5 Top-view of the Photosystem II-LHCII supercomplex
6 Peripheral Light-Harvesting Complex II of Plants. Binds 50% of all Chlorophyll on this planet
7 From Photosynthesis to Artificial Photosynthesis The major design principles of photosynthesis
8 1. ExcitonsThe effective energy storage in antenna complexes is possible due to the presence of light-harvesting pigments (chlorophylls, carotenoids, bilins) with long-lived excited states and a high cross-section for light absorption.The elementary excitation of the antenna is described by the wavefuction n, which correspond to excitation of the n-th pigment. Quantum mechanics dictates that when neighbouring pigments are coupled because they are closeby, the excited state of the complex is given by a superposition of such wavefunctions, i.e. c1n1+c2n2+…, where one elementary excitation is shared between a number of molecules.Such a collective excitation (denoted ‘exciton’) is different from independently excited molecules n1, n2,… due to correlations (‘coherences’) between them given by c1*c2…… Such coherences can be produced if the electronic Hamiltonian contains off-diagonal terms, i.e. Hn2n1. In this coherent state one molecule ‘knows’ about the excitation of its neighbours.This dramatically changes the spectrum of a pigment aggregate as well as the energy transfer dynamics. In natural antenna complexes these features produce more efficient light absorption, faster conversion from short- to long-wavelength spectral bands, and increase the irreversible trapping of excitations by the RC.
9 Transfer rates between two Chl molecules (as a function of the energy gap and interaction energy between them) calculated according to modified Redfield (A) and Förster (B) expressions.The specific non-monotonous dependence of the rates on the energy gap and interaction energy is determined by the shape of exciton-phonon spectral density for Chl.
10 Relaxation in the Exciton Manifold of LH2 Relaxation between one-exciton states (k,r) and (p,s), where kr and ps for coherence transfer or decay, or k=r and p=s for population transfer, is given by the term nmcnkcnpcmrcmsJkp<vnvm>.Bottleneckk-th exciton state
41 Principles Excitons\ Quantum Coherence Concentration Spatial OrganizationSupramolecular OrganizationMultiple entries to catalytic centerMultiple ET pathwaysPhotoprotection
42 AcknowledgementsVladimir Novoderezhkin, Alexander Doust, Jan Dekker, Chantal van der Weij-de Wit, Ivo van Stokkum, Bruno Robert, Alessandro Marin, Tjaart Krueger, Natalia Pawlowicz, Sandrine d’Haene, Henny van Roon, Maxime Alexandre, Thomas Cohen Stuart, Cosimo Bonetti, Rudi Berera, John Kennis, Neil Hunter, Marcus Wendling, Eli Romero, Christian Ilioalia, Mariangela DiDonato, Manolis Papagiannakis, Mikas Vengris, Delmar Larson, Herbert van Amerongen, Marloes Groot, Miguel Palacios, Raoul Frese, Greg Scholes, Roberta Croce, Andy Stahl, Graham Fleming, Leonas Valkunas, Andy Pascal, Lavanya Premvardhan, Gert van der Zwan, Sacha Ruban, Peter Horton, Jos Thieme, etc etc