The structure of gellan in dilute aqueous solution

Area of Science:

• Biochemistry
• Biophysics
• Polymer Chemistry

Background:

• Gellan is a microbial polysaccharide with diverse applications.
• Understanding its conformational dynamics is crucial for its use.
• Previous studies assumed rigid sugar residues in gellan.

Purpose of the Study:

• To fully assign high-field nuclear magnetic resonance (NMR) spectra of gellan.
• To investigate the conformational flexibility of gellan's sugar residues.
• To elucidate the dynamic behavior of gellan in aqueous solution.

Main Methods:

• Selective one-dimensional NMR experiments were performed.
• Nuclear Overhauser Effect (NOE) analysis was conducted.
• Molecular dynamics calculations were utilized.

Main Results:

• NMR data indicated that sugar residues are not rigidly fixed.
• The rhamnose residue exists in an equilibrium between chair and boat conformations.
• Molecular dynamics simulations supported a stiff single chain with rhamnose flipping.
• Low-temperature NMR revealed distinct methyl group resonances, confirming slow conformational equilibrium.

Conclusions:

• Gellan's structure is more flexible than previously assumed.
• The rhamnose residue undergoes conformational transitions.
• These dynamics are important for gellan's solution behavior.