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News Article | May 22, 2017
Site: phys.org

We can refer to electrons in non-conducting materials as 'sluggish'. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence relatively still in a dielectric crystal lattice. This idyll has now been heavily shaken up by a team of physicists led by Matthias Kling, the leader of the Ultrafast Nanophotonics group in the Department of Physics at Ludwig-Maximilians-Universitaet (LMU) in Munich, and various research institutions, including the Max Planck Institute of Quantum Optics (MPQ), the Institute of Photonics and Nanotechnologies (IFN-CNR) in Milan, the Institute of Physics at the University of Rostock, the Max Born Institute (MBI), the Center for Free-Electron Laser Science (CFEL) and the University of Hamburg. For the first time, these researchers managed to directly observe the interaction of light and electrons in a dielectric, a non-conducting material, on timescales of attoseconds (billionths of a billionth of a second). The study was published in the latest issue of the journal Nature Physics. The scientists beamed light flashes lasting only a few hundred attoseconds onto 50 nanometer thick glass particles, which released electrons inside the material. Simultaneously, they irradiated the glass particles with an intense light field, which interacted with the electrons for a few femtoseconds (millionths of a billionth of a second), causing them to oscillate. This resulted, generally, in two different reactions by the electrons. First, they started to move, then collided with atoms within the particle, either elastically or inelastically. Because of the dense crystal lattice, the electrons could move freely between each of the interactions for only a few ångstrom (10-10 meter). "Analogous to billiard, the energy of electrons is conserved in an elastic collision, while their direction can change. For inelastic collisions, atoms are excited and part of the kinetic energy is lost. In our experiments, this energy loss leads to a depletion of the electron signal that we can measure," explains Professor Francesca Calegari (CNR-IFN Milan and CFEL/University of Hamburg). Since chance decides whether a collision occurs elastically or inelastically, with time inelastic collisions will eventually take place, reducing the number of electrons that scattered only elastically. Employing precise measurements of the electrons' oscillations within the intense light field, the researchers managed to find out that it takes about 150 attoseconds on average until elastically colliding electrons leave the nanoparticle. "Based on our newly developed theoretical model we could extract an inelastic collision time of 370 attoseconds from the measured time delay. This enabled us to clock this process for the first time," describes Professor Thomas Fennel from the University of Rostock and Berlin's Max Born Institute in his analysis of the data. The researchers' findings could benefit medical applications. With these worldwide first ultrafast measurements of electron motions inside non-conducting materials, they have obtained important insight into the interaction of radiation with matter, which shares similarities with human tissue. The energy of released electrons is controlled with the incident light, such that the process can be investigated for a broad range of energies and for various dielectrics. "Every interaction of high-energy radiation with tissue results in the generation of electrons. These in turn transfer their energy via inelastic collisions onto atoms and molecules of the tissue, which can destroy it. Detailed insight about electron scattering is therefore relevant for the treatment of tumors. It can be used in computer simulations to optimize the destruction of tumors in radiotherapy while sparing healthy tissue," highlights Professor Matthias Kling of the impact of the work. As a next step, the scientists plan to replace the glass nanoparticles with water droplets to study the interaction of electrons with the very substance which makes up the largest part of living tissue. More information: L. Seiffert et al, Attosecond chronoscopy of electron scattering in dielectric nanoparticles, Nature Physics (2017). DOI: 10.1038/nphys4129


