Scission hydrolytic

Scheme 4 The hydrolytic scission of a cellulose chain providing the sites for free radical oxidation.

Anhydro-D-glucose resulted, as mentioned, from the hydrolytic removal of a halogen atom at C6. Similar hydrolytic scission of sugar esters of carboxylic acids takes place without dehydration and with the liberation of the normal sugar. Thus, saponification of 6-benzoyl- or... 

Amylose is thus extremely susceptible to degradation in the presence of hydroxyl ion. Two mechanisms may be involved (1) a stepwise degradation caused by the reducing end-group s undergoing enolization followed by degradation to acidic products (this must occur in the presence or absence of oxygen), and (2) a random, catalytic, hydrolytic scission of 4—>l-a-D... 

In 1896, Fischer developed the phenylhydrazine test" for the detection of hydrolytic scission of disaccharides, especially by enzymes this depends on the fact that the phenylosazones of disaccharides are soluble in hot water, whereas those of the monosaccharides are not. Lactose is hydrolyzed by emulsin (1894) and by lactase it is not fermentable by yeast, and is unaffected by invertase (1894). An extract of the small intestine of horses and cattle, especially from young animals, hydrolyzes lactose (1896). The action of enzymes on lactose allowed it to be classified, along with cellobiose and maltose, with the normal (and not the y-type of) methyl glucoside (1914). In the discussion of maltose, the relationship of lactose to the /9-series will be mentioned later. 

For the release of an unaltered base, the sugar moiety must be damaged. In principle, the base could already be released from a radical site at the sugar moiety, i.e. on the time-scale of the lifetime of the DNA radicals. The observation of 2-dRL incorporated into DNA as a product formed upon OH attack shows that a damage at C(l ) contributes to the release of an unaltered base. In the carbohydrate series, hydrolytic scission at the glycosidic linkage when this site contains a free-radical is a well-documented phenomenon, and it has been estimated that the rate of reaction must be faster than 35 s 1 (von Sonntag and Schuchmann 2001). As it stands, it cannot be excluded, that under certain conditions the base release from the C(l ) radical [reaction (38)] occurs in competition to its oxidation [reaction (2)]. In a cellular environment, there is also the reduction of DNA... 

Formation of Hot Spots" for Hydrolytic Scission at a Predetermined Position... 

Approximately 150 different amino acid residues have been reported in proteins (1 5). At least half of these could undergo chemical deteriorations under the conditions of stress usually encountered. Many of these deteriorative reactions involve hydrolytic scissions, not only of peptide bonds but of the many different nonprotein substances added covalently to proteins postribosomally. These susceptible side chain groups are indole, phenoxy, thioether, amino, imidazole, sulfhydryl, and derivatives of serine and threonine (such as 0-glycosyl or O-phosphoryl), the disulfides of cystine, and, of course, the amides (such as asparagine and glutamine). With strong acid or alkali, other residues, such as serine and threonine, also are less stable. 

Hydrolytic scissions of disulfides have been intensively studied, particularly by the laboratory of Schoberl in Germany (30). It has been shown that reactions such as these can occur on the addition of small amounts of metal ions, such as copper or mercury (31 ). Lysozyme, for example, is rapidly inactivated by small amounts of cupric ion (Figure 15). But in many cases, results of this nature have not been definitely shown to be due to disulfide bond splitting. Other possible causes, such as racemization, must also be considered. 

M. Komiyama, Sequence-Specific and Hydrolytic Scission of DNA and RNA by Lanthanide Complex-OligoDNA Hybrid , J. Biochem., 118,665 (1995)... 

The measurements indicated that each molecule of a pyrrole homolog takes up about 1.6 to 1.7 moles of ozone. After hydrolytic scission of the reaction product, 80 to 87% of the nitrogen bound in the pyrrole molecule is recovered in the form of ammonia (methylamine). If the quantity of ammonia is assumed to be a measure of the quantity of pyrrole which has reacted with ozone, the conclusion can be drawn that 1 molecule of pyrrole homolog has reacted with 2 molecules of ozone. 

Hydroxylation of one aromatic ring Conjugation of phenolic products with glucuronic acid or sulfate Hydrolytic scission of the hydantoin ring at the bond between carbons-3 and -4 to give 5,5-diphenylhydantoic acid... 

Codeine dihydromethine [xn] has now been prepared by the sodium-ammonia reduction of codeine methiodide, together with dihydrodesoxy-codeine-C dihydromethine [xiii]. Both [xii] and [xni] result from the sodium and liquid ammonia reduction of a-codeimethine [xiv] [2] (cf. p. 106). The sodium and liquid ammonia reduction of dihydrocodeine methiodide affords a-tetrahydrocodeimethine, and the reduction of /3-codeimethine [xv] yields neopine dihydromethine [xvi]. When the methiodide of the latter is heated with sodium cyciohexyloxide in cyciohexanol a mixture of methyl-morphenol [xvn] and (-f-)-6-hydroxy-3-methoxy-5 6 7 8 9 10-hexahydro-phenanthrylene-4 5-oxide [xviii] is obtained. The latter structure is assigned to the product on account of the close resemblance of its ultra-violet absorption spectrum to that of a-codeimethine. This represents a new type of degradation with hydrolytic scission of the side-chain [2]. Metathebainone methine has also been degraded in this way [2]. 

Further chemical changes that occur during dextrinization should be discussed separately for the case of formation of British gum, and for variously catalyzed thermal processes. Thus, when starch (1) is heated in the presence of moisture, random hydrolytic scission at the (1 - 6), and more readily at the (1 — 4), linkages has been proposed to occur in the branched chains of amylopectin, to give more-linear structures, leading to the observed decrease in viscosity. o-Glucosyl oxocarbonium ions (2) were postulated as intermediates, but free radicals (3) formed by homolytic fission at the (1 4)-glycosidic bond are also feasible. 

Maturation is the next stage in the preparation of dextrins. It is necessary to allow the catalyst to penetrate into the starch granule, in order to correct imprecise distribution of acid, should this have happened in the first stage. The matured source is then subjected to drying, to avoid hydrolytic scission of the starch in the first period of roasting (as well as gelatinization, or... 

When resist films coated with formulations comprising this endcapped polymer with 10% by weight of various onium salts are exposed to DUV photons or an electron beam, acids are generated from the onium salts that go on to catalyze the hydrolytic scission process of the endcap moieties, as shown in Scheme 7.45, with the net result being the evaporation of the irradiated areas, with rather catastrophic implications for the contamination of the optical elements of exposure tools. In this mechanism, the acid attacks the lone electron pair on oxygen and brings about the depolymerization of the entire polymer. This, in essence, was the first resist system that self-developed reliably at room temperature without any further processing or special conditions. ... 

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