Energy transfer mechanisms in light-harvesting complexes of Rhodobacter sphaeroides / Magnetoreception and the radical pair mechanism

Abstract

During the light dependent reactions of photosynthesis of purple bacteria, light harvesting (LH) complexes absorb and direct energy towards a reaction centre with an efficiency of  approximately 95% [1]. One of the hypotheses explaining this phenomenon argues that such high efficiency is achieved thanks to a quantum coherent state occurring between the bacteriochlorophyll molecules enclosed within these proteins. In the present study we will genetically modify the scaffold of LHs expressed by Rhodobacter sphaeroides for tuning the interactions occurring between their pigment molecules. A series of time-resolved spectroscopic analysis will be then carried for a set of the variants obtained. The data collected throughout this project will constitute a foundation for experiments aiming at understanding whether quantum coherence plays a non-trivial role in photosynthesis. Moreover, it represents the first step in the development of high-performance technologies for sunlight harvesting.

[1] Fleming, G. R., van Grondelle, R. (1997). Femtosecond spectroscopy of photosynthetic light-harvesting systems. Current opinion in structural biology, 7(5), 738-748.

Abstract

Magnetoreception is the phenomenon by which some birds and other animals make seasonal migrations using the Earth’s magnetic field (MF) for directional information. But how can the Earth, with magnetic fields ~ 500 times smaller than your average refrigerator magnet, be effecting change on the robust nature of biology? Since the early 2000’s the ‘radical pair mechanism’ has been the forerunning theory to explain how animals, plants and insects are able to ‘see’ magnetic field lines. As prevalent as radicals are throughout biology, however, there are very few systems with conditions sufficient to give rise to even a potential radical pair mechanism. Whether the biological system has evolved to harness it is yet another layer to the proverbial onion. In my talk I will briefly take you through the history of research into animal magnetoreception, the radical pair mechanism and the constraints on such a system.