News Article | May 22, 2017
Site: www.eurekalert.org

An international team of physicists has monitored the scattering behavior of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy. We can refer to electrons in non-conducting materials as 'sluggish'. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence relatively still in a dielectric crystal lattice. This idyll has now been heavily shaken up by a team of physicists led by Matthias Kling, the leader of the Ultrafast Nanophotonics group in the Department of Physics at Ludwig-Maximilians-Universitaet (LMU) in Munich, and various research institutions, including the Max Planck Institute of Quantum Optics (MPQ), the Institute of Photonics and Nanotechnologies (IFN-CNR) in Milan, the Institute of Physics at the University of Rostock, the Max Born Institute (MBI), the Center for Free-Electron Laser Science (CFEL) and the University of Hamburg. For the first time, these researchers managed to directly observe the interaction of light and electrons in a dielectric, a non-conducting material, on timescales of attoseconds (billionths of a billionth of a second). The study was published in the latest issue of the journal Nature Physics. The scientists beamed light flashes lasting only a few hundred attoseconds onto 50 nanometer thick glass particles, which released electrons inside the material. Simultaneously, they irradiated the glass particles with an intense light field, which interacted with the electrons for a few femtoseconds (millionths of a billionth of a second), causing them to oscillate. This resulted, generally, in two different reactions by the electrons. First, they started to move, then collided with atoms within the particle, either elastically or inelastically. Because of the dense crystal lattice, the electrons could move freely between each of the interactions for only a few ångstrom (10-10 meter). "Analogous to billiard, the energy of electrons is conserved in an elastic collision, while their direction can change. For inelastic collisions, atoms are excited and part of the kinetic energy is lost. In our experiments, this energy loss leads to a depletion of the electron signal that we can measure," explains Professor Francesca Calegari (CNR-IFN Milan and CFEL/University of Hamburg). Since chance decides whether a collision occurs elastically or inelastically, with time inelastic collisions will eventually take place, reducing the number of electrons that scattered only elastically. Employing precise measurements of the electrons' oscillations within the intense light field, the researchers managed to find out that it takes about 150 attoseconds on average until elastically colliding electrons leave the nanoparticle. "Based on our newly developed theoretical model we could extract an inelastic collision time of 370 attoseconds from the measured time delay. This enabled us to clock this process for the first time," describes Professor Thomas Fennel from the University of Rostock and Berlin's Max Born Institute in his analysis of the data. The researchers' findings could benefit medical applications. With these worldwide first ultrafast measurements of electron motions inside non-conducting materials, they have obtained important insight into the interaction of radiation with matter, which shares similarities with human tissue. The energy of released electrons is controlled with the incident light, such that the process can be investigated for a broad range of energies and for various dielectrics. "Every interaction of high-energy radiation with tissue results in the generation of electrons. These in turn transfer their energy via inelastic collisions onto atoms and molecules of the tissue, which can destroy it. Detailed insight about electron scattering is therefore relevant for the treatment of tumors. It can be used in computer simulations to optimize the destruction of tumors in radiotherapy while sparing healthy tissue," highlights Professor Matthias Kling of the impact of the work. As a next step, the scientists plan to replace the glass nanoparticles with water droplets to study the interaction of electrons with the very substance which makes up the largest part of living tissue.


