%0 Journal Article %1 Stokke2000 %A Stokke, B. T. %A Draget, K. I. %A Smidsrod, O. %A Yuguchi, Y. %A Urakawa, H. %A Kajiwara, K. %C 1155 16TH ST, NW, WASHINGTON, DC 20036 USA %D 2000 %I AMER CHEMICAL SOC %J Macromolecules %K ;; [ISI:] acid; aqueous-solution; binding; calcium; components; crystalline-structure; divalent-cations; gellan; high-field; microcapsules structural %N 5 %P 1853 -- 1863 %T Small-angle X-ray scattering and rheological characterization of alginate gels. 1. Ca-alginate gels %V 33 %X Ca-alginate gels were studied by small-angle X-ray scattering and rheology to determine relations between chemical composition and concentrations of the alginate and the elasticity and structure of the gels. The gels were prepared by in situ release of Ca2+ from either Ca-EGTA or CaCO3 with total Ca2+ concentration in the range 5-30 mM. Alginates with low (39%), intermediate (50%), and high (68%) fractions of alpha-L-GulA originating from the brown algae Ascophyllum nodosum, Laminaria hyperborea leaf, and Laminaria hyperborea stipe, respectively, were employed. Two to three different degrees of polymerization for each chemical composition were used in the experiments. The excess small-angle X-ray scattering for the alginates in solution yielded linear cross-sectional Guinier plots, and the cross-sectional radius of gyration, R-g,R-c, was determined to be 3.1-4.6 Angstrom. The SAXS profiles of the alginate gels depended on the alginate concentration, Ca2+ concentration, and the alginate composition. The SAXS data suggested that dimerization of chain segments was the principal association mode at low fractional Ca2+ saturation of guluronic acid of the alginate. Increasing the fractional Ca2+ saturation of guluronic acid, either by the concentrations or selection of alginate source, yielded coexisting lateral association modes, as manifested in a curvature in the cross-sectional plots. The coexisting junction zone multiplicities occur because of a delicate balance between the block length distribution of the alpha-L-GulA residues, polymer concentration, and Ca2+. These results are quantitative extensions of the "egg-box" model used to describe ionotropic gelation of alginate and hence enhance the understanding of the structure-function relationship of alginate gels.

@article{Stokke2000, __markedentry = {[phpts:6]}, abstract = {Ca-alginate gels were studied by small-angle X-ray scattering and rheology to determine relations between chemical composition and concentrations of the alginate and the elasticity and structure of the gels. The gels were prepared by in situ release of Ca2+ from either Ca-EGTA or CaCO3 with total Ca2+ concentration in the range 5-30 mM. Alginates with low (39%), intermediate (50%), and high (68%) fractions of alpha-L-GulA originating from the brown algae Ascophyllum nodosum, Laminaria hyperborea leaf, and Laminaria hyperborea stipe, respectively, were employed. Two to three different degrees of polymerization for each chemical composition were used in the experiments. The excess small-angle X-ray scattering for the alginates in solution yielded linear cross-sectional Guinier plots, and the cross-sectional radius of gyration, R-g,R-c, was determined to be 3.1-4.6 Angstrom. The SAXS profiles of the alginate gels depended on the alginate concentration, Ca2+ concentration, and the alginate composition. The SAXS data suggested that dimerization of chain segments was the principal association mode at low fractional Ca2+ saturation of guluronic acid of the alginate. Increasing the fractional Ca2+ saturation of guluronic acid, either by the concentrations or selection of alginate source, yielded coexisting lateral association modes, as manifested in a curvature in the cross-sectional plots. The coexisting junction zone multiplicities occur because of a delicate balance between the block length distribution of the alpha-L-GulA residues, polymer concentration, and Ca2+. These results are quantitative extensions of the "egg-box" model used to describe ionotropic gelation of alginate and hence enhance the understanding of the structure-function relationship of alginate gels.