title: Characterization of methylprednisolone esters of hyaluronan in aqueous solution: conformation and aggregation behavior.
abstract: Methylprednisolone steroid esters of hyaluronan differing in degree of functionalization and molecular weight were investigated in aqueous solution. Conformation and aggregation phenomena were elucidated by means of circular dichroism, viscometry, rheology, and nuclear magnetic resonance, mainly by (1)H pulsed field gradient (PFG) NMR, which allows the determination of the diffusion coefficient of the species under investigation. The functionalization of hyaluronan with the steroid induces a reduction of the molecular volume, as a consequence of intramolecular hydrophobic interactions. For concentrated samples we have observed the coexistence of unimolecular collapsed chains and of aggregates, the latter disappearing upon dilution. The methylprednisolone ester of lower molecular weight hyaluronan has a larger molecular volume than its higher molecular weight analogue, even though still smaller than the underivatized polymer. This effect can be explained with the reduced flexibility of the polymer backbone probably impairing intramolecular interactions.
authors.affiliation: Department of Chemistry, University "La Sapienza", Piazzale Aldo Moro 5, 00185 Rome, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Taglienti
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Valentini
authors.forename: Paolo
authors.initials: P
authors.lastname: Sequi
authors.forename: Vittorio
authors.initials: V
authors.lastname: Crescenzi
mesh_terms: D004952:Esters; D006820:Hyaluronic Acid / Q000032:analysis / Q000737:chemistry*; D008775:Methylprednisolone / Q000032:analysis / Q000737:chemistry*; D008968:Molecular Conformation; D012996:Solutions; D014867:Water / Q000032:analysis / Q000737:chemistry
chemical_list: D004952:Esters; D012996:Solutions; D014867:Water; D006820:Hyaluronic Acid; D008775:Methylprednisolone