Biological properties of hyaluronan in aqueous solution are controlled and sequestered by reversible tertiary structures, defined by NMR spectroscopy.
Hyaluronan (HA) is a ubiquitous polysaccharide of (predominantly) animal origin that has important medical applications in joint, skin, and eye conditions. Biological activities shown by HA fragments in angiogenesis, inflammation, etc. are absent from highly polymerized HA. We propose that HA physiological properties are controlled by molecular mass dependent transitions between tertiary structures (e.g., beta sheets) and 2-fold helices, - reversible "denaturation", which is central to HA solution behavior. We demonstrate this phenomenon by 13C NMR. Four different acetamido C=O resonances, assigned to secondary, tertiary, and disordered HA structures, monitored "denaturation" by (a) warming, (b) alkalinizing to pH >12.0, (c) hyaluronidase digestion, and (d) methylation of carboxylates. (a) and (b) acted reversibly but (c) and (d) are irreversible. 1H NMR implicated H-bonded acetamido NH in (b). Temperature dependencies of other 13C chemical shifts were small and unspecific. Arrhenius plots indicate that hyaluronan tertiary structures are on the edge of instability under physiological conditions. The results help to explain the appearance of biological activities on "denaturation" or degradation of HA.
Scott
John E
JE
Chemical Morphology, Medical School, Manchester University, Oxford Road, Manchester M13 9PT, UK. jescott@fs1.scg.man.ac.uk
Heatley
Frank
F
D000818:Animals; D002236:Carbohydrate Conformation; D006358:Hot Temperature; D006820:Hyaluronic Acid / Q000737:chemistry* / Q000378:metabolism; D006821:Hyaluronoglucosaminidase / Q000378:metabolism; D008745:Methylation; D019906:Nuclear Magnetic Resonance, Biomolecular; D012756:Sheep; D012996:Solutions; D013329:Structure-Activity Relationship
D012996:Solutions; D006820:Hyaluronic Acid; D006821:Hyaluronoglucosaminidase