Probing Helical Hydrophobic Binding Sites in Branched Starch Polysaccharides Using NMR Spectroscopy

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Abstract

Branched starch polysaccharides are capable of binding multiple hydrophobic guests, but their exploitation as multivalent hosts and in functional materials is limited by their structural complexity and diversity. Linear (1-4)-linked glucose oligosaccharides are known to bind hydrophobic guests inside left-handed single helices in solution and the solid state. Here, we describe the development of an amphiphilic probe that binds to linear (1-4)-linked glucose oligosaccharides and undergoes a conformational switch upon complexation, which gives rise to dramatic changes in the (HNMR)-H-1 spectrum of the probe. We use this probe to explore hydrophobic binding sites in the branched starch polysaccharides amylopectin and -limit dextrin. Diffusion-ordered (DOSY), nuclear Overhauser effect (NOESY) and chemical shift perturbation (HSQC) NMR experiments are utilised to provide evidence that, in aqueous solution, branched polysaccharides bind hydrophobic guests in well-defined helical binding sites, similar to those reported for complexation by linear oligosaccharides. By examining the binding affinity of the probe to systematically enzymatically degraded polysaccharides, we deduce that the binding sites for hydrophobic guests can be located on internal as well as external branches and that proximal (1-6)-linked branch points weaken but do not prevent complexation.
Original languageEnglish
JournalChemistry-a European Journal
Volume19
Issue number48
Pages (from-to)16314-16320
Number of pages7
ISSN0947-6539
DOIs
Publication statusPublished - 2013
Externally publishedYes

Keywords

  • Amylopectin
  • Binding Sites
  • Dextrins
  • Molecular Structure
  • Nuclear Magnetic Resonance, Biomolecular
  • Polysaccharides
  • Starch
  • 9005-25-8 Starch
  • 9037-22-3 Amylopectin
  • CHEMISTRY,
  • AMYLOSE-INCLUSION COMPLEXES
  • SURFACE-TENSION MEASUREMENTS
  • SODIUM DODECYL-SULFATE
  • HEXADECYLTRIMETHYLAMMONIUM BROMIDE
  • V-AMYLOSE
  • AMYLOPECTIN
  • CONFORMATION
  • RETROGRADATION
  • CYCLODEXTRINS
  • GRANULES
  • carbohydrates
  • hydrophobic effect
  • molecular recognition
  • NMR spectroscopy
  • polysaccharides
  • Binding energy
  • Carbohydrates
  • Functional materials
  • Glucose
  • Hydrophobicity
  • Molecular recognition
  • Oligosaccharides
  • Probes
  • Nuclear magnetic resonance spectroscopy
  • Binding affinities
  • Chemical shift perturbations
  • Conformational switches
  • Hydrophobic binding
  • Hydrophobic effect
  • Hydrophobic guests
  • Nuclear overhauser effects
  • Structural complexity

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