scholarly journals New opportunities in structural biology with XFEL: from sources to structures

2014 ◽  
Vol 70 (a1) ◽  
pp. C19-C19
Author(s):  
Soichi Wakatsuki
Keyword(s):  
Data Collection ◽  
Radiation Damage ◽  
Structural Biology ◽  
Single Particle ◽  
De Novo ◽  
Reconstruction Algorithm ◽  
Simultaneous Recording ◽  
Atomic Resolution ◽  
X Ray ◽  
Biology Research

X-ray free electron lasers (XFEL) have shown the promise of providing new opportunities in structural biology research with their extremely high peak brilliance and short pulses. It is reaching the stage where biologically important questions can be tackled using XFEL based on the "diffract-before-destroy" concept. The first part of this presentation will focus on macromolecular crystallography using XFEL with results obtained at LCLS so far and future scope. R&D efforts being pursued at SLAC/LCLS include new beam modes, (two-color beam for de novo phasing, wider bandwidth for SAXS/WAXS and spectroscopy), beam multiplexing, a dedicated new station for in-air data collection, next generation detectors, data analysis incorporating pulse-by-pulse spectrometer measurements and post refinement. These projects are being pursued in collaboration with many groups locally and globally with a goal to provide integrated facilities for cutting edge structural biology research. For example, two-color self-seeded XFEL mode is being developed for simultaneous recording of diffraction data at two energies in order to optimize the dispersive difference between the two wavelengths for phasing. Another area of collaborative effort is a development of dedicated station for in-air data collection with a variety of sample delivery schemes. The second part will discuss a possible roadmap towards atomic resolution single particle imaging using XFEL. Here, key questions are ·Can XFEL single particle 3D structural analysis at atomic resolution be done? ·What is the pulse characteristics required? ·Can we overcome the radiation damage at soft X-ray regime? ·What is the highest resolution attainable in comparison with cryoEM? A workshop at LCLS is being organized to discuss these questions in 4 areas: radiation damage, image reconstruction algorithm, beam modes and instrumentation, sample delivery and heterogeneity. The outcome of the workshop and follow-up discussions will be presented.

scholarly journals The future is bright-- structural biology at FELs

2014 ◽  
Vol 70 (a1) ◽  
pp. C35-C35
Author(s):  
Ilme Schlichting
Keyword(s):  
Data Collection ◽  
Radiation Damage ◽  
De Novo ◽  
Temperature Dependent ◽  
Short Pulses ◽  
High Resolution Data ◽  
X Ray ◽  
Radiation Sources ◽  
Damage Data ◽  
Theoretical Considerations

Protein crystallography using synchrotron radiation sources has had tremendous impact on biology, having yielded the structures of thousands of proteins and given detailed insight into their working mechanisms. However, the technique is limited by the requirement for macroscopic crystals, which can be difficult to obtain, as well as by the often severe radiation damage caused in diffraction experiments, in particular when using tiny crystals. To slow radiation damage, data collection is typically performed at cryogenic temperatures. With the advent of X-ray free-electron lasers (FELs) this situation appears remedied. Theoretical considerations had predicted that with sufficiently short pulses useful diffraction data can be collected before the onset of significant radiation damage that ultimately results in Coulomb explosion of the sample. This has been shown recently at the first hard X-ray FEL, the LCLS at Stanford. High resolution data collected of a stream of microcrystals of the model system lysozyme agree well with conventional data collected of a large macroscopic crystal [1] With the demonstration that de-novo phasing is feasible [2], serial femtosecond crystallography has been established as a useful tool for the analysis of tiny crystals [3] and thus the large group of proteins that resist yielding macroscopic crystals such as membrane proteins. In addition to ensure the required fast exchange of the microcrystals upon exposure, liquid jet delivery has the advantage of allowing data collection at room temperature. As demonstrated recently, this is important since structural dynamics and thus the observed conformation is often temperature dependent. Recent results will be described.

scholarly journals On the explicit use of experimental images in high resolution cryo-EM refinement

F1000Research ◽  
2019 ◽  
Vol 8 ◽  
pp. 665
Author(s):  
Jacqueline Cherfils ◽  
Jorge Navaza
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Structural Biology ◽  
Single Particle ◽  
Atomic Resolution ◽  
Full Potential ◽  
X Ray ◽  
X Ray Crystallography ◽  
Atomic Models

Single particle cryogenic electron microscopy (cryo-EM) is transforming structural biology by enabling the analysis of difficult macromolecular specimens, such as membrane proteins or large complexes with flexible elements, at near atomic resolution with an accuracy close to that of X-ray crystallography. As the technique continues to improve, it is important to assess and exploit its full potential to produce the most possible reliable atomic models. Here we propose to use the experimental images as the data for refinement and validation, instead of the reconstructed maps as currently used. This procedure, which is in spirit quite similar to that used in X-ray crystallography where the data include experimental phases, should contribute to improve the quality of the cryo-EM atomic models.

scholarly journals On the explicit use of experimental images in high resolution cryo-EM refinement

F1000Research ◽  
2019 ◽  
Vol 8 ◽  
pp. 665
Author(s):  
Jacqueline Cherfils ◽  
Jorge Navaza
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Membrane Proteins ◽  
Structural Biology ◽  
Single Particle ◽  
Atomic Resolution ◽  
Full Potential ◽  
X Ray ◽  
X Ray Crystallography

Single particle cryogenic electron microscopy (cryo-EM) is transforming structural biology by enabling the analysis of difficult macromolecular specimens, such as membrane proteins or large complexes with flexible elements, at near atomic resolution with an accuracy close to that of X-ray crystallography. As the technique continues to improve, it is important to assess and exploit its full potential to produce the most possible reliable atomic models. Here we propose to use the experimental images as the data for refinement and validation, instead of the reconstructed maps as currently used. This procedure, which is in spirit quite similar to that used in X-ray crystallography where the data include experimental phases, should contribute to improve the quality of the models.

Intensity measurements

2002 ◽  
Author(s):  
David Blow
Keyword(s):  
Data Collection ◽  
Radiation Damage ◽  
Resolution Limit ◽  
Strategic Decisions ◽  
Experimental Conditions ◽  
X Ray ◽  
Intensity Measurements ◽  
Data Collection Technique ◽  
Molecular Structure Investigation ◽  
Disordered Crystal

Once a suitable crystal has been obtained, a molecular structure investigation requires measurement of the intensities of as many Bragg reflections as possible. In this chapter, some of the options that must be decided by the experimenter will be considered, and some of the criteria used to assess the accuracy and completeness of the data will be presented. The experimenter has to make a number of strategic decisions in collecting the crystal intensity data. These include: • What X-ray source should be used? • What X-ray detector should be used? • Under what conditions should the crystal be maintained? • How long should each crystal be exposed? • What data collection technique will be used? • What resolution limit should be applied? The choice of source and detector will depend largely on what is available, but the major decision is whether to use facilities in the home laboratory or whether to use a synchrotron at a central facility. The energy released by absorption of X-rays in a crystal inevitably damages it. The process of radiation damage increases crystal disorder and reduces the intensity of scattering. The experimenter will ultimately have to abandon data collection from the damaged and disordered crystal. Under ideal experimental conditions, all the useful diffraction data can be obtained from a crystal long before radiation damage takes its toll, and radiation damage does not create a practical problem. At the other end of the scale, it may be necessary to combine the measurements from many crystals in order to obtain a complete set of diffracted intensities. There is no definite criterion to decide when a crystal is so badly damaged that it must be discarded. But if the measurements are going to be of highest quality, any observable change is bad news. The most serious effects occur in the part of the diffraction pattern at the highest observed resolution, where the observed intensities of the Bragg reflections will be altered most rapidly. The first observable effect of radiation damage is usually a reduction of high angle intensities due to increased disorder.

Uncovering the structures of modular polyketide synthases

2015 ◽  
Vol 32 (3) ◽  
pp. 436-453 ◽  
Author(s):  
Kira J. Weissman
Keyword(s):  
Electron Microscopy ◽  
Structural Biology ◽  
Structural Characterization ◽  
Small Angle ◽  
Single Particle ◽  
Polyketide Synthases ◽  
X Ray ◽  
X Ray Scattering ◽  
Cryo Electron Microscopy

This review covers a breakthrough in the structural biology of the gigantic modular polyketide synthases (PKS): the structural characterization of intact modules by single-particle cryo-electron microscopy and small-angle X-ray scattering.

RADDOSE-3D: time- and space-resolved modelling of dose in macromolecular crystallography

2013 ◽  
Vol 46 (4) ◽  
pp. 1225-1230 ◽  
Author(s):  
Oliver B. Zeldin ◽  
Markus Gerstel ◽  
Elspeth F. Garman
Keyword(s):  
Data Collection ◽  
Radiation Damage ◽  
Diffraction Experiment ◽  
Macromolecular Crystallography ◽  
X Ray Diffraction ◽  
Time Resolved ◽  
X Ray ◽  
Online Methods ◽  
Crystal Volume ◽  
Number Of Iterations

RADDOSE-3D allows the macroscopic modelling of an X-ray diffraction experiment for the purpose of better predicting radiation-damage progression. The distribution of dose within the crystal volume is calculated for a number of iterations in small angular steps across one or more data collection wedges, providing a time-resolved picture of the dose state of the crystal. The code is highly modular so that future contributions from the community can be easily integrated into it, in particular to incorporate online methods for determining the shape of macromolecular crystals and better protocols for imaging real experimental X-ray beam profiles.

scholarly journals Identifying, studying and making good use of macromolecular crystals

2014 ◽  
Vol 70 (8) ◽  
pp. 993-1008 ◽  
Author(s):  
Guillermo Calero ◽  
Aina E. Cohen ◽  
Joseph R. Luft ◽  
Janet Newman ◽  
Edward H. Snell
Keyword(s):  
Data Collection ◽  
Visible Light ◽  
Structural Biology ◽  
Protein Structures ◽  
Data Bank ◽  
Potential Outcomes ◽  
Structural Knowledge ◽  
X Ray ◽  
X Ray Crystallography ◽  
Molecular Scale

Structural biology has contributed tremendous knowledge to the understanding of life on the molecular scale. The Protein Data Bank, a depository of this structural knowledge, currently contains over 100 000 protein structures, with the majority stemming from X-ray crystallography. As the name might suggest, crystallography requires crystals. As detectors become more sensitive and X-ray sources more intense, the notion of a crystal is gradually changing from one large enough to embellish expensive jewellery to objects that have external dimensions of the order of the wavelength of visible light. Identifying these crystals is a prerequisite to their study. This paper discusses developments in identifying these crystals during crystallization screening and distinguishing them from other potential outcomes. The practical aspects of ensuring that once a crystal is identified it can then be positioned in the X-ray beam for data collection are also addressed.

scholarly journals Advancing Native-SAD Phasing at Synchrotron with 13 Real-life Case Studies

2014 ◽  
Vol 70 (a1) ◽  
pp. C601-C601
Author(s):  
Meitian Wang
Keyword(s):  
Data Collection ◽  
Single Crystal ◽  
Measurement Errors ◽  
Model Building ◽  
De Novo ◽  
Real Life ◽  
Data Sets ◽  
X Ray ◽  
Recent Developments ◽  
Sad Phasing

The key step in elucidating de novo 3D X-ray structures relies on the incorporation of heavy elements into proteins or crystals. Selenomethionine incorporation or heavy metal derivatization are however not always possible and require additional efforts. Exploiting anomalous signals from intrinsically present elements like S, P, and Ca2+ from proteins and nucleic acids, as well as Cl-, SO42-, and PO42- from crystallization solutions, is therefore an appealing alternative. Such a method has been shown to be valid by collecting data from several crystals and combining them(1). Recent developments at macromolecular crystallography beamlines are however pushing the limits of what could be obtained out of a single crystal. Here we introduce a novel data collection routine for native-SAD phasing, which distributes tolerable X-ray life-doses to very high multiplicity X-ray diffraction data sets measured at 6 keV energy and at different crystal orientations on a single crystal. This allows the extraction of weak anomalous signals reliably by reducing both systematic and random measurement errors. The data collection method has been applied successfully to thirteen real-life examples including membrane proteins, a protein/DNA complex, and a large protein complex. In addition to de novo structure determination, we advocate such a data collection protocol for molecular replacement solvable structures where unbiased phase information is crucial in objective map interpretation and model building, especially for medium and low-resolution cases.

scholarly journals Energy optimization of a regular macromolecular crystallography beamline for ultra-high-resolution crystallography

2015 ◽  
Vol 22 (1) ◽  
pp. 172-174 ◽  
Author(s):  
Gerd Rosenbaum ◽  
Stephan L. Ginell ◽  
Julian C.-H. Chen
Keyword(s):  
High Resolution ◽  
Data Collection ◽  
Structural Biology ◽  
Practical Method ◽  
Accurate Data ◽  
Macromolecular Crystallography ◽  
X Ray ◽  
Standard Operating ◽  
Photon Source ◽  
Synchrotron Beamlines

A practical method for operating existing undulator synchrotron beamlines at photon energies considerably higher than their standard operating range is described and applied at beamline 19-ID of the Structural Biology Center at the Advanced Photon Source enabling operation at 30 keV. Adjustments to the undulator spectrum were critical to enhance the 30 keV flux while reducing the lower- and higher-energy harmonic contamination. A Pd-coated mirror and Al attenuators acted as effective low- and high-bandpass filters. The resulting flux at 30 keV, although significantly lower than with X-ray optics designed and optimized for this energy, allowed for accurate data collection on crystals of the small protein crambin to 0.38 Å resolution.

scholarly journals Synchrotron microcrystal native-SAD phasing at a low energy

IUCrJ ◽  
2019 ◽  
Vol 6 (4) ◽  
pp. 532-542 ◽  
Author(s):  
Gongrui Guo ◽  
Ping Zhu ◽  
Martin R. Fuchs ◽  
Wuxian Shi ◽  
Babak Andi ◽  
...  
Keyword(s):  
Data Analysis ◽  
Data Collection ◽  
Diffraction Data ◽  
De Novo ◽  
Low Energy ◽  
Anomalous Scattering ◽  
Free Electron Lasers ◽  
X Ray ◽  
Structural Evaluation ◽  
Sad Phasing

De novo structural evaluation of native biomolecules from single-wavelength anomalous diffraction (SAD) is a challenge because of the weakness of the anomalous scattering. The anomalous scattering from relevant native elements – primarily sulfur in proteins and phosphorus in nucleic acids – increases as the X-ray energy decreases toward their K-edge transitions. Thus, measurements at a lowered X-ray energy are promising for making native SAD routine and robust. For microcrystals with sizes less than 10 µm, native-SAD phasing at synchrotron microdiffraction beamlines is even more challenging because of difficulties in sample manipulation, diffraction data collection and data analysis. Native-SAD analysis from microcrystals by using X-ray free-electron lasers has been demonstrated but has required use of thousands of thousands of microcrystals to achieve the necessary accuracy. Here it is shown that by exploitation of anomalous microdiffraction signals obtained at 5 keV, by the use of polyimide wellmounts, and by an iterative crystal and frame-rejection method, microcrystal native-SAD phasing is possible from as few as about 1 200 crystals. Our results show the utility of low-energy native-SAD phasing with microcrystals at synchrotron microdiffraction beamlines.

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