The largest light-harvesting antenna in nature, the chlorosome, is a heterogeneous helical BChl self-assembly that has evolved in green bacteria to harvest light for performing photosynthesis in... Show moreThe largest light-harvesting antenna in nature, the chlorosome, is a heterogeneous helical BChl self-assembly that has evolved in green bacteria to harvest light for performing photosynthesis in low-light environments. Guided by NMR chemical shifts and distance constraints for Chlorobaculum tepidum wild-type chlorosomes, the two contrasting packing modes for syn-anti parallel stacks of BChl c to form polar 2D arrays, with dipole moments adding up, are explored. Layered assemblies were optimized using local orbital density functional and plane wave pseudopotential methods. The packing mode with the lowest energy contains syn-anti and anti-syn H-bonding between stacks. It can accommodate R and S epimers, and side chain variability. For this packing, a match with the available EM data on the subunit axial repeat and optical data is obtained with multiple concentric cylinders for a rolling vector with the stacks running at an angle of 21° to the cylinder axis and with the BChl dipole moments running at an angle ß ∼ 55° to the tube axis, in accordance with optical data. A packing mode involving alternating syn and anti parallel stacks that is at variance with EM appears higher in energy. A weak cross-peak at -6 ppm in the MAS NMR with 50 kHz spinning, assigned to C-181, matches the shift of antiparallel dimers, which possibly reflects a minor impurity-type fraction in the self-assembled BChl c. Show less
The standard Lambda Cold Dark Matter (Lambda CDM) cosmological model provides a good description of a wide range of astrophysical and cosmological data. However, there are a few big open questions... Show moreThe standard Lambda Cold Dark Matter (Lambda CDM) cosmological model provides a good description of a wide range of astrophysical and cosmological data. However, there are a few big open questions that make the standard model look like an approximation to a more realistic scenario yet to be found. In this paper, we list a few important goals that need to be addressed in the next decade, taking into account the current discordances between the different cosmological probes, such as the disagreement in the value of the Hubble constant H-0, the sigma(8)-S-8 tension, and other less statistically significant anomalies. While these discordances can still be in part the result of systematic errors, their persistence after several years of accurate analysis strongly hints at cracks in the standard cosmological scenario and the necessity for new physics or generalisations beyond the standard model. In this paper, we focus on the 5.0 sigma tension between the Planck CMB estimate of the Hubble constant H-0 and the SH0ES collaboration measurements. After showing the H-0 evaluations made from different teams using different methods and geometric calibrations, we list a few interesting new physics models that could alleviate this tension and discuss how the next decade's experiments will be crucial. Moreover, we focus on the tension of the Planck CMB data with weak lensing measurements and redshift surveys, about the value of the matter energy density Omega(m), and the amplitude or rate of the growth of structure (sigma(8), f sigma(8)). We list a few interesting models proposed for alleviating this tension, and we discuss the importance of trying to fit a full array of data with a single model and not just one parameter at a time. Additionally, we present a wide range of other less discussed anomalies at a statistical significance level lower than the H-0-S-8 tensions which may also constitute hints towards new physics, and we discuss possible generic theoretical approaches that can collectively explain the non-standard nature of these signals. Finally, we give an overview of upgraded experiments and next-generation space missions and facilities on Earth that will be of crucial importance to address all these open questions. (C) 2022 The Author(s). Published by Elsevier B.V. Show less
