In-place inactivation

Phytostabilization (also known as in-place inactivation or phytoimmobilization) is the use of certain plant species to immobilize contaminants in the soil through absorption and accumulation by roots, adsorption onto roots, or precipitation, complexation, and metal valence reduction within the root zone. The following three mechanisms determine the fate of the contaminants within the phytostabilization process46 ... 

Berti, W. R. Cunningham, S. D. 1997. In-place inactivation of Pb in Pb-contaminated soils. Environmental Science Technology, 31,1359-1364. 

N-terminal end. The researchers also found that inactivation peptides are effective when attached to the N-terminal ends of either the a or p subunits of the TI4P4 complex apparently because these sites are close to each other in the complex. Through several experiments co-expressing elements of the different TI4P4 complexes the authors determined that the T1 domain does not participate directly in activation but serves to hold the p subunit in place. 

When these acidic residues where mutated to alanine (neutral) or lysine (positive), rates of inactivation were affected. The largest effect took place with the positive amino acid mutation. The authors found that mutations in the inactivation peptide are tied to those in the Tl-Sl linker near the T1 domain in other words, the inactivation peptide must be near the Tl-Sl linker when it inactivates the pore. The conclusion reached is that since the inactivation peptide cannot fit through the center of the TI4P4 complex, it must reach the ion conduction pore through lateral openings above the T1 tetramer. 

When a 2 -Cl or -F analog of UDP was used in place of the substrate an irreversible side reaction occurred by which Cl or F, inorganic pyrophosphate, and uracil were released 349 When one of these enzyme-activated inhibitors containing 3H in the 3 position was tested, the tritium was shifted to the 2 position with loss of Cl and formation of a reactive 3 -carbonyl compound (Eq. 16-24) that can undergo P elimination at each end to give an unsaturated ketone which inactivates the enzyme. This suggested that the Fe-tyrosyl radical abstracts an electron (through a... 

Once the activation had taken place, lowering the temperature did not result in a decrease to a lower level of activation. On the other hand, temperatures below 10° might result in cold inactivation. 

Enzyme-enzyme conversion employs heat and an enzyme for starch liquefaction in place of acid. This is the most common form of com processing today Subsequent hydrolysis is by enzymes, as above. The choice of hydrolytic system depends upon economics and the kind of endproduct desired. Enzymes are usually inactivated by heating the symp to 75-80°C, with the exception of the heat-stable a-amylases that have come on the market in the last 10 to 15 years. 

Once all of the controllable factors are in place, it is critical to select the proper bacterial combination(s) that enables the appropriate rate of biomass growth and enzyme production. For instance, the primary step in trichloroethylene bioremediation is the production of oxygenases, such as toluene dioxygenase (tod). However, oxidation of trichloroethylene generates intermediates that inactivate the tod enzyme and can even be toxic to the cells themselves, i.e., catabolite repression. Thus, the biomass growth rate and... 

Chlorolaevulinic acid 28 is a potent competitive inhibitor of bovine PEG synthase, presumably due to binding in the active site in place of ALA, and it also inactivates the enzyme by alkylation of a specific cysteine residue [24] (Scheme 9). The concentration required for the inactivation is much greater than that required for competitive inhibition, however, which suggests that the processes occur at different sites on the enzyme. Electrospray mass spectrometry has shown that 28 can alkylate at multiple sites on the B. subtilis enzyme without causing more than about 50% loss of activity [18]. It is likely that there is no cysteine residue in the active site of this latter enzyme. 

Analogues of cyclic AMP per se may also be worthy of investigation in view of the fact that a specific enzyme synthesizes this compound. The enzyme may be localized selectively in various tissues and a specific cyclic phosphodiesterase inactivates the substance by forming 5 -AMP. Thus, enzyme systems in which the medicinal chemist can evaluate compounds in a direct manner for their ability to act in place of cyclic AMP or inhibit its action or degradation... 

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