News Article | May 25, 2017
Site: www.sciencedaily.com

An international team of physicists has monitored the scattering behavior of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy. We can refer to electrons in non-conducting materials as 'sluggish'. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence relatively still in a dielectric crystal lattice. This idyll has now been heavily shaken up by a team of physicists led by Matthias Kling, the leader of the Ultrafast Nanophotonics group in the Department of Physics at Ludwig-Maximilians-Universitaet (LMU) in Munich, and various research institutions, including the Max Planck Institute of Quantum Optics (MPQ), the Institute of Photonics and Nanotechnologies (IFN-CNR) in Milan, the Institute of Physics at the University of Rostock, the Max Born Institute (MBI), the Center for Free-Electron Laser Science (CFEL) and the University of Hamburg. For the first time, these researchers managed to directly observe the interaction of light and electrons in a dielectric, a non-conducting material, on timescales of attoseconds (billionths of a billionth of a second). The study was published in the latest issue of the journal Nature Physics. The scientists beamed light flashes lasting only a few hundred attoseconds onto 50 nanometer thick glass particles, which released electrons inside the material. Simultaneously, they irradiated the glass particles with an intense light field, which interacted with the electrons for a few femtoseconds (millionths of a billionth of a second), causing them to oscillate. This resulted, generally, in two different reactions by the electrons. First, they started to move, then collided with atoms within the particle, either elastically or inelastically. Because of the dense crystal lattice, the electrons could move freely between each of the interactions for only a few ångstrom (10-10 meter). "Analogous to billiard, the energy of electrons is conserved in an elastic collision, while their direction can change. For inelastic collisions, atoms are excited and part of the kinetic energy is lost. In our experiments, this energy loss leads to a depletion of the electron signal that we can measure," explains Professor Francesca Calegari (CNR-IFN Milan and CFEL/University of Hamburg). Since chance decides whether a collision occurs elastically or inelastically, with time inelastic collisions will eventually take place, reducing the number of electrons that scattered only elastically. Employing precise measurements of the electrons' oscillations within the intense light field, the researchers managed to find out that it takes about 150 attoseconds on average until elastically colliding electrons leave the nanoparticle. "Based on our newly developed theoretical model we could extract an inelastic collision time of 370 attoseconds from the measured time delay. This enabled us to clock this process for the first time," describes Professor Thomas Fennel from the University of Rostock and Berlin's Max Born Institute in his analysis of the data. The researchers' findings could benefit medical applications. With these worldwide first ultrafast measurements of electron motions inside non-conducting materials, they have obtained important insight into the interaction of radiation with matter, which shares similarities with human tissue. The energy of released electrons is controlled with the incident light, such that the process can be investigated for a broad range of energies and for various dielectrics. "Every interaction of high-energy radiation with tissue results in the generation of electrons. These in turn transfer their energy via inelastic collisions onto atoms and molecules of the tissue, which can destroy it. Detailed insight about electron scattering is therefore relevant for the treatment of tumors. It can be used in computer simulations to optimize the destruction of tumors in radiotherapy while sparing healthy tissue," highlights Professor Matthias Kling of the impact of the work. As a next step, the scientists plan to replace the glass nanoparticles with water droplets to study the interaction of electrons with the very substance which makes up the largest part of living tissue.


News Article | October 25, 2016
Site: phys.org

Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how the ultrafast light-induced modulation of the atomic positions in a material can control its magnetization. An international research team led by Andrea Cavalleri from the Max Planck Institute for the Structure and Dynamics of Matter at CFEL in Hamburg used terahertz light pulses to excite pairs of lattice vibrations in a magnetic crystal. These short bursts of light caused the lattice ions to rotate around their equilibrium positions, acting as an ultrafast effective magnetic field on the electronic spins to coherently drive a magnetic wave. These findings represent an important hallmark on how light interacts with matter and establish a novel approach in the control of magnetization at terahertz speed, making the research potentially relevant for magnetic storage technologies.


