Plasmid DNA Undergoes Two Compaction Regimes under Macromolecular Crowding.

Area of Science:

• Biophysics
• Polymer Science
• Molecular Biology

Background:

• Macromolecular crowding influences biological processes by altering molecular behavior.
• Understanding plasmid compaction is crucial for gene delivery and molecular biology applications.

Purpose of the Study:

• To investigate the effect of dextran size on plasmid compaction in vitro.
• To characterize the relationship between crowder size, plasmid conformation, and diffusion dynamics.

Main Methods:

• Laser light scattering experiments were used to measure plasmid compaction.
• Varying concentrations of dextran (2.6, 6.9, 17.0 nm) were used as macromolecular crowders.
• Plasmid diffusivity and radius of gyration were analyzed.

Main Results:

• Two compaction regimes were observed, correlating with normal diffusion and subdiffusion.
• Plasmid conformation was dependent on dextran size, with smaller crowders inducing larger changes.
• Generalized scaling law R_g ~ ϕ^-1/(1+x) was reported for plasmid compaction.

Conclusions:

• Entropic depletion, excluded volume, and interplasmid repulsion drive plasmid conformational changes.
• Plasmid diffusion coefficients and second virial coefficients support these findings.
• Crowder size is a critical factor in determining plasmid compaction and behavior.