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Updated: May 8, 2026

Practical Aspects of Sample Preparation and Setup of 1H R1ρ Relaxation Dispersion Experiments of RNA
Published on: July 9, 2021
1H R1ρ relaxation identifies a hidden intermediate in DNA base-pairing
Rubin Dasgupta1,2, Christian Steinmetzger1,2, Julian Ilgen1,3
1Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.
Proton R1ρ relaxation dispersion NMR reveals a new DNA excited state, ES2, beyond the standard Watson-Crick-Franklin and Hoogsteen forms. This discovery advances biomolecular dynamics studies and shows how drugs can alter DNA structures.
Area of Science:
- Biophysics
- Structural Biology
- NMR Spectroscopy
Background:
- Proton R1ρ relaxation dispersion (RD) NMR is crucial for studying biomolecular dynamics.
- Cross-relaxation artifacts can complicate the interpretation of ¹H R1ρ RD experiments.
- Expanding ¹H R1ρ RD applicability requires addressing these artifacts.
Purpose of the Study:
- To quantify cross-relaxation effects on ¹H R1ρ relaxation rates.
- To establish reliable conditions for ¹H R1ρ RD studies at natural abundance.
- To investigate DNA base-pairing dynamics and identify novel conformational states.
Main Methods:
- Quantification of cross-relaxation effects on ¹H R1ρ relaxation rates.
- ¹H R1ρ RD NMR experiments at natural abundance.
- DNA modifications, metadynamics simulations, and DFT calculations for structural modeling.
Main Results:
- Cross-relaxation artifacts are negligible for protons >3 Å apart.
- A novel DNA excited state (ES2) was identified, extending the GS-HG equilibrium.
- Actinomycin D stabilized the ES2 state, demonstrating drug-induced conformational remodeling.
Conclusions:
- Methodological advances enable reliable ¹H R1ρ RD studies by managing cross-relaxation.
- A drug-stabilized intermediate (ES2) in DNA base-pairing dynamics was discovered.
- ¹H R1ρ RD is a powerful tool for probing transient biomolecular states.
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