Boundaries of the Topologically Frustrated Dynamical State in Polymer Dynamics

Area of Science:

• Biophysics
• Polymer Science
• Soft Matter Physics

Background:

• DNA dynamics in confined environments are crucial for understanding biological processes and developing nanotechnology.
• The topologically frustrated dynamical state (TFDS) describes complex DNA behavior in intermediate confinement regimes.
• Understanding entropic barriers is key to predicting and controlling macromolecule motion.

Purpose of the Study:

• To directly observe and quantify the dynamics of lambda-DNA within poly(acrylamide-co-acrylate) hydrogels under an electric field.
• To investigate the emergence and characteristics of the topologically frustrated dynamical state (TFDS) in confined DNA.
• To determine the role and magnitude of entropic barriers in DNA immobility and mobility transitions.

Main Methods:

• Utilizing fluorescence microscopy for high-resolution imaging.
• Employing single-particle tracking to monitor individual lambda-DNA molecule movements.
• Applying external electric fields to probe DNA response and mobility thresholds.

Main Results:

• Lambda-DNA remains immobile in the absence of an electric field, consistent with the TFDS.
• Electrophoretic mobility is initiated only when the electric field strength exceeds a critical threshold (Ec).
• A significant entropic barrier (up to 130 kBT) was quantified, responsible for the metastable TFDS, which varies non-monotonically with confinement.

Conclusions:

• The study confirms the existence and characteristics of the TFDS for DNA in hydrogels.
• An electric field threshold is necessary to overcome a substantial entropic barrier, enabling DNA translocation.
• The findings provide insights into hydrogel mesh size effects on DNA diffusion and the transition out of the TFDS.