Is a Multistep Process

The manufacture of polydimethylsiloxane polymers is a multistep process. The hydrolysis of the chlorosilanes obtained from the direction process yields a mixture of cycHc and linear sdanol-stopped oligomers, called hydrolysate (eq. 7) (21). In some cases, chloro-stopped polymers can also be obtained (59). 

The Permeation Process Barrier polymers limit movement of substances, hereafter called permeants. The movement can be through the polymer or, ia some cases, merely iato the polymer. The overall movement of permeants through a polymer is called permeation, which is a multistep process. First, the permeant molecule coUides with the polymer. Then, it must adsorb to the polymer surface and dissolve iato the polymer bulk. In the polymer, the permeant "hops" or diffuses randomly as its own thermal kinetic energy keeps it moving from vacancy to vacancy while the polymer chains move. The random diffusion yields a net movement from the side of the barrier polymer that is ia contact with a high concentration or partial pressure of the permeant to the side that is ia contact with a low concentration of permeant. After crossing the barrier polymer, the permeant moves to the polymer surface, desorbs, and moves away. 

Agronomic Properties and Nutrient Release Mechanism. The conversion of UF reaction products to plant available nitrogen is a multistep process, involving dissolution and decomposition. Materials are slow to enter the soil solution by virtue of their low solubiUty. Longer polymer chain products are less soluble than shorter chains and take longer to become available to the plants. 

Step 4 of Figure 29.12 Oxidative Decarboxylation The transformation of cr-ketoglutarate to succinyl CoA in step 4 is a multistep process just like the transformation of pyruvate to acetyl CoA that we saw in Figure 29.11. In both cases, an -keto acid loses C02 and is oxidized to a thioester in a series of steps catalyzed by a multienzynie dehydrogenase complex. As in the conversion of pyruvate to acetyl CoA, the reaction involves an initial nucleophilic addition reaction to a-ketoglutarate by thiamin diphosphate vlide, followed by decarboxylation, reaction with lipoamide, elimination of TPP vlide, and finally a transesterification of the dihydrolipoamide thioester with coenzyme A. 

The relative yields of the photoproducts Fe(CO)4, Fe(CO)3, and Fe(CO)2 were strongly wavelength dependent, and the relative amount of Fe(CO)2 increased as shorter wavelength uv light was used. The formation of all of these photoproducts appeared to involve absorption of only a single uv photon by a molecule of Fe(CO)5 (46,68,75). This is quite different from photochemistry in a matrix. When Fe(CO)3 and Fe(CO)2 are produced photolytically from matrix-isolated Fe(CO)5, one uv photon is required to remove each CO group, and the formation of the lower carbonyl species is a multistep process (87,88). 

The development of malignancy is a multistep process with preinvasive (or noninvasive) and invasive phases. The goal of treatment for noninvasive carcinomas is to prevent the development of invasive disease. 

Development of a colorectal neoplasm is a multistep process of genetic and phenotypic alterations of normal bowel epithelium structure and function leading to unregulated cell growth, proliferation, and tumor development. 

The formation of metastasis is a multistep process involving a number of linked sequential events (F5). The main steps are as follows ... 

Belgorodsky et al. (2006) studied the binding of pristine fullerene complexed with cyclodextrin on bovine serum albumin protein demonstrating that the binding is a multistep process. First, the cyclodextrin dissociation from C60 takes place, exposing a fullerene hydrophobic portion, than this portion binds to the protein. 

Reduction Nitro Groups. Nitro reduction is catalyzed by the cytochrome P450 system in the presence of the NADPH cofactor it is a multistep process in which the reduction of the nitro group to a nitroso group is a rate-limiting step. The metabolic conversion of the nitro group in clonazepam to an amine is a representative example. 

Tumorigenesis is a multistep process that begins with cellular transformation, progresses to hyperproliferation and culminates with the acquisition of invasive potential, angiogenic properties and establishment of metastatic lesions [256]. 

Suppose that nucleation is a multistep process characterized by rate constants k0, ku kp, and that once a nucleus containing p atoms of product is formed it becomes an active growth nucleus. The rate of formation of active growth nuclei is therefore... 

The product of the DAHP synthase, 3-deoxy-D-arabino-heptulosonate 7-phosphate, is shown in its cyclic hemiacetal form at the beginning of Eq. 25-2. Its conversion to 3-dehydroquinate is a multistep process that is catalyzed by a single enzyme, 14/15 which is the product of E. coli gene am B. The elimination of... 

The myc Gene Product The jun and fos Gene Products The Transition from Protooncogene to Oncogene Carcinogenesis Is a Multistep Process... 

Animals need to digest food in order to produce the glucose their cells need to respire. Digestion is a multistep process during which food is broken down into substances that can be absorbed by the body. Enzymes speed up digestion by catalyzing the breakdown of food. 

A recent example is the hydrolysis of chloranil with aqueous sodium hydroxide, which is a multistep process leading to the chloranilate dianion, Fig. 5.21 [26]. In a two-phase reaction system consisting of solid chloranil and aqueous sodium hydroxide, the rate-limiting step is the initial attack of hydroxide ion on chloranil. Hydrolysis rates at the 010, 100 and 001 cleavage planes of chloranil were separately measured [27], and different reactivities were found this was rationalised by considering the exposure of the initially reactive functionality (assumed to be the carbonyl group) at the surface, as shown in Fig. 5.22. Hydrolysis at the 010 and 100 planes was shown to be a surface reaction driven by the hydroxide concentration adjacent to the interface the 001 plane was shown to react more slowly by prior dissolution of chloranil before reaction. 

Apply for a Test Account. Applying for an FDA ESG Web Interface Test account is a multistep process. Before beginning the process, the following information should be known ... 

Parallel with the observations of Morrow,30 Mutovkin and Plyuto evidenced that the PCl3-chemisorption is a multistep process according to... 

The fluorescence spectrum shows a red shift at higher pressures (729), indicating that quenching is a multistep process with consecutive vibrational... 

In case of local gastrointestinal treatments nucleic acid drugs shall be taken up by enterocytes, usually through endocytosis. The route of uptake determines, subsequently, nucleic acid trafficking and lifetime in the cell. Endocytosis is a multistep process involving binding, internalization, formation of endosomes, fusion with lysosomes, and lysis. The low pH and enzymes within... 

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