Hyaluronic Acid

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Macromolecular characterConformationSecondary structure of HA in DMSO (a) and in DMSOcontaining water (b) as proposed by Heatley et al. The dottedlines indicate hydrogen bonds. Arrows indicate the glycolgroups which are resistant to periodate oxidation.24
Macromolecular characterConformationAlthough light scattering33 and intrinsic viscosity experiments in the 1950s and 1960ssuggested that HA chains in solution have an expanded “somewhat stiff” random coilstructure. Cleland showed that the size of HA varies with pH and salt concentration aswould be expected for a flexible polyelectrolyte.In the 1970s, 2-, 3-, and 4-fold (both single and double) helical conformations of HA inthe solid state were discovered from X-ray diffraction.35-39 It was also shown that thehelical form of HA in the solid state depends on the counterion type, pH, temperature,and extent of hydration.By nuclear magnetic relaxation (NMR) measurements on HA solutions, Darke et al.identified two types of residues in HA chains. The relationship between the relaxationtimes and conformational mobility showed that there are two types of domain withdifferent mobility. While one had the mobility of a flexible polymer, the other was so stiffthat it had to contain cooperative structure. The stiff part represented 55-70% of the HAstructure, and this proportion was not altered by changes in ionic strength ortemperature, by addition of a denaturant such as urea, or by moderate changes in pH.Therefore, they suggested that the stiff chain segments differed from the flexible chainsegments by minor covalent features. According to Darke et al. the stiff segments werecomposed of at least 60 disaccharide units.25
Page 1 and 2: Hyaluronic Acid: Structure, Propert
Page 3: Types of network structuresDivided
Page 7 and 8: Mechanical properties of polymeric
Page 9 and 10: Gel systemsGel definition:In 19. ce
Page 11 and 12: Gel systemsGel definition:Newtonian
Page 13 and 14: Gelation of polymersIs influenced b
Page 15 and 16: Natural biomaterials application In
Page 17 and 18: Intelligent polymeric surfaces/inte
Page 19 and 20: Intelligent polymeric surfaces/inte
Page 21 and 22: Role of gel systems in initiation o
Page 23: Macromolecular characterPolyelectro
Page 27 and 28: Hydrodynamic behavior and interacti
Page 29 and 30: Chemical derivatization of HA - Hyl
Page 31 and 32: CHEMICAL MODIFICATION OFHYALURONIC
Page 33 and 34: Molecular StructureThe monomer unit
Page 35 and 36: Rheological BehaviorThe dynamic vis
Page 37 and 38: Size Exclusion ChromatographyTo con
Page 39 and 40: DSC Thermal AnalysisEndothermic fre
Page 41 and 42: DSC Thermal AnalysisThe main DSC ch
Page 43 and 44: HA Alkylation - ConclusionsBased on

Hyaluronic Acid

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