Primary Structure of Hyaluronic Acid

The molecular structure (chemical structure) of any polymeric substance, that is, its chemical composition and way the atoms are connected in the molecule, does not unambiguously determine the behaviour and properties of biopolymer materials constructed of these macromolecules. The properties of such substances depend also on their supramolecular (physical) structure. This refers to the three-dimensional organization of the macromolecules. The supramolecular structures of the polymeric compounds have various forms that determine the structural and functional properties of biopolymers. It is impossible to observe the structure of biological molecules and their dynamics at the atomic level in vivo, though several different physical research methods could be used including hydrodynamic, optical, low-angle X-rays and neutrons diffraction. X-ray structural and neutron-structural analyses, NMR, electron microscopy and scan micro-calorimetry. 

Hyaluronic Acid Preparation, Properties, Application in Biology and Medicine, First Edition. Mikhail A. Selyanin, Petr Ya. Boykov and Vladimir N. Khabarov. 

The presence of polar and non-polar fragments in the macromolecule s structure determines hyaluronan s ability to interact with different chemical compounds and plays a major role in the various conformational transformations. Hyaluronan may exist on the cell surface in an incredibly large number of conformational states (elongated chains, relaxed (non-condensed) helixes, condensed rod-shaped structures, helixes, the structures similar to the pearl necklace and chps ). The HA chains, when interacting with each other, form fibrils, webs and other structures. 

Using NMR spectroscopy it was revealed that HA has such three dimensional arrangements of donor and acceptor groups, which is necessary for a creation of stable hydrogen bonds between the aeetamide, carboxylate groups [7]. 

IR-spectroscopy allowed researchers to find that the arrangement of hydrogen bonds in the hyaluronan macromolecule depends on the nature of the cation. Using NMR and HA oxidation with periodate, it was shown that conformational features of the macromolecule related to the hydrogen bonds between the carboxy, acetamide and hydroxyl groups are preserved in aqueous solutions of the polysaccharide [6]. 

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