The H/D primary kinetic isotope effect (KIE) for the hydride transfer reaction catalyzed by Escherichia coli dihydrofolate reductase (ecDHFR) is calculated as a function of temperature employing ensemble-averaged variational transition-state theory with multidimensional tunneling. The calculated KIEs display only a small temperature dependence over the temperature range of 5 to 45 degrees C. We...

1. The denaturation rate of partially dried crystallizable egg albumin is greatly decreased by decreasing its water content. 2. The temperature of denaturation, defined as the temperature at which half of the protein becomes insoluble in distilled water after a definite time of heating, is a linear function of the relative humidity with which the protein is in equilibrium. 3. By applying the Ar...

Abstract: Biodiesel is produced through transesterification of vegetable oils or animal fats. It significantly depends on many reaction parameters among which temperature and stirring are most important. In transesterification, reaction rates follow Arrhenius equation (i.e. function of temperature). Also, effect of stirring effect on reaction rate can be described as Boltzmann sigmoid form (as ...

The gelatinization properties of starch extracted from corn and waxy corn dried at different temperatures were determined at various water contents and heating rates by differential scanning calorimetry. All gelatinization transition temperatures increased with drying temperature and heating rate. Onset and peak temperatures remained relatively constant, whereas end temperature decreased in the...

In a species of Oscillatoria exhibiting movement of type suitable for exact measurement the velocity of linear translatory motion is found to be controlled by the temperature (6 - 36 degrees C.) in accordance with Arrhenius' equation for irreversible reactions. The value of the critical increment (micro) is 9,240. The extreme variates in series of measurements at different temperatures yield th...

We examined the effects of temperature on the activity and steady-state kinetic properties of alkaline phosphatase (EC 3.1.3.1). Purified isoenzymes from human liver, intestine, and placenta were used, as was human serum, and the enzyme from porcine kidney. Phosphatase activity was estimated by two different assay techniques. For all isoenzymes, apparent Michaelis constants for the substrate 4-...

We consider in this work the analysis of the excess heat capacity C(p)(ex) versus temperature profiles in terms of a model of thermal protein denaturation involving one irreversible step. It is shown that the dependences of ln C(p)(ex) on 1 T (T is the absolute temperature) obtained at various temperature scanning rates have the same form. Several new methods for estimation of parameters of the...

1. The rate of pulsation of the anterior contractile vacuole of Paramecium caudatum under chloretone anesthesia has been determined over a range of temperatures from 9-31 degrees C. It has been found that the rate is a logarithmic function of the temperature according to the Arrhenius equation. From 9-16 degrees the temperature characteristic (micro) has the value 25,600; from 16-22 degrees it ...

A nonlinear mathematical model was developed and experimentally validated to investigate the effects of changes in optical properties during interstitial laser photocoagulation (ILP). The effects of dynamic optical properties were calculated using the Arrhenius damage model, resulting in a nonlinear optothermal response. This response was experimentally validated by measuring the temperature ri...

The aim of this study was to evaluate the influence of the extra virgin olive oil (EVOO) physical state on the kinetics of oxidative reactions. To this purpose, EVOO was stored at increasing temperatures from 3 to 60 degrees C and the oxidation was followed by measuring both primary and secondary oxidation products. Results highlighted that crystallization plays an important role in determining...