Single-Molecule Dynamics of Confined Branched Polymers

Branched biopolymers such as lubricin and mucin play crucial roles in controlling biolubrication behavior. Investigating the behavior of branched biopolymers at the single-molecule level is critical to understanding their ensemble biolubrication properties. Because branched biopolymers often exist at interfaces, confined environments are good model environments within which to study single-molecule behavior. In this study, we investigate the dynamics of DNA-based branched biopolymers in 1D slit-like confinement. We find that stronger electric fields are required to introduce branched polymers into confined environments than linear polymers of equivalent backbone length, indicating a larger energy penalty to confine branched polymers. Using single-molecule fluorescence microscopy, we measure the center-of-mass diffusion and molecular relaxation times of single branched polymers in slits ranging from 75 nm to 150 nm in height. Confined branched polymers adopt larger conformations and exhibit slower diffusion coefficients than linear polymers of equivalent backbone length. Broadly, understanding of molecular-scale contributions to biolubrication will enable the design of novel materials to treat lubrication-deficient diseases.