Solution Conformation of Konjac Glucomannan Single Helix

Abstract

The possibility of the existence of konjac glucomannan (KGM) single helix in dilute solution was discussed finely by ultraviolet-visible spectrophotometer (UV-Vis) with Congo red complex, viscosimetry and circular dichroism (CD). KGM bound to Congo red and the λ max characteristic shifted markedly to longer wavelength (514 nm) in 0.25 M aq NaOH. The shifts of λ max and intrinsic viscosity were also compared in different mediums, such as different concentrations of KGM, NaOH, urea solutions or temperatures. The results indicated that KGM had an ordered, single-helical conformation in neutral, slight NaOH (<0.15 M) and urea (<3.0 M) solutions or at a moderate temperature (T<55ºС ), while it was transformed disorder, random coils in high NaOH (>0.45 M), urea (>4.0 M) solutions or at a high temperature (T>60ºС ). So it can be conclude that the outside factors play an important role on the stability of the single-helix conformation for KGM solution. The induced CD spectra by Congo red and the CD spectra of KGM in aqueous and urea solution indicated further that KGM had a single-helical structure. The new conclusion laid the foundation of determining helical radius, pitch and length of KGM in the future studies.