Functional properties modification

There has been an extensive search for additional opioid receptor genes with homology to p, 8, and k receptors which was, however, unsuccessfiil. It is likely, therefore, that the functional properties of the subdivision of p, 8, and k receptors as well as that of the e and X receptors results from alternate mRNA processing, posttranslational modification of the receptor, and/ or from the formation of homo- and heterodimeric receptor complexes. 

Within the scope of this review, the contributions of the last decade concerning cell-wall polysaccharides isolated from woody and other plant tissues will be reviewed according to the above-proposed classification of hemicelluloses including larch arabinogalactans. The present review article updates and extends previous reviews [3-5] and will focus in particular on new investigated plant sources, isolation methods, structural features, physicochemical and various functional properties of hemicelluloses. Attention will also be paid to the modification of isolated hemicelluloses or hemicellulosic materials and the appHcation possibiUties of hemicelluloses and their derivatives, including their use for the production of composite materials and other biomaterials. 

Due to the lack of a commercial supply, as well as their usually low molecular weight and poor solubility, xylans have found little industrial utility and interest in their modification has been rather low in comparison to commercially available polysaccharides such as cellulose or starch. With the aim of improving the functional properties of xylans and/or imparting new functionalities to them, various chemical modifications have been investigated during the past decade. Most of them were presented in recent reviews [3,399]. 

The early works by Muzzarelh et al. [179] showed that tyrosinase converts a wide range of phenohc substrates into electrophihc o-quinones [180]. Tyrosinase was used to convert phenols into reactive o-quinones which then underwent chemical reactions leading to grafting onto chitosan. A review article showed that in general the tyrosinase-catalyzed chitosan modifications resulted in dramatic changes in functional properties [181]. 

The introduction of redox activity through a Co11 center in place of redox-inactive Zn11 can be revealing. Carboxypeptidase B (another Zn enzyme) and its Co-substituted derivative were oxidized by the active-site-selective m-chloroperbenzoic acid.1209 In the Co-substituted oxidized (Co111) enzyme there was a decrease in both the peptidase and the esterase activities, whereas in the zinc enzyme only the peptidase activity decreased. Oxidation of the native enzyme resulted in modification of a methionine residue instead. These studies indicate that the two metal ions impose different structural and functional properties on the active site, leading to differing reactivities of specific amino acid residues. Replacement of zinc(II) in the methyltransferase enzyme MT2-A by cobalt(II) yields an enzyme with enhanced activity, where spectroscopy also indicates coordination by two thiolates and two histidines, supported by EXAFS analysis of the zinc coordination sphere.1210... 

Functional property tests were conducted in duplicate. AACC (21) methods were used for the determination of water hydration capacity (Method 88-04) and nitrogen solubility index (NSI) (Method 46-23). Oil absorption capacity was measured by the procedures of Lin et al. (22) and oil emulsification by a modification (22) of the Inklaar and Fortuin (23) method. Pasting characteristics of 12.0% (w/v, db) slurries of the flours and processed products were determined on a Brabender Visco/Amylograph (Method 22-10). The slurries were heated from 30 to 95°C before cooling to 50°C to obtain the cold paste viscosity value. Gelation experiments were conducted by heating 15% (w/v db) slurries in sealed stainless steel containers to 90°C for 45 min in a water bath C3). 

It is also essential that any functional properties of the mutant protein that can be assessed be assessed. Although the substitution of one particular residue for another may be made in an attempt to determine the effect of the mutation on a specific property of a protein, it is quite possible that other properties that are not of immediate concern may be modified unintentionally and that these modifications may have important, otherwise occult, implications for the functional studies that are of immediate interest (vide infra). In the case of electron transfer proteins it may be useful, for example, to produce a family of mutants the members of which differ from each other only in their reduction potentials. This result may prove to be difficult to achieve because many mutations that perturb the reduction potential of a protein may also change its electrostatic properties or its reorganizational barrier to electron transfer. Depending on the experiments to be conducted with the mutants, these other properties may prove to be more important considerations than the reduction potentials of the mutants. In summary, new mutant proteins are ideally studied as if they were altogether new proteins of the same general class as the wild-type protein, and assumptions regarding the properties of such mutants should be kept to a minimum. 

Initial attempts at producing the Thr mutant of Pro-35 were unsuccessful in producing sufficient quantities of the mutant protein for functional analysis [129], suggesting that cytochrome c is significantly more sensitive to modifications at this prolyl residue than at Pro-71. Either the Thr-35 mutant is not properly processed to mature cytochrome c, it is less thermally stable than wild-type iso-2-cytochrome c, or its functional properties are sufficiently perturbed that it cannot function adequately under physiological conditions to support yeast growth. 

The increase in levels of tissue CAT is compatible with previous results which showed that LLLT induced an increase in CAT activity of irradiated isolated cardio-myocytes compared to controls. It was suggested that laser therapy efficacy in chronic wounds and ulcers can be attributed to the activation of CAT in tissue fluids [62]. He-Ne laser has been shown to cause photoactivation and structural modifications of catalase enzymes that positively correlated with its functional properties in cell free system [63]. 

Ena matic Modification of Soy Proteins To Improve Their Functional Properties for Food Use... 

Soy protein is a low-cost food protein with good nutritional value, but its uses in foods are limited because of inferior functional properties as compared to those of commonly used animal proteins such as casein and albumin (1.2). Therefore, modifications are often required to make soy protein more suitable for food use. Improved functional properties, particularly in the pH range of 3 to 7 where most food systems belong, have been achieved by non-enzymatic methods, including succinylation (3-5), deamidation (6.7), and phosphorylation (8.9). 

Modler, H.W. (1985). Functional properties of nonfat dairy ingredients — a review. Modification of products containing casein. Journal of Dairy Science, 68, 2195-2205. 

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