NV Center Electron Paramagnetic Resonance of a Single Nanodiamond Attached to an Individual Biomolecule

TL;DR

This paper demonstrates the use of electron paramagnetic resonance (EPR) on a single biomolecule by attaching a nanodiamond with NV centers to DNA, enabling single-molecule magnetic resonance studies.

Contribution

It introduces a novel method combining EPR with single-molecule detection using nanodiamonds, advancing biomolecular structural analysis.

Findings

Nanodiamond probe exhibits complete rotational freedom.

Reorientation time of nanodiamond is slow relative to spin relaxation.

Successful EPR detection on a single DNA molecule.

Abstract

A key limitation of electron paramagnetic resonance (EPR), an established and powerful tool for studying atomic-scale biomolecular structure and dynamics is its poor sensitivity, samples containing in excess of 10^12 labeled biomolecules are required in typical experiments. In contrast, single molecule measurements provide improved insights into heterogeneous behaviors that can be masked by ensemble measurements and are often essential for illuminating the molecular mechanisms behind the function of a biomolecule. We report EPR measurements of a single labeled biomolecule that merge these two powerful techniques. We selectively label an individual double-stranded DNA molecule with a single nanodiamond containing nitrogen-vacancy (NV) centers, and optically detect the paramagnetic resonance of NV spins in the nanodiamond probe. Analysis of the spectrum reveals that the nanodiamond probe has complete rotational freedom and that the characteristic time scale for reorientation of the nanodiamond probe is slow compared to the transverse spin relaxation time. This demonstration of EPR spectroscopy of a single nanodiamond labeled DNA provides the foundation for the development of single molecule magnetic resonance studies of complex biomolecular systems.