Hamburg Center for Ultrafast Imaging

Hamburg, Germany

Hamburg Center for Ultrafast Imaging

Hamburg, Germany
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Atomic model of the crystalline occlusion bodies, derived from the X-ray diffraction images recorded at the X-ray free-electron laser LCLS at SLAC National Accelerator Laboratory. The individual proteins (right) stick together to form the building blocks (left, seen from the side; center, seen from above) of the crystalline occlusion bodies. Credit: Dominik Oberthuer, CFEL/DESY An international team of scientists has used high-intensity X-ray pulses to determine the structure of the crystalline protein envelope of an insect virus. Their analysis reveals the fine details of the building blocks that make up the viral cocoon down to a scale of 0.2 nanometres (millionths of a millimetre) - approaching atom-scale resolution. The tiny viruses with their crystal casing are by far the smallest protein crystals ever analysed using X-ray crystallography. This opens up new opportunities in the study of protein structures, as the team headed by DESY's Leading Scientist Henry Chapman from the Center for Free-Electron Laser Science reports in the Proceedings of the National Academy of Sciences (PNAS). "The granulovirus attacks certain insects and kills them. This initially leaves it stranded inside the decaying host, so it has to protect itself, perhaps for years, against adverse environmental conditions such as heat, ultraviolet radiation and drought, until it is once again ingested by an insect. To achieve this, the virus wraps itself in a cocoon made of protein crystals, which only dissolve again once it reaches an insect's gut," explains Cornelius Gati from DESY, the main author of the paper. These viruses are a particular interest of Peter Metcalf from the University of Auckland in New Zealand and Johannes Jehle from the Julius Kühn Institute in Darmstadt, who teamed up with DESY for this research. The researchers examined the cocoon of the Cydia pomonella granulovirus (CpGV), which infects the caterpillars of the codling moth (Cydia pomonella) and is used in agriculture as a biological pesticide. The virus is harmless to humans. Scientists are interested in the spatial structure of proteins and other biomolecules because this sheds light on the precise way in which they work. This has led to a specialised science known as structural biology. "Over the past 50 years, scientists have determined the structures of more than 100,000 proteins," says Chapman, who is also a professor of physics at the University of Hamburg. "By far the most important tool for this is X-ray crystallography." In this method, a crystal of the protein under investigation is grown and irradiated with bright X-rays. This produces a characteristic diffraction pattern, from which the spatial structure of the crystal and its building blocks can be calculated. "One of the big challenges of this procedure is, however, growing the crystals," adds Chapman. Many proteins do not readily align to form crystals, because that is not their natural state. The smaller the crystals that can be used for the analysis, the easier it is to grow them, but the harder it is to measure them. "We are hoping that in future we will be able to dispense altogether with growing crystals and study individual molecules directly using X-rays," says Chapman, "so we would like to understand the limits". "These virus particles provided us with the smallest protein crystals ever used for X-ray structure analysis," explains Gati. The occlusion body (the virus "cocoon") has a volume of around 0.01 cubic micrometres, about one hundred times smaller than the smallest artificially grown protein crystals that have until now been analysed using crystallographic techniques. To break this limit in crystal size, an extremely bright X-ray beam was needed, which was obtained using a so-called free-electron laser (FEL), in which a beam of high-speed electrons is guided through a magnetic undulator causing them to emit laser-like X-ray pulses. The scientists used the free-electron laser LCLS at the SLAC National Accelerator Laboratory in the U.S., and employed optics to focus each X-ray pulse to a similar size as one of the virus particles. "Directing the entire power of the FEL onto one tiny virus exposed it to the tremendous radiation levels," reports Gati, who now works at SLAC. The dose was 1.3 billion Grays; for comparison: the lethal dose for humans is around 50 Grays. The FEL dose was certainly lethal for the viruses too - each was completely vaporised by a single X-ray pulse. But the femtosecond-duration pulse carries the information of the pristine structure to the detector and the destruction of the virus occurs only after the passage of the pulse. The analysis of the recorded diffraction showed that even tiny protein crystals which are bombarded with extremely high radiation doses can still reveal their structure on an atomic scale. "Simulations based on our measurements suggest that our method can probably be used to determine the structure of even smaller crystals consisting of only hundreds or thousands of molecules," reports Chapman, who is also a member of the Hamburg Center for Ultrafast Imaging (CUI). "This takes us a huge step further towards our goal of analysing individual molecules." More information: Atomic structure of granulin determined from native nanocrystalline granulovirus using an X-ray free-electron laser, PNAS,

