Influence of Nitroxide Spin Labels on RNA Structure: A Molecular Dynamics Simulation Study.

Area of Science:

• Biophysics
• Structural Biology
• Computational Chemistry

Background:

• Pulsed electron double resonance (PELDOR) is a powerful technique for measuring nanometer-scale distances in biomolecules.
• Attaching nitroxide spin labels, essential for PELDOR, may potentially alter the native structure of nucleic acids like RNA.
• Understanding these structural perturbations is crucial for accurate interpretation of PELDOR data.

Purpose of the Study:

• To investigate the conformational effects of nitroxide spin labels on RNA structure.
• To evaluate the influence of spin label placement (major vs. minor groove) on RNA conformation.
• To develop and validate a force field parametrization for accurate molecular dynamics simulations of spin-labeled RNA.

Main Methods:

• All-atom molecular dynamics simulations in explicit solvent were performed on six double-labeled RNA duplexes.
• A novel force field parametrization for nitroxide spin labels was developed and applied.
• Simulated intramolecular distances were compared with experimental PELDOR results.

Main Results:

• The new force field parametrization yielded intramolecular distances consistent with experimental data.
• Conformational effects of spin labels were found to be dependent on their attachment site.
• Major-groove spin labeling showed some perturbation of nearby base pair conformation.
• Minor-groove spin labeling demonstrated a significant advantage in preserving the overall RNA conformation.

Conclusions:

• Minor-groove attachment of nitroxide spin labels is recommended for PELDOR studies on RNA to minimize structural artifacts.
• The developed force field parametrization enhances the accuracy of molecular dynamics simulations for spin-labeled nucleic acids.
• This study provides critical insights for optimizing experimental design in PELDOR investigations of RNA structure and dynamics.