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Westberry BP, Mansel BW, Lundin L, Williams MAK. Molecular dynamics simulations and X-ray scattering show the κ-carrageenan disorder-to-order transition to be the formation of double-helices. Carbohydr Polym 2023; 302:120417. [PMID: 36604079 DOI: 10.1016/j.carbpol.2022.120417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Revised: 10/20/2022] [Accepted: 11/23/2022] [Indexed: 12/12/2022]
Abstract
Recent molecular dynamics simulations, verified experimentally by solution-state x-ray scattering experiments, have found that κ-carrageenan chains contain helical secondary structure, akin to that found in the solid-state, even in aqueous solution. Furthermore, upon the addition of ions to single chains the simulations found no evidence that any conformational transitions take place. These findings challenge the long-held assumption that the so-called disorder-to-order transition in carrageenan systems involves a uni-molecular 'coil-to-helix transition'. Herein, the results of further molecular dynamics simulations undertaken using pairs of κ-carrageenan chains in 0.1 M NaI solutions are reported, and are validated experimentally using state-of-the-art solution-state WAXS experiments. From initially separated chains double-helices are shown to form, leading the authors to propose 'two single helices-to-stabilized double-helix' as a description of the molecular events taking place during the disorder-to-order transition.
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Affiliation(s)
- Benjamin P Westberry
- School of Natural Sciences, Massey University, Palmerston North, New Zealand; MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington, New Zealand.
| | - Bradley W Mansel
- National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu Science Park, Hsinchu, 30076, Taiwan, ROC
| | - Leif Lundin
- CSIRO Agriculture and Food, 671 Sneydes Road, Werribee, Victoria 3030, Australia
| | - M A K Williams
- School of Natural Sciences, Massey University, Palmerston North, New Zealand; MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington, New Zealand
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2
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Westberry BP, Mansel BW, Ryan TM, Lundin L, Williams M. X-ray scattering and molecular dynamics simulations reveal the secondary structure of κ-carrageenan in the solution state. Carbohydr Polym 2022; 296:119958. [DOI: 10.1016/j.carbpol.2022.119958] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Revised: 07/31/2022] [Accepted: 08/02/2022] [Indexed: 11/02/2022]
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3
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Understanding nanostructural differences in hydrogels from commercial carrageenans: Combined small angle X-ray scattering and rheological studies. ALGAL RES 2020. [DOI: 10.1016/j.algal.2020.101882] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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4
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Gasilova ER, Aleksandrova GP. Dilute solutions of compositionally heterogeneous κ-carrageenan studied by combined dynamic and static light scattering. INTERNATIONAL JOURNAL OF POLYMER ANALYSIS AND CHARACTERIZATION 2017. [DOI: 10.1080/1023666x.2017.1366190] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- E. R. Gasilova
- Institute of Macromolecular Compounds, Russian Academy of Sciences, St.-Petersburg, Russia
| | - G. P. Aleksandrova
- A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Division, Russian Academy of Sciences, Irkutsk, Russia
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5
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Obituary. Carbohydr Polym 2017. [DOI: 10.1016/j.carbpol.2017.03.056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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6
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7
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Schefer L, Adamcik J, Mezzenga R. Unravelling Secondary Structure Changes on Individual Anionic Polysaccharide Chains by Atomic Force Microscopy. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201402855] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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8
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Schefer L, Adamcik J, Mezzenga R. Unravelling secondary structure changes on individual anionic polysaccharide chains by atomic force microscopy. Angew Chem Int Ed Engl 2014; 53:5376-9. [PMID: 24740853 DOI: 10.1002/anie.201402855] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Indexed: 11/07/2022]
Abstract
The structural conformations of the anionic carrageenan polysaccharides in the presence of monovalent salt close to physiological conditions are studied by atomic force microscopy. Iota-carrageenan undergoes a coil-helix transition at high ionic strength, whereas lambda-carrageenan remains in the coiled state. Polymer statistical analysis reveals an increase in persistence length from 22.6±0.2 nm in the random coil, to 26.4±0.2 nm in the ordered helical conformation, indicating an increased rigidity of the helical iota-carrageenan chains. The many decades-long debated issue on whether the ordered state can exist as single or double helix, is conclusively resolved by demonstrating the existence of a unimeric helix formed intramolecularly by a single polymer chain.
