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[论文解读] Coarse grained modeling of self assembled DNA 3D structure using pragmatic soft ellipsoid contact potential

Abhirup Das, Jayashree Saha|arXiv (Cornell University)|Feb 9, 2026
DNA and Nucleic Acid Chemistry被引用 0
一句话总结

该论文使用软椭球接触势来捕捉碱基间相互作用，结合弯曲、二面角、溶剂、排斥体积和静电项，构建粗粒化DNA模型，并通过再杂交相变和熔解曲线的再现来验证。

ABSTRACT

In this paper, we present a coarse-grained model of DNA based on the soft ellipsoid contact potential (ECP) to evaluate the base pairing interaction properly. We extend the ellipsoid contact like potential model (ECP), suitably modified and used previously by our group to model lipid bilayer phases with considerable success. This potential is used for base-base interactions, along with other potentials to capture bending, dihedral and solvent effects. The model shows a phase transition during hybridization and is able to reproduce the experimental melting curves with sufficient adequacy. Thermodynamical, along with conformational characteristics and structural properties of our model are studied in detail.

研究动机与目标

  • Develop a coarse-grained DNA model that accurately captures base pairing and structural properties.
  • Incorporate anisotropic ellipsoid interactions to reflect base geometry and orientation.
  • Include bending, dihedral, excluded volume, solvent, and electrostatic effects in a unified potential.
  • Demonstrate phase transition during hybridization and compare melting behavior with experiments.
  • Provide structural and thermodynamic characterizations of the model across temperatures.

提出的方法

  • Extend the soft ellipsoid contact potential (ECP) to model DNA base-base interactions.
  • Combine V_bend, V_dihedral, V_exc, V_el, V_ECP, and V_solv into a six-term potential for CG DNA.
  • Use hard constraints via RATTLE for bonds, with low bending/dihedral constants to allow equilibrium formation.
  • Model base pairing with a directional ECP akin to Gay–Berne, including a flat-bottom extension and a pairing vs stacking separation.
  • Represent bases as uniaxial ellipsoids with specified geometry and energy anisotropies; employ implicit solvent via Morse-type V_solv and a WCA-like V_exc.
  • Anneal two 20-base strands from high temperature to low temperature in NVT with Langevin thermostat and velocity Verlet rotational integrator; analyze PMF, specific heat, and pairing fraction to identify a transition.
Figure 1: Potential energy profiles for the flat bottom implicit solvent potential for side-side $\theta=90^{\circ}$ and end-end configurations $\theta=0^{\circ}$ .
Figure 1: Potential energy profiles for the flat bottom implicit solvent potential for side-side $\theta=90^{\circ}$ and end-end configurations $\theta=0^{\circ}$ .

实验结果

研究问题

  • RQ1Can a coarse-grained model with soft ellipsoid interactions reproduce DNA hybridization and 3D structural features?
  • RQ2How do bending, dihedral, excluded volume, solvent, and electrostatic terms shape DNA renaturation and duplex stability in the CG framework?
  • RQ3Does the model reproduce experimental melting behavior and structural metrics such as helix diameter and rise per base pair?
  • RQ4What is the nature (thermodynamic signature) of the DNA hybridization transition in this CG setup?

主要发现

  • A first-order-like phase transition is observed in the potential of mean force with temperature, indicating ssDNA to dsDNA hybridization.
  • Specific heat shows a peak near the transition, reflecting enhanced energy fluctuations at hybridization.
  • The model yields a melting curve in reasonable agreement with experimental references, with a transition temperature around T* = 0.483 (in reduced units), corresponding to about 348.6 K for their scaling.
  • Bending and dihedral angle distributions converge to equilibrium values (approximately 99° for bending and 17° for dihedral) as temperature decreases.
  • Estimated helix diameter from simulations is about 20 Å, and the average rise per base pair is 3.677 Å, close to the experimental ~3.4 Å value.
  • Snapshots illustrate a sequential hybridization process starting at an end and progressing along the strand, leading to duplex formation.
Figure 2: Phase transition curves obtained from simulation. (A) Variation of the potential of mean force (PMF) with temperature. The jump at $T^{\ast}=0.48$ indicates a phase change where ssDNA hybridizes into dsDNA. (B) Variation of specific heat capacity obtained from fluctuations in total energy
Figure 2: Phase transition curves obtained from simulation. (A) Variation of the potential of mean force (PMF) with temperature. The jump at $T^{\ast}=0.48$ indicates a phase change where ssDNA hybridizes into dsDNA. (B) Variation of specific heat capacity obtained from fluctuations in total energy

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