News Article | November 18, 2016
Site: phys.org

The preferred structure of a crown ether changes when water molecules bind to it (dashed lines). Credit: © C. Pérez et al. In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers led by Melanie Schnell from the Max Planck Institute for the Structure and Dynamics of Matter at CFEL show that water promotes the reshaping of crown ethers and biphenyl molecules, two classes of chemically fascinating molecules. Crown ethers are key systems in catalysis, separation and encapsulation processes, while biphenyl-based systems are employed in asymmetric synthesis and drug design. Water has profound implications in our world. From its known, yet not fully understood role in mediating protein folding dynamics and proton transport in membranes, water is a key player, influencing the mechanics of many biological and synthetic processes. In the present studies, the researchers used high-resolution rotational spectroscopy to investigate the structural effects that water induces in two types of molecular systems with different roles in the chemical realm. Isolated micro-solvated molecules in the gas phase have become an appealing target to reveal the stepwise hydration of molecular systems. The Hamburg group of Melanie Schnell took this route to reveal the effects that organic molecules undergo when the first water molecules bind around them, forming the so-called first solvation shell. Crown ethers are cyclic molecules in a motif that resembles a crown. They have an extraordinary affinity for catching cations inside the crown. This function is either useful or harmful depending on the size of the crown and its consequent ability to bind smaller or larger cations such as potassium, sodium or lithium. Crown ethers are thus highly functional systems. In this work, the authors discovered that when binding to water, the crown ether's preferred shape changes. "The unexpected structural changes induced by the hydration of the crown ethers reveals new roads for host-guest interactions to take place," says Cristóbal Pérez, postdoc at the MPSD and first author of this work. The expected efficiency for catching other species may be altered in the presence of water. Given the abundance of water at the molecular scale where many biological processes take place, this revelation is important for chemists working with catalysis where crown ethers are employed. Biphenyl-based systems have a core consisting of two benzene (C H ) rings connected via an axis. By overcoming a small energy barrier, the two rings are allowed to rotate with respect to each other. Clockwise and counterclockwise rotation generates mirror images of the same molecule that are not superimposed onto each other and can thus be termed chiral. Identifying and assigning the mirror image forms of chiral molecules are key steps in drug design in the pharmaceutical industry. As an example, the biphenyl motif occurs in drug designs against tuberculosis. In this study, the researchers discovered that when hydrated, the biphenyl system uses two water molecules to form what the authors call a "water-wire." The water wire links the two rings of the biphenyl motif and consequently locks the position of the two rings with respect to each other. With this locking mechanism due to the presence of water, a measurable change in the angle between the rings is observed. "The observed phenomenon provides us with new clues to how water may mediate the interactions between a molecule and its potential receptor," says Sérgio Domingos, postdoc at the MPSD and first author of this work. The observed structural changes induced by water are insightful on the role of hydration for the regulation of more complex biological processes taking place where water is the dominant medium. Explore further: Crown ethers flatten in graphene for strong, specific binding More information: Cristóbal Pérez et al. Water-Induced Structural Changes in Crown Ethers from Broadband Rotational Spectroscopy, The Journal of Physical Chemistry Letters (2016). DOI: 10.1021/acs.jpclett.6b01939 Sérgio R. Domingos et al. Communication: Structural locking mediated by a water wire: A high-resolution rotational spectroscopy study on hydrated forms of a chiral biphenyl derivative, The Journal of Chemical Physics (2016). DOI: 10.1063/1.4966584


