Single-molecule Magnetic Resonance Spectroscopy
Energy transfer and signal transduction processes in cells represent critical questions of complex dynamics in biological systems. We aim to answer the questions by imaging physical behaviors of biological molecules at the single molecule level through a new magnetic resonance technique. Magnetic resonance such as nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) is an extremely powerful technique for three-dimensional structure determination of proteins and nucleic acids at nanometer and sub-nanometer resolution. However, its intrinsically low sensitivity precludes analyses of very small amount of samples. For example, more than 1010 electron spins are required to observe EPR signals under normal conditions. We are currently developing a magnetic resonance system that will overturn the current limit of magnetic resonance sensitivity such that a single electron spin will be detected.
Nitrogen-vacancy (NV) centers are paramagnetic impurities existing within a diamond lattice. Because of the exceptional spin properties of NV centers, including the capability of a single NV detection using optically detected EPR even at room temperature, and extremely high sensitivity to other electron and nuclear spins located near the NV center, a single NV center is an excellent candidate for a magnetic sensor which enables magnetic resonance analyses with single spin sensitivity. Our developing magnetic resonance system consists of a single NV impurity in diamond and a state-of-the-art high-field EPR spectrometer in order to realize single spin sensitivity and nanometer spatial resolution.
Our magnetometer will be a robust tool, enabling magnetic resonance analysis at the single-molecule level. In conjunction with the site-directed spin-labeling technique, we will investigate structure and conformation of an individual bio-macromolecule.