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Spectral Tuning of Chlorophylls in Proteins – Electrostatics vs. Ring Deformation

preprint
submitted on 27.05.2020 and posted on 29.05.2020 by Yigal Lahav, Dror Noy, Igor Schapiro
In photosynthetic complexes, tuning of chlorophyll light-absorption spectra by the protein environment is crucial to their efficiency and robustness. Water Soluble Chlorophyll-binding Proteins from Brassicaceae (WSCPs) are useful for studying spectral tuning mechanisms due to their symmetric homotetramer structure, the ability to rigorously modify the chlorophyll’s protein surroundings, and the availability of crystal structures. Here, we present a rigorous analysis based on hybrid Quantum Mechanics and Molecular Mechanics simulations with conformational sampling to quantify the relative contributions of steric and electrostatic factors to the absorption spectra of WSCP-chlorophyll complexes. We show that when considering conformational dynamics, chlorophyll ring deformation accounts for about one-third of the spectral shift, whereas protein electrostatics accounts for the remaining two-thirds. From a practical perspective, protein electrostatics is easier to manipulate than chlorophyll conformations, thus, it may be more readily implemented in designing artificial protein-chlorophyll complexes with desired spectral shift.

Funding

ERC Starting Grant 678169

ERC Consolidator Grant 615217

Israel Ministry of Science and Technology (grant 3-16311)

Israel Science Foundation personal grant 558/14

Israel Science Foundation personal grant 1338/19

History

Email Address of Submitting Author

igor.schapiro@mail.huji.ac.il

Institution

The Hebrew University of Jerusalem

Country

Israel

ORCID For Submitting Author

0000-0001-8536-6869

Declaration of Conflict of Interest

no conflict of interest

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