News Article | November 22, 2016
Site: www.cemag.us

In a multi-national effort, an interdisciplinary team of researchers from DESY and the Massachusetts Institute of Technology (MIT) has built a new kind of electron gun that is just about the size of a matchbox. Electron guns are used in science to generate high-quality beams of electrons for the investigation of various materials, from biomolecules to superconductors. They are also the electron source for linear particle accelerators driving X-ray free-electron lasers. The team of DESY scientist Franz Kärtner, who is also a professor at University of Hamburg and continues to run a research group at MIT, where he taught till 2010 before coming to Hamburg, presents its new electron gun in the scientific journal Optica. The new device uses laser generated terahertz radiation instead of the usual radio-frequency fields to accelerate electrons from rest. As the wavelength of the terahertz radiation is much shorter than radio-frequency radiation, the device can shrink substantially. While state-of-the-art electron guns can have the size of a car, the new device measures just 34 by 24.5 by 16.8 millimeters. “Electron guns driven by terahertz radiation are miniature and efficient,” explains main author Dr. W. Ronny Huang from MIT, who carried out this work at the Center for Free-Electron Laser Science CFEL in Hamburg, a cooperation of DESY, the University of Hamburg and the German Max Planck Society. “Also, the materials used to guide the radiation are susceptible to much higher fields at terahertz wavelengths as compared to radio frequency wavelengths, allowing terahertz radiation to give a much stronger 'kick' to the electrons. This has the effect of making the electron beams much brighter and shorter.” Ultrashort electron beams with narrow energy spread, high charge and low jitter are essential for ultrafast electron diffraction experiments to resolve phase transitions in metals, semiconductors and molecular crystals, for example. “Our device has a nanometer thin film of copper which, when illuminated with ultraviolett light from the back, produces short bursts of electrons,” describes Huang. “Laser radiation with Terahertz frequency is fed into the device which has a microstructure specifically tailored to channel the radiation to maximize its impact on the electrons.” This way the device reached an accelerating power of 350 Megavolts per metre. “The accelerating field was almost twice that of current state-of-the-art guns,” says Huang. “We achieved an acceleration of a dense packet of 250,000 electrons from rest to 0.5 kilo-elecronvolts (keV) with minimal energy spread. Because of this, the electron beams coming out of the device could already be used for low-energy electron diffraction experiments.” In their set-up, the researchers used the large CFEL laser lab. The ultraviolet flash used to eject the electrons from the copper film is generated from the same laser as the accelerating terahertz radiation. “This ensures absolute timing synchronisation, substantially reducing jitter,” explains Huang. The device worked stably over at least one billion shots, easing every-day operation. “Electron guns are used ubiquitously for making atomic-resolution movies of chemical reactions via ultrafast electron diffraction as pioneered in Prof. Dwayne Miller's group at the Max Planck Institute for the Structure and Dynamics of Matter and CFEL,” says Kärtner. “With smaller and better electron guns, biologists can gain better insight to the intricate workings of macromolecular machines, including those responsible for photosynthesis. And physicists can better understand the fundamental interaction processes in complex materials.” “Furthermore, electron guns are an important component of X-ray light source facilities,” explains Kärtner. Next generation terahertz electron guns producing ultrashort and ultrabright electron bunches up to relativistic energies and of ten femtoseconds (quadrillionth of a second) duration are currently in development at CFEL, according to Kärtner. “These devices will be used as photo injectors for attosecond table-top free-electron lasers to be constructed within the program AXSIS,” says Kärtner. An attosecond is a thousandth of a femtosecond. AXSIS (frontiers of Attosecond X-ray Science-Imaging and Spectroscopy) , funded by the European Research Council through an ERC Synergy Grant which also funded this work, also involves DESY scientists Prof. Henry Chapman and Dr. Ralph Aßman and Arizona State University Professor Petra Fromme.


