%0 Journal Article %1 Christensen1996b %A Christensen, B. E. %A Myhr, M. H. %A Smidsrod, O. %C PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS %D 1996 %I ELSEVIER SCIENCE BV %J Carbohydr. Res. %K ; ;; [ISI:] acid chemical-composition; degradation; gum hydrolysis temperature; thermal-stability; xanthan; %N 1 %P 85 -- 99 %T Degradation of double-stranded xanthan by hydrogen peroxide in the presence of ferrous ions: Comparison to acid hydrolysis %V 280 %X Conformationally ordered, double-stranded xanthan, degraded in the presence of H2O2 and Fe2+ (at 20 degrees C) or in dilute acid (0.1 M HCl at 80 degrees C), produced xanthan variants with weight-average molecular weights (M(w)) ranging from 2 X 10(6) to 5.4 X 10(4). In both cases the fraction of cleaved linkages in the glucan backbone (alpha), measured as reducing ends, increased to very high values (0.05 for M(w) = 2-3 X 10(4)), demonstrating that a large number of linkages in the backbone could be cleaved without a correspondingly large reduction in M(w), in accordance with the double-stranded nature of xanthan. Extensive degradation (more than 10-fold reduction in M(w)) in both cases released single-stranded, conformationally disordered oligomers; this release was accompanied by an increase in the rate of acid hydrolysis of the glucan backbone and a pronounced increase in the rate of release of glucose monomer. In contrast, there was no significant change in the rate of reducing end-group formation associated with the release of oligomers upon degradation with H2O2/Fe2+. Both types of degradation were accompanied by changes in the composition of the side chains. However, in contrast to acid hydrolysis, where the terminal beta-D-mannose is preferentially hydrolyzed, the reaction with H2O2/Fe2+ resulted in removal of both mannose and glucuronic acid at approximately equal rates. This observation can be explained by a preferential attack on the inner alpha-D-mannose, with concomitant removal of the entire side chain. Removal of side chains and the release of single-stranded oligomers by H2O2/Fe2+ strongly influenced the optical rotation and also broadened the chiroptically detected conformational transition, whereas no change in the transition temperature was observed.

@article{Christensen1996b, __markedentry = {[phpts:6]}, abstract = {Conformationally ordered, double-stranded xanthan, degraded in the presence of H2O2 and Fe2+ (at 20 degrees C) or in dilute acid (0.1 M HCl at 80 degrees C), produced xanthan variants with weight-average molecular weights (M(w)) ranging from 2 X 10(6) to 5.4 X 10(4). In both cases the fraction of cleaved linkages in the glucan backbone (alpha), measured as reducing ends, increased to very high values (0.05 for M(w) = 2-3 X 10(4)), demonstrating that a large number of linkages in the backbone could be cleaved without a correspondingly large reduction in M(w), in accordance with the double-stranded nature of xanthan. Extensive degradation (more than 10-fold reduction in M(w)) in both cases released single-stranded, conformationally disordered oligomers; this release was accompanied by an increase in the rate of acid hydrolysis of the glucan backbone and a pronounced increase in the rate of release of glucose monomer. In contrast, there was no significant change in the rate of reducing end-group formation associated with the release of oligomers upon degradation with H2O2/Fe2+. Both types of degradation were accompanied by changes in the composition of the side chains. However, in contrast to acid hydrolysis, where the terminal beta-D-mannose is preferentially hydrolyzed, the reaction with H2O2/Fe2+ resulted in removal of both mannose and glucuronic acid at approximately equal rates. This observation can be explained by a preferential attack on the inner alpha-D-mannose, with concomitant removal of the entire side chain. Removal of side chains and the release of single-stranded oligomers by H2O2/Fe2+ strongly influenced the optical rotation and also broadened the chiroptically detected conformational transition, whereas no change in the transition temperature was observed.}, added-at = {2011-11-04T13:47:04.000+0100}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, author = {Christensen, B. E. and Myhr, M. H. and Smidsrod, O.}, biburl = {https://www.bibsonomy.org/bibtex/271403deae7647b37a90b6e0b98d159fe/pawelsikorski}, citedref = {CALLET F, 1987, INT J BIOL MACROMOL, V9, P291 ; CHEETHAM NWH, 1992, CARBOHYD POLYM, V17, P127 ; CHRISTENSEN BE, 1991, CARBOHYD RES, V214, P55 ; CHRISTENSEN BE, 1993, BIOPOLYMERS, V33, P151 ; CHRISTENSEN BE, 1993, CARBOHYDRATES CARBOH, P166 ; CHRISTENSEN BE, 1993, MACROMOLECULES, V26, P6111 ; DEMILLER JN, 1976, ADV CARBOHYD CHEM, V22, P25 ; FOSS P, 1987, CARBOHYD POLYM, V7, P421 ; HERP A, 1980, CARBOHYDRATES CHEM B, V1, P1276 ; HJERDE T, 1994, CARBOHYD POLYM, V24, P265 ; HODGE JE, 1962, METHODS CARBOHYDRATE, V1, P386 ; KIERULF C, 1988, CARBOHYD POLYM, V9, P185 ; LAMBERT F, 1985, POLYMER, V26, P1549 ; LITTMANN W, 1992, SOC PETROL ENG J ; RINAUDO M, 1983, MACROMOLECULES, V16, P816 ; SMIDSROD O, 1963, ACTA CHEM SCAND, V17, P2628 ; SMIDSROD O, 1965, ACTA CHEM SCAND, V19, P143 ; STOKKE BT, 1989, INT J BIOL MACROMOL, V11, P137 ; STOKKE BT, 1992, MACROMOLECULES, V25, P2209 ; STOKKE BT, 1995, IN PRESS FOOD HYDROC ; THOMAS CA, 1956, J AM CHEM SOC, V78, P1861 ; UCHIYAMA H, 1990, J BIOL CHEM, V265, P7753 ; WEISS J, 1952, ADV CATAL, V4, P343 ; WELLINGTON SL, 1983, SOC PET ENG J DEC, P901}, interhash = {8934c3e3b4d2593df10c320f8527b029}, intrahash = {71403deae7647b37a90b6e0b98d159fe}, isifile-dt = {Article}, isifile-ga = {TM906}, isifile-j9 = {CARBOHYD RES}, isifile-nr = {24}, isifile-pi = {AMSTERDAM}, isifile-rp = {Christensen, BE, UNIV TRONDHEIM,DEPT BIOTECHNOL,NORWEGIAN BIOPOLYMER ; LAB,N-7034 TRONDHEIM,NORWAY.}, isifile-sc = {Biochemistry & Molecular Biology; Chemistry, Applied; Chemistry, Organic}, isifile-tc = {8}, issn = {0008-6215}, journal = {Carbohydr. Res.}, keywords = {; ;; [ISI:] acid chemical-composition; degradation; gum hydrolysis temperature; thermal-stability; xanthan;}, language = {English}, month = {JAN 4}, number = 1, owner = {phpts}, pages = {85 -- 99}, publisher = {ELSEVIER SCIENCE BV}, size = {15 p.}, sourceid = {ISI:A1996TM90600007}, timestamp = {2011-11-04T13:47:07.000+0100}, title = {Degradation of double-stranded xanthan by hydrogen peroxide in the presence of ferrous ions: Comparison to acid hydrolysis}, volume = 280, year = 1996 }