| 1. |
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| 2. |
- Kirian, Richard A., et al.
(författare)
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Structure-factor analysis of femtosecond micro-diffraction patterns from protein nanocrystals
- 2011
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Ingår i: Acta Crystallographica Section A. - 0108-7673 .- 1600-5724. ; 67:2, s. 131-140
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Tidskriftsartikel (refereegranskat)abstract
- A complete set of structure factors has been extracted from hundreds of thousands of femtosecond single-shot X-ray microdiffraction patterns taken from randomly oriented nanocrystals. The method of Monte Carlo integration over crystallite size and orientation was applied to experimental data from Photosystem I nanocrystals. This arrives at structure factors from many partial reflections without prior knowledge of the particle-size distribution. The data were collected at the Linac Coherent Light Source (the first hard-X-ray laser user facility), to which was fitted a hydrated protein nanocrystal injector jet, according to the method of serial crystallography. The data are single 'still' diffraction snapshots, each from a different nanocrystal with sizes ranging between 100 nm and 2 mu m, so the angular width of Bragg peaks was dominated by crystal-size effects. These results were compared with single-crystal data recorded from large crystals of Photosystem I at the Advanced Light Source and the quality of the data was found to be similar. The implications for improving the efficiency of data collection by allowing the use of very small crystals, for radiation-damage reduction and for time-resolved diffraction studies at room temperature are discussed.
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| 3. |
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| 4. |
- Olovsson, Ivar
(författare)
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Hydrated proton in solids
- 1972
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Ingår i: Acta Crystallographica Section A. - 0108-7673 .- 1600-5724. ; 28, s. S107-S107
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 5. |
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| 6. |
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| 7. |
- Westenhoff, Sebastian, 1978, et al.
(författare)
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Time-resolved structural studies of protein reaction dynamics : a smorgasbord of X-ray approaches
- 2010
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Ingår i: Acta Crystallographica Section A. - 0108-7673 .- 1600-5724. ; 66:2, s. 207-219
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Forskningsöversikt (refereegranskat)abstract
- Proteins undergo conformational changes during their biological function. As such, a high-resolution structure of a protein's resting conformation provides a starting point for elucidating its reaction mechanism, but provides no direct information concerning the protein's conformational dynamics. Several X-ray methods have been developed to elucidate those conformational changes that occur during a protein's reaction, including time-resolved Laue diffraction and intermediate trapping studies on three-dimensional protein crystals, and time-resolved wide-angle X-ray scattering and X-ray absorption studies on proteins in the solution phase. This review emphasizes the scope and limitations of these complementary experimental approaches when seeking to understand protein conformational dynamics. These methods are illustrated using a limited set of examples including myoglobin and haemoglobin in complex with carbon monoxide, the simple light-driven proton pump bacteriorhodopsin, and the superoxide scavenger superoxide reductase. In conclusion, likely future developments of these methods at synchrotron X-ray sources and the potential impact of emerging X-ray free-electron laser facilities are speculated upon.
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| 8. |
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| 9. |
- Liljas, Anders
(författare)
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Background to the nobel prize to the Braggs
- 2013
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Ingår i: Acta crystallographica. Section A, Foundations of crystallography. - 1600-5724. ; 69:Pt 1, s. 10-15
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Tidskriftsartikel (refereegranskat)abstract
- The Nobel Committees have to follow the nominations submitted for a specific year. During the early phase of X-ray crystallography, a limited number of scientists were active. In 1914 Max von Laue and William Henry Bragg were both nominated and could have been awarded a joint Nobel Prize. However, a member of the Nobel Committee for Physics, Allvar Gullstrand, was well aware of the activities in the field and strongly recommended that only von Laue should receive the prize since a main contributor, William Laurence Bragg, was not nominated. Next year, when the First World War had started, there were few nominations, but now both Braggs, father and son, were nominated. Gullstrand was very pleased and recommended them both for the 1915 Nobel Prize in Physics. The rest of the committee agreed and this then became the decision of the Royal Academy for Sciences, Stockholm.
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| 10. |
- Mellergard, A, et al.
(författare)
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Reverse Monte Carlo modelling of neutron powder diffraction data
- 1999
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Ingår i: ACTA CRYSTALLOGRAPHICA SECTION A. - : MUNKSGAARD INT PUBL LTD. - 0108-7673. ; 55, s. 783-789
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- A new reverse Monte Carlo (RMC) method for modelling both lattice and magnetic disorder in powder crystalline materials by direct calculation of the structure factor has been developed. The method, the program and the basic theory are described in some de
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| 11. |
- Miller, R. J. Dwayne, et al.
(författare)
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'Making the molecular movie': first frames
- 2010
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Ingår i: Acta crystallographica. Section A, Foundations of crystallography. - 0108-7673. ; 66, s. 137-156
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Tidskriftsartikel (refereegranskat)abstract
- Recent advances in high-intensity electron and X-ray pulsed sources now make it possible to directly observe atomic motions as they occur in barrier-crossing processes. These rare events require the structural dynamics to be triggered by femtosecond excitation pulses that prepare the system above the barrier or access new potential energy surfaces that drive the structural changes. In general, the sampling process modifies the system such that the structural probes should ideally have sufficient intensity to fully resolve structures near the single-shot limit for a given time point. New developments in both source intensity and temporal characterization of the pulsed sampling mode have made it possible to make so-called 'molecular movies', i.e. measure relative atomic motions faster than collisions can blur information on correlations. Strongly driven phase transitions from thermally propagated melting to optically modified potential energy surfaces leading to ballistic phase transitions and bond stiffening are given as examples of the new insights that can be gained from an atomic level perspective of structural dynamics. The most important impact will likely be made in the fields of chemistry and biology where the central unifying concept of the transition state will come under direct observation and enable a reduction of high-dimensional complex reaction surfaces to the key reactive modes, as long mastered by Mother Nature.
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| 12. |
- Panas, Itai, 1959
(författare)
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PROPERTIES OF MOLECULAR-CRYSTALS BY MEANS OF THEORY
- 1993
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Ingår i: Acta Crystallographica Section A: Foundations of Crystallography. - 0108-7673. ; 49:6, s. 881-889
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Tidskriftsartikel (refereegranskat)abstract
- A novel quantum-chemical approach to the properties of molecular crystals has recently been developed. This Hartree-Fock-based self-consistent-crystal-field method is outlined and applied to the intramolecular torsion angle in solid hydrogen peroxide, the cold-phase structure of solid dinitrogen and the hot-phase structure of solid acetylene. The potential-energy surfaces are calculated with the assumption of perfectly ordered crystals and coherent molecular potential-energy surfaces are produced. Agreement with experiment is obtained for hydrogen peroxide. It is suggested that discrepancies between calculated and observed structures of N2(s) and C2H2(s) result from static and dynamic disorder, respectively. This interpretation is consistent with the experimentally observed intramolecular-bond shortenings in these two solids. Lattice energies in good agreement with experiment are obtained in all three cases.
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| 13. |
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| 14. |
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| 15. |
- Szoke, A
(författare)
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Diffraction of partially coherent X-rays and the crystallographic phase problem
- 2001
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Ingår i: ACTA CRYSTALLOGRAPHICA SECTION A. - : MUNKSGAARD INT PUBL LTD. - 0108-7673. ; 57, s. 586-603
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a new physical method for the partial solution of the crystallographic phase problem by illuminating the crystal with an X-ray beam of limited coherence. The diffraction spots broaden and, if the coherence length of the incident beam i
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