Modeling DNA beacons at the mesoscopic scale.

Area of Science:

• Biophysics
• Computational Biology
• Molecular Biology

Background:

• DNA single strands can form hairpin structures, crucial for various biological processes.
• Understanding the dynamics and thermodynamics of hairpin formation and melting is essential for molecular biology applications.
• Existing models often simplify the complex interplay of factors governing DNA hairpin stability.

Purpose of the Study:

• To develop and apply model calculations for DNA single strands to describe hairpin formation and melting dynamics.
• To investigate the influence of strand rigidity and loop length on hairpin stability and kinetics.
• To compare model predictions with experimental data from fluorescent DNA beacons.

Main Methods:

• Utilized single-base resolution modeling for DNA strands.
• Employed polymer models (freely rotating chain, discrete Kratky-Porod) to describe strand rigidity.
• Applied the Peyrard-Bishop-Dauxois Hamiltonian for stem formation.
• Modeled kinetics using diffusion-controlled motion in an effective free-energy landscape.

Main Results:

• Model calculations demonstrated semiquantitative agreement with experimental melting profiles and kinetic time scales for poly(T) loops.
• Discrepancies were observed for poly(A) loops, where strand rigidity variations did not fully explain activation enthalpy and loop length dependence.
• The study provides insights into the equilibrium dynamics and kinetics of DNA hairpin formation and melting.

Conclusions:

• The developed models offer a framework for understanding DNA hairpin dynamics at a fundamental level.
• Findings suggest that factors beyond simple strand rigidity are critical for accurately modeling poly(A) loop hairpins.
• The study has implications for refining models of single-stranded DNA and RNA behavior.