Reedijk Symposium 2013 - Guest Lecturers: Dr. Dorothee Kern & Prof. dr. Bernard Dam

Published on August 22, 2013
Reedijk Symposium 2013 - Guest Lecturers: Dr. Dorothee Kern & Prof. dr. Bernard Dam

On Friday October 25th the fourth annual Jan Reedijk Symposium will be held. The main lectures of the day will be "The choreography of an enzyme's dance - dynamics during catalysis" by invited speaker Dr. Dorothee Kern (Department of Biochemistry and Howard Hughes Medical Institute, Brandeis University), and "Hydrogenography: A combinatorial method to analyse the thermodynamic and kinetic properties of metal hydrides" by Prof. dr. Bernard Dam (Delft University of Technology).

The complete programme can be found here.

Dr. Dorothee Kern: The choreography of an enzyme's dance - dynamics during catalysis

Understanding biological function, such as the fascinating rate acceleration of enzymes, specificity of protein/protein interactions or the delicately controlled action of signaling has been a long-standing challenge. Despite remarkable information generated using chemical tools in the last 100 years, complemented more recently with structural and computational approaches, we cannot yet identify with a complete energy inventory how ANY protein works. The secret of enzymes lies in their ability to partition energetic contributions among many atoms in a well-coordinated style.  To unravel these secrets, proteins in action are spied on at atomic resolution to provide a comprehensive description of enzyme catalysis in the form of an energy landscape. Since the rate of catalysis is determined by the climb over a sequence of energy barriers, we focus here on the critical question of transition pathways with the highest energy state being the transition state.

I will discuss our exploration of the full energy landscape of enzyme catalysis through a combination of time-resolved NMR including high-pressure NMR, crystallography, single-molecule FRET and MD simulation. Allosteric is in play for 3 very different systems: an enzyme, a phoshorylation-mediated signaling protein and the inhibition of rhodopsin kinase via protein/protein interactions.  For the latter example, binding by conformational selection and not via an induced fit is directly demonstrated by flux measurements, the only rigorous test for the two opposing mechanisms.

The presented data stress the point that highly choreographed chemical integrity AND optimized conformational sampling is a prerequisite for efficient enzyme catalysis. The power of an intimate marriage between NMR and other biophysical methods and MD simulations including a variety of novel pathway algorithms will be illustrated.

Prof. dr. Bernard Dam: Hydrogenography: A combinatorial method to analyse the thermodynamic and kinetic properties of metal hydrides

Metal hydrides may find their use in energy storage, separation membranes, hydrogen sensors and smart windows. On hydrogenation, often optical changes are observed in the visual range of the spectrum. Since metal hydride films are stable on repeated hydrogenation, these optical changes allow for the development of effective combinatorial methods. In thin films, one may thus quickly scan thousands of materials systems and identify the most attractive compositions. For this we coined the term Hydrogenography.
While the focus of our thin film research in general has been on the discovery of new hydrogen storage materials, it can also be used to study the effect of doping, interface energy and elastic/ plastic effects. These effects would allow one tune the thermodynamics of melt-infiltrated, nano-sized metal hydrides.

We studied the hydrogenation of 10nm Mg layers sandwiched between Ti layers and demonstrated that these films are indeed are destabilized due to the increased surface-to-volume ratio. The pressure plateau is increased both in absorption and desorption. The flat pressure plateaus at the phase transition imply that MgH2 nuclei form over the whole layer thickness and co-exist with the metallic Mg matrix.  Recently, we found that we can observe these nuclei optically. From an analysis of the growth dynamics we derived that the critical nucleus is around 30 microns in diameter. We propose that this anomalous large value is due to the plastic deformation that has to take place at the edges of the nucleus, in order to accommodate the 30% lattice expansion of the hydride. Using a kinetic (JMA) analysis we correlate the optical data with a growth-dimension >2, which exemplifies a mixed 2D-nucleation and growth behavior. On desorption no such 2D growth is observed. It appears that the plastic deformation in this case is decoupled from the dehydrogenation.
 
Our thin film study makes use of the possibility to do thickness dependent studies in well-defined environments. It shows that the thermodynamics of nano-phase materials is mainly determined by plastic effects.

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