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Affiliation(s)
- Larissa Schefer
- Food & Soft Materials Science, Institute of Food, Nutrition & Health, Department of Health Sciences & Technology, ETH Zürich, Schmelzbergstraße 9, LFO E23, 8092 Zürich (Switzerland) http://www.ifnh.ethz.ch/lwm
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9
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Using power ultrasound for cold gelation of kappa-carrageenan in presence of sodium ions. INNOV FOOD SCI EMERG 2013. [DOI: 10.1016/j.ifset.2013.06.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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10
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Azizi R, Farahnaky A. Ultrasound assisted cold gelation of kappa carrageenan dispersions. Carbohydr Polym 2013; 95:522-9. [DOI: 10.1016/j.carbpol.2013.02.073] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2012] [Revised: 01/31/2013] [Accepted: 02/28/2013] [Indexed: 11/28/2022]
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11
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Zhao Q, Brenner T, Matsukawa S. Molecular mobility and microscopic structure changes in κ-carrageenan solutions studied by gradient NMR. Carbohydr Polym 2013; 95:458-64. [PMID: 23618293 DOI: 10.1016/j.carbpol.2013.02.049] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2012] [Revised: 01/21/2013] [Accepted: 02/26/2013] [Indexed: 10/27/2022]
Abstract
Changes in the molecular mobility of κ-carrageenan were observed by the pulsed field gradient stimulated echo (PGSTE) and Carr-Purcell-Meiboom-Gill (CPMG) methods for elucidating the molecular aspect of the sol-to-gel transition. The echo signal intensity of κ-carrageenan without a gradient, Ikap(0), decreased steeply near the sol-to-gel temperature (Tsg), suggesting that κ-carrageenan chains formed aggregates and a network structure. Below Tsg, the spin-spin relaxation time T2 and the diffusion coefficient of κ-carrageenan (Dkap) increased with decreasing temperature, indicating that the solute κ-carrageenan chains have a lower molecular weight Mw than chains involved in the aggregation. The diffusion coefficient of pullulan (Dpul) added as a probe molecule in κ-carrageenan solutions was measured, and the characteristic hydrodynamic screening length, ξ, was then estimated from the degree of diffusion restriction. Below a certain temperature, Dkap reached a higher value than that of Dpul, suggesting that the Mw of solute κ-carrageenan became lower than that of pullulan. GPC measurements confirmed the presence of κ-carrageenan chains with a lower Mw than that of pullulan. A simple physical model of the structural change in κ-carrageenan solution was proposed with a bimodal distribution of κ-carrageenan with higher and lower Mw than the pullulan probe. The higher Mw chains form the gel network restricting the probe's diffusion, and the lower Mw chains increase the effective viscosity. The concentration of the high Mw solute κ-carrageenan chains in 1%, 2% and 4% κ-carrageenan solutions was estimated from Ikap(0) and the total κ-carrageenan concentration, and the relation with pullulan diffusion was studied.
