| 1. |
- Carrillo, M., et al.
(author)
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High-resolution crystal structures of transient intermediates in the phytochrome photocycle
- 2021
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In: Structure. - : Elsevier BV. - 0969-2126. ; 29:7
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Journal article (peer-reviewed)abstract
- Phytochromes are red/far-red light photoreceptors in bacteria to plants, which elicit a variety of important physiological responses. They display a reversible photocycle between the resting Pr state and the light-activated Pfr state. Light signals are transduced as structural change through the entire protein to modulate its activity. It is unknown how the Pr-to-Pfr interconversion occurs, as the structure of intermediates remains notoriously elusive. Here, we present short-lived crystal structures of the photosensory core modules of the bacteriophytochrome from myxobacterium Stigmatella aurantiaca captured by an X-ray free electron laser 5 ns and 33 ms after light illumination of the Pr state. We observe large structural displacements of the covalently bound bilin chromophore, which trigger a bifurcated signaling pathway that extends through the entire protein. The snapshots show with atomic precision how the signal progresses from the chromophore, explaining how plants, bacteria, and fungi sense red light.
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| 2. |
- Dods, Robert, 1989, et al.
(author)
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Ultrafast structural changes within a photosynthetic reaction centre.
- 2021
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In: Nature. - : Springer Science and Business Media LLC. - 1476-4687 .- 0028-0836. ; 589:7841, s. 310-314
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Journal article (peer-reviewed)abstract
- Photosynthetic reaction centres harvest the energy content of sunlight by transporting electrons across an energy-transducing biological membrane. Here we use time-resolved serial femtosecond crystallography1 using an X-ray free-electron laser2 to observe light-induced structural changes in the photosynthetic reaction centre of Blastochloris viridis on a timescale of picoseconds. Structural perturbations first occur at the special pair of chlorophyll molecules of the photosynthetic reaction centre that are photo-oxidized by light. Electron transfer to the menaquinone acceptor on the opposite side of the membrane induces a movement of this cofactor together with lower amplitude protein rearrangements. These observations reveal how proteins use conformational dynamics to stabilize the charge-separation steps of electron-transfer reactions.
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| 3. |
- Kübel, Joachim, 1988, et al.
(author)
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Giving voice to the weak: Application of active noise reduction in transient infrared spectroscopy
- 2021
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In: Chemical Physics Letters. - : Elsevier BV. - 0009-2614. ; 783
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Journal article (peer-reviewed)abstract
- The analysis and interpretation of time-resolved spectroscopic data is challenging in the presence of high levels of noise. This problem is particularly common when studying light-activated proteins with transient absorption (TA) spectroscopy. For the same reason, transient 2D-IR remains a notoriously challenging technique that so far has mostly been applied to studying strong oscillators, such as metal carbonyls. Here, we present a detailed implementation of transient 1D and 2D-IR spectroscopy that synchronizes three independent laser sources and applies advanced referencing algorithms for efficient noise suppression. The applied referencing method improves data quality considerably and allows for extracting additional spectroscopic information that is otherwise beyond reach due to very low signal-to-noise ratio. We apply the approach to monitor the complete Pr-to-Pfr transition in the Y263F mutant of a bacterial phytochrome (phi Pr_Pfr < 0.1) covering six orders of magnitude in time, from nanoseconds to milliseconds. We further extend the noise suppression method to transient 2D-IR spectroscopy and conduct a technical feasibility test on a solid-state semiconductor sample (InAs). The presented solutions come at no extra cost when a reference detector is present and are expected to find applications in many spectroscopic studies due to the enhanced ability to detect and interpret very weak signals on multiple timescales.
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