News Article | November 22, 2016
Site: www.eurekalert.org

In a multi-national effort, an interdisciplinary team of researchers from DESY and the Massachusetts Institute of Technology (MIT) has built a new kind of electron gun that is just about the size of a matchbox. Electron guns are used in science to generate high-quality beams of electrons for the investigation of various materials, from biomolecules to superconductors. They are also the electron source for linear particle accelerators driving X-ray free-electron lasers. The team of DESY scientist Franz Kärtner, who is also a professor at University of Hamburg and continues to run a research group at MIT, where he taught till 2010 before coming to Hamburg, presents its new electron gun in the scientific journal Optica. The new device uses laser generated terahertz radiation instead of the usual radio-frequency fields to accelerate electrons from rest. As the wavelength of the terahertz radiation is much shorter than radio-frequency radiation, the device can shrink substantially. While state-of-the-art electron guns can have the size of a car, the new device measures just 34 by 24.5 by 16.8 millimetres. "Electron guns driven by terahertz radiation are miniature and efficient," explains main author Dr. W. Ronny Huang from MIT, who carried out this work at the Center for Free-Electron Laser Science CFEL in Hamburg, a cooperation of DESY, the University of Hamburg and the German Max Planck Society. "Also, the materials used to guide the radiation are susceptible to much higher fields at terahertz wavelengths as compared to radio frequency wavelengths, allowing terahertz radiation to give a much stronger 'kick' to the electrons. This has the effect of making the electron beams much brighter and shorter." Ultrashort electron beams with narrow energy spread, high charge and low jitter are essential for ultrafast electron diffraction experiments to resolve phase transitions in metals, semiconductors and molecular crystals, for example. "Our device has a nanometer thin film of copper which, when illuminated with ultraviolett light from the back, produces short bursts of electrons," describes Huang. "Laser radiation with Terahertz frequency is fed into the device which has a microstructure specifically tailored to channel the radiation to maximize its impact on the electrons." This way the device reached an accelerating power of 350 Megavolts per metre. "The accelerating field was almost twice that of current state-of-the-art guns," says Huang. "We achieved an acceleration of a dense packet of 250,000 electrons from rest to 0.5 kilo-elecronvolts (keV) with minimal energy spread. Because of this, the electron beams coming out of the device could already be used for low-energy electron diffraction experiments." In their set-up, the researchers used the large CFEL laser lab. The ultraviolet flash used to eject the electrons from the copper film is generated from the same laser as the accelerating terahertz radiation. "This ensures absolute timing synchronisation, substantially reducing jitter," explains Huang. The device worked stably over at least one billion shots, easing every-day operation. "Electron guns are used ubiquitously for making atomic-resolution movies of chemical reactions via ultrafast electron diffraction as pioneered in Prof. Dwayne Miller's group at the Max Planck Institute for the Structure and Dynamics of Matter and CFEL," says Kärtner. "With smaller and better electron guns, biologists can gain better insight to the intricate workings of macromolecular machines, including those responsible for photosynthesis. And physicists can better understand the fundamental interaction processes in complex materials." "Furthermore, electron guns are an important component of X-ray light source facilities," explains Kärtner. Next generation terahertz electron guns producing ultrashort and ultrabright electron bunches up to relativistic energies and of ten femtoseconds (quadrillionth of a second) duration are currently in development at CFEL, according to Kärtner. "These devices will be used as photo injectors for attosecond table-top free-electron lasers to be constructed within the program AXSIS," says Kärtner. An attosecond is a thousandth of a femtosecond. AXSIS (frontiers of Attosecond X-ray Science-Imaging and Spectroscopy) , funded by the European Research Council through an ERC Synergy Grant which also funded this work, also involves DESY scientists Prof. Henry Chapman and Dr. Ralph Aßman and Arizona State University Professor Petra Fromme. Deutsches Elektronen-Synchrotron DESY is the leading German accelerator centre and one of the leading in the world. DESY is a member of the Helmholtz Association and receives its funding from the German Federal Ministry of Education and Research (BMBF) (90 per cent) and the German federal states of Hamburg and Brandenburg (10 per cent). At its locations in Hamburg and Zeuthen near Berlin, DESY develops, builds and operates large particle accelerators, and uses them to investigate the structure of matter. DESY's combination of photon science and particle physics is unique in Europe.


