Biopolymers, hydrolysis

The availability of unbound, essential metals such as zinc and copper would not be without toxic consequences. As with iron, low molecular weight zinc complexes can catalyse biopolymer hydrolysis (O Halloran... 

Nucleophilic attack by water generally results in the cleavage of the amide, glycoside, or ester bonds that hold biopolymers together. This process is termed hydrolysis. Conversely, when monomer units are joined together to form biopolymers such as proteins or glycogen, water is a product, as shown below for the formation of a peptide bond between two amino acids. 

A fluid loss additive for hard brine environments has been developed [1685], which consists of hydrocarbon, an anionic surfactant, an alcohol, a sulfonated asphalt, a biopolymer, and optionally an organophilic clay, a copolymer of N-vinyl-2-pyrrolidone and sodium-2-acrylamido-2-methylpropane sulfonate. Methylene-bis-acrylamide can be used as a crosslinker [1398]. Crosslinking imparts thermal stability and resistance to alkaline hydrolysis. 

TEOS is of considerable current use on an industrial scale owing to some advantages over sodium metasilicate. Limitations on the sol-gel processing with TEOS arise in the entrapment of biopolymers in silica. They are caused primarily by the alcohol that is separated in the course of precursor hydrolysis Equation (7). Most... 

Organically-modified silica precursors have three alkoxy groups. As a result, alcohol is separated after the hydrolysis. Its appearance causes a detrimental effect on biopolymers typical to that ofalkoxides. The next disadvantage of these precursors is the absence of universality. They are appropriate only in particular cases. 

Optically active 3-hydroxybutanoic acid and its methyl ester were first prepared by McKenzie, Magnus-Levy, and Emil Fischer.3 The biopolymer PHB and mixed polymers containing (R)-3-hydroxybutanoate and (R)-3-hydroxypentanoate were also discovered long ago,4 5 and are now produced on an industrial scale. .7 As described here, depolymerization by transesterification [H+ or Ti(OR)4 catalysis], or by hydrolysis, produces8-9 the corresponding monomeric (R)-esters and (R)-acids 1. The 3-hydroxybutanoic acid can also be prepared by hydrolysis of the ester.2-10... 

The aliphatic components of SOM, derived from various sources, tend to persist in soil (Almendros et al. 1998 Lichtfouse et al. 1998a Lichtfouse et al. 1998b Mosle et al. 1999 Poirier et al. 2000). The principal source of aliphatic materials in soil is plant cuticular materials, especially cutin, an insoluble polyester of cross-linked hydroxy-fatty acids and hydroxy epoxy-fatty acids (Kolattukudy 2001). Some plant cuticles also contain an acid and base hydrolysis-resistant biopolymer, comprised of aliphatic chains attached to aromatic cores known as cutan (Tegelaar et al. 1989 McKinney et al. 1996 Chefetz 2003 Sachleben et al. 2004). 

Swann, P. G. Casanova, R. A. Desai, A. Frauenhoff, M. M. Urbancic, M. Slomczynska, U. Hopfmger, A. J. Le Breton, G. C. Venton, D. L. Nonspecific protease-catalyzed hydrolysis/synthesis of a mixture of peptides Product diversity and ligand amplification by a molecular trap. Biopolymers 1997, 40, 617-625. 

Enzymatic Hydrolysis in the Presence of Biopolymer Adsorbed Layers... 

There is currently little understanding of the influence of interfacial composition and (nano)structure on the kinetics of enzymatic hydrolysis of biopolymers and lipids. However, a few preliminary studies are beginning to emerge (McClements et al., 2008 Dickinson, 2008). Thus, for example, Jourdain et al. (2009) have shown recently that, in a mixed5 sodium caseinate + dextran sulfate system, the measured interfacial viscosity increased from qs = 220 mN s m 1 without enzyme to qs = 950 mN s m 1 with trypsin present. At the same time, the interfacial elasticity was initially slightly reduced from (7S = 1.6 mN m 1 to (h = 0.7 mN m, although it later returned to close to its original value. Conversely, in the... 

Recall that the equilibria for reactions by which monomers are linked to form biopolymers (whether amides, esters, phosphodiesters, or glycosides) usually favor hydrolysis rather than formation (condensation). The equilibrium positions depend on the exact structures. Some linkages are formed easily if monomer concentrations are high enough, but others are never formed in significant concentrations. Likewise, hydrolysis may be partial at equilibrium or it may be 99.9% or more complete. 

These two processes may be coupled because hydrolysis of biopolymers may contribute to the production of various free monomers such as DFAA and monosaccharides. Polymers and other macromolecules must be hydrolyzed first to LMW compounds (approximately 500 Da) before transport by... 

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