of several com...