title: Effect of microwave irradiation on the molecular and structural properties of hyaluronan.
abstract: Hyaluronan (Na(+) salt of hyaluronic acid, HA) was extensively depolymerised by HCl-catalyzed hydrolysis at pH 3 for up to 500min under temperature-controlled microwave irradiation. The effects of microwave heating on the hydrodynamic properties of the polysaccharide were determined by SEC-MALLS and viscometry. The weight-average molecular mass (Mw) of HA decreased from 1.44×10(6) to ∼5000, reaching the region of higher oligosaccharides. The scission of HA chains was found to proceed randomly during the whole degradation process. Treatment of the Mw and intrinsic viscosity data according to the Mark-Houwink equation, [η]=k×Mw(α) suggested three relationships with α1=0.46 for Mw>500,000, α2=0.84 for Mw between 500,000 and 50,000, and α3=1.13 for Mw<50,000. The results revealed that HA with Mw>10,000 adopts a stiffish coil conformation in solution. As monitored by FT-IR and NMR spectroscopic techniques, the primary structure of the HA chains was maintained during the microwave-assisted hydrolysis at pH 3 at 105°C. At reaction times larger than 240min, uv spectroscopy suggested the depolymerisation of HA was accompanied by formation of by-products produced by side reaction.
authors.affiliation: CPN spol. s r.o., Dolní Dobrouč 401, 561 02 Dolní Dobrouč, Czech Republic.
authors.forename: Zuzana
authors.initials: Z
authors.lastname: Bezáková
authors.affiliation: CPN spol. s r.o., Dolní Dobrouč 401, 561 02 Dolní Dobrouč, Czech Republic.
authors.forename: Martina
authors.initials: M
authors.lastname: Hermannová
authors.affiliation: CPN spol. s r.o., Dolní Dobrouč 401, 561 02 Dolní Dobrouč, Czech Republic.
authors.forename: Eugenie
authors.initials: E
authors.lastname: Dřímalová
authors.affiliation: Institute of Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, 845 38 Bratislava, Slovakia.
authors.forename: Anna
authors.initials: A
authors.lastname: Malovíková
authors.affiliation: Institute of Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, 845 38 Bratislava, Slovakia. Electronic address: chemebri@savba.sk.
authors.forename: Anna
authors.initials: A
authors.lastname: Ebringerová
authors.affiliation: CPN spol. s r.o., Dolní Dobrouč 401, 561 02 Dolní Dobrouč, Czech Republic.
authors.forename: Vladimír
authors.initials: V
authors.lastname: Velebný
keywords: Depolymerisation; FT-IR, NMR and UV-spectroscopy; Hyaluronan; Microwave irradiation; SEC-MALLS; Viscometry