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Protein Crystallography

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Cover of 'Protein Crystallography'

Table of Contents

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    Book Overview
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    Chapter 1 Expression and Purification of Recombinant Proteins in Escherichia coli with a His6 or Dual His6-MBP Tag
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    Chapter 2 Protein Crystallization
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    Chapter 3 Advanced Methods of Protein Crystallization
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    Chapter 4 The “Sticky Patch” Model of Crystallization and Modification of Proteins for Enhanced Crystallizability
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    Chapter 5 Crystallization of Membrane Proteins: An Overview
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    Chapter 6