Enzymes model for

The reactivity of the methyl complexes 14a and 15 with carboxylic acid was examined to provide carboxylato complexes as useful precursors for enzyme models. For example, a slight excess of acetic acid does cleave the Zn-CHa bond by elimination of methane and yields [Zn(bd bpza)02CCH3] (17) (Scheme 16) and [Zn(bpa ) O2CCH3] (18). 

The carbonato complexes of lanthanides and actinides are of importance with regard to the metal ion speciation in the environment. These are, however, not linked with the enzyme models for carbon dioxide hydration and hence are not dealt with in further detail. 

Emgenbroich M, Wulff G (2003) A new enzyme model for enantioselective esterases based on molecularly imprinted polymers. Chem Eur J 9 4106... 

M. Hassan, U. S. Svensson, P. Ljungman, B. Bjorkstrand, H. Olsson, M. Bielentein, M. Abdel-Rehim, C. Nilsson, M Johansson, and M. O. Karlsson, A mechanism-based pharmacokinetic-enzyme model for cyclophosphamide autoinduction in breast cancer patients. Br J Clin Pharmacol 48 669-677 (1999). 

Koga, K., Sasaki, S., Functionalization of Crown Ethers. An Approach to the Enzyme Model for Peptide Synthesis , Pure Appl. Chem. 60 (1988) 539-543. 

The study of the nine-variable system (5.6) is of course rather cumbersome. It would be useful to simplify it by reducing the number of variables. Such a reduction is often possible because certain variables evolve more rapidly than others. A quasi-steady-state hypothesis adopted for the fast variables then allows us to transform the corresponding kinetic equations into algebraic relations. Such an approach was followed in chapter 2 for the reduction of an 11-variable system, obtained in the case of a dimeric enzyme model for glycolytic oscillations, to the form of system (2.7), which contains only two variables. 

The kinetics of the reaction of heptene with H2SO4 at various concentrations has been elucidated by UV spectrometry. The efficiency of proton transfer to carbon on the intramolecular ring closing of enol ethers in Kirby s enzyme model for aldolase and isomerase has been investigated computationally by using ab initio and DFT calculation methods... 

Multi-Functionalized Chiral Crown Ethers as Enzyme Models for the Synthesis of Peptides. 

We recently reported a novel enzyme model for the synthesis of peptides by using the multi-functionalized chiral 18-crown-6 derivatives [3]. The new hosts have achieved the assembly of plural guests by covalent bonds formed through non-covalent complexes between the host and the guest, and then enhanced the bond formation between the bound guests. This enzyme model has mimicked the general concept of enzyme catalysis, in which the reactive enzyme-substrate covalent intermediate (E/v aSi) is formed from the noncovalent complex (E Si), and then reacts with the second substrate (S2) to give the product (Sj—S2) as shown in Equation (1) [4]. 

Sasaki, S. and K. Koga - Multi-functionaUzed chiral crown ethers as enzyme models for the synthesis of peptides. Multiple chiral recognition in the enzyme model 267 Schuette, J. M. see Kaifer, A. E. et al. 107 See, K. A. - see Gutsche, C. D. et al. 61... 

A series of papers has appeared " dealing with the photosensitized oxygenation of various hydroxy- and methoxy-benzenes and their use as non-enzymic models for enzymatic cleavage of phenol rings. In each case complex reaction pathways are proposed involving both oxiran and dioxetan intermediates. 

One now needs to evaluate how well the inhibition constant (.Sri) can afford a fit to the pattern predicted for the inhibited enzyme (upper curve in Fig. 14.14a) of the two-enzyme model. One approach would be to apply a nonlinear regression (which in this case did not allow for convergence or a good fit). An alternative approach is a more pencil-and-paper type of exercise to test the inhibited enzyme (of the two-enzyme model) for fit by rearranging Eq. (14.12) to solve for A l by calculating A l for the inhibited enzyme component for each datum point or observation made ... 

As a representative serine protease, R-chymotrypsin (ChT) provides an excellent enzyme model for studying the modulation of activity due to its well-defined structure and extensively characterized enzymatic properties [109]. As illustrated in Fig. 5.6a, the active pocket of ChT is surrounded by a ring of positively charged residues. Meanwhile, a number of hydrophobic hot spots are distributed on the... 

The one-point mutated ALS except for the mutation of serine at position 627 to isoleucine exhibited a high resistance to the SU herbicide, chlorsulfuron. On the contrary, the resistance level of these mutated ALS s to the IM herbicide, imazaquin, was lower than that of chlorsulfuron. The mutation of proline at position 171 to alanine and histidine did not confer resistance to imazaquin. On the odier hand, the resistance level of die proline mutated ALS s to the PC herbicides was moderate between diose of chlorsulfuron and imazaquin. These results were correlated to the cross-resistance pattern of the proline-mutated ALS of K. scoparia as already described. From these results, it is considered that rice mutated recombinant ALS s, especially the proline mutants, are useful as resistant enzyme models for the herbicide resistance management at newly developed or developing ALS-inhibiting herbicides. We are now preparing other kinds of proline mutants to confirm this idea. 

Figure 1 Models for analyzing tissue PO2 disappearance rates measured with PO2 microelectrodes after stopping perfusate flow to the carotid body, (a) Inhibitory effects of NO on a single enzyme model for C3tiochrome oxidase (high-affinity pathway) are shown, based on a decrease in maximum tissue PO2 disappearance rate (top panel) and increase in (middle panel) with NO. Predicted 02-dependent PO2 disappearance rates (bottom panel) for NO concentrations of 0 (circle), 100 (triangle). 250 (diamond), and 500 nM (square) are shown, (b) The single-oxidase model was modified by adding a second, low-affinity (high enzyme (top panel) for 02-dependent production of NO by neuronal nitric oxide synthase (nNOS). Predicted 02-dependent PO2 disappearance rates (bottom panel) are shown with the additional amount of O2 consumed by the low-affinity pathway (dashed lines) over that required by the high-affinity pathway (solid lines) for each NO concentration (symbols same as above).

In 1956, Hillman suggested that the tirst step in the formation of thyroxine from di-iodo-L-tyrosine (75) might be the deamination of the ammo acid to its keto analogue (81), and later work has shown that the oxidative coupling of (75) and (81) is an efficient non-enzymic model for the biosynthesis of thyroxine The... 

Organic phase enzyme electrodes (OPEEs) have attracted considerable interest for their applications in environmental and clinical monitoring. The use of organic solvents facilitates, indeed, the detection of compounds poorly soluble in water, prevents microbial contamination, and may circumvent side reactions leading to enzyme deactivation or electrode fouling. Among the various enzymes successfully applied to the fabrication of OPEEs, polyphenol oxidase (PPO) was widely used because Kazandjian and Klibanov demonstrated, 30 years ago, the possibility for this enzyme to work in chloroform. Thanks to its excellent activity in both aqueous and organic solvents, this enzyme which catalyzes the oxidation of phenols and o-diphenols to o-quinone constitutes a convenient enzyme model for the concept and the development of new procedures of OPEE construction. 

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