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Tuesday 30 January
Gerhard M.J. Schmidt Lecture Hall 02:30
Joint Structural Biological and Magnetic Resonance Seminar Prof. Mei Hong [Info]

Joint Structural Biological and Magnetic Resonance Seminar

Membrane proteins carry out a myriad of biological functions such as ion conduction, substrate transport, and signaling. Solid-state NMR spectroscopy allows us to obtain exquisite atomic-level information of the structures and structural changes that underlie these functions. In this talk, I will present our investigations of the structure and dynamics of a multifunctional influenza virus membrane protein, matrix protein 2 (M2), which conducts protons and causes membrane scission. 13C, 15N, and 1H chemical shifts provided detailed information about pH-dependent conformational changes and equilibria between the open and closed states of the proton channel. Motionally averaged NMR spectra revealed microsecond-timescale dynamics of the proton-selective histidine and the gating tryptophan of the channel, while 2D exchange NMR spectra revealed millisecond-timescale dynamics of the entire tetrameric complex. Hydrogen bonding between water and the proton-selective histidine and proton exchange dynamics have been directly observed in 15N NMR spectra, giving insight into the atomic processes of proton transfer through the hydrated channel. In the second function, the M2 protein interacts with membrane cholesterol to cause scission of the emerging virus particle from the host cell in the final step of virus budding. By measuring 13C-19F distances between cholesterol and the protein, we determined the first cholesterol-binding site structure of a membrane protein in lipid bilayers. The structure gave unexpected insight into how M2 is attracted to the neck of the budding virus to cause membrane scission. Such intermolecular binding studies are crucially enabled by long-range distance constraints. We are exploring 19F-19F dipolar coupling measurements that probe distances up to 2 nm, to determine protein structures and protein-ligand interactions. Massachusetts Institute of Technology
Thursday 01 February
Gerhard M.J. Schmidt Lecture Hall 09:30
Magnetic Resonance Seminar Prof. Alexej Jerschow [Info]

Magnetic Resonance Seminar

Batteries are drivers of alternative energy solutions and the electric vehicle market, and are central to portable electronic devices. In this talk I will describe our work on the development of techniques for assessment of Li-ion batteries, supercapacitors, and battery materials via magnetic resonance imaging (MRI). The goal of these studies is to analyze the devices and energy storage mechanisms in situ during charging or discharging conditions by imaging changes in both the electrolyte and the electrodes in a noninvasive fashion. In situ NMR/MRI have proven to be powerful tools to probe the structure of Li-ion batteries. These techniques have the potential to monitor dynamics and visually monitor changes in functioning electrochemical systems in real time. The operation of some energy storage devices where only the electrolyte is involved in the electrochemical process (such as supercapacitors) can only be studied in situ, as the electrolyte concentration gradients will relax as a potential is removed from the cell. I will discuss how the rf field is perturbed by the presence of conducting materials in the probe, how susceptibility shifts can be used for assessing the morphology of microstructure buildup on electrodes, how the location and concentration of both cations and anions can be followed separately. I will also discuss the opportunities for indirectly monitoring SEI layer properties and Li-dendrite growth mechanisms. Recent results on MRI of commercial-type cells, and the determination of state of charge and health will also be presented. This last development is of importance for analyzing, for example, cell-phone cells nondestructively, and may hence be of value for assessing the state of these devices under various conditions. New York University