Room-Temperature Excitation-Emission Spectra of Single LH2 Complexes Show Remarkably Little Variation.
Esther GellingsRichard J CogdellNiek F van HulstPublished in: The journal of physical chemistry letters (2020)
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.
Keyphrases
- energy transfer
- single molecule
- room temperature
- quantum dots
- data analysis
- density functional theory
- solid state
- atomic force microscopy
- living cells
- high resolution
- optical coherence tomography
- air pollution
- ionic liquid
- particulate matter
- magnetic resonance
- binding protein
- blood brain barrier
- magnetic resonance imaging
- brain injury
- protein protein