The molecular geometry and supramolecular packing of two bichromophoric prototypic light harvesting compounds D1A2 and D2A2, consisting of two naphthylimide energy donors that were attached to the... Show moreThe molecular geometry and supramolecular packing of two bichromophoric prototypic light harvesting compounds D1A2 and D2A2, consisting of two naphthylimide energy donors that were attached to the 1,7 bay positions of a perylene monoimide diester energy acceptor, have been determined by a hybrid approach using magic angle spinning NMR and electron nano crystallography (ENC), followed by modelling. NMR shift constraints, combined with the P-1 space group obtained from ENC, were used to generate a centrosymmetric dimer of truncated perylene fragments. This racemic packing motif is used in a biased molecular replacement approach to generate a partial 3D electrostatic scattering potential map. Resolving the structure of the bay substituents is guided by the inversion symmetry and the distance constraints obtained from heteronuclear correlation spectra. The antenna molecules form a pseudocrystalline lattice of antiparallel centrosymmetric dimers with pockets of partially disordered bay substituents. The two molecules in a unit cell form a butterfly-type arrangement. The hybrid methodology that we have developed is robust and widely applicable for critical structural underpinning of self-assembling structures of large organic molecules. Show less
Thomas, B.; Rombouts, J.A.; Oostergetel, G.T.; Sai Sankar Gupta, K.B.; Buda, F.; Lammertsma, K.; ... ; Groot, H.J.M. de 2017
Photosynthesis is a highly cross linked process. However, we can distinguish a set of fundamental building blocks like chlorophylls, which interact to form photosystem, which performs the complex... Show morePhotosynthesis is a highly cross linked process. However, we can distinguish a set of fundamental building blocks like chlorophylls, which interact to form photosystem, which performs the complex function of water splitting. The key challenge in artificial photosynthesis is to learn how to design systems that can adapt and optimize their topologies in line with self-assembly of natural photosystem. In this thesis I combine different techniques of cross polarization Magic angle spinning Nuclear Magnetic Resonance and Transmission Electron Microscopy with simulation and modeling, to resolve the global packing of molecules which are potential candidates for efficient solar fuel cell devices. This thesis focuses on the packing analysis of three-dimensional structures, which are heterogeneous in nature. I demonstrate a new and general structure determination approach that, in combination with first-principles quantum chemical calculations, establishes the structures of molecularly ordered antenna complexes that lack long-range 3D atomic crystalline order. This is possible despite the absence of a priori information on the space group or atomic coordinates. Chapter 2 describes DATZnS(3ʹ-NMe) parallel stacking in an antiparallel framework with the P2/c space group. 13C CP/MAS NMR yields number of asymmetric sites in the structure and recognition motif. This in conjunction with unit cell parameters and diffraction spots from the Fourier transformation of a TEM image is used to resolve the structure. Supramolecular recognition motif is a characteristic of the packing of the DATZnS(3ʹ-NMe) molecule. The molecular recognition and molecular symmetry steer the packing into a racemic mixture with a c-glide plane and inversion symmetry to release the steric hindrance. Simulation of the LGCP build up curve between specific pairs and electron diffraction were used to validate the proposed packing. Chapter 3 describes the centerosymmetric dimer formation with NMI extending outwards to capture the solar energy. MAS NMR chemical shifts were used to generate a truncated 1,7-perylene-3,4,9,10-tetracarboxylic monoimide dibutylester motif. This motif is further optimized and used for molecular replacement approach to generate a partial 3D electron density approach. The P-1 symmetry obtained from Electron Nano Crystallography is used to graft the naphathelene monoimide substituents. The alkyl chains are modeled using the intermolecular correlation observed in HETCOR. Naphthalene monoimide antennas projecting out from the rows of dimers formed out of rod type D1A2 could capture the light energy and transfer to dimers through FRET. Finally, in chapter 4 C2 molecular symmetry obtained from MAS NMR and DFT modeling is used as the core motif to propose the packing of the DATZnS(4H). Intermolecular correlations obtained from the HETCOR shows the folding of the tails along the phenazine moiety. The analogous modeling showed how the packing could be steered by the NCH3 functional group between antiparallel and parallel dipoles. This understanding opens the way for the evidence based design of light harvesting antenna. In summary, a novel methodology to resolve the structure of chromophore antenna from a structural background with static and dynamic heterogeneity that strongly limits the diffraction response is shown. Furthermore, I anticipate that the insights into packing of the antenna are key to the design of the organic solar fuel cell device in the future. Show less
