On the structure and dynamics of duplex GNA

Area of Science:

• Synthetic biology
• Biochemistry
• Structural biology

Background:

• Glycol nucleic acid (GNA) is a structural analog of DNA with a unique propylene glycol-based backbone.
• GNA exhibits remarkable biophysical properties, including stable antiparallel duplex formation and high base-pairing fidelity.
• Previous studies identified two distinct backbone conformations (M-type and N-type) in double-stranded GNA (dsGNA) crystals.

Purpose of the Study:

• To determine the solution-state conformation of dsGNA.
• To elucidate the structural basis for GNA's enhanced thermal stability.
• To compare the conformational flexibility of GNA with that of DNA.

Main Methods:

• X-ray crystallography of a GNA duplex at 1.8 Å resolution.
• 20 ns molecular dynamics simulations of dsGNA in solution.
• Analysis of backbone torsions, helical twist, and entropic changes upon duplex formation.

Main Results:

• A new crystal structure revealed an N-type conformation with alternating gauche-anti backbone torsions.
• Molecular dynamics simulations showed dsGNA adopts conformations intermediate between M-type and N-type.
• Simulated dsGNA exhibited the M-type all-gauche conformation and N-type helical twist.
• dsGNA displayed greater conformational flexibility and a smaller entropic penalty upon duplex formation than dsDNA.

Conclusions:

• dsGNA exhibits significant conformational flexibility in solution, bridging previously observed crystalline forms.
• This inherent flexibility, alongside base stacking and preorganization, underlies GNA's exceptional thermal stability.
• GNA represents a promising alternative nucleic acid with tunable stability for various applications.