Beil K.,University of Hamburg | Deppe B.,University of Hamburg | Deppe B.,Hamburg Center for Ultrafast Imaging | Krankel C.,University of Hamburg | Krankel C.,Hamburg Center for Ultrafast Imaging
Optics Letters | Year: 2013

Thin-disk laser experiments with Yb:CaGdAlO4 (Yb:CALGO) have been performed. A slope efficiency of 70% and an optical-to-optical efficiency of 57% could be achieved with a maximum output power of 30.7 W. These are so far the highest efficiencies obtained with this material. Furthermore, tuning experiments were carried out leading to a tuning range of 90 nm in total and 50 nm with more than 20Wof output power. This is to the best of our knowledge the widest wavelength tuning range of any material demonstrated at this power level. For all experiments the thermal evolution of the crystal surface temperature during laser operation was investigated. © 2013 Optical Society of America.

Calendron A.-L.,German Electron Synchrotron | Calendron A.-L.,Hamburg Center for Ultrafast Imaging
Optics Express | Year: 2013

This paper reports on a high-power dual-crystal Yb:CALGO laser head with greatly reduced sensitivity to thermal lensing in the gain medium. In continuous-wave operation 23 W of power were extracted from 2% doped crystals, and tunablity between 1018 nm and 1060 nm was demonstrated. This is the highest output power reported from a bulk Yb:CALGO laser to date, as well as the demonstration of the broadest tuning range. 4 mJ pulses at 1040 nm were achieved in cavity-dumped operation with quasi-CW pumping at 1 kHz repetition rate with nearly diffraction-limited beam quality. When seeded at 1030 nm with stretched femtosecond pulses, 3 mJ were achieved. ©2013 Optical Society of America.

Rohlsberger R.,German Electron Synchrotron | Rohlsberger R.,Hamburg Center for Ultrafast Imaging
Physical Review Letters | Year: 2014

A new type of spectroscopy for high-resolution studies of spin waves that relies on resonant scattering of hard x rays is introduced. The energy transfer in the scattering process is encoded in the precession of the polarization vector of the scattered photons. Thus, the energy resolution of such a spectroscopy is independent of the bandwidth of the probing radiation. The measured quantity resembles the intermediate scattering function of the magnetic excitations in the sample. At pulsed x-ray sources, especially x-ray lasers, the proposed technique allows us to take single-shot spectra of the magnetic dynamics. The method opens new avenues to study low-energy nonequilibrium magnetic processes in a pump-probe setup. © 2014 American Physical Society.

Nalbach P.,University of Hamburg | Nalbach P.,Hamburg Center for Ultrafast Imaging
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2014

We investigate the dissipative influence of environmental fluctuations on the dynamics of driven quantum systems at an avoided crossing. We derive two simple approximative equations valid for weak system-bath coupling and compare results for the dissipative Landau-Zener problem with numerically exact results. Very good agreement is found for slow, i.e., adiabatic, driving. Specifically, the minimum in the Landau-Zener probability resulting from the competition of driving and dissipation is well described. For system-bath couplings and temperatures, where this minimum is observed in the adiabatic driving regime, good agreement is also observed for fast driving when the dynamics tends toward nonadiabatic behavior. Otherwise, however, for large temperatures and fast driving our approximation fails even for weak system-bath couplings, for which an undriven system is still accurately described by weak-coupling approximations. © 2014 American Physical Society.

Singh V.P.,University of Hamburg | Mathey L.,Hamburg Center for Ultrafast Imaging
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2014

We analyze density-density correlations of expanding clouds of weakly interacting two-dimensional Bose gases below and above the Berezinskii- Kosterlitz-Thouless transition, with particular focus on short-time expansions. During time-of-flight expansion, phase fluctuations of the trapped system translate into density fluctuations, in addition to the density fluctuations that exist in situ. We calculate the correlations of these fluctuations both in real space and in momentum space and derive analytic expressions in momentum space. Below the transition, the correlation functions show an oscillatory behavior, controlled by the scaling exponent of the quasicondensed phase, due to constructive interference. We argue that this can be used to extract the scaling exponent of the quasicondensate experimentally. Above the transition, the interference is rapidly suppressed when the atoms travel an average distance beyond the correlation length. This can be used to distinguish the two phases qualitatively. © 2014 American Physical Society.

