Thermosensitive sol-gel reversible hydrogels.

Polyionic hydrocolloids for the intestinal delivery of protein drugs: alginate and chitosan--a review.

Protein release from alginate matrices.

Introduction. Agar. Starch. Gelatin. Carrageenan. Xanthum Gum. Gellan Gum. Gallactomannans. Gum Arabic. Pectins. Milk Proteins. Cellulosis. Tragacanth and Karaya. Xyloglucan. Curdlan. Glucans. Soluble Soybean Polysaccharide. Bacterial Cellulose. Microcrystalline Cellulose. Gums for Coating and Adhesives.Chitosan Hydrogels. Alginates. Frutafit-Inulin. The CRC Emulsifying Biopolymer.

Handbook of hydrocolloids.

The structural and mechanical properties of gels formed from biopolymers are discussed both in terms of the techniques used to characterise these systems, and in terms of the systems themselves The techniques included are spectroscopic, chiroptical and scattering methods, optical and electron microscopy, thermodynamic and kinetic methods and rheological characterisation The systems considered are presented in order of increasing complexity of secondary, tertiary and quaternary structure, starting with gels which arise from essentially ‘disordered’ biopolymers via formation of ‘quasicrystalline’ junction zones (eg gelatin, carrageenans, agarose, alginates etc), and extending to networks derived from globular and rod-like species (fibrin, globular proteins, caseins, myosin) by a variety of crosslinking mechanisms Throughout the text, efforts are made to pursue the link (both from experiment and from theory) between the structural methods and mechanical measurements As far as we are aware this is the first major Review of this area since that of J D Ferry in 1948 — The interest shown by polymer physicists in more complex biochemical systems, and the multi-disciplinary approaches now being applied in this area, make the format adopted here, in our opinion, the most logical and appropriate

Structural and mechanical properties of biopolymer gels

Associations of like and unlike polysaccharides: Mechanism and specificity in galactomannans, interacting bacterial polysaccharides, and related systems

Many polysaccharide chains can adopt ordered helical and ribbon-like secondary structures. It seems however that these chains are often so stiff and extended that the cooperative interactions necessary for stability in the solvent environment can only be achieved when inter-chain as well as intra-chain interactions are favorable. Hence we commonly find two-or more-stranded associations of helices, of ribbons, or of helices with ribbons. These can be regarded as tertiary and higher levels of structure. The ordered secondary structure characteristically requires a regular repeating sequence of sugar residues, and the termination of this sequence by insertion of a residue of different type may also terminate the secondary structure and hence the association in which it is involved. This is the mechanism by which native polysaccharides may link up to form three dimensional networks, or gels, in which state they perform their natural roles in maintaining the hydration and integrity of biological tissues. For several polysaccharides there is evidence that the mechanism of biological control over the fine topology and properties of the gel network is mediated by enzymes which modify sugar residues at the polymer level to change the pattern of “interrupting” sugar residues.

Secondary and Tertiary Structure of Polysaccharides in Solutions and Gels

Complete assignments are given for the 1H nuclear magnetic resonance (NMR) spectra at 300 MHz of chondroitin 4-sulphate, chondroitin 6-sulphate and hyaluronate in deuterium oxide solution, supported by spin decoupling and computer simulation. Coupling constants and chemical shifts are as expected from spectra of the model glycosides, methyl β-d-glucopyranosiduronate, methyl 2-acetamido-2-deoxy-β-d-glucopyranoside and methyl 2-acetamido-2-deoxy-β-d-galactopyranoside, when allowance is made for systematic influences on chemical shifts of interglycosidic linkages and sulphate substitution.



As reported elsewhere, addition of alkali causes the hyaluronate spectrum to sharpen considerably. This is taken to indicate that segmental motion is enhanced by disruption of some system of inter-residue bonding on ionisation of hydroxy groups. Concomitant changes in chemical shifts are seen mainly for H-2 of the glucuronate residue, and the CH3 and H-2 of the acetamidodeoxyglucose residue. Similar effects are not seen for chondroitin sulphates, either in line widths or chemical shifts.



Comparison of the spectra of hyaluronate, chondroitin sulphates, and the model glycosides, indicates that proton chemical shifts are sensitive to the conformation differences between the polysaccharides in alkaline solution, but do not detect the differences in neutral solution that are known from NMR relaxation to be present. The altered configuration and/or substitution pattern of the acetamidodeoxyhexose residue in hyaluronate compared with chondroitin sulphates appears to have a critical influence on overall conformation in both alkaline and neutral solution.

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1432-1033.1979.tb12919.x

Solution Conformation of Glycosaminoglycans: Assignment of the 300‐MHz 1H‐Magnetic Resonance Spectra of Chondroitin 4‐Sulphate, Chondroitin 6‐Sulphate and Hyaluronate, and Investigation of an Alkali‐Induced Conformation Change

Conformation and intermolecular interactions of carbohydrate chains

In an attempt to relate conformational features to overall chain flexibilities of polysaccharides as determined by hydrodynamic volume and (for polyelectrolytes) response to ionic strength, a series of carrageenans was derived from the same alternating copolymeric backbone (2) by controlled chemical intoduction of 3,6-anhydro-D-galactose 2-sulphate residues in place of D-galactose 2,6-disulphate. This change is equivalent to replacement of residues in the 4C1 chair conformation with ‘stiff’ linkages to their neighbours, by those in the 1C4 conformation joined by ‘flexible’ linkages. Chain flexibilities are characterised in terms of the parameter B introduced by Smidsrod and Haug, whcih is determined from the response of intrinsic viscosity to ionic strength. Semi-empirical values are calculated for comparison by assuming a chain with fixed, standard bond lengths, angles, and ring conformations, within which motions are constrained only by van der Waals attractions and repulsions. Standard methods of configurational statistics lead to values for the Kuhn persistence length Am, which were then converted by use of an empirical relationship into B values. Experimetal evidence is given that residue replacement does indeed occur at random, as supposed in the theoretical calculations. Good agreement is found between calculation and experiment and we therefore propose a simple method for semi-quantitative prediction of statistical segment length and response of polysaccharide polyelectrolyte to salt, taking into account (i) stereochemical features which determine local freedom of rotation about glycosidic and aglycone bonds and (ii) geometry of individual sugar residues in the chain.

E. Jane Welsh

Papers

Associations of like and unlike polysaccharides: Mechanism and specificity in galactomannans, interacting bacterial polysaccharides, and related systems

Secondary and Tertiary Structure of Polysaccharides in Solutions and Gels

Solution Conformation of Glycosaminoglycans: Assignment of the 300‐MHz 1H‐Magnetic Resonance Spectra of Chondroitin 4‐Sulphate, Chondroitin 6‐Sulphate and Hyaluronate, and Investigation of an Alkali‐Induced Conformation Change

Conformation and intermolecular interactions of carbohydrate chains

Relation between primary structure and chain flexibility of random coil polysaccharides: calculation and experiment for a range of model carrageenans