Related Experiment Video
Updated: Jul 12, 2025
11:27
Studying DNA Looping by Single-Molecule FRET
Published on: June 28, 2014
15.5K
Entropy of Charge Inversion in DNA including One-Loop Fluctuations
Matthew D Sievert1, Marilyn F Bishop2, Tom McMullen2
1Department of Physics, New Mexico State University, Las Cruces, NM 88003-8001, USA.
Entropy (Basel, Switzerland)
|October 28, 2023
Summary
Fluctuations in polyelectrolyte models significantly reduce entropy, even below non-interacting levels. This finding impacts understanding DNA charge condensation in solutions.
Area of Science:
- Biophysics
- Physical Chemistry
- Computational Biology
Background:
- DNA in charged solutions exhibits complex behavior like charge inversion and condensation.
- Polyelectrolytes play a crucial role in these observed phenomena.
- Understanding these interactions requires advanced theoretical models.
Purpose of the Study:
- To calculate entropy and charge distributions for polyelectrolytes on DNA.
- To investigate the impact of fluctuations beyond mean-field theory.
- To model polyelectrolyte adsorption using a lattice gas approach.
Main Methods:
- Field-theoretic method incorporating one-loop order fluctuations.
- Lattice gas model for doubly charged polyelectrolyte dimers.
- Calculation of entropy and charge distributions.
Main Results:
- Fluctuation terms decreased entropy by approximately 50% in the weak-binding regime.
- Repulsion between dimers and DNA competed with chemical potential.
- Entropy reduction due to correlations significantly lowered total entropy.
Conclusions:
- Fluctuations play a critical role in polyelectrolyte-DNA interactions.
- The model provides insights into entropy changes driven by correlations.
- The methodology can be extended to more complex, realistic models.
Related Concept Videos
01:16Electrostatic Boundary Conditions
481
Consider an external electric field propagating through a homogeneous medium. When the electric field crosses the surface boundary of the medium, it undergoes a discontinuity. The electric field can be resolved into normal and tangential components. The amount by which the field changes at any boundary is given by the difference between the field components above and below the surface boundary.
The surface integral of an electric field is given by Gauss's law in integral form and is related to...
The surface integral of an electric field is given by Gauss's law in integral form and is related to...
481
02:02DNA Topoisomerases
31.4K
Topoisomerases are enzymes that relax overwound DNA molecules during various cell processes, including DNA replication and transcription. These enzymes regulate positive and negative DNA supercoiling without changing the nucleotide sequence. DNA overwinding in a clockwise direction results in positively supercoiled DNA, whereas underwinding in a counterclockwise direction produces negatively supercoiled DNA.
Types and Mechanism of action
Topoisomerases are divided into two main types. ...
Types and Mechanism of action
Topoisomerases are divided into two main types. ...
31.4K
02:05DNA as a Genetic Template
22.0K
Two structural features of the DNA molecule provide a basis for the mechanisms of heredity: the four nucleotide bases and its double-stranded nature. The Watson-Crick model of double-helical DNA structure, proposed in 1952, drew heavily upon the X-ray crystallography work of researchers Rosalind Franklin and Maurice Wilkins. Watson, Crick, and Wilkins jointly received the Nobel Prize in Physiology or Medicine for their work in 1962. Franklin was, controversially, excluded from the prize for...
22.0K
01:22Entropy within the Cell
10.7K
A living cell's primary tasks of obtaining, transforming, and using energy to do work may seem simple. However, the second law of thermodynamics explains why these tasks are harder than they appear. None of the energy transfers in the universe are completely efficient. In every energy transfer, some amount of energy is lost in a form that is unusable. In most cases, this form is heat energy. Thermodynamically, heat energy is defined as the energy transferred from one system to another that...
10.7K
01:21Energy Associated With a Charge Distribution
1.5K
The work done to bring a charge through a distance r is given by the potential difference between the initial and the final position. To assemble a collection of point charges, the total work done can be expressed in terms of the product of each pair of charges divided by their separation distance, defined with respect to a suitable origin. Solving this expression gives the energy stored in a point charge distribution.
1.5K
01:07The DNA Helix
20.8K
Deoxyribonucleic acid, or DNA, is the genetic material responsible for passing traits from generation to generation in all organisms and most viruses. DNA is composed of two strands of nucleotides that wind around each other to form a spring-like structure called a double helix. However, the double helix is not perfectly symmetrical. Instead, there are regularly occurring grooves in the structure. The major groove occurs where the sugar-phosphate backbones are relatively far apart. This space...
20.8K