}, added-at = {2011-11-04T13:47:04.000+0100}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, author = {Stokke, B. T. and Draget, K. I. and Smidsrod, O. and Yuguchi, Y. and Urakawa, H. and Kajiwara, K.}, authoraddress = {Norwegian Univ Sci & Technol, NTNU, Dept Phys, NOBIPOL, N-7491 Trondheim, Norway. ; Norwegian Univ Sci & Technol, NTNU, Dept Biotechnol, NOBIPOL, N-7491 Trondheim, Norway. ; Kyoto Inst Technol, Fac Engn & Design, Sakyo Ku, Kyoto 6068585, Japan.}, biburl = {https://www.bibsonomy.org/bibtex/28a16468039538636aaa9cd5d97e2433e/pawelsikorski}, citedref = {ALMDAL K, 1993, POLYM GELS NETW, V1, P5 ; ATKINS EDT, 1973, BIOPOLYMERS, V12, P1865 ; ATKINS EDT, 1973, BIOPOLYMERS, V12, P1879 ; BURCHARD W, 1996, MACROMOLECULES, V29, P5934 ; CHANDRASEKARAN R, 1988, CARBOHYD RES, V181, P23 ; CHANDRASEKARAN R, 1992, CARBOHYD RES, V224, P1 ; CHRISTENSEN BE, COMMUNICATION ; DRAGET KI, 1991, CARBOHYD POLYM, V14, P159 ; DRAGET KI, 1993, HYDROBIOLOGIA, V260, P563 ; ERTESVAG H, 1995, MOL MICROBIOL, V16, P719 ; GLATTER O, 1980, ACTA PHYS AUSTRIACA, V52, P243 ; GLATTER O, 1982, SMALL ANGLE XRAY SCA ; GRANT GT, 1973, FEBS LETT, V32, P195 ; GRASDALEN H, 1983, CARBOHYD RES, V118, P255 ; GUENET JM, 1992, THERMOREVERSIBLE GEL, P89 ; HAUG A, 1970, ACTA CHEM SCAND, V24, P843 ; KAJIWARA K, 1991, POLYM GELS FUNDAMENT, P3 ; KOHN R, 1975, PURE APPL CHEM, V42, P371 ; KULSENG B, 1997, CELL TRANSPLANT, V6, P387 ; MACKIE W, 1983, INT J BIOL MACROMOL, V5, P329 ; MARTHINSEN A, 1992, BIOTECHNOL BIOENG, P186 ; MIKKELSEN A, 1995, BIOPOLYMERS, V36, P17 ; MIMURA M, UNPUB ; MIMURA M, 1996, CARBOHYD RES, V289, P25 ; MOE ST, 1995, FOOD POLYSACCHARIDES, P245 ; MORRIS ER, 1978, CARBOHYD RES, V66, P145 ; SKJAKBRAEK G, 1986, INT J BIOL MACROMOL, V8, P330 ; SKJAKBRAEK G, 1989, CARBOHYD POLYM, V10, P31 ; SMIDSROD O, 1968, ACTA CHEM SCAND, V22, P1989 ; SMIDSROD O, 1974, FARADAY DISCUSS, V57, P263 ; SOONSHIONG P, 1992, TRANSPLANTATION, V54, P769 ; SOONSHIONG P, 1993, P NATL ACAD SCI USA, V90, P5843 ; SOONSHIONG P, 1994, LANCET, V343, P950 ; STEGINSKY CA, 1992, CARBOHYD RES, V225, P11 ; STOKKE BT, 1991, MACROMOLECULES, V24, P4637 ; THOM D, 1982, CARBOHYD RES, V100, P29 ; THU B, 1996, BIOMATERIALS, V17, P1069 ; THU B, 1997, CARBOHYD RES, V297, P101 ; THU B, 2000, IN PRESS BIOPOLYMERS, V53 ; UEKI T, 1983, PHOTON FACTORY ACTIV, V1, V170 ; UEKI T, 1983, PHOTON FACTORY ACTIV, V1, V29 ; UEKI T, 1983, PHOTON FACTORY ACTIV, V1, V7 ; WANG ZY, 1995, BIOPOLYMERS, V35, P227 ; YUGUCHI Y, UNPUB ; YUGUCHI Y, 1993, FOOD HYDROCOLLOID, V7, P373}, interhash = {c176962281fd0c9ebbc2524674dbb760}, intrahash = {8a16468039538636aaa9cd5d97e2433e}, isifile-dt = {Article}, isifile-ga = {293BY}, isifile-j9 = {MACROMOLECULES}, isifile-nr = {45}, isifile-pi = {WASHINGTON}, isifile-rp = {Stokke, BT, Norwegian Univ Sci & Technol, NTNU, Dept Phys, NOBIPOL, ; N-7491 Trondheim, Norway.}, isifile-sc = {Polymer Science}, isifile-tc = {27}, issn = {0024-9297}, journal = {Macromolecules}, keywords = {;; [ISI:] acid; aqueous-solution; binding; calcium; components; crystalline-structure; divalent-cations; gellan; high-field; microcapsules structural}, language = {English}, month = {MAR 7}, number = 5, owner = {phpts}, pages = {1853 -- 1863}, publisher = {AMER CHEMICAL SOC}, size = {11 p.}, sourceid = {ISI:000085832700061}, timestamp = {2011-11-04T13:47:24.000+0100}, title = {Small-angle X-ray scattering and rheological characterization of alginate gels. 1. Ca-alginate gels}, volume = 33, year = 2000 }