Home > Press > Scientists shrink electron gun to matchbox size: Terahertz technology has the potential to enable new applications Abstract: In a multi-national effort, an interdisciplinary team of researchers from DESY and the Massachusetts Institute of Technology (MIT) has built a new kind of electron gun that is just about the size of a matchbox. Electron guns are used in science to generate high-quality beams of electrons for the investigation of various materials, from biomolecules to superconductors. They are also the electron source for linear particle accelerators driving X-ray free-electron lasers. The team of DESY scientist Franz Kärtner, who is also a professor at University of Hamburg and continues to run a research group at MIT, where he taught till 2010 before coming to Hamburg, presents its new electron gun in the scientific journal Optica. The new device uses laser generated terahertz radiation instead of the usual radio-frequency fields to accelerate electrons from rest. As the wavelength of the terahertz radiation is much shorter than radio-frequency radiation, the device can shrink substantially. While state-of-the-art electron guns can have the size of a car, the new device measures just 34 by 24.5 by 16.8 millimetres. "Electron guns driven by terahertz radiation are miniature and efficient," explains main author Dr. W. Ronny Huang from MIT, who carried out this work at the Center for Free-Electron Laser Science CFEL in Hamburg, a cooperation of DESY, the University of Hamburg and the German Max Planck Society. "Also, the materials used to guide the radiation are susceptible to much higher fields at terahertz wavelengths as compared to radio frequency wavelengths, allowing terahertz radiation to give a much stronger 'kick' to the electrons. This has the effect of making the electron beams much brighter and shorter." Ultrashort electron beams with narrow energy spread, high charge and low jitter are essential for ultrafast electron diffraction experiments to resolve phase transitions in metals, semiconductors and molecular crystals, for example. "Our device has a nanometer thin film of copper which, when illuminated with ultraviolett light from the back, produces short bursts of electrons," describes Huang. "Laser radiation with Terahertz frequency is fed into the device which has a microstructure specifically tailored to channel the radiation to maximize its impact on the electrons." This way the device reached an accelerating power of 350 Megavolts per metre. "The accelerating field was almost twice that of current state-of-the-art guns," says Huang. "We achieved an acceleration of a dense packet of 250,000 electrons from rest to 0.5 kilo-elecronvolts (keV) with minimal energy spread. Because of this, the electron beams coming out of the device could already be used for low-energy electron diffraction experiments." In their set-up, the researchers used the large CFEL laser lab. The ultraviolet flash used to eject the electrons from the copper film is generated from the same laser as the accelerating terahertz radiation. "This ensures absolute timing synchronisation, substantially reducing jitter," explains Huang. The device worked stably over at least one billion shots, easing every-day operation. "Electron guns are used ubiquitously for making atomic-resolution movies of chemical reactions via ultrafast electron diffraction as pioneered in Prof. Dwayne Miller's group at the Max Planck Institute for the Structure and Dynamics of Matter and CFEL," says Kärtner. "With smaller and better electron guns, biologists can gain better insight to the intricate workings of macromolecular machines, including those responsible for photosynthesis. And physicists can better understand the fundamental interaction processes in complex materials." "Furthermore, electron guns are an important component of X-ray light source facilities," explains Kärtner. Next generation terahertz electron guns producing ultrashort and ultrabright electron bunches up to relativistic energies and of ten femtoseconds (quadrillionth of a second) duration are currently in development at CFEL, according to Kärtner. "These devices will be used as photo injectors for attosecond table-top free-electron lasers to be constructed within the program AXSIS," says Kärtner. An attosecond is a thousandth of a femtosecond. AXSIS (frontiers of Attosecond X-ray Science-Imaging and Spectroscopy) , funded by the European Research Council through an ERC Synergy Grant which also funded this work, also involves DESY scientists Prof. Henry Chapman and Dr. Ralph Aßman and Arizona State University Professor Petra Fromme. About Deutsches Elektronen-Synchrotron DESY Deutsches Elektronen-Synchrotron DESY is the leading German accelerator centre and one of the leading in the world. DESY is a member of the Helmholtz Association and receives its funding from the German Federal Ministry of Education and Research (BMBF) (90 per cent) and the German federal states of Hamburg and Brandenburg (10 per cent). At its locations in Hamburg and Zeuthen near Berlin, DESY develops, builds and operates large particle accelerators, and uses them to investigate the structure of matter. DESY's combination of photon science and particle physics is unique in Europe. For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.


