Protein/polysaccharide composites

A polysaccharide can be added as a component in a protein system to produce a protein-polysaccharide composite structure. Tolstoguzov (2003) reviewed the main function of protein and polysaccharide in protein-polysaccharide food formulation. Generally, polysaccharides have less surface activity in comparison to proteins. This inferiority is related to their low flexibility and monotonic repetition of the monomer units in the backbone. The low surface activity of polysaccharides results in their inability to form a primary adsorbed layer in the system. The nature of interactions between polysaccharides and adsorbed proteins, as well as their influence on colloid stability, can either stabilize or destabilize the emulsions. Attractive protein-polysaccharide interactions can enhance the emulsion stability by forming a thicker and stronger steric-stabilizing layer. In contrast, the attractive interactions... 

Chemical analyses of capsular material from a number of bacteria show wide differences in composition. For this reason it is impossible to make statements which apply to all bacteria. In some organisms the capsular material appears to be a glycoprotein in others, a protein-polysaccharide complex in still others, a polysaccharide framework with the spaces filled in by a larger amount of glutamyl polypeptide. 

Finally, the versatility of the technique and its use as a chemical imaging technique allow retrieval of the structural composition of a sample, in order to understand its complete recipe [Mazel et al. 2008]. The composition of a sample from the Dogon statuette 71.1935.105.169 has been studied. Proteins, polysaccharides, lipids and minerals have been found. The distribution of these different chemicals shows that the patina sample can be divided into four different layers (Figure 15.14). Layers 1 and 3 are mainly composed of proteins whereas layer 2 consists of lipids and polysaccharides. Minerals can be found at the interface of layers 1 and 2, and 2 and 3. Finally, layer 4 is the more complex because it contains all the types of compounds. One can suppose that it is in fact composed of different layers that do not appear clearly on the cross-section. 

In general, surface activity behaviour in food colloids is dominated by the proteins and the low-molecular-weight surfactants. The competition between proteins and surfactants determines the composition and properties of adsorbed layers at oil-water and air-water interfaces. In the case of mixtures of proteins with non-surface-active polysaccharides, the resulting surface-activity is usually attributed to the adsorption of protein-polysaccharide complexes. By understanding relationships between the protein-protein, protein-surfactant and protein-polysaccharide interactions and the properties of the resulting adsorbed layers, we can aim to... 

Smith, Q. T., Lindenbaum, A. Composition and calcium-binding of protein-polysaccharides of calf nasal septum and scapula. Calc. Tiss. Res. 7, 290 (1971)... 

Chiral separations can be considered as a special subset of HPLC. The FDA suggests that for drugs developed as a single enantiomer, the stereoisomeric composition should be evaluated in terms of identity and purity [6]. The undesired enantiomer should be treated as a structurally related impurity, and its level should be assessed by an enantioselective means. The interpretation is that methods should be in place that resolve the drug substance from its enantiomer and should have the ability to quantitate the enantiomer at the 0.1% level. Chiral separations can be performed in reversed phase, normal phase, and polar organic phase modes. Chiral stationary phases (CSP) range from small bonded synthetic selectors to large biopolymers. The classes of CSP that are most commonly utilized in the pharmaceutical industry include Pirkle type, crown ether, protein, polysaccharide, and antibiotic phases [7]. 

For historical reasons many pharmaceutical enzymes are assayed with physiological or biopolymeric substrates (proteins, polysaccharides, bacteria, oil emulsions), which causes a number of theoretical and practical problems. The interpretation of results is difficult when natural substrates are converted into products that are substrates themselves for the next enzymatic attack. Reaction rates often depend on the position of the scissile bonds in the molecule and the chemical nature of the moieties. Hydrolysis can proceed simultaneously on various bonds at various rates. In proteolysis it is assumed that some products are liberated only after denaturation and that during the reaction course new peptide bonds become accessible for hydrolysis. In these cases the enzymatic mechanisms become exceedingly complex, kinetic parameters are apparent values, and experimental results are strongly influenced by the reaction conditions. Reproducibility problems can occur upon assaying proteinases with a limited specificity for particular casein types. Bromelain and pancreatic proteinase, FEP pharmaceutical enzyme standards, are assayed with a casein substrate. The extent of soluble peptide release is a measure of proteolytic activity. However, due to limited specificity, some proteinases release peptides with a nonrandom aromatic amino acid composition. Contamination of casein preparations with protein and of test enzyme substances with other proteinases biases the assay results. Under these conditions, relative assay methods are indicated. 

Articular cartilage is a complex composite polymeric material that consists principally of a network of collagen (in various states of aggregation), protein-polysaccharides, living cells (chondrocytes) and Inorganic ions. The latter are primarily counterions to the charged moieties of the polyelectrolytes of the matrix. The entire network is swollen with water, a major fraction of which is in regions between its fibrous elements. On compression this water is exuded. The tissue s network structure, composition, and equilibrium fluid contents vary with depth from the surface ( >A> ) Its structure and chemical composition have been extensively reviewed ... 

Biological organisms make use of proteins, polysaccharides and combinations of these two types of molecule in the polymeric phases that are found in a living organism together with simple calcium salts. Chemical composition... 

The aim of this work is to determine the values of the interfacial tension in a two-phasic water-protein-polysaccharide mixture close to its critical condition, i.e. at phase compositions as close as possible to the critical point. The distance with respect to the critical point is expressed as the density difference between the coexisting phases, since at the critical point, this density difference becomes zero. A rheo-optical methodology [21, 22] based on the analysis of the SALS patterns dnring fibril break-np was nsed. 

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