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Affiliation(s)
- Qiuhua Zhao
- Department of Food Science and Technology, Tokyo University of Marine Science and Technology, 4-5-7 Konan, Tokyo 108-8477, Japan
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Patel BK, Campanella OH, Janaswamy S. Impact of urea on the three-dimensional structure, viscoelastic and thermal behavior of iota-carrageenan. Carbohydr Polym 2012; 92:1873-9. [PMID: 23399231 DOI: 10.1016/j.carbpol.2012.11.026] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2012] [Revised: 10/19/2012] [Accepted: 11/08/2012] [Indexed: 11/17/2022]
Abstract
Urea breaks hydrogen bonds among biopolymers leading to structural destabilization. In the case of hydrocolloids urea addition is thought to impact gelation. Detailed information about its pertinent role on influencing the structure-function relationships of hydrocolloids is still elusive, however. The present investigation is aimed at delineating hydrocolloids structural behavior in the presence of urea employing iota-carrageenan as a model system. X-ray fiber diffraction, rheological and thermal properties of two iota-carrageenan solutions with weight concentrations 4.5 and 6.0% (w/w) at two urea molar concentrations (0.5 and 2.0 M) with and without heat treatments have been analyzed. X-ray results suggest that the canonical double helical structural arrangement of iota-carrageenan is maintained even after urea addition. However, improved crystallinity, ordering and altered unit cell dimensions especially with heat treatments of the binary mixtures indicate the promotion of favorable interactions among carrageenan helices in the presence of urea. Increased elastic modulus and onset temperature of melting endotherm with the heat treatment compared to cold addition further attests the X-ray observations of enhanced structural ordering. Overall, results suggest that urea molecules synergistically aid iota-carrageenan interactions and stabilize structure of junction zones. Our findings are deemed to be helpful in the design and development of novel non-food applications of hydrocolloids.
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Affiliation(s)
- Bhavesh K Patel
- Department of Agricultural and Biological Engineering, Purdue University, West Lafayette, IN 47907-2093, USA
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Abstract
Red algae (Rhodophyta) are known as the source of unique sulfated galactans, such as agar, agarose, and carrageenans. The wide practical uses of these polysaccharides are based on their ability to form strong gels in aqueous solutions. Gelling polysaccharides usually have molecules built up of repeating disaccharide units with a regular distribution of sulfate groups, but most of the red algal species contain more complex galactans devoid of gelling ability because of various deviations from the regular structure. Moreover, several red algae may contain sulfated mannans or neutral xylans instead of sulfated galactans as the main structural polysaccharides. This chapter is devoted to a description of the structural diversity of polysaccharides found in the red algae, with special emphasis on the methods of structural analysis of sulfated galactans. In addition to the structural information, some data on the possible use of red algal polysaccharides as biologically active polymers or as taxonomic markers are briefly discussed.
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Grinberg VY, Burova TV, Grinberg NV, Dubovik AS, Tur DR, Usov AI, Papkov VS, Khokhlov AR. Conformational energetics of interpolyelectrolyte complexation between ι-carrageenan and poly(methylaminophosphazene) measured by high-sensitivity differential scanning calorimetry. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:7714-7721. [PMID: 21612233 DOI: 10.1021/la200785g] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The interaction of poly(methylaminophosphazene) hydrochloride (PMAP·HCl) of varying degrees of ionization (f) with the potassium salt of ι-carrageenan was studied by high-sensitivity differential scanning calorimetry at a KCl concentration of 0.15 M, which is included for the purpose of stabilizing the helix conformation of the polysaccharide up to 55 °C. The conditions of strong (pH 3.8, I = 0.15), moderate (pH 7.4, I = 0.15), and weak (pH 7.4, I = 0.25) electrostatic interactions of the polyelectrolytes were considered. The thermodynamic parameters of the helix-coil transition of ι-carrageenan were determined as a function of the polycation/polyanion ratio. We show that the interpolyelectrolyte reaction between PMAP·HCl and ι-carrageenan results in a complete unfolding of the polysaccharide helix under conditions of strong electrostatic interaction and increases its stability under conditions of medium and weak electrostatic interactions. The formation of stoichiometric PMAP-carrageenan interpolyelectrolyte complexes proceeded via a cooperative mechanism at pH 3.8 (f = 0.5) and pH 7.4 (f = 0.2) at an ionic strength of 0.15. In contrast, the complexation at pH 7.4 and an ionic strength of 0.25 could be considered to be a consecutive competitive binding of charged units of poly(methylaminophosphazene) to the oppositely charged polysaccharide matrix in the helix or coil conformation. Binding constants of the polycation to the helix and coil forms of ι-carrageenan were estimated. They revealed a preferential binding of the polycation to the helix form of the polysaccharide.
