Wednesday, January 17, 2024
12:00 - 14:00
Eduard Elias - PhD Candidate, Vrije Universiteit Amsterdam
The Ultrafast Excitation Energy Equilibration Dynamics in the Plant Photoynthetic LHCII-CP24-CP29 Assembly
In photosynthesis light is primarily captured by Photosystem I and II. The photosystems consist of a modular assembly of pigment-protein complexes, commonly referred to as the light-harvesting complexes (LHCs), which absorb light and shuttle excitation energy via their vast network of pigments to the photosystem reaction center where the energy is used for charge separation. In order to outcompete the natural excited-state decay processes, it is vital that the LHCs very rapidly transfer the excitation energy to the reaction center (on the order of ~10-11 - 10-10 s). Ultrafast transient absorption measurements on isolated LHC complexes have yielded detailed pictures of the intra-LHC energy transfer pathways, yet the inter-LHC pathways remain elusive. This is mainly because the photosystem contain a large number of pigments, many iso-energetic, meaning that the energy equilibration between them is not always directly observable as a spectral evolution in the ultrafast measurements. To circumvent this problem, we have performed transient absorption measurements providing high excitation densities to our samples. In this way, excitations that combine in the assemblies annihilate and show up as a detectable quenching signal, which corresponds to the inter-LHC energy equilibration time. We have applied this method to a sub-complex of Photosystem II, which is an assembly of the LHCs CP24, CP29 and LHCII and is composed of 5 subunits. By combining annihilation measurements on the complex and its constituents and by leveraging structural modelling, we have shed light on the inter-LHC energy transfer pathways between these complexes.
Prof. Dr. Andreas Freise (Vrije Universiteit Amsterdam and Nikhef)
Gravitational wave observatories have started to make significant contributions to physics and astronomy. Now the gravitational wave community has the responsibility to provide adequate observational capability for gravitational waves for 2030 and beyond. The ‘Einstein Telescope’ (ET) is our vision to build a new gravitational wave observatory in Europe, possibly near Maastricht. In this talk he will give a brief overview of the vision behind this plan and the current status of the project. He will then highlight the challenges in realising such an ambitious project, including organisational and political aspects. Of course he will also present recent research results from our people at the VU and Nikhef.
Vrije Universiteit, WN-building
astrophysics, gravitational and astroparticle physics
Prof. Dr. Andreas Freise and Eduard Elias