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Multiple conformations coexist and interchange in natural B DNA fibers
Journal of Molecular Biology
|March 25, 1984
Summary
Nuclear magnetic resonance (NMR) reveals distinct conformational behaviors of DNA fibers. Sodium DNA (NaDNA) exhibits slow transitions between A and B forms, while Lithium DNA (LiDNA) shows rapid interconversion between B-form conformations.
Area of Science:
- Biophysics
- Molecular Biology
- Structural Biology
Background:
- DNA exists in various forms (A, B, Z) influenced by environmental factors like hydration.
- Understanding DNA conformational dynamics is crucial for comprehending its biological functions.
Purpose of the Study:
- To investigate the conformational changes of NaDNA and LiDNA fibers.
- To analyze the humidity dependence of DNA structures using 31P nuclear magnetic resonance (NMR).
Main Methods:
- 31P nuclear magnetic resonance (NMR) spectroscopy.
- Analysis of highly oriented NaDNA and LiDNA fibers across a relative humidity range (66%-98%).
Main Results:
- NaDNA: A form is conformationally uniform; B form exhibits multiple conformations with slow interconversion between A and B forms.
- LiDNA: Two stable B-form conformations exist at low humidity, rapidly interconverting at high humidity.
- LiDNA spectral patterns align with known double-stranded oligonucleotide crystal structures.
Conclusions:
- DNA conformational flexibility is modulated by counterions (Na+ vs. Li+) and hydration levels.
- NMR is a powerful tool for probing DNA structural dynamics in oriented fibers.