Molecular behavior of DNA in a cell-sized compartment coated by lipids

TL;DR

This study investigates how DNA molecules behave within cell-sized lipid-coated droplets, revealing size-dependent adsorption and conformational changes influenced by membrane phase and free energy considerations.

Contribution

It introduces a model explaining size-dependent DNA behavior in confined lipid environments, integrating experimental observations with free energy analysis.

Findings

DNA adsorption depends on vesicle size

Globular DNA unfolds on the membrane in a size-dependent manner

DNA selectively adsorbs on membrane phases based on conformation

Abstract

The behavior of long DNA molecules in a cell-sized confined space was investigated. We prepared water-in-oil droplets covered by phospholipids, which mimic the inner space of a cell, following the encapsulation of DNA molecules with unfolded coil and folded globule conformations. Microscopic observation revealed that the adsorption of coiled DNA onto the membrane surface depended on the size of the vesicular space. Globular DNA showed a cell-size-dependent unfolding transition after adsorption on the membrane. Furthermore, when DNA interacted with a two-phase membrane surface, DNA selectively adsorbed on the membrane phase, such as an ordered or disordered phase, depending on its conformation. We discuss the mechanism of these trends by considering the free energy of DNA together with a polyamine in the solution. The free energy of our model was consistent with the present experimental data. The cooperative interaction of DNA and polyamines with a membrane surface leads to the size-dependent behavior of molecular systems in a small space. These findings may contribute to a better understanding of the physical mechanism of molecular events and reactions inside a cell.