Cesàro A, Tomasi G, Gamini A, Vidotto S, Navarini L
Department of Biochemistry, Biophysics, and Macromolecular Chemistry, University of Trieste, Italy.
Carbohydr Res. 1992 Jul 2;231:117-35. doi: 10.1016/0008-6215(92)84013-i.
The physicochemical solution properties of the galactoglucan excreted by Rhizobium meliloti strain YE-2(S1) have been investigated by capillary viscometry, potentiometric titration, isothermal mixing microcalorimetry, and circular dichroism. Potentiometric and chiro-optical data, as a function of the degree of ionisation, indicate the absence of a co-operative conformational transition. Solution properties, as a function of ionic strength and temperature, suggest that the galactoglucan adopts a disordered conformation characterised by moderate flexibility. Polyelectrolyte theory is used to fit the enthalpy of dilution data with a suitable linear charge-density parameter. Conformational calculations and chain modelling, using molecular mechanics, give an unperturbed characteristic ratio, (C infinity) of 20, which was smaller than that estimated from intrinsic-viscosity and molecular-weight data for an expanded-coil chain model.
