Room-temperature excitation-emission spectra of single LH2 complexes show remarkably little variation

Gellings, E., Cogdell, R. J. and van Hulst, N. F. (2020) Room-temperature excitation-emission spectra of single LH2 complexes show remarkably little variation. Journal of Physical Chemistry Letters, 11(7), pp. 2430-2435. (doi: 10.1021/acs.jpclett.0c00375) (PMID:32142282)

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Excitation spectroscopy gives direct insight into the excited state manifold, energy transfer, transient intermediates, vibrations, and so on. Unfortunately, excitation spectroscopy of single molecules under ambient conditions has remained challenging. Here we present excitation spectra alongside emission spectra of the same individual light-harvesting complex LH2 of the purple bacteria Rps. acidophila. The acquisition of both the excited and ground state spectra allows us to quantify disorder and interband correlations, which are key variables for the interpretation of observed long-lasting coherences. We have overcome the low photostability and small fluorescence quantum yield that are inherent to many biologically relevant systems by combining single-molecule Fourier transform spectroscopy, low excitation intensities, and effective data analysis. We find that LH2 complexes show little spectral variation (130–170 cm–1), that their two absorption bands (B800–B850) are uncorrelated, and that the Stokes shift is not constant. The low amount of spectral disorder underlines the protective role of the protein scaffold, benefiting the efficient energy transport throughout the light-harvesting membrane.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Cogdell, Professor Richard
Authors: Gellings, E., Cogdell, R. J., and van Hulst, N. F.
College/School:College of Medical Veterinary and Life Sciences > Institute of Molecular Cell and Systems Biology
Journal Name:Journal of Physical Chemistry Letters
Publisher:American Chemical Society
ISSN (Online):1948-7185
Published Online:06 March 2020
Copyright Holders:Copyright © 2020 American Chemical Society
First Published:First published in Journal of Physical Chemistry Letters 11(7): 2430-2435
Publisher Policy:Reproduced in accordance with the publisher copyright policy

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