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 λmaxcharacteristic shifted markedly to longer wavelength (514 nm) in 0.25 M aq NaOH. The shifts of λmaxand 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.