Undulations enhance the effect of helical structure on DNA interactions

Area of Science:

• Biophysics
• Structural Biology
• Physical Chemistry

Background:

• DNA-DNA interactions in hydrated aggregates are governed by helical patterns and counterion binding.
• X-ray diffraction confirms parallel molecular alignment, facilitating electrostatic interactions via sugar-phosphate backbones and groove-bound counterions.
• The influence of intrinsic and thermal fluctuations on this alignment and interaction remained unclear.

Purpose of the Study:

• To develop a comprehensive theory of DNA-DNA interactions that incorporates stretching, bending, and twisting fluctuations.
• To investigate how these fluctuations affect the helical structure and alignment of DNA molecules in hydrated aggregates.
• To compare theoretical predictions with experimental measurements of osmotic pressure in DNA.

Main Methods:

• Development of a theoretical model incorporating torsional, stretching, and bending fluctuations of DNA.
• Analysis of how these fluctuations influence the electrostatic interactions and alignment between DNA molecules.
• Quantitative comparison of theoretical predictions with experimental osmotic pressure data.

Main Results:

• Stretching and twisting fluctuations have similar effects on DNA-DNA interactions.
• Bending fluctuations (undulations) significantly amplify helical structure effects, contrary to expectations.
• DNA undulations enhance structural adaptation, leading to improved molecular alignment and a more ideal helical backbone geometry.

Conclusions:

• Bending fluctuations play a critical role in DNA-DNA interactions within hydrated aggregates.
• The helical structure of DNA is more robust and adaptable to fluctuations than previously thought.
• Theoretical predictions align with experimental osmotic pressure data, supporting the model's validity.