Electron spin resonance studies of starch-water-probe interactions |
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| Affiliation: | 1. Sorbonne University, UPMC Univ Paris 06, CNRS, UMR 8234, PHENIX Laboratory, case 51, 4 place Jussieu, 75252 Paris cedex 05, France;2. Laboratory of Polymer Chemistry and Technology, Department of Chemistry, Aristotle University of Thessaloniki, Thessaloniki, 54124, Greece;3. Solid State Physics Department, School of Physics, Aristotle University of Thessaloniki, Thessaloniki 541424, Greece;4. Department of Physics, National Technical University of Athens, Zografou Campus, 15780, Athens, Greece;1. Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland;2. Departement de Chimie, Ecole Normale Superieure, PSL Research University, UPMC Univ Paris 06, CNRS, Laboratoire des Biomolecules (LBM), 24 rue Lhomond, 75005 Paris, France;3. Sorbonne Universites, UPMC Univ Paris 06, Ecole Normale Superieure, CNRS, Laboratoire des Biomolecules (LBM), Paris, France;4. Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA;5. Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA;6. National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310, USA;7. Univ Lyon, CNRS, Université Claude Bernard Lyon 1, ENS de Lyon, Institut des Sciences Analytiques, UMR 5280, 5 rue de la Doua, 69100 Villeurbanne, France;8. Amgen Inc., 360 Binney Street Cambridge, MA 02142, USA;9. 2 Allée Geneviève Anthonioz de Gaulle, 93260 Les Lilas, France;1. Pharmaceutics Division, Department of Pharmaceutical Sciences and Drug Research, Punjabi University, Patiala 147002, India;2. Dr. Reddy’s Laboratory, Hyderabad 500049, India |
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| Abstract: | ![]()
Interactions between starch, water and stable nitroxide radicals were studied by electron spin resonance. The motional properties of TEMPO, 4-(2-bromoacetamido) TEMPO (BrAcTEMPO), 5-DOXYL-stearic acid and 16-DOXYL-stearic acid probes as well as a label covalently attached to amylopectin were investigated in concentrated (10–50%) starch-water systems as a function of temperature, concentration of polymer and storage period. Compared with the free probes in solution, TEMPO and BrAcTEMPO showed slower tumbling rates in starch-water dispersions or gels, suggesting a higher microviscosity in the probe's environment. The spectra, however, remained motionally narrowed. In contrast, the three line spectra of the fatty acid probes in solution became highly anisotropic in the presence of starch. The results indicated that these probes were highly immobilized at room temperature by the starch granules or by the polysaccharide gel matrix. These interactions are weakened at elevated temperatures where the spectra revealed the presence of both motionally narrowed and motionally slowed spin populations. The nitroxide label on the amylopectin exhibited a much slower mobility than the corresponding free probe as well as being found to be more motionally sensitive to temperature changes; such motional behavior was interpreted as reflecting contributions from rotation of the label around the chain backbone as well as local segmental motion of the polymer chain itself. Starch gels doped with free probes or the spin labelled amylopectin displayed no change in the motion of the nitroxide group upon storage, i.e. the tumbling rates did not follow the time-dependent conformational changes associated with the retrogradation phenomenon. |
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