Hydrolysis chemical

An alternative approach to peptide sequencing uses a dry method in which the whole sequence is obtained from a mass spectrum, thereby obviating the need for multiple reactions. Mass spec-trometrically, a chain of amino acids breaks down predominantly through cleavage of the amide bonds, similar to the result of chemical hydrolysis. From the mass spectrum, identification of the molecular ion, which gives the total molecular mass, followed by examination of the spectrum for characteristic fragment ions representing successive amino acid residues allows the sequence to be read off in the most favorable cases. 

Degradation of a herbicide by abiotic means may be divided into chemical and photochemical pathways. Herbicides are subject to a wide array of chemical hydrolysis reactions with sorption often playing a key role in the process. Chloro-j -triazines are readily degraded by hydrolysis (256). The degradation of many other herbicide classes has been reviewed (257,258). 

Carboxyhc acid ester, carbamate, organophosphate, and urea hydrolysis are important acid/base-catalyzed reactions. Typically, pesticides that are susceptible to chemical hydrolysis are also susceptible to biological hydrolysis the products of chemical vs biological hydrolysis are generally identical (see eqs. 8, 11, 13, and 14). Consequentiy, the two types of reactions can only be distinguished based on sterile controls or kinetic studies. As a general rule, carboxyhc acid esters, carbamates, and organophosphates are more susceptible to alkaline hydrolysis (24), whereas sulfonylureas are more susceptible to acid hydrolysis (25). 

The detergent industry is the largest user of industrial enzymes. The starch industry, the first significant user of enzymes, developed special symps that could not be made by means of conventional chemical hydrolysis. These were the first products made entirely by enzymatic processes. Materials such as textiles and leather can be produced in a more rational way when using enzyme technology. Eoodstuffs and components of animal feed can be produced by enzymatic processes that require less energy, less equipment, or fewer chemicals compared with traditional techniques. 

Hydrolysis of Nitriles. The chemical hydrolysis of nitriles to acids takes place only under strong acidic or basic conditions and may be accompanied by formation of unwanted and sometimes toxic by-products. Enzymatic hydrolysis of nitriles by nitrile hydratases, nittilases, and amidases is often advantageous since amides or acids can be produced under very mild conditions and in a stereo- or regioselective manner (114,115). 

Alcohol and alcohol ether sulfates are commonly considered as extremely rapid in primary biodegradation. The ester linkage in the molecule of these substances, prone to chemical hydrolysis in acid media, was considered the main reason for the rapid degradation. The hydrolysis of linear primary alcohol sulfates by bacterial enzymes is very easy and has been demonstrated in vitro. Since the direct consequence of this hydrolysis is the loss of surfactant properties, the primary biodegradation, determined by the methylene blue active substance analysis (MBAS), appears to be very rapid. However, the biodegradation of alcohol sulfates cannot be explained by this theory alone as it was proven by Hammerton in 1955 that other alcohol sulfates were highly resistant [386,387]. 

Because 0-acyl chitins appear to be scarcely susceptible to lysozyme, the susceptibility of DBG to Upases has been studied to obtain insight into its biodegradability in vivo. The changes in infrared and X-ray diffraction spectra of the fibers support the slow degradation of DBG by Upases [125,126]. The chemical hydrolysis of DBG to chitin is the most recent way to produce regenerated chitin. 

Faust SD, Gomaa HM. 1972. Chemical hydrolysis of some organic phosphorus and carbamate pesticides in aquatic environments. Environ Lett 3 171 -201. 

Carbamates are subject to chemical hydrolysis, which takes place relatively slowly under neutral or acid conditions, but more rapidly under alkaline conditions. 

First, it should be stated that most of the systems to be described are erodible by nonenzymatic hydrolysis. With one exception, no evidence exists yet that an in vivo degradation is different in mechanism from an uncatalyzed chemical hydrolysis. 

The substrates also underwent 1-3% spontaneous chemical hydrolysis the E values shown were corrected for this hydrolysis. 

The results presented in Tables 3 and 4 deserve some comments. First, a variety of enzymes, including whole-cell preparations, proved suitable for the resolution of different hydroxyalkanephosphorus compounds, giving both unreacted substrates and the products of the enzymatic transformation in good yields and, in some cases, even with full stereoselectivity. Application of both methodologies, acylation of hydroxy substrates rac-41 and rac-43 or the reverse (hydrolysis of the acylated substrates rac-42 and rac-44), enables one to obtain each desired enantiomer of the product. This turned out to be particularly important in those cases when a chemical transformation OH OAc or reverse was difficult to perform. As an example, our work is shown in Scheme 3. In this case, chemical hydrolysis of the acetyl derivative 46 proved difficult due to some side reactions and therefore an enzymatic hydrolysis, using the same enzyme as that in the acylation reaction, was applied. Not only did this provide access to the desired hydroxy derivative 45 but it also allowed to improve its enantiomeric excess. In this way. 

Alcohol obtained by chemical hydrolysis of the corresponding enzymatically resolved acyloxy derivative. 

Each enantiomer of 67 was earlier obtained by an a-chymotrypsin-catalysed resolution of its diethyl ester 68 or its cyclic analogue 69, followed by chemical hydrolysis (Scheme 6)7°... 

Our parallel experiments, in which subtilisin Carlsberg was used to promote hydrolysis of A-acetyl-A-benzyl arenesulfinamides, led to exclusive S-N bond breaking. However, the recovered substrates were racemic. Moreover, blank experiments showed that a spontaneous chemical hydrolysis contributed to the process to a much higher degree than that in the cases shown in Ref. 47. Hence, a conclusion was drawn that in our case the hydrolysis proceeded without involvement of the subtilisin active site Kielbasihski, P. Albrycht, M. Mikolajczyk, M. Unpublished results. 

Tetrachloroethene may be degraded by bacteria via the epoxide, and chemical hydrolysis of this produces CO and CO2 from oxalyl chloride as major products, whereas only low amounts of trichloroacetate were produced (Yoshioka et al. 2002). 

Another example of a biocatalytic transformation ousting a chemical one, in a rather simple reaction, is provided by the Lonza nitotinamide process (Fig. 2.34) (Heveling, 1996). In the final step a nitrile hydratase, produced by whole cells of Rh. rhodoccrous, catalyses the hydrolysis of 3-cyano-pyridine to give nitotinamide in very high purity. In contrast, the conventional chemical hydrolysis afforded a product contaminated with nicotinic acid. 

In soil, the chances that any enzyme will retain its activity are very slim indeed, because inactivation can occur by denaturation, microbial degradation, and sorption (61,62), although it is possible that sorption may protect an enzyme from microbial degradation or chemical hydrolysis and retain its activity. The nature of most enzymes, particularly size and charge characteristics, is such that they would have very low mobility in soils, so that if a secreted enzyme is to have any effect, it must operate close to the point of secretion and its substrate must be able to diffuse to the enzyme. Secretory acid phosphatase was found to be produced in response to P-deficiency stress by epidermal cells of the main tap roots of white lupin and in the cell walls and intercellular spaces of lateral roots (63). Such apoplastic phosphatase is safe from soil but can be effective only when presented with soluble organophosphates, which are often present in the soil. solution (64). However, because the phosphatase activity in the rhizo-sphere originates from a number of sources (65), mostly microbial, and is much higher in the rhizosphere than in bulk soil (66), it seems curious that plants would have a need to secrete phosphatase at all. 

Degradation products of LDPE/(BHT, Chimassorb 944) after long-term exposure to compost, water and air (chemical hydrolysis at pH 5 and pH 7) at room temperature were examined by GC-MS [277] the structural changes in the LDPE film were monitored by DSC and SEC. Among the 79 low-MW degradation products identified by GC-MS the main components were... 

The hydrolysis of esters and thiol esters is a classical reaction. In nature, these reactions are catalyzed by a variety of enzymes in an aqueous environment. Chemically, hydrolysis of esters and thiol esters is catalyzed both by acids and bases (Scheme 9.2). There has been... 

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