Study On Helical Microscopic Conformation And Property Of Konjac Glucomannan

Konjac glucomannan (KGM) is a good water-soluble polysaccharide that produced from the tubers of Amorphophallus konjac C. Koch., which has especial biological function, such as antitumor, enhancing the immunity. As we know, helical structure is the foundation of property and biological function of polysaccharide. However, at present, limited reports in this filed were focused on the existence of helical structure, its formation mechanism and stability haven't been discussed deeply, and furthermore, the formation rule and stability mechanism under different environments also haven't been studied. It has become a barrier for deeply development and biological function regulation of Konjac glucomannan.In this work, we disclose formation sites, parameters, Hydrogen bond sites of the helical structure, especially, the effect of ions, microwave field, and hydrostatic pressure on helical microscopic conformation with experimental and theoretical methods. Furthermore, the helical structure and Formation Mechanism was researched, so as to provide the structural basis for regulation of biological function of KGM, which will pave a new way for the study of natural biological molecule. Main results1 Formation Mechanism of Konjac Glucomannan Helical StructureThe molecular conformation of KGM is a non-typical helical structure. In detail, helical structure of KGM is mainly sustained by acetyl group, whose size and staility is affected by molecular polymerization degree of KGM. In vacuum among the non-bonding interactions, electrostatic force is the greatest factor affecting its helical structure, but in water solution, hydrogen bond affects the helical arrangement greatly. To our interest, temperature exhibits a reversible destroying effect to some extent; the helical structure will disappear completely and present a ruleless clew-like arrangement till 341K.2 Single Helical Conformation of Konjac Glucomannan without Side ChainTo investigate the effect of side chain on helical structure of Konjac Glucomannan (KGM) and the conformation of de-side chain Konjac Glucomannan., molecular dynamics simulation was used. The research indicated that the side chain greatly affected the characteristics of the helical conformation of KGM, and its conformation was composed of several partial folding fragments. The conformation of de-side chain KGM was more stable than KGM with side chain. Electrostatic was the most important non-bonded function affecting molecular chain in vacuum, and hydrogen bond in solution; when temperature increased to 343K, the helical structure disappeared fully, and the molecular chain was in extensional straight chain.3 Hydration Shell of Single-helical of Konjac GlucomannanThe local maxima of water density near Konjac glucomannan, as well as the dominant conformation of the system were studied by molecular dynamics under the water environment. The results indicate that the hydration shell, potential energy, and its hydrogen bond network with water bridges of the left-handed single-helix conformation was favored compared to those of right-handed single-helix conformation. This work suggests that the left-handed single-helix conformation was the dominant conformation of KGM in water environment.4 Complex of Konjac Glucomannan with Borate in waterThe complex of Konjac Glucomannan with Borate in water was investigated by molecular dynamic simulation and experimental method. The energy, Radical distribution function of borax ion, and mean square displacement of the complex was studied during the simulation. The results indicate that the helical chain of KGM and borate ion formed complex which has helical conformation. The hydrogen bonds in the complex can be found at–OH groups on C (6) of mannose and glucose residues between borax ions. The hydrogen bond was the main non-bounding maintaining the helical conformation of the complex. Temperature has little effect on the complex conformation, and the complex may form gel through the aggregation arrangement of helical chain.5 Helical Structure of Konjac Glucomannan in Different SolutionsThe mechanism and stability of KGM elical structure in different alkaline earth metal ions and pH solutions was investigated by molecular dynamic simulation, circular dichroism and optical rotation method. The results indicate that the helical cavity of KGM increase in metal ion solution, and the helical conformation remain. Hydrogen ion has little effect on the conformation, and part of the helical chain change into stretching conformation in alkaline solution. In detail, metal ions modify the helical structure of KGM by changing electrostatic distribution of solution. Hydrogen ion has little effect on the non-bounding function of molecular chain. Hydroxide ions effectively increase the effect of Hydrogen Bond on molecular chain. This work suggests that the method of combining molecular dynamic simulation and experiment tools can be effective in the study of KGM helical structure in solution.6 Effect of Microwave Irradiation on Solution Behavior and Gel Performance of KGMThe Effect of the microwave treating condition on gel strength, the freezing point, the instinct viscosity and the weight losing ratio of konjac glucomannan were studied. The results showed that the gel strength and instinct viscosity increased slight after 1min irradiation in the 33% export power, and then decreased lineally. However, the entire index decreased lineally in 66% and 100% export power. Helical structure of KGM was partly destroyed after microwave treatment. It could be made conclusion that the gel performance and solution behavior of KGM was greatly affected by microwave.7 Effects of Ultra-High Hydrostatic Pressure on Conformation and Gel Properties of KGMEffects of Ultra-high Hydrostatic Pressure on the complex of KGM with Congo red, circular dichroism spectrum, roman spectrum, and textural analysis of KGM were studied. The results showed that hydrostatic treatment promoted the formation of KGM-CR complex, and the specific hydrogen bonding function significantly enhanced between KGM and CR. Quadratic equation relationship ofλmax of the complex to concentrations of KGM remained after treatment. The dichrosim spectrum showed the helical structure of KGM remained after treatment, and hydrostatic pressure treatment had no little effect on the gel properties, i.e. KGM has significant stability to the treatment.