Extending the high-field dynamic nuclear polarization platform to study water structure

Northwestern University At Chicago, Evanston IL

Investigators

Abstract

With the support of the Chemical Measurement and Imaging Program in the Division of Chemistry, Professor Songi Han of Northwestern University will develop novel magnetic resonance instrumentation modules that enable molecular-level interrogation of the structure and dynamics of liquid water near biomolecular and material interfaces. Water is critical to biomolecular function, yet its properties remain enigmatic due to its ability to adopt diverse structures and ordering in the liquid state. Understanding how this seemingly simple molecule behaves at surfaces and interfaces will allow the Han lab to gain insight into fundamental processes in the life sciences involving water. The properties and role of so-called biological water have long been a source of both excitement and controversy. Advancing our understanding in this area requires new measurement tools as critical drivers. Magnetic resonance offers direct experimental access to water but suffers from low sensitivity. The technique developed in this proposal will enhance magnetic resonance signal and surface specificity, enabling Professor Han to expand the scope of structural biology to include the solvation layer and the structural evolution of light- and pressure-activated proteins. These developments will provide graduate students, postdocs, and undergraduates with rare hands-on experience in hardware design and instrumentation development. Additionally, Professor Han will leverage the outcomes of this work to bridge the gap between the scientific and broader public communities on the topic of water research. The proposed goal is to achieve liquid-state Overhauser Dynamic Nuclear Polarization (ODNP) at high magnetic fields for the study of surface water near proteins and interfaces. The well-known heating problem caused by microwave irradiation in ODNP studies at high magnetic fields will be mitigated by reducing the sample volume to below the wavelength of the Electron Paramagnetic Resonance (EPR) frequency of spin labels at 7 T. The first aim is to develop a new experimental ODNP platform that integrates magnetic resonance, microcoil detection, and optical access. The second aim is to extend this platform to high-pressure ODNP measurements in diamond anvil cells with simultaneous microwave and optical access. Professor Han will employ these tools to investigate evolving water structure and dynamics near the liquid–ice phase transition and in the vicinity of proteins activated by light and/or pressure. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.