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Affiliation(s)
- Valerij Y Grinberg
- N. M. Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Kosygin St. 4, 119334 Moscow, Russian Federation.
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15
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Keppeler S, Ellis A, Jacquier J. Cross-linked carrageenan beads for controlled release delivery systems. Carbohydr Polym 2009. [DOI: 10.1016/j.carbpol.2009.07.029] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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16
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Campo VL, Kawano DF, Silva DBD, Carvalho I. Carrageenans: Biological properties, chemical modifications and structural analysis – A review. Carbohydr Polym 2009. [DOI: 10.1016/j.carbpol.2009.01.020] [Citation(s) in RCA: 782] [Impact Index Per Article: 52.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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17
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Berth G, Vukovic J, Lechner MD. Physicochemical characterization of carrageenans-A critical reinvestigation. J Appl Polym Sci 2008. [DOI: 10.1002/app.28937] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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18
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Heterogeneity in iota-carrageenan molecular structure: insights for polymorph II→III transition in the presence of calcium ions. Carbohydr Res 2008; 343:364-73. [DOI: 10.1016/j.carres.2007.10.020] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2007] [Revised: 10/08/2007] [Accepted: 10/24/2007] [Indexed: 11/16/2022]
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19
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Burova TV, Grinberg NV, Grinberg VY, Usov AI, Tolstoguzov VB, Kruif CGD. Conformational Changes in ι- and κ-Carrageenans Induced by Complex Formation with Bovine β-Casein. Biomacromolecules 2006; 8:368-75. [PMID: 17291059 DOI: 10.1021/bm060761f] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The formation of electrostatic complexes between beta-casein and iota- and kappa-carrageenans is well-known. However, the molecular mechanism of the complexation has yet to be determined, particularly with respect to the conformational changes of the interacting macromolecules. High-sensitivity differential scanning calorimetry was used to study beta-casein/carrageenan mixtures at different pH values (3.0 to 7.5), ionic strengths (0.03 and 0.15 M), and various molar protein/polysaccharide ratios (3-400). The effects of these variables on the temperature, enthalpy, and width of the helix-coil transition of iota- and kappa-carrageenans were investigated. Neither pH nor the protein/polysaccharide ratio influenced the transition temperature of either carrageenan in the complexes. However, the transition enthalpy of both carrageenans in complexes with beta-casein decreased to zero with both decreasing pH and increasing protein/polysaccharide ratio. This may reflect an unwinding of the polysaccharide double helix induced by beta-casein, a conformational change which is fully reversible in conditions of sufficiently high ionic strength. The interaction of beta-casein with iota- and kappa-carrageenans was approximated in terms of the model of binding of large ligands to macromolecules, that provides the binding constants for these biopolymers.
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Affiliation(s)
- Tatiana V Burova
- N.M. Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Vavilov St. 28, 119991, Moscow, Russia.
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20
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Marcelo G, Saiz E, Tarazona MP. Unperturbed dimensions of Carrageenans in different salt solutions. Biophys Chem 2005; 113:201-8. [PMID: 15620505 DOI: 10.1016/j.bpc.2004.09.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2004] [Revised: 09/10/2004] [Accepted: 09/10/2004] [Indexed: 10/26/2022]
Abstract
Commercial samples of kappa-, iota-, and lambda-carrageenans were studied by means of Size Exclusion Chromatography with dual detection, i.e. employing a Refractive Index (concentration sensitive) and Multiangle Light Scattering (size sensitive) detectors. The eluent was water containing 0.1 M concentration of different ionic salts, namely LiCl, NaCl, KCl and NaI, with the exception of kappa-carrageenan that aggregates in presence of KCl. Molecular weight distributions and averages, coefficients of the scaling law of molecular dimensions and unperturbed dimensions were thus obtained from a single polydisperse sample of each polymer. Measurements were performed at 25 degrees C and all the systems were above theta conditions with values of the q exponent of the scaling law ranging from 0.51 to 0.59. Extrapolation to unperturbed conditions provides values of the characteristic ratio C(N)=56+/-1 and 40+/-5 respectively for lambda- and iota-carrageenans regardless of the ionic salt employed. However, kappa-carrageenan gives C(N)=31, 35 and 59, respectively, in presence of LiCl, NaCl and NaI, which clearly indicates that this polymer behaves on a different way in presence of NaI than with the other two salts. A tentative explanation of this difference is provided.
