Kinetic studies with alternative

Hexokinase provides another example of the stereochemical inferences that can be drawn on the basis of kinetic studies with alternative substrates and competi-... 

Also consistent with LCM uptake being an active (endo-cytic) process is the separate finding, in an in vitro kinetic study with both C6 and 9L tumor cells, that both dinitrophenol and sodium azide (i.e., energy blockers) inhibit LCM uptake in both tumor cell lines. Addition of glucose to the medium as an alternate source of energy restored the LCM uptake, indicating an energy-dependent uptake (ref. 534). 

Kinetic studies with calcineurin yielded a modest solvent isotope effect of 1.35, and a proton inventory and fractionation factor data that were most consistent with a mechanism involving a single proton transfer from a water molecule coordinated to a metal ion.136 No transphosphorylation products were found in the presence of alternate nucleophiles, consistent with direct phosphoryl transfer to a metal-coordinated water.137 No calcineurin-catalyzed oxygen exchange of 180 labeled water with phosphate could be detected.138 In a study using / NPP as the substrate, product inhibition studies found that both phosphate and p-nitrophenol are... 

The formation of an acyclic intermediate during the process of mutarota-tion was long ago postulated by Lowry,and has recently been confirmed by isotopic and polarographic i investigations of aqueous solutions, and by kinetic studies with non-aqueous solvents. -i The small amounts of the reactive aldehydo forms in equilibrium, which are directly related to the configuration and structure of the sugars, have been estimated by alternative methods. ... 

It may happen that AH is not available for the buffer substance used in the kinetic studies moreover the thermodynamic quantity A//° is not precisely the correct quantity to use in Eq. (6-37) because it does not apply to the experimental solvent composition. Then the experimentalist can determine AH. The most direct method is to measure AH calorimetrically however, few laboratories Eire equipped for this measurement. An alternative approach is to measure K, under the kinetic conditions of temperature and solvent this can be done potentiometrically or by potentiometry combined with spectrophotometry. Then, from the slope of the plot of log K a against l/T, AH is calculated. Although this value is not thermodynamically defined (since it is based on the assumption that AH is temperature independent), it will be valid for the present purpose over the temperature range studied. 

An alternating copolymer of a-methyl styrene and oxygen as an active polymer was recently reported [20]. When a-methyl styrene and AIBN are pressurized with O2, poly-a-methylstyreneperoxide is obtained. Polymerization kinetic studies have shown that the oligoperoxides mentioned above were as reactive as benzoyl peroxide, which is a commercial peroxidic initiator. Table 1 compares the overall rate constants of some oligoperoxides with that of benzoyl peroxide. 

Recent kinetic studies of this polymerization 14) revealed that some parasitic reactions cause termination and induction periods in the overall process. Their nature is not known yet. It is tentatively suggested that the activated polymers react with the dormant ones yielding some destruction products, although the nucleophile capable of activating the still available dormant chains is regenerated. Alternatively it is possible that the intermediate 3 is labile and may decompose before collapsing into 4 with regeneration of the nucleophile. Whatever the cause of these side reactions, one should stress that the conversion of the monomer into polymer is almost quantitative. 

Such conclusions have been initially regarded with reluctance by some experimentalists [40], Despite its potential interest, the new alternative does not fit the large body of experimental observations available so far. As pointed out by Fischer and Hofmann [40], kinetic studies are not consistent with the associative mechanism and are clearly in favor of a dissociative path. However, in a recent kinetic study, Waters, Bos, and Wulff (WBW) [41] have provided the first example of a bimolecular reaction of a... 

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