Structure, Dynamics, and Function in the Major Light-Harvesting Complex of Photosystem II

Abstract

In natural light-harvesting systems, pigment-protein complexes (PPC) convert sunlight to chemical energy with near unity quantum efficiency. PPCs exhibit emergent properties that cannot be simply extrapolated from knowledge of their component parts. In this Perspective, we examine the design principles of PPCs, focussing on the major light-harvesting complex of Photosystem II (LHCII), the most abundant PPC in green plants. Studies using two-dimensional electronic spectroscopy (2DES) provide an incisive tool to probe the electronic, energetic, and spatial landscapes that enable the efficiency observed in photosynthetic light-harvesting. Using the information about energy transfer pathways, quantum effects, and excited state geometry contained within 2D spectra, the excited state properties can be linked back to the molecular structure. This understanding of the structure-function relationships of natural systems constitutes a step towards a blueprint for the construction of artificial light-harvesting devices that can reproduce the efficacy of natural systems.

Principles of light harvesting from single photosynthetic complexes

“…Photosynthetic organisms have met this challenge, and are able to use sunlight to fuel almost all life on Earth [2]. The molecular machinery behind this large-scale power conversion process can serve as a guide for the development of solar energy sources [3][4][5][6]. The efforts towards artificial photosynthesis can be considered in three categories: (i) create elements inspired by photosynthetic systems [7][8][9][10][11]; (ii) incorporate components from photosynthetic organisms [12][13][14][15]; and (iii) use living organisms, either wild-type or genetically modified [16][17][18][19].…”

Possible role of interference, protein noise, and sink effects in nonphotochemical quenching in photosynthetic complexes

“…In order to better characterize the ET properties inside the peripheral lightharvesting supercomplex, it is conventionally divided into (i) the most peripheral "major" LHCs [16,18] which have a trimeric structure, and (ii) minor complexes more closely associated with the PSII RC which include CP24, CP26, CP29, CP43, and CP47, located between the RC and the peripheral LHCII complex [16]. All these LHCII and minor complexes include a network of chlorophylls and carotenoids that absorb the solar quanta, and, as it was mentioned above, transfer the excitons from the antenna to the RC.…”

“…All five excitonic sites interact with their protein environment, which we model by the stochastic process of stationary telegraph noise. Note, that there are many different approaches for modeling the influence of the protein environment on the excitonic and electron sites in bio-systems [7,9,11,12,18,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78]. Some of them use a thermal bath (for example, as a set of harmonic oscillators in the initial Gibbs distribution, at a given temperature); some approaches use the external sources of noise; and some approaches are based on hybrid schemes [76,77].…”

Towards Global Artificial Photosynthesis (Global Solar Fuels): Energy, Nanochemistry, and Governance

“…The authors conclude that such characteristics should be included in any practical light-harvesting device. [17] Electron Transport The next paper by Joseph Hughes and Elmars Krausz from ANU ('The Chemical Problem of Energy Change: Multi-Electron Processes') follows on nicely in evaluating the centrality of the relatively poorly understood role of multi-electron processes in the ultrafast kinetics, energy-trapping events, and catalytic fourelectron water oxidation chemistry of PSII. An important aspect of such research is proton-coupled electron transfer where multi-electron aspects do not sit easily within the dominant Marcus Theory framework.…”