%0 Journal Article %1 VARUM1992 %A VARUM, K. M. %A SMIDSROD, O. %A BRANT, D. A. %C WALTON ST JOURNALS DEPT, OXFORD, ENGLAND OX2 6DP %D 1992 %I OXFORD UNIV PRESS UNITED KINGDOM %J Food Hydrocolloids %K ;; [ISI:] dimensions molecular-weight; %N 6 %P 497 -- 511 %T LIGHT-SCATTERING REVEALS MICELLE-LIKE AGGREGATION IN THE (1-3),(1-4)-BETA-D-GLUCANS FROM OAT ALEURONE %V 5 %X Fractionated samples of (1 --> 3),(1 --> 4)-beta-D-glucans from oat aleurone ('oat bran') with a relatively narrow molecular weight distribution were characterized by total intensity light scattering. Typical Zimm plots showed that for each concentration the angular dependence could be fitted with a straight line. For each angle, however, the concentration dependence showed a distinctive curvature and the negative second virial coefficient typical of a reversibly aggregating system. The shape of the Zimm plots was the same at increased temperature (60-degrees-C) in different solvents (1 mol/dm3 aqueous LiI, 4 mol/dm3 aqueous urea and dimethylsulfoxide) and after ultracentrifugation (300 000 g for 4 h). The extrapolated data at zero concentration and zero angle nevertheless yielded weight average molecular weights (M(w)) in the same range as the osmometric number average molecular weights (M(n)) determined previously. The relationship between the root-mean-square z-average radius of gyration (R(g)) and M(w) was found to be R(g) (nm) = 0.03 x M(w)0.59 in good accord with expectation from polysaccharides of similar structure and consistent with earlier realistic molecular modeling of these beta-D-glucans. A cooperative, closed association model is described, and it is shown that the apparent M(w) obtained at different concentrations from the light scattering data at zero angle can be closely fitted with the M(w) calculated from the model, assuming that multimers consisting of 4-5 unimers are formed. This model predicts-in contrast to experimental observation-a strongly negative osmotic second virial coefficient. A refined aggregation model in which only a fraction of the unimers are assumed capable of involvement in association to form large, cooperatively stabilized aggregates fits both the present light scattering and the earlier osmotic pressure data quite satisfactorily.

@article{VARUM1992, __markedentry = {[phpts:6]}, abstract = {Fractionated samples of (1 --> 3),(1 --> 4)-beta-D-glucans from oat aleurone ('oat bran') with a relatively narrow molecular weight distribution were characterized by total intensity light scattering. Typical Zimm plots showed that for each concentration the angular dependence could be fitted with a straight line. For each angle, however, the concentration dependence showed a distinctive curvature and the negative second virial coefficient typical of a reversibly aggregating system. The shape of the Zimm plots was the same at increased temperature (60-degrees-C) in different solvents (1 mol/dm3 aqueous LiI, 4 mol/dm3 aqueous urea and dimethylsulfoxide) and after ultracentrifugation (300 000 g for 4 h). The extrapolated data at zero concentration and zero angle nevertheless yielded weight average molecular weights (M(w)) in the same range as the osmometric number average molecular weights (M(n)) determined previously. The relationship between the root-mean-square z-average radius of gyration (R(g)) and M(w) was found to be R(g) (nm) = 0.03 x M(w)0.59 in good accord with expectation from polysaccharides of similar structure and consistent with earlier realistic molecular modeling of these beta-D-glucans. A cooperative, closed association model is described, and it is shown that the apparent M(w) obtained at different concentrations from the light scattering data at zero angle can be closely fitted with the M(w) calculated from the model, assuming that multimers consisting of 4-5 unimers are formed. This model predicts-in contrast to experimental observation-a strongly negative osmotic second virial coefficient. A refined aggregation model in which only a fraction of the unimers are assumed capable of involvement in association to form large, cooperatively stabilized aggregates fits both the present light scattering and the earlier osmotic pressure data quite satisfactorily.}, added-at = {2011-11-04T13:47:04.000+0100}, address = {WALTON ST JOURNALS DEPT, OXFORD, ENGLAND OX2 6DP}, author = {VARUM, K. M. and SMIDSROD, O. and BRANT, D. A.}, authoraddress = {UNIV CALIF IRVINE,DEPT CHEM,IRVINE,CA 92717.}, biburl = {https://www.bibsonomy.org/bibtex/200d3b390e028f0e3e249cefae10b94e3/pawelsikorski}, citedref = {BAILEY RW, 1978, AM J CLIN NUTR, V31, S77 ; BULIGA GS, 1986, CARBOHYD RES, V157, P139 ; BULIGA GS, 1987, INT J BIOL MACROMOL, V9, P71 ; CASASSA EF, 1964, ADV PROTEIN CHEM, V19, P287 ; ELIAS HG, 1972, LIGHT SCATTERING POL, P397 ; ELIAS HG, 1973, ADV POLYM SCI, V11, P111 ; FISHMAN ML, 1986, ACS SYM SER, V310, P22 ; FLORY PJ, 1969, STATISTICAL MECHANIC, P9 ; HAACHE LS, 1987, MACROMOLECULES, V20, P2179 ; HARDING SE, 1991, ADV CARBOHYDRATE ANA, V1, P63 ; HUGLIN MB, 1972, LIGHT SCATTERING POL, P165 ; STRAND KA, 1982, MACROMOLECULES, V15, P570 ; TALASHEK TA, 1989, FRONTIERS CARBOHYDRA, V1, P271 ; TANFORD C, 1961, PHYS CHEM MACROMOLEC, P306 ; URBANI R, 1989, CARBOHYD POLYM, V11, P169 ; VARUM KM, 1988, CARBOHYD POLYM, V9, P103 ; VARUM KM, 1991, FOOD HYDROCOLLOID, V5, P363 ; WOODWARD JR, 1983, CARBOHYD POLYM, V3, P143}, interhash = {d732217b25ee882b9bc92e8e90e0cb41}, intrahash = {00d3b390e028f0e3e249cefae10b94e3}, isifile-dt = {Article}, isifile-ga = {HH487}, isifile-j9 = {FOOD HYDROCOLLOID}, isifile-nr = {18}, isifile-pi = {OXFORD}, isifile-rp = {VARUM, KM, UNIV TRONDHEIM,NORWEGIAN INST TECHNOL,DIV ; BIOTECHNOL,NORWEGIAN BIOPOLYMER LAB,N-7034 TRONDHEIM,NORWAY.}, isifile-sc = {Chemistry, Applied; Food Science & Technology}, isifile-tc = {22}, issn = {0268-005X}, journal = {Food Hydrocolloids}, keywords = {;; [ISI:] dimensions molecular-weight;}, language = {English}, month = FEB, number = 6, owner = {phpts}, pages = {497 -- 511}, publisher = {OXFORD UNIV PRESS UNITED KINGDOM}, size = {15 p.}, sourceid = {ISI:A1992HH48700001}, timestamp = {2011-11-04T13:47:27.000+0100}, title = {LIGHT-SCATTERING REVEALS MICELLE-LIKE AGGREGATION IN THE (1-]3),(1-]4)-BETA-D-GLUCANS FROM OAT ALEURONE}, volume = 5, year = 1992 }