Sodium hyaluronate structure

Mitra et al.AS have also re-refined the structures of the regular (26) and relaxed 4-fold sodium hyaluronate (27) helices for direct comparison with their own analysis of the relaxed 4-fold helix of potassium hyaluronate (29). Within experimental error, their final models strongly support the original results, which have been described here. 

The vitreous humor volume is about 4 ml in an adult. Its viscosity is 2-4 times that of water and is dependent on the concentration of sodium hyaluronate. Although it has the outward appearance of a transparent, viscoelastic gel, it contains fine diameter type II collagen fibers (8-12 nm diameter) that entrap the large coiled hyaluronic acid molecules. These fibers give the gel a spherical structure with a dent in the anterior surface (the hyaloid fossa). The main constituent of the vitreous is water (98%) with a refractive index of 1.33, but the gel is... 

Study on the rapid transport of a polymer in dextran solutions, first observed by Preston et al., is extended into two directions. They arc (1) enhancement effect on the transport rate of polyvinylpyrrolidone (PVP) by the addition of a simple salt, and (2) extension to the transport of linear polyelectrolytes. The enhancement effect was observed on the structured flow as well as on the transport rate. The enhancement effect was correlated with the densities of the solutions in the lower compartment of the diffusion cell. The correlation was improved when the rate was corrected for the differences in viscosities. We have found that effects of charges on the polymers favor the rapid transport of polyacrylates (PA) and sodium hyaluronate. Counterion condensation was manifested in the transport rate of PA. Transport rates of several salts of PA in the absence of added salt increased linearly with their partial specific volumes in water. 

Figure 16.8 Structure of sodium hyaluronate (hyaluronic acid, HA).

Hyaluronate. Synthetic polymers and polysaccharides have been subjected to dichroism studies for structural information (Liang and Marchessault, 1959b Pearson et al, 1960). Quinn and Bettelheim (1963) used such methods on sodium hyaluronate isolated from umbilical cords. Figures 6.7a and 6.7b show the spectrum of an oriented sodium hyaluronate film which has been elongated by 40%. Table 6.6 contains band assignments made by these workers based on data reported in the literature. 

Fig. 21. Chemical structure formula of the hyaluronic acid, consisting of a repetitive basic unit made up by /1-D-glucuronic acid (1) and N-acetyl-/ -D-galactosamine (2). The glycosidic bonds are alternating p 1-3 and p 1-4 bonded. The molecular formula of the linear polymeric sodium hyaluronic acid reads as follows (Ci4H2oNNaOn)n...

Ultrapurified forms of sodium hyaluronate from these different sources always retain the same structure. The molecular weight can vary considerably, changing the physical characteristics and, therefore, representing a considerable influence. 

The glycosaminoglycans, sodium hyaluronate and chondroitin sulfate, bear structural resemblance to heparin. Several studies have demonstrated a slight an-ticoagulative effect of these materials (Pandolfi 8c Hedner, 1984). Viscoelastic substances work hemostatically which is caused predominantly through tamponade (Packer et al., 1985). 

Mengher LS, Pandher KS, Bron AJ, Davey CC. Effect of sodium hyaluronate (0.1%) on break-up time (NIBUT) in patients with dry eyes. Br J Ophthalmol 1986 70 442-447 Meyer DR, McCulley JP. Different prospects of risk management from in vitro toxicology and its relevance to the evolution of viscoelastic formulations. Rosen ES (ed) Viscoealstic Materials Basic Science and Clinical Applications. New York, Pergamon Press, 1989, S. 45-90 Meyer K, Palmer JW. The polysaccharide of the vitreous humor. J Biol Chem 1934 107 629-634 Meyer K. Chemical structure of hyaluronic acid. Fed Proc 1958 17 1075-1077... 

Dougados M. Sodium hyaluronate therapy in osteoarthritis arguments for a potential beneficial structural effect. Semin Arthritis Rheum 2000 30 19-25. 

The vitreous situates behind the lens and occupies 80% of the volume of the eyeball. It is a gel that is 99% water, with collagen fiber, sodium hyaluronic acid, and a small amount of soluble protein and glycoproteins. The proposed structure is a composite of collagen fibers and coiled hyaluronic acid in a network. This stmcture operates as a stable hydrogel to maintain the mechanical and optical properties of the vitreous (humor) [18]. A stmcture in which hyaluronic acid is entangled with collagen fibers was proposed based on electron microscopy as shown in Fig. 2 [19]. This fiber is a one-dimensional (ID) rather than two-dimensional (2D) stmcture for the cornea and is fiuee-dimensional (3D) for the lens. 

Hyaluronic acid is a linear polysaccharide found in the highest concentrations in soft connective tissues where it fills an important structural role in the organization of the extracellular matrix (23,24). It has been used in ophthalmic preparations to enhance ocular absorption of timolol, a beta blocker used for the treatment of glaucoma (25), and in a viscoelastic tear formulation for conjunctivitis (26). The covalent binding of adriamycin and daunomycin to sodium hy-aluronate to produce water-soluble conjugates was recently reported (27). 

Because glycosaminoglycans do not have significant structural differences, their Py-MS spectra are also similar. As an example, the Py-MS results for hyaluronic acid potassium salt and for chondroitin 6-sulfate sodium salt are shown in Figures 7.14.1 and 7.14.2 respectively [3],... 

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