News Article | October 12, 2016
Site: www.nanotech-now.com

Abstract: Scientists at Moscow Institute of Physics and Technology (MIPT) and several universities in the US came up with a technology for faster structure analysis of receptor proteins, which are important for human health. An international team of scientists has learnt how to determine the spatial structure of a protein obtained with an X-ray laser using the sulfur atoms it contains. This development is the next stage in the project of a group led by Vadim Cherezov to create an effective method of studying receptor proteins. A detailed description of the study has been published in the journal Science Advances. Receptor proteins (GPCRs) allow signals to be transmitted within cells, which, in turn, enables the cells to obtain information about their environment and interact with one another. As a result, we are able to see, feel, maintain blood pressure etc., i.e. everything that is needed for the functioning of our bodies. Any disorders in the way these proteins work can result in serious consequences, such as blindness. Developing medicines to restore the normal function of receptors is not possible without a precise understanding of the way in which GPCRs operate, which, as with other proteins, is determined by their spatial structure, i.e. the way in which the protein folds. The best method of doing this is to use X-ray crystallography. For X-rays, a crystal is a three-dimensional diffraction lattice in which the radiation is scattered on the atoms. A particular problem with this method is obtaining protein crystals. In order to do this, receptor proteins have to be extracted from a cell membrane and placed in a special lipid environment. Then, by selecting the temperature and using substances to speed up the nucleation process, the protein crystallizes. One challenge with GPCRs is that they are highly mobile and dynamic molecules that frequently change their spatial structure. This means that it is difficult for them to grow large crystals that are needed for the classical diffraction procedure. This procedure involves exposing the crystal to radiation at different angles for a relatively long period of time. X-rays ionize the atoms, which destroys the protein molecules. Large crystals of a few dozen microns are what is needed to compensate for this effect. Thanks to the new experimental method of Serial Femtosecond Crystallography, it is now possible to solve this problem. The method has been developed over the past few years by an international team of scientists from Arizona State University and the University of Zurich, SLAC National Accelerator Laboratory in Stanford, the iHuman Institute at ShanghaiTech University, the Institute of Biophysics of the Chinese Academy of Sciences, the CFEL center in Hamburg, the University of Southern California and MIPT. One of the leaders of the team is Vadim Cherezov, a professor at the University of Southern California and MIPT. The method is based on the use of new generation X-ray sources - free-electron lasers. The radiation they emit is so powerful that it fully ionizes atoms in a crystal as it passes through, essentially destroying it. However, as the laser pulse has a very short duration (a few femtoseconds, 10-15 s), a diffraction pattern can be recorded before the atoms move from their position. This has meant that the scientists are able to avoid the difficulties associated with radiation damage. As the crystal is destroyed immediately, it is not possible to measure it at different orientations. To solve this problem, scientists collect and process data from several crystals. Using a special injector, the lipid environment in which the crystals are situated is exposed to an X-ray pulse. The whole process is similar to squeezing toothpaste out of a tube. The result is millions of diffraction images that need to be processed: by selecting images with crystals, finding their orientation, and then putting them together in a three-dimensional diffraction pattern. Two parameters must be known in order to decipher the structure: the amplitude and the phase of the reflected radiation. The amplitude value is measured on a detector during the experiment, however determining the phase is a complex task and there are a number of ways of solving the problem. For example, if we know of a certain protein that has a similar structure, we can use it as a first approximation. Of course, this is not possible in all cases. Another popular method is to use an effect known as anomalous scattering. This occurs when the X-ray wavelength is close to the electron transition energy in the atoms, which results in the wave being absorbed and re-emitted. This causes a change in the amplitudes and phases. If the amplitudes are measured very precisely, the differences between them can be used to reconstruct the phases. However, most of the atoms that make up proteins (carbon, oxygen and nitrogen) are not suitable for this. A relatively heavy element found in almost all proteins is sulfur, and this is the element the researchers used in their most recent study to reconstruct the phases. Special software had to be developed specifically for the task. Out of 7 million images obtained, the researchers had to pick out those with diffracted reflections. They then had to determine the orientation of the crystal and the intensity of all reflections and subsequently collate all the data obtained. 600,000 diffraction patterns were found and then used to successfully reconstruct the structure of a protein with a resolution of 2.5Å. By combining the data with the results obtained at a different X-ray wavelength, the researchers were able to increase the resolution to 1.9Å. This level of precision not only enables the structure of receptor proteins to be determined with high accuracy, but also allows scientists to see molecules of water, ions and lipids that surround them, which is extremely important for understanding how proteins function and modeling their interaction with other substances. "When I participated in a study to determine the structure of the first receptor protein, it took me about a year to obtain crystals that were large enough to conduct classical X-ray diffraction. We hope that the method we have developed will help to greatly increase the speed of this process," said Prof. Cherezov commenting on the significance of the research. Of the 800 receptor proteins that exist, we currently know the structure of only 34. The experimental method developed by the scientists will significantly speed up the studies of the remaining proteins. This, in turn, will help in developing new and effective drugs to treat a vast number of diseases. 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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, www.pnas.org/cgi/doi/10.1073/pnas.1609243114

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