Hanze M.,Max Planck Institute for Intelligent Systems (Stuttgart) | Adolff C.F.,Max Planck Institute for Intelligent Systems (Stuttgart) | Weigand M.,Hamburg Center for Ultrafast Imaging | Meier G.,Max Planck Institute for Intelligent Systems (Stuttgart) | Meier G.,Hamburg Center for Ultrafast Imaging
Applied Physics Letters | Year: 2014

We study the magnetization dynamics of coupled vortices in arrays of Permalloy disks via analytical calculations and scanning transmission x-ray microscopy. The Thiele approach is used to derive linear equations of motion of the vortices. Thereby, vortex motions following a nanosecond field pulse are described by a superposition of eigenmodes that depend on the vortex polarizations. Eigenmodes are calculated for a specific polarization pattern of a 3 × 3 vortex array. With magnetic field pulses distinct oscillations are excited and imaged in space and time. The calculated eigenmodes precisely describe the measured oscillations. © 2014 AIP Publishing LLC.

Takahashi E.J.,RIKEN | Lan P.,RIKEN | Lan P.,Huazhong University of Science and Technology | Mucke O.D.,German Electron Synchrotron | And 3 more authors.
Nature Communications | Year: 2013

High-energy isolated attosecond pulses required for the most intriguing nonlinear attosecond experiments as well as for attosecond-pump/attosecond-probe spectroscopy are still lacking at present. Here we propose and demonstrate a robust generation method of intense isolated attosecond pulses, which enable us to perform a nonlinear attosecond optics experiment. By combining a two-colour field synthesis and an energy-scaling method of high-order harmonic generation, the maximum pulse energy of the isolated attosecond pulse reaches as high as 1.3 mJ. The generated pulse with a duration of 500 as, as characterized by a nonlinear autocorrelation measurement, is the shortest and highest-energy pulse ever with the ability to induce nonlinear phenomena. The peak power of our tabletop light source reaches 2.6GW, which even surpasses that of an extreme-ultraviolet free-electron laser. © 2013 Macmillan Publishers Limited. All rights reserved.

Kronke S.,University of Hamburg | Schmelcher P.,University of Hamburg | Schmelcher P.,Hamburg Center for Ultrafast Imaging
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2015

We perform a comparative beyond-mean-field study of black and gray solitonic excitations in a finite ensemble of ultracold bosons confined to a one-dimensional box. An optimized density-engineering potential is developed and employed together with phase imprinting to cleanly initialize gray solitons. By means of ab initio simulations with the multiconfiguration time-dependent Hartree method for bosons, we demonstrate that quantum fluctuations limit the lifetime of the soliton contrast, which increases with increasing soliton velocity. A natural orbital analysis reveals a two-stage process underlying the decay of the soliton contrast. The broken parity symmetry of gray solitons results in a local asymmetry of the orbital mainly responsible for the decay, which leads to a characteristic asymmetry of remarkably localized two-body correlations. The emergence and decay of these correlations as well as their displacement from the instantaneous soliton position are analyzed in detail. Finally, the role of phase imprinting for the many-body dynamics is illuminated and additional nonlocal correlations in pairs of counterpropagating gray solitons are observed. © 2015 American Physical Society.

Nalbach P.,University of Hamburg | Nalbach P.,Hamburg Center for Ultrafast Imaging
AIP Conference Proceedings | Year: 2014

Chlorosomes, as part of the light-harvesting system of green bacteria, are the largest and most efficient antennae systems in nature. We have studied energy transfer dynamics in the chlorosome in a simplified toy model employing a master equation. Dephasing and relaxation due to environmental fluctuations are included by Lindblad dephasing and Redfield thermalization rates. We find at room temperature three separate time scales, i.e. 25 fs, 250 fs and 2.5 ps and determine the according energy pathways through the hierarchical structure in the chlorosome. Quantum coherence lives up to 150 fs at which time the energy is spread over roughly 12 pigments in our model. © 2014 AIP Publishing LLC.

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