Subatomic MRI could lead to new drug treatments

A new imaging technique that uses quantum science may lead to new drug treatments and treatment options, according to a recent study.

Researchers at the University of Waterloo and supported by Transformative Quantum Technologies have demonstrated the feasibility of nuclear magnetic resonance diffraction (NMRd) to probe the lattice structure of crystalline solids at the atomic scale, 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 study’s lead authors and a graduate of the Institute for Quantum Computing (IQC) in Waterloo, now at IBM. “At the time, the authors dismissed their idea as ridiculous. Our work comes tantalizingly close to realizing this crazy idea of ​​theirs – we have shown that it is possible to study atomic-length-scale structures in sample volumes that are relevant to many biological and physical systems ».

“NMRd opens up a huge variety of possibilities in many research directions, including the study of both nanocrystals and organic compounds,” added Haas. The ability to image biological structures, such as protein molecules and virus particles, at the atomic scale can advance understanding of their function and potentially lead to new drug treatments and therapeutic options.

NMRd works by exploiting a property in nuclei called spin, a fundamental unit of magnetism. When placed in a magnetic field, the nuclei essentially act as magnets due to this spin. A time-varying magnetic field can perturb the spins, changing the spin angle—in technical terms, this is called encoding a phase in each spin. At a certain encoding moment, all rotations will point back to the original direction. When this happens, a diffraction echo is observed, a signal that can be measured to find the lattice constant and shape of the sample. Each nucleus will produce a unique signal, which can be used to discern the structure of the molecule.

The challenge in achieving atomic-scale NMR was the difficulty of encoding large relative phase differences between neighboring nuclear spins at the atomic scale, meaning that diffraction echoes could not be observed. The researchers overcame this limitation by using quantum control techniques and creating large, time-dependent magnetic field gradients. With this, they could encode and detect the atomic-scale configuration in a set of two million spins and measure the displacement of the set of spins in a sample with subatomic precision.

This research represents significant progress in establishing atomic-scale NMR as a tool for studying material structure.

Sahand Tabatabaei, study co-leader and Ph.D. student in the Department of Physics and Astronomy at IQC and Waterloo, adds, “now that we are close to being able to do NMRd on a lattice at the atomic length scale, we can also really start to study more fundamental quantum physics, such as quantum transport effects and many-body quantum physics, at the atomic length scale, which has never been done before in samples of this size.”

The study, “Nuclear magnetic resonance diffraction with subangstrom precision,” appears in Proceedings of the National Academy of Sciences.