Stretching Response of Knotted and Unknotted Polymer Chains

Area of Science:

• Polymer Physics
• Soft Matter Physics
• Single-Molecule Biophysics

Background:

• Knotting significantly alters polymer chain properties under tension.
• Understanding weak mechanical stretching response of knotted chains remains crucial.
• Distinguishing knotted from unknotted chains under force requires further investigation.

Purpose of the Study:

• To profile the complete mechanical stretching response of knotted polymer chains.
• To investigate differences in stretching behavior between knotted and unknotted chains.
• To explore the impact of knot complexity on chain extension under force.

Main Methods:

• Computational profiling of the stretching response for chains with varying topologies.
• Analysis of chain extension as a function of applied force.
• Comparison of behavior across different knot complexities and chain lengths.

Main Results:

• The ratio of knotted to unknotted chain extension varies non-monotonically with applied force.
• This non-monotonicity signifies a crossover between high-force and low-force stretching regimes.
• Differences in response increase with knot complexity.

Conclusions:

• The study reveals distinct stretching behaviors for knotted and unknotted polymer chains.
• Observed differences are sensitive to knot complexity, offering a potential detection method.
• Findings could enable inference of physical knot presence and complexity in biomolecules.