Subatomic MRI could lead to new drug therapies

A new imaging technique using quantum science could lead to novel drug therapies and treatment options, a recent study has found.

Researchers at the University of Waterloo, with support from Transformative Quantum Technologies, have demonstrated the feasibility of nuclear magnetic resonance diffraction (NMRd) to study the lattice structure of crystalline solids at the atomic level, a feat only possible for larger-scale imaging applications such as magnetic resonance imaging (MRI).

“NMRd was proposed in 1973 as a method to study the structure of materials,” said Dr. Holger Haas, one of the lead authors of the study and a graduate of the Institute for Quantum Computing (IQC) in Waterloo, now at IBM. “Back then, the writers dismissed their idea as ridiculous. Our work comes tantalizingly close to realizing this crazy idea – we have shown that it is possible to probe atomic-length structures over sample volumes relevant to many biological and physical systems.”

“NMRd opens up an enormous variety of possibilities in many research directions, including the study of nanocrystals and organic compounds,” added Haas. The ability to map biological structures such as protein molecules and virus particles at the atomic level can advance understanding of their function and potentially lead to new drug therapies and treatment options.

NMRd uses a core property called spin, a fundamental unit of magnetism. Because of this spin, when placed in a magnetic field, the nuclei essentially act like magnets. A time-varying magnetic field can perturb the spins and change the angle of the spin—in technical terms, this is called phase encoding in each spin. At a given encoding time, all spins are pointing back in the original direction. When this occurs, a diffraction echo is observed, a signal that can be measured to find the lattice constant and shape of the sample. Each nucleus produces a unique signal that can be used to discern the structure of the molecule.

The challenge in achieving atomic-level NMR was the difficulty to encode large relative phase differences between adjacent nuclear spins at the atomic level, meaning that no diffraction echo could be observed. The researchers overcame this limitation by using quantum control techniques and creating large, time-dependent magnetic field gradients. This enabled them to encode and detect the atomic modulation in an ensemble of two million spins and measure the spin ensemble shift in a sample with subatomic precision.

This research represents a major advance in the establishment of atomic-scale NMR as a tool to study the structure of materials.

Sahand Tabatabaei, co-leader of the study and Ph.D. Student at the IQC and the Department of Physics and Astronomy at Waterloo, adds: “Now that we are close to performing NMRd on a lattice at the atomic length scale, we can really start to study more fundamental quantum physics, such as quantum transport phenomena and quanta -Many-body physics on the atomic length scale, which has never been done before with samples of this size.”

The study “Nuclear Magnetic Resonance Diffraction with Subangstrom Precision” appears in the Proceedings of the National Academy of Sciences.