Structure, rheology, and copper-complexation of a hyaluronan-like exopolysaccharide from Vibrio

MO245 exopolysaccharide (EPS) was produced in laboratory conditions from Vibrio genus microorganism isolated from bacterial mats found in Moorea Island. Its structure consists of a linear tetrasaccharide repeating unit â 4)-β-D-GlcpA-(1â 4)-α-D-GalpNAc-(1â 3)-β-D-GlcpNAc-(1â 4)-β-D-GlcpA-(1â containing covalently-linked 5% of glucose, galactose, and rhamnose, determined by methylation analyses and NMR spectroscopy. The molecular weight, radius of gyration (Rg) and intrinsic viscosity, [η], determined by gel permeation chromatography with light scattering and viscosity detection, were 513â ±â 4â kDa (PDI, 1.42â ±â 0.01), 6.7â ±â 0.3â dl/g and 56â ±â 0.3â nm respectively. The chelation of the EPS with copper divalent ions leads to the instantaneous formation of gels. The structural similitude proposed, based in an equal ratio of GlcA to N-acetylated sugars and in the same type of glyosidic linkages present in the repeating unit (alternated 1â 3 and 1â 4 linkages), is translated into analogous physicochemical properties: MO245 EPS is a flexible polyelectrolyte, with scaling exponents similar to that described for HA. This similitude opens opportunities in future drug delivery, tissue engineering, and cosmetic applications.
RIAIDT, CACTUS at the University of Santiago de Compostela and in the "Manuel Rico" NMR laboratory (LMR) of the Spanish National Research Council (CSIC) were the 750 MHz and 800 MHz NMR spectra were carried out respectively. FCT/MEC for the financial support to CICECO (FCT UID /CTM /50011/2013; POCI-01-0145-FEDER-007679) and QOPNA research Unit (FCT UID/QUI/00062/2013), through national founds and co-financed by the FEDER, within the PT2020 Partnership Agreement. RNC (IF/00373/2014), CN (SFRH/BPD/100627/2014), and ASF (SFRH/BD/102471/2014) thank the FCT foundation for funding.