New studies on gum ghatti (Anogeissus latifolia) part 5: Theconformational properties of gum ghatti

The conformational properties of gum ghatti and its fractions were investigated using high performance size exclusion chromatography (HPSEC) coupled with multiple detectors, static light scattering (SLS) and dynamic light scattering (DLS) methods. The measured Mark-Houwink equation parameters α (0.5<α<0.8) indicated a random coil conformation of four fractions: F50 was more rigid than the other fractions, whereas F65 exhibited a loosely extended chain that is close to a spherical conformation. DLS and SLS measurements in aggregate free (0.5M NaOH) solution further confirmed the conformational properties. The high positive A2 value of each fraction indicated that 0.5M NaOH solution is a good solvent for gum ghatti. The values of Rg and Rh decreased with molecular weight in the order of F80, F65 and F50. The less branched fraction F50 (ρ=1.694) has a random coil conformation in 0.5M NaOH solution, whereas F65 and F80 exhibited random coil close to spherical conformation due to their highly branched structure.