Molecular Diffusion in Living Systems: NMR studies Event
For more information regarding this event, please telephone Kim Lipscombe on 02380597747 or email K.R.Lipscombe@soton.ac.uk .
Event details
Philip Kuchel FAA is a Leverhulme Visiting Professor in the Department of Chemistry with Malcolm Levitt. He was here in 2014 for 3.5 months, and this is his second stint in Southampton. He is known for his work on applying NMR spectroscopy to cellular systems to probe their metabolism, membrane transport on the sub-second time scale, and the rates of diffusion of solutes, including proteins, inside cells. He was appointed to a Chair of Biochemistry at the University of Sydney in 1980 and in 2013 was made Emeritus Professor. He is the coordinating author of ‘Schaum’s Outline of Theory and Problems of Biochemistry’ McGraw-Hill, and coauthor of ‘Modelling Metabolism with Mathematica’ CRC Press. His 440 scientific papers include the first description of 1H spin-echo NMR spectroscopy used to monitor metabolism in cells, the discovery of the transmembrane ‘split peak effect’ that is used to measure rapid membrane transport, and the first observation of ‘diffusion-diffraction’ of water in a cellular system.
A fundamental attribute of ions and molecules is the rate at which they diffuse in their surroundings. In cells this potentially influences the encounter frequency with enzymes and hence whether ‘diffusion control’ operates for enzyme-catalyzed reactions. The ‘best’ method for measuring molecular motion in heterogeneous mixtures of (bio)chemical species, including the complex and viscous interior of cells, is the pulsed field gradient spin-echo (PGSE) NMR experiment. When recording the diffusion of water in suspensions of red blood cells it becomes clear that the motion is restricted on the timescale (seconds) of the measurements. And this leads to the curious phenomenon, ‘diffusion diffraction’. It is an analogue of optical diffraction so the experimental data provide a new way of non-invasively estimating cell dimensions. Because diffusion rate of a solute differs between the inside and outside of cells the PGSE method can be used to measure the kinetics of membrane transport of water and solutes; and it can be used to measure metabolite binding to proteins inside intact cells. Phil will describe the basic theory of the PGSE method and several applications to cells that yield information that is unique to it.
Speaker information
Prof Philip Kuchel,The University of Sydney