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Affiliation(s)
- Gema Marcelo
- Departamento de Química Física, Universidad de Alcalá, 28871-Alcalá de Henares, Madrid, Spain
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21
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Nickerson M, Paulson A, Hallett F. Dilute solution properties of κ-carrageenan polysaccharides: effect of potassium and calcium ions on chain conformation. Carbohydr Polym 2004. [DOI: 10.1016/j.carbpol.2004.06.017] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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22
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Bose SM, Git Y. Mathematical Modelling and Computer Simulation of Linear Polymer Degradation: Simple Scissions. MACROMOL THEOR SIMUL 2004. [DOI: 10.1002/mats.200300036] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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23
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Janaswamy S, Chandrasekaran R. Effect of calcium ions on the organization of iota-carrageenan helices: an X-ray investigation. Carbohydr Res 2002; 337:523-35. [PMID: 11890890 DOI: 10.1016/s0008-6215(02)00017-4] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
X-ray fiber diffraction analysis confirms that calcium iota-carrageenan forms a threefold, right-handed, half-staggered, parallel, double helix of pitch 26.42 A stabilized by interchain hydrogen bonds. According to the detailed structural results, three helices are packed in a trigonal unit cell (a=23.61 and c=13.21 A). Strong interactions between the sulfate groups of neighboring helices, mediated by calcium ions and water molecules, are responsible for stabilizing the three-dimensional structure.
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Affiliation(s)
- Srinivas Janaswamy
- Whistler Center for Carbohydrate Research, Food Science Building, Purdue University, West Lafayette, IN 47907-1160, USA
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24
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Grinberg VY, Grinberg NV, Usov AI, Shusharina NP, Khokhlov AR, de Kruif KG. Thermodynamics of conformational ordering of iota-carrageenan in KCl solutions using high-sensitivity differential scanning calorimetry. Biomacromolecules 2002; 2:864-73. [PMID: 11710043 DOI: 10.1021/bm0100460] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Thermodynamic properties of aqueous solutions of iota-carrageenan as affected by KCl (0.15-1.2 M) or iota-carrageenan (0.5-6 mg/mL) content were studied by high-sensitivity differential scanning calorimetry. The polysaccharide was found to undergo two consecutive cooperative conformational transitions, which can be represented by the scheme: [H2]2<-->2H2<-->4C where C is the random coil, H2 is the double helix, and [H2]2 is the double helix dimer. The first transition follows by the "all or none" mechanism. The profile of the second transition resembles that of a second-order phase transition. The parameter sigma (of order 1), estimated for this latter transition, suggests that the stacking effect in helices of iota-carrageenan is rather small. The cooperativity of the transition is mainly defined by the loop factor. Free energies of both transitions at 273 K were calculated as a function of salt concentration. These experimental data were found to agree with Manning's theory.
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Affiliation(s)
- V Y Grinberg
- Institute of Biochemical Physics, Russian Academy of Sciences, Vavilov St. 28, 117813 Moscow GSP-1, Russia.
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25
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Fredheim GE, Braaten SM, Christensen BE. Molecular weight determination of lignosulfonates by size-exclusion chromatography and multi-angle laser light scattering. J Chromatogr A 2002; 942:191-9. [PMID: 11822385 DOI: 10.1016/s0021-9673(01)01377-2] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
A lignosulfonate sample was fractionated according to the solubility in ethanol-water. The fractions were analysed by aqueous size exclusion chromatography (SEC) combined with in-line multi-angle laser light scattering (MALLS), and by static MALLS. Satisfactory SEC results were obtained with aqueous phosphate buffer containing DMSO and SDS. The refractive index increment (dn/dc) varied from 0.186 to 0.205 ml/g, depending on Mw and the degree of sulfonation. The second viral coefficient (A2) was 7 x 10(-3) ml mol/g2. The weight-average molecular weight (Mw) of the fractions varied from 4600 up to 398 000 g/mol. and the polydispersity (Mw/Mn) varied between 1.3 and 3.5.
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26
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Chapter 9 Molar mass determination of complex bioglycopolymers by size exclusion chromatography and light scattering detection. ACTA ACUST UNITED AC 2002. [DOI: 10.1016/s0301-4770(02)80034-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Abstract
The three-dimensional structure of the sodium salt of iota-carrageenan has been determined by using X-ray diffraction data collected from its polycrystalline and oriented fibers. The molecule forms a half-staggered, parallel, threefold, right-handed double helix that is stabilized by interchain hydrogen bonds from 2- and 6-hydroxyl groups in the galactosyl units. Three helices are organized in a trigonal unit cell, of dimensions a=24.02 and c=12.93 A, with a lateral separation of 13.9 A for each pair. Both 2- and 4-sulfate groups are essential in helix-helix interactions that are mediated only by sodium ions and water molecules.
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Affiliation(s)
- S Janaswamy
- Whistler Center for Carbohydrate Research, Food Science Building, Purdue University, West Lafayette, IN 47907-1160, USA
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28
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Meunier V, Nicolai T, Durand D. Structure of aggregating kappa-carrageenan fractions studied by light scattering. Int J Biol Macromol 2001; 28:157-65. [PMID: 11164233 DOI: 10.1016/s0141-8130(00)00166-5] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We have studied kappa-carrageenan fractions with varying molar mass, obtained by sonication, using static and dynamic light scattering and polarimetry. The samples were characterised in 0.1 M NaCl and 0.1 M NaI, i.e. in the coil and helix conformation, respectively. We find that the molar mass and size of the untreated sample are the same in the coil and helix conformation. For the sonicated samples, we find larger average molar masses and sizes in the helix conformation. The critical temperature, T(c), below which the coil-helix transition sets in, decreases with decreasing molar mass. Aggregation is induced by lowering the temperature in the presence of 0.01 M KCl, which leads to the formation of locally rigid bundles of kappa-carrageenan chains. The thickness of the bundles increases slowly with time and we have not observed stabilisation, even after 24 h at 10 degrees C below T(c). The local structure of the aggregates is the same for all fractions, but at a given temperature, the rate of aggregation decreases with decreasing molar mass.
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Affiliation(s)
- V Meunier
- Polymères Colloides et Interfaces, UMR-CNRS 6120, Université du Maine, 72085, Cedex 9, Le Mans, France
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29
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Meunier V, Nicolai T, Durand D. Structure and Kinetics of Aggregating κ-Carrageenan Studied by Light Scattering. Macromolecules 2000. [DOI: 10.1021/ma991433t] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Vincent Meunier
- Chimie et Physique des Matériaux Polymères, UMR-CNRS 6515, Université du Maine, 72085 le Mans Cedex 9, France
| | - Taco Nicolai
- Chimie et Physique des Matériaux Polymères, UMR-CNRS 6515, Université du Maine, 72085 le Mans Cedex 9, France
| | - Dominique Durand
- Chimie et Physique des Matériaux Polymères, UMR-CNRS 6515, Université du Maine, 72085 le Mans Cedex 9, France
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