Visualizing single-stranded nucleic acids in solution.

Area of Science:

• Biochemistry
• Structural Biology
• Biophysics

Background:

• Single-stranded nucleic acids (ssNAs) play vital roles in cellular functions.
• Their inherent flexibility poses challenges for high-resolution structural determination, often resulting in ensemble-averaged data.
• Understanding ssNA conformational distributions is key to characterizing biological interactions.

Purpose of the Study:

• To develop and apply a novel computational approach for dynamically building and refining sets of ssNA structures.
• To gain insights into the conformational heterogeneity of ssNAs in solution.
• To provide a detailed understanding of ssNA conformations relevant to biological processes.

Main Methods:

• Integration of small-angle X-ray scattering (SAXS) with ensemble-optimization methods (EOM).
• Construction of candidate ssNA structures based on dinucleotide steps.
• Iterative refinement of structural models against experimental SAXS data.

Main Results:

• Successfully generated diverse sets of ssNA structures reflecting varying solution conditions and sequences.
• Provided unprecedented, detailed insights into phosphate backbone and strand conformations.
• Demonstrated the ability to characterize large-scale structural parameters and finer conformational details.

Conclusions:

• The combined SAXS-EOM approach offers a powerful means to study flexible ssNA structures.
• Detailed conformational information obtained will enhance understanding of protein-ssNA binding, RNA folding, and NA polymer dynamics.
• The methodology is potentially extensible to other flexible biological macromolecules.