Bonds hydrolysis

A major advance was devised by Pehr Edman (University of Lund Sweden) that has become the standard method for N terminal residue analysis The Edman degrada tion IS based on the chemistry shown m Figure 27 12 A peptide reacts with phenyl iso thiocyanate to give a phenylthwcarbamoyl (PTC) denvative as shown m the first step This PTC derivative is then treated with an acid m an anhydrous medium (Edman used mtromethane saturated with hydrogen chloride) to cleave the amide bond between the N terminal ammo acid and the remainder of the peptide No other peptide bonds are cleaved m this step as amide bond hydrolysis requires water When the PTC derivative IS treated with acid m an anhydrous medium the sulfur atom of the C=S unit acts as... 

Aspaityl proteinases are proteinases that utilize the terminal carboxyl moiety of the side chain of aspartic acid to effect peptide bond hydrolysis. 

Silicon alkoxide groups, 455 Silicon-containing polymers, 450-460 Silicon-methoxy bonds, hydrolysis of,... 

Bada, XL., Schoeninger, M.J. and Schimmelmann, M. 1989 Isotopic fractionation during peptide bond hydrolysis. Geochimica et CosmochimicaActa 53 3337-3341. 

Lipases are the enzymes for which a number of examples of a promiscuous activity have been reported. Thus, in addition to their original activity comprising hydrolysis of lipids and, generally, catalysis of the hydrolysis or formation of carboxylic esters [107], lipases have been found to catalyze not only the carbon-nitrogen bond hydrolysis/formation (in this case, acting as proteases) but also the carbon-carbon bond-forming reactions. The first example of a lipase-catalyzed Michael addition to 2-(trifluoromethyl)propenoic acid was described as early as in 1986 [108]. Michael addition of secondary amines to acrylonitrile is up to 100-fold faster in the presence of various preparations of the hpase from Candida antariica (CAL-B) than in the absence of a biocatalyst (Scheme 5.20) [109]. 

Aldehydes and diethyl(triethylgermyl)phosphine give (38) while unsaturated aldehydes and ketones form 1,4-dipolar addition products (39), presumably via ionic cleavage of the germanium-phosphorus bond. Hydrolysis of these compounds produces the y-substituted phosphorus aldehydes or ketones. -... 

Acidity of the reaction mixes after incubation increased as the activity of the probe ro —se during determination of pectinesterase activity of the samples.1t was caused by the for—mation of carboxyl groups as a result of pectin ester bonds hydrolysis under pectinesterase ac—tion.That is why kinetic characteristics of substrate hydrolysis were measured according to the speed of pectin hydrolysis by continuously recorded titration of the free carboxyl groups (11). 

Schulz, W. G. Nieman, R. A. Skibo, E. B. Evidence for DNA phosphate backbone alkylation and cleavage by pyrrolo[l,2-a] benzimidazoles, small molecules capable of causing sequence specific phosphodiester bond hydrolysis. Proc. Natl. Acad. Sci. USA 1995, 92, 11854-11858. 

One of the chief defects of the phosphorus based pyrazolyl (PZ) ligands appears to be the hydrolytic sensitivity of the P—N bond particularly after interaction of the ligand with transition metal ions. The interactions of PhP(0)(3,5-Me2pz)2 and Ph2P(0)(3,5-Me2pz)2 with Pd11 salts accelerates the P—N bond hydrolysis.177... 

Reports on the sensitivity of many neutral and cationic NHP derivatives towards air and moisture reveal in most cases pronounced reactivity even with traces of H20 causing P-X bond hydrolysis whereas genuine oxidation processes appear to play a role only for P-H and P-alkyl NHPs [71]. Controlled hydrolysis proceeds at low temperature as depicted in Scheme 9 to give secondary phosphine oxides 17 as initial product which may react further with excess NHP to phosphinous acid anhydrides 18.3 Both products may be obtained as isolable products starting from P-chloro NHPs [48], Hydrolysis at ambient temperature may be unselective and... 

Fig. 19 Structure of LA-PRX (above) and degradation of LA-PRX (below), (a) Threaded a-CDs prevent hydrolysis of PLLA in LA-PRX. (b) LA-PRX converts into LA-pPRX by peptide linkage cleavage at bulky end-capping groups through action of papain, (c) Ester bond hydrolysis in the PLLA chain begins by an exposure of PLLA to water by release of a-CDs from LA-pPRX. Reprinted from [292] with permission...

M. N. James, and A. R. Sielecki, Stereochemical analysis of peptide bond hydrolysis catalyzed by the aspartic proteinase penicillopepsin, Biochemistry 24 3701 (1985). 

Other Primary Active Transporters (not Diphosphate-Bond-Hydrolysis Driven)... 

In contrast to cellulosic dyeing with reactive dyes, the fibroin-dye bonds are remarkably stable in aqueous media of pH 4 to 10 [117]. Since there exists only a negligible amount of bond hydrolysis even at high temperature and in a medium of pH 2, the cleavage of the fibroin-dye bond is not a problem in reactive-dyed silk. The stability of these bonds when dyeing with difluoropyrimidine dyes is the highest in both acidic and basic media [118]. 

Fig. 3.2. Common catalytic groups of hydrolases involved in ester and amide bond hydrolysis (Z+ = electrophilic component polarizing the carbonyl group Y = nucleophilic group attacking the carbonyl C-atom H-B = proton donor transforming the -OR or -NR R" moiety into...

Fig. 3.10. Mechanism of peptide bond hydrolysis by pepsin, an aspartic endopeptidase [2]...

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