Twist-encoded magnetic plasmon interferometry for label-free, orientation-resolved single-molecule imaging

Area of Science:

• Nanotechnology
• Surface Science
• Molecular Biophysics

Background:

• Understanding molecular torsion at interfaces is crucial for recognition and energy dissipation.
• Direct visualization of single-molecule twist dynamics has been a significant challenge.

Purpose of the Study:

• To introduce a novel label-free technique for real-time, orientation-resolved measurement of molecular twist.
• To probe interfacial molecular mechanics and conformational changes with high sensitivity.

Main Methods:

• Developed twist-encoded magnetic plasmon interferometry (TEMPi) using gold nanorods and a metal film.
• Utilized near-field coupling to excite magnetic plasmons, converting nanorod twist into an optical phase signal.
• Enabled wide-field, label-free operation in native buffers for real-time tracking.

Main Results:

• Resolved three distinct confinement-dependent rotational regimes.
• Differentiated between dual- and single-contact protein anchoring based on rotational behavior.
• Quantified a ninefold increase in torsional stiffness and faster twisting relaxation during DNA hybridization.

Conclusions:

• TEMPi provides a general twist-resolved metrology for interfacial molecular mechanics.
• The technique enables the design of torsion-responsive interfaces for various applications.
• Demonstrated TEMPi's capability in probing protein binding and DNA hybridization dynamics.