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

Area of Science:

• Nanotechnology
• Surface Science
• Molecular Biophysics

Background:

• Molecular torsion dynamics at interfaces are crucial for biological and chemical processes.
• Direct visualization of single-molecule twist has been a significant technical challenge.

Purpose of the Study:

• To introduce a novel technique, twist-encoded magnetic plasmon interferometry (TEMPi), for label-free, real-time monitoring of molecular torsion.
• To demonstrate TEMPi's capability in resolving rotational dynamics and interfacial conformational changes at the single-molecule level.

Main Methods:

• TEMPi utilizes the near-field coupling between a gold nanorod and a metal film to generate a phase-encoded optical signal.
• This signal quantitatively maps nanorod twist to interferometric phase, enabling orientation-resolved measurements.
• The technique operates in wide-field, label-free mode within native buffers.

Main Results:

• TEMPi successfully resolved three distinct confinement-dependent rotational regimes.
• The method distinguished between dual- and single-contact protein anchoring and localized binding sites via twist-dependent shifts.
• Application to DNA hybridization revealed a ninefold increase in torsional stiffness and faster relaxation upon duplex formation.

Conclusions:

• TEMPi provides a general twist-resolved metrology for studying interfacial molecular mechanics.
• The technique is valuable for designing and understanding torsion-responsive interfaces in various scientific fields.
• This advancement opens new avenues for probing molecular behavior at solid-liquid interfaces.