| Popis: |
A fractionated sample of S. salivarius levan was examined in aqueous solution at 25° by the method of small-angle X-ray scattering. The high molecular weight of 16.9 × 10 6 and low radius of gyration of 395 A suggest that this levan is branched. The mass per unit length [( m u ) b ] was found to be 72.94 daltons/A. Based on the molecular weight of the monomer unit (2,6-anhydro-β- d -fructofuranose) and its length, the mass per unit length of a linear levan [( m u ) l ] was calculated as 28.94 daltons/A. The observation that ( m u ) b > ( m u ) l is a positive indication of branching. The g -factor, a measure of branching, was computed as 0.39 from the derived expression, g = ( m u ) l /( m u ) b = L/L l , where L and L l are the hydrodynamic length (total stretched length) of the backbone of the branched levan and linear levan, respectively. Values of 42.79 A for persistence length, L = 2.313 × 10 5 A, and 22 A for the radius of gyration of the cross-section were also obtained for the branched levan. |
