%0 Journal Article %1 ANTHONSEN1994 %A ANTHONSEN, M. W. %A VARUM, K. M. %A HERMANSSON, A. M. %A SMIDSROD, O. %A BRANT, D. A. %C THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB %D 1994 %I ELSEVIER SCI LTD %J Carbohydr. Polym. %K ;; [ISI:] alginate; association; chitins chitosans; chromatography; deacetylated field gel-permeation nmr-spectroscopy; pectin; size viscometry; %N 1 %P 13 -- 23 %T AGGREGATES IN ACIDIC SOLUTIONS OF CHITOSANS DETECTED BY STATIC LASER-LIGHT SCATTERING %V 25 %X Chitosans having degrees of N-acetylation, F-A, ranging from 0 to 0.6, were randomly degraded to different molecular weights and studied by multi angle static laser light scattering (LLS). Under the given experimental conditions, negative second virial coefficients of the solutions, A'(2), revealed the presence of concentration dependent aggregates. Attempts to remove the aggregates, or to influence the aggregation behavior, were made by ultracentrifugation and extensive filtering of the solutions. Modification of the solvent conditions such as pH, ionic strength and temperature were carried out, and chitosan solutions were digested with an acidic proteinase. Non-degraded samples and chitosans prepared by both heterogeneous and homogeneous N-deacetylation of chitin were also studied. In all cases, the negative A'(2) remained. However, it was observed that ultracentrifugation and filtering of the solutions decreased the measured molecular weights and radii of gyration, indicating that some of the material of high molecular weight and size could be removed by ultracentrifugation and filtration. The chemical nature of the physical basis of the molecular association was not revealed. Nevertheless, by the use of gel permeation chromatography coupled to an on-line low angle laser light scattering instrument and a differential refractive index concentration detector (HPSEC-LALLS-RI), a bimodal molecular weight distribution was observed in which about 5% of the sample had a very high molecular weight. These results coupled with the positive virial coefficients obtained earlier from osmotic pressure measurements suggest that a small fraction of the chitosan is aggregated to high molecular weight material, probably following a closed association model. Electron microscopy revealed the presence of some supramolecular structures. The positive second virial coefficients obtained earlier from osmometry are in harmony with these findings. The results demonstrate the occurrence of reversible aggregation in chitosan solutions. Static laser light scattering therefore cannot readily be used to determine molecular weights and sizes of chitosans under these conditions. It was not possible to correlate the extent of aggregation with the chemical composition of the chitosans.

@article{ANTHONSEN1994, __markedentry = {[phpts:6]}, abstract = {Chitosans having degrees of N-acetylation, F-A, ranging from 0 to 0.6, were randomly degraded to different molecular weights and studied by multi angle static laser light scattering (LLS). Under the given experimental conditions, negative second virial coefficients of the solutions, A'(2), revealed the presence of concentration dependent aggregates. Attempts to remove the aggregates, or to influence the aggregation behavior, were made by ultracentrifugation and extensive filtering of the solutions. Modification of the solvent conditions such as pH, ionic strength and temperature were carried out, and chitosan solutions were digested with an acidic proteinase. Non-degraded samples and chitosans prepared by both heterogeneous and homogeneous N-deacetylation of chitin were also studied. In all cases, the negative A'(2) remained. However, it was observed that ultracentrifugation and filtering of the solutions decreased the measured molecular weights and radii of gyration, indicating that some of the material of high molecular weight and size could be removed by ultracentrifugation and filtration. The chemical nature of the physical basis of the molecular association was not revealed. Nevertheless, by the use of gel permeation chromatography coupled to an on-line low angle laser light scattering instrument and a differential refractive index concentration detector (HPSEC-LALLS-RI), a bimodal molecular weight distribution was observed in which about 5% of the sample had a very high molecular weight. These results coupled with the positive virial coefficients obtained earlier from osmotic pressure measurements suggest that a small fraction of the chitosan is aggregated to high molecular weight material, probably following a closed association model. Electron microscopy revealed the presence of some supramolecular structures. The positive second virial coefficients obtained earlier from osmometry are in harmony with these findings. The results demonstrate the occurrence of reversible aggregation in chitosan solutions. Static laser light scattering therefore cannot readily be used to determine molecular weights and sizes of chitosans under these conditions. It was not possible to correlate the extent of aggregation with the chemical composition of the chitosans.}, added-at = {2011-11-04T13:47:04.000+0100}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB}, author = {ANTHONSEN, M. W. and VARUM, K. M. and HERMANSSON, A. M. and SMIDSROD, O. and BRANT, D. A.}, authoraddress = {SWEDISH INST FOOD RES,S-40229 GOTHENBURG,SWEDEN. ; UNIV CALIF IRVINE,DEPT CHEM,IRVINE,CA 92717.}, biburl = {https://www.bibsonomy.org/bibtex/20b17bba187a9889cb49955e1e24be408/pawelsikorski}, citedref = {ALLAN GG, 1989, CHITIN CHITOSAN ; ANTHONSEN M, 1993, CARBOHYDR POLYM, V22 ; BERKOVICH LA, 1980, POLYM SCI USSR, V22, P2009 ; BERTH G, 1988, CARBOHYD POLYM, V8, P105 ; BERTH G, 1992, CARBOHYD POLYM, V19, P1 ; BISHAY IE, 1989, THESIS U CALIFORNIA ; BURCHARD W, 1972, LIGHT SCATTERING POL, P725 ; BURCHARD W, 1993, TRENDS POLYM SCI, V1, P192 ; DAVIS MAF, 1980, INT J BIOL MACROMOL, V2, P330 ; DOMARD A, 1983, INT J BIOL MACROMOL, V5, P49 ; DOMARD A, 1984, POLYM COMMUN, V25, P55 ; DOMARD A, 1986, CHITIN NATURE TECHNO, P315 ; ELIAS HG, 1972, LIGHT SCATTERING POL, P397 ; ELIAS HG, 1973, ADV POLYM SCI, V11, P111 ; FISHMAN ML, 1986, ACS SYM SER, V31, P22 ; HAACHE LS, 1987, MACROMOLECULES, V20, P2179 ; HOLT C, 1976, POLYMET, V17, P1027 ; JACKSON C, 1989, J APPL POLYM SCI APP, V43, P99 ; JOHNSON BL, 1972, LIGHT SCATTERING POL, P27 ; JORDAN RC, 1989, BIOPOLYMERS, V17, P2885 ; KRAVTCHENKO TP, 1992, CARBOHYD POLYM, V18, P253 ; MACKIE W, 1980, BIOPOLYMERS, V19, P1839 ; MATSUBARA H, 1971, ENZYMES, V3, P721 ; MATSUMOTO T, 1989, J SOC RHEOL, V17, P43 ; MATSUMOTO T, 1991, BIOPOLYMERS, V31, P1721 ; MATSUMOTO T, 1991, J SOC RHEOL, V19, P152 ; MUZZARELLI RAA, 1987, CARBOHYD RES, V164, P433 ; RHA C, 1984, ANN MIT SEA GRANT LE, P1 ; SMIDSROD O, 1968, ACTA CHEM SCAND, V22, P797 ; SMIDSROD O, 1984, HYDROBIOLOGIA, V116, P178 ; STOKKE BT, 1987, CARBOHYD RES, V160, P13 ; TANNER DW, 1974, J POLYM SCI POL PHYS, V12, P941 ; TERBOJEVICH M, 1986, CARBOHYD RES, V149, P363 ; TERBOJEVICH M, 1989, MAKROMOL CHEM, V190, P2847 ; TERBOJEVICH M, 1991, CARBOHYD RES, V209, P251 ; TERBOJEVICH M, 1992, CARBOHYD POLYM, V18, P35 ; URBANI R, 1989, CARBOHYD POLYM, V11, P169 ; VANNESTE K, 1993, THESIS U LEUVEN BELG ; VARUM KM, 1991, CARBOHYD RES, V211, P17 ; VARUM KM, 1991, CARBOHYD RES, V217, P19 ; VARUM KM, 1992, FOOD HYDROCOLLOID, V5, P497 ; WANG W, 1991, INT J BIOL MACROMOL, V13, P281 ; ZIMM BH, 1948, J CHEM PHYS, V16, P1093 ; ZIMM BH, 1948, J CHEM PHYS, V16, P1099}, interhash = {59fd940e608003f8a1c9baf2084d0870}, intrahash = {0b17bba187a9889cb49955e1e24be408}, isifile-dt = {Article}, isifile-ga = {PV258}, isifile-j9 = {CARBOHYD POLYM}, isifile-nr = {44}, isifile-pi = {OXFORD}, isifile-rp = {ANTHONSEN, MW, UNIV TRONDHEIM,NORWEGIAN INST TECHNOL,DIV ; BIOTECHNOL,NORWEGIAN BIOPOLYMER LAB,N-7034 TRONDHEIM,NORWAY.}, isifile-sc = {Chemistry, Applied; Chemistry, Organic; Polymer Science}, isifile-tc = {45}, issn = {0144-8617}, journal = {Carbohydr. Polym.}, keywords = {;; [ISI:] alginate; association; chitins chitosans; chromatography; deacetylated field gel-permeation nmr-spectroscopy; pectin; size viscometry;}, language = {English}, number = 1, owner = {phpts}, pages = {13 -- 23}, publisher = {ELSEVIER SCI LTD}, size = {11 p.}, sourceid = {ISI:A1994PV25800003}, timestamp = {2011-11-04T13:47:05.000+0100}, title = {AGGREGATES IN ACIDIC SOLUTIONS OF CHITOSANS DETECTED BY STATIC LASER-LIGHT SCATTERING}, volume = 25, year = 1994 }