Kinetics of regeneration

C. Larsen, P. Kurtzhals, M. Johansen, Kinetics of Regeneration of Metronidazole from Hemiesters of Maleic Acid, Succinic Acid and Glutaric Acid in Aqueous Buffer, Human Plasma and Pig Liver Homogenate , Int. J. Pharm. 1988, 41, 121 - 129. 

Fig. 24. Kinetics of regeneration of 0.06% ferrihemoglobin at 1.7°C. in formate buffer, pH 4.761. Protein previously denatured at pH 3.5, 25°C. for 2, 4, 8, and 16 times the half-period for denaturation under those conditions.

Under the conditions used in our experiments the kinetics of regeneration of the flagella of Chlamydomonas reinhardii can be described in terms of Eqs. (10) and (12). It remains to be seen from further work why this is so and what changes in kinetics are brought about by variations in these conditions. Our experiments have been of... 

NOTE A practical problem resulting from the rapid reaction kinetics of HQ is that when water containing HQ passes through an MBDl, it turns the resin black, obscuring visual observation of resin separation during regeneration. 

Fig. 3.18. Kinetics of conductivity of ZnO film during adsorption of methyl radicals CH3 at room temperature depending on the degree of preliminary alloying of the surface by titanium atoms. 1 - Blank experiment with a clean (Ti-atom free) film (O - before doping - after heating of alloyed film at 350 C, i. e. after the film has been regenerated) 2-5 - Experiments with doped films. Doping degree increases in the following row 2<3<4<5.

Adsorption/desorption kinetics the time of the adsorption-regeneration cycle greatly depends on the kinetics of the C02 adsorption-desorption profile, which is measured in breakthrough experiments. Sorbents that adsorb and desorb C02 in a shorter time are preferred as these reduce the cycle time as well as the amount of sorbent required, and ultimately the cost of C02 separation. 

Serine peptidases can hydrolyze both esters and amides, but there are marked differences in the kinetics of hydrolysis of the two types of substrates as monitored in vitro. Thus, the hydrolysis of 4-nitrophenyl acetate by a-chy-motrypsin occurs in two distinct phases [7] [22-24]. When large amounts of enzyme are used, there is an initial rapid burst in the production of 4-nitro-phenol, followed by its formation at a much slower steady-state rate (Fig. 3.7). It was shown that the initial burst of 4-nitrophenol corresponds to the formation of the acyl-enzyme complex (acylation step). The slower steady-state production of 4-nitrophenol corresponds to the hydrolysis of the acetyl-enzyme complex, regenerating the free enzyme. This second step, called deacylation, is much slower than the first, so that it determines the overall rate of ester hydrolysis. The rate of the deacylation step in ester hydrolysis is pH-dependent and can be slowed to such an extent that, at low pH, the acyl-enzyme complex can be isolated. 

The substitution process permeates the whole realm of coordination chemistry. It is frequently the first step in a redox reaction and in the dimerization or polymerization of a metal ion, the details of which in many cases are still rather scanty (e.g. for Cr(III) ). An understanding of the kinetics of substitution can be important for defining the best conditions for a preparative or analytical procedure. Substitution pervades the behavior of metal or metal-activated enzymes. The production of apoprotein (demetalloprotein and the regeneration of the protein, as well as the interaction of substrates and inhibitors with metalloproteins are important examples. ... 

The three above-mentioned types of kinetics also influence other aspects of sensor performance (Fig. 2.20). Thus, the signal-time profiles they provide are critically dependent on the kinetics of the processes involved for example, if the sensor regeneration is rather slow, baseline restoration is much too slow. As noted earlier, a slow chemical kinetics can be used to perform reaction rate measurements. 

The reversibility of the sensing process is determined by the features of the (bio)chemical reaction, immobilized species (reagent and/or catalyst) and separation process involved. Very often, the slow kinetics of some such processes make them apparently irreversible in practice when in fact they are not in theory. Many of these sensors are of the irreversible-reusable type and require two steps (sensing and regeneration) for proper functioning. Only... 

Electron transfer from I- into the oxidized Ru photosensitizer (cation), or regeneration of the Ru photosensitizer, is one of the primary processes needed to achieve effective charge separation. The kinetics of this reaction has also been investigated by time-resolved laser spectroscopy [48,51]. The electron-transfer rate from I into the Ru(III) cation of the N3 dye was estimated to be 100 nsec... 

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