13C-N.M.R. study of the conformation of helical complexes of amylodextrin and of amylose in solution |
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| Authors: | J L Jane J F Robyt D H Huang |
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| Institution: | 1. State Key Laboratory of Biobased Material and Green Papermaking, Qilu University of Technology, Shandong Academy of Sciences, Jinan 250353, China;2. Department of Food Science and Engineering, Shandong Agricultural University, Taian 271018, China;3. School of Food Science and Engineering, Qilu University of Technology, Shandong Academy of Sciences, Jinan, Shandong 250353, China;4. The State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, 6 China;5. College of Food Science and Engineering, Qingdao Agricultural University, Qingdao 266109, Shandong, China;6. Department of Pharmacology, Faculty of Veterinary Medicine, Cairo University, 12211 Giza, Egypt;7. Department of Medical Pharmacology, Medical Faculty, Ataturk University, Erzurum, Turkey;1. Jiangsu Key Laboratory of Crop Genetics and Physiology/Co-Innovation Center for Modern Production Technology of Grain Crops, Yangzhou University, Yangzhou 225009, China;2. Testing Center, Yangzhou University, Yangzhou 225009, China;1. Department of Food Science & Engineering, Jinan University, Huangpu West Avenue 601, Guangzhou City, 510632, China;2. School of Food Science and Engineering, South China University of Technology, Guangzhou City, China;3. The University of Queensland, Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, Brisbane, QLD, 4072, Australia;1. School of Food and Biological Engineering, Jiangsu University, Zhenjiang;2. Institute of Food Physical Processing, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu 212013, China;3. Department of Integrative Food, Bioscience and Biotechnology, Chonnam National University, Gwangju 61186, South Korea;4. University Institute of Diet and Nutritional Sciences, Faculty of Allied Health Sciences, The University of Lahore, Lahore 54000 Pakistan;5. School of Food Science and Biotechnology, Kyungpook National University, Daegu 41566, South Korea;6. Institute of Food Science and Nutrition, University of Sargodha, Sargodha 40100, Pakistan;1. Bi-State School of Food Science, University of Idaho and Washington State University, 875 Perimeter Drive MS2312, Moscow, ID 83844, USA;2. Whistler Center for Carbohydrate Research, Department of Food Science, Purdue University, 745 Agriculture Mall Drive, W. Lafayette, IN 47907, USA;3. Department of Food Science and Biotechnology, College of BioNano Technology, Gachon University, Seongnam 461-701, South Korea;4. Department of Food Science, National Pingtung University of Science and Technology, Neipu, Pingtung 91201, Taiwan, ROC;1. College of Food Science, Fujian Agriculture and Forestry University, Fuzhou, Fujian, PR China;2. Fujian Provincial Key Laboratory of Quality Science and Processing Technology in Special Starch, Fuzhou, Fujian, PR China;3. China-Ireland International Cooperation Centre for Food Material Science and Structure Design, Fujian Agriculture and Forestry University, Fuzhou, PR China;4. Teagasc Food Research Centre, Moorepark, Fersmoy, Co. Cork, Ireland |
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| Abstract: | Amylose (average d.p. 1000) and amylodextrin (average d.p. 25) have identical 13C-n.m.r. spectra, except for some minor signals from the small amount of alpha-1----6 branch linkages present in amylodextrin. Amylodextrin can be obtained as stable solutions in much higher concentrations than amylose and so requires only 1/100th as many scans to obtain a spectrum comparable to that of amylose. 13C-N.m.r. spectroscopy has been used to study the formation of amylodextrin complexes with organic complexing agents in aqueous solution. A control study using dextran, which does not form helical complexes, showed that, when complexing agents are added, the signals from all of the carbons show a slight downfield shift due to a general solvent effect. In the case of amylodextrin, the addition of increasing concentrations of complexing agent also produced a downfield shift of the signals of all the carbons, but there was a greater shift of the signals for carbons 1 and 4 than for carbons 2, 3, and 6, indicating that something more than a solvent effect was occurring. The cycloamyloses (cyclic alpha-1----4 linked D-glucose oligosaccharides which may be considered as model for an amylose helix) in water have chemical shifts for carbons 1 and 4 that are comparable to those shown by the amylodextrin complexes. It is thus proposed that the formation of a helical complex with amylodextrin results in a change in the conformation of the glycosidic linkage, which is reflected by greater downfield shifts of the signals for carbons 1 and 4, relative to those for carbons 2, 3, and 6. It was observed that differences in the ratio of the downfield shifts of C-1 and C-4 of the different amylodextrin complexes indicate differences in the degree of compactness of the helical structures. A comparison of the 13C chemical shifts of methyl alpha-D-glucoside and methyl alpha-maltoside showed that, for a molecule as small as a disaccharide, there is a conformational change about the glycosidic linkage when complexing agents are added. |
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