DNA relaxation dynamics in crowded environments: Influence of PEG molecular weight and viscosity.

The coil-globule transition is a key phenomenon in polymer physics, where polymer chains shift between collapsed and extended states. This study investigates the relaxation dynamics of T4 DNA transitioning from an electrohydrodynamically compressed globule to a relaxed coil state in polyethylene glycol (PEG) solutions of varying molecular weights. Using an AC electric field to induce globule formation, we analyzed DNA expansion upon field cessation. Higher molecular weight PEG, particularly PEG 20000, markedly prolonged relaxation times and exhibited broader distributions compared to PEG 4000 and PEG 6000. In PEG 20000, exceeding the overlap concentration stabilized multi-core structures and delayed DNA relaxation. These dynamics diverged from simple exponential relaxation due to persistent entanglements and compressed regions. The findings highlight the significance of crowding effects and viscosity in influencing polymer dynamics, providing insights relevant to biological systems and synthetic applications, such as drug delivery and gene therapy.