Study On Molecular Information Characteristics And Structure Stability Of Corncob Heteropolysaccharide

Polysaccharide,as a natural active material,its important biofunction usually is associated with its molecular structure.Nowadays,many scientists focus on its structure-activity relationship.In this paper corncob polysaccharide(CP)was as a research subjective to study its molecular information and structure property,after it was extracted and purified from corncob by alkali treatment and DEAE-cellulose52 exchange column.For this reason,some methods were used to interpret CP's spectra and chromatographic characteristics,analyze its thermal and chemical stability by circular dichroism(CD)and thermogravimeter(TG).Conclusions as follows:1 Compared to four factors on CP purification,4 mL sample volume,4%sample concentration,1.5 mL/min elute speed and 4:2 ratio of VdH2O:VNacl were optimal.Under this condication,CP yield was nearly 9.8%.2 It appeared a special peak for CP-? and CP-? at 190 nm/?,respectively,without any peaks at 260 nm/?,280 nm/? and 565 nm/?.It evidenced both of them belong into polysaccharide by UV spectra firstly.3 Total solube sugars of CP-? and CP-? were 72.13%and 61.64%with 272.49 kDa and 267.43 kDa molecular weight,respectively.CP-? was composed of five monosaccharides,in which D-Glc was up to 79.27%.CP-? consisted of seven monosaccharides,D-Man was 38.90%and D-Glc was 20.25%mostly.These monosaccharides were identified as hexose or pentose by HPLC-ion so that CP-?and CP-? were suggested heteropolysaccharides.4 For CP-? and CP-? microstructure,the former appeared longer thin fibres,while the latter was shorter fibres with special ring under microscope by 10×10 times.As fourier transform infrared spectra(FT-IR),both of CP-? and CP-? high structure looked like dynamics.They had O-H and C-H stretching vibration with C=O and C-H coordinating groups in charateristic frequency,specifically.According to their typical FT-IR,CP-? and CP-? also were directed as polysaccharides.Analyzed by Gauss Integrals,both of them had C-C skeleton structure as the main chain,containing pyranose functional groups which were basic units of polysaccharides in fingerprint region.The results showed that there were a-glycoside bond and ?-glycoside bond among C-main chain,and also ?-glycoside bond was the mostly.At 1200-1320 cm-1 of fingerprint region,some secondary structures of CP-?and CP-? were interpreted by FT-IR.CP-? contained 25%?-helix,while CP-? had no this secondary structure with only random coil.It supposed the high structure of CP-? and CP-? was similar to protein's secondary and tertiary structures.5 The high structure of CP-? and CP-? was stable during 19?-60?.Their glass transition temperature was at 43.94? or at 44.59? respectively.These showed CP structure was thermal stability below 45?.CP molecular dehydrated gradually with its high structure loosing and allosteric from 60? to 120?.When it was heated above 200?,CP high structure was broken and irreversible change at all.CP-? structure was stable under pH 4.5,CP-? structure was also stable nearly pH 9.0.It was found that the structure stability of CP molecule was relative small region of pH value.If far away from optimal pH value,both CP structures were destroyed,after their glycosidic bonds and side chains broken with hydrogen bond mistaken.