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Quieting a noisy antenna reproduces photosynthetic light-harvesting spectra

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Science  26 Jun 2020:
Vol. 368, Issue 6498, pp. 1490-1495
DOI: 10.1126/science.aba6630

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Pairs of peaks stabilize output power

A counterintuitive feature of photosynthesis is that the primary pigments involved in absorbing light—for example, chlorophyll a and b in plants—do not all absorb right at the peak of the spectrum but instead are offset from the peak and each other. Arp et al. formulated a network model that explains how using pigments with this absorption-peak pattern can mitigate internal and external fluctuations in energy transfer, minimizing noise in output power (see the Perspective by Duffy). The model accurately reproduces absorption peaks for three diverse photosynthetic systems from different spectral environments. Such a mechanism may provide an underlying robustness to biological photosynthetic processes that can be further tuned and tweaked to adapt to longer-scale fluctuations in light intensity.

Science, this issue p. 1490; see also p. 1427

Abstract

Photosynthesis achieves near unity light-harvesting quantum efficiency yet it remains unknown whether there exists a fundamental organizing principle giving rise to robust light harvesting in the presence of dynamic light conditions and noisy physiological environments. Here, we present a noise-canceling network model that relates noisy physiological conditions, power conversion efficiency, and the resulting absorption spectra of photosynthetic organisms. Using light conditions in full solar exposure, light filtered by oxygenic phototrophs, and light filtered under seawater, we derived optimal absorption characteristics for efficient solar power conversion. We show how light-harvesting antennae can be tuned to maximize power conversion efficiency by minimizing excitation noise, thus providing a unified theoretical basis for the observed wavelength dependence of absorption in green plants, purple bacteria, and green sulfur bacteria.

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