Helix untwisting and bubble formation in circular DNA.

Area of Science:

• Molecular Biophysics
• Computational Biology
• Genomics

Background:

• Understanding DNA structural dynamics is crucial for gene regulation and replication.
• Circular DNA molecules exhibit unique conformational properties due to topological constraints.
• Previous models often simplified the complex interplay of twisting and bending in DNA.

Purpose of the Study:

• To develop and apply a realistic mesoscopic model for analyzing base pair fluctuations and helix untwisting in circular DNA.
• To investigate the influence of temperature on DNA conformation and structural transitions.
• To predict sequence-specific structural features like helical repeat, opening sites, and bubble formation.

Main Methods:

• A mesoscopic model incorporating twisting degrees of freedom and molecular axis bending was developed.
• Path integral techniques were employed for computational simulation.
• The model simulates a distribution of topoisomers to determine energetically favorable conformations at varying temperatures.

Main Results:

• The model successfully predicts the helical repeat of circular DNA molecules.
• It identifies preferred loci for helix opening and quantifies DNA bubble sizes.
• Results demonstrate temperature-dependent conformational changes and structural stability.

Conclusions:

• The proposed model provides a powerful tool for predicting DNA structural dynamics in circular molecules.
• It offers insights into sequence-specific structural behaviors relevant to DNA function.
• The findings are applicable to understanding DNA structures, such as those found in mammalian cells.