| 1. |
- Brändén, Gisela, 1975, et al.
(author)
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Coherent diffractive imaging of microtubules using an X-ray laser.
- 2019
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In: Nature communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 10:1
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Journal article (peer-reviewed)abstract
- X-ray free electron lasers (XFELs) create new possibilities for structural studies of biological objects that extend beyond what is possible with synchrotron radiation. Serial femtosecond crystallography has allowed high-resolution structures to be determined from micro-meter sized crystals, whereas single particle coherent X-ray imaging requires development to extend the resolution beyond a few tens of nanometers. Here we describe an intermediate approach: the XFEL imaging of biological assemblies with helical symmetry. We collected X-ray scattering images from samples of microtubules injected across an XFEL beam using a liquid microjet, sorted these images into class averages, merged these data into a diffraction pattern extending to 2nm resolution, and reconstructed these data into a projection image of the microtubule. Details such as the 4nm tubulin monomer became visible in this reconstruction. These results illustrate the potential of single-molecule X-ray imaging of biological assembles with helical symmetry at room temperature.
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| 2. |
- Båth, Petra, 1988, et al.
(author)
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Lipidic cubic phase serial femtosecond crystallography structure of a photosynthetic reaction centre
- 2022
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In: Acta Crystallographica Section D-Structural Biology. - : International Union of Crystallography (IUCr). - 2059-7983. ; 78, s. 698-708
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Journal article (peer-reviewed)abstract
- Serial crystallography is a rapidly growing method that can yield structural insights from microcrystals that were previously considered to be too small to be useful in conventional X-ray crystallography. Here, conditions for growing microcrystals of the photosynthetic reaction centre of Blastochloris viridis within a lipidic cubic phase (LCP) crystallization matrix that employ a seeding protocol utilizing detergent-grown crystals with a different crystal packing are described. LCP microcrystals diffracted to 2.25 angstrom resolution when exposed to XFEL radiation, which is an improvement of 0.15 angstrom over previous microcrystal forms. Ubiquinone was incorporated into the LCP crystallization media and the resulting electron density within the mobile Q(B) pocket is comparable to that of other cofactors within the structure. As such, LCP microcrystallization conditions will facilitate time-resolved diffraction studies of electron-transfer reactions to the mobile quinone, potentially allowing the observation of structural changes associated with the two electron-transfer reactions leading to complete reduction of the ubiquinone ligand.
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| 3. |
- Dods, Robert, 1989, et al.
(author)
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From Macrocrystals to Microcrystals: A Strategy for Membrane Protein Serial Crystallography.
- 2017
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In: Structure. - : Elsevier BV. - 1878-4186 .- 0969-2126. ; 25:9, s. 1461-1468
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Journal article (peer-reviewed)abstract
- Serial protein crystallography was developed at X-ray free-electron lasers (XFELs) and is now also being applied at storage ring facilities. Robust strategies for the growth and optimization of microcrystals are needed to advance the field. Here we illustrate a generic strategy for recovering high-density homogeneous samples of microcrystals starting from conditions known to yield large (macro) crystals of the photosynthetic reaction center of Blastochloris viridis (RCvir). We first crushed these crystals prior to multiple rounds of microseeding. Each cycle of microseeding facilitated improvements in the RCvir serial femtosecond crystallography (SFX) structure from 3.3-Å to 2.4-Å resolution. This approach may allow known crystallization conditions for other proteins to be adapted to exploit novel scientific opportunities created by serial crystallography.
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| 4. |
- 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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| 5. |
- Hammarin, Greger, 1981
(author)
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Microtubule structure and function as perturbed by electromagnetic fields
- 2022
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Doctoral thesis (other academic/artistic)abstract
- Frontlinjen för strukturbiologisk forskning ligger idag i att avbilda proteiner i rörelse. För att förstå hur proteiner fungerar rent strukturellt krävs avbildningsmetoder med en tid- och rums-upplösning anpassad för den specifika biologiska funktionen. Tidigare forskning rörande ljuskänsliga proteinkomplexs reaktion på ljus har genomförts med hög tidsmässig upplösning, men det saknas en generell metod för att initiera och koordinera proteinrörelser. Tidigare forskning har också indikerat att protein i starka elektromagnetiska fält kan induceras att uppvisa relevanta strukturella rörelser. Mikrotubuli är essentiella komponenter i cellskelettet i allt eukaryot liv. De är i huvudsak uppbyggda av de två proteiner alfa- och beta-tubulin. Tillsammans bildar de en heterodimer som kan organisera sig i en tubformade mikrotubuli. Denna avhandling inkluderar tre undersökningar av mikroubulis struktur och funktion. Den mest högupplösta avbildningen av mikrotubuli, och proteiner generellt, baseras idag på metoder som kräver att proteinkomplexet fryses ned eller torkas ut. Avhandlingens första studie utgör ett försök att avbilda mikrotubuli under fysiologiskt mer relevanta omständigheter, i en rumstempererad lösning. Den rumsliga upplösning med vilken mikrotubuli avbildades är lägre än vad som uppnåtts med beprövade metoder, men samtidigt visar studien på potentialen att avbilda enskilda partiklar i flytande lösning och vid rumstemperatur. I denna avhandling presenteras även två studier som avsåg att undersöka om alternerande elektromagnetiska fält, med frekvenser motsvarande dagens mobiltelefoni och Wifi, påverkar mikrotubulis struktur och funktion. Studierna fann ingen sådan påverkan utöver de som kan associeras med värmeutveckling eller rumslig orientering.
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| 6. |
- Safari, Cecilia, 1989, et al.
(author)
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Time-resolved serial crystallography to track the dynamics of carbon monoxide in the active site of cytochrome c oxidase
- 2023
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In: Science advances. - 2375-2548. ; 9:49
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Journal article (peer-reviewed)abstract
- Cytochrome c oxidase (CcO) is part of the respiratory chain and contributes to the electrochemical membrane gradient in mitochondria as well as in many bacteria, as it uses the energy released in the reduction of oxygen to pump protons across an energy-transducing biological membrane. Here, we use time-resolved serial femtosecond crystallography to study the structural response of the active site upon flash photolysis of carbon monoxide (CO) from the reduced heme a3 of ba3-type CcO. In contrast with the aa3-type enzyme, our data show how CO is stabilized on CuB through interactions with a transiently ordered water molecule. These results offer a structural explanation for the extended lifetime of the CuB-CO complex in ba3-type CcO and, by extension, the extremely high oxygen affinity of the enzyme.
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| 7. |
- Sharma, Amit, et al.
(author)
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A simple adaptation to a protein crystallography station to facilitate difference X-ray scattering studies
- 2019
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In: Journal of Applied Crystallography. - : International Union of Crystallography (IUCr). - 0021-8898 .- 1600-5767. ; 52, s. 378-386
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Journal article (peer-reviewed)abstract
- The X-ray crystallography station I911-2 at MAXLab II (Lund, Sweden) has been adapted to enable difference small- and wide-angle X-ray scattering (SAXS/WAXS) data to be recorded. Modifications to the beamline included a customized flow cell, a motorized flow cell holder, a helium cone, a beam stop, a sample stage and a sample delivery system. This setup incorporated external devices such as infrared lasers, LEDs and reaction mixers to induce conformational changes in macromolecules. This platform was evaluated through proof-of-principle experiments capturing light-induced conformational changes in phytochromes. A difference WAXS signature of conformational changes in a plant aquaporin was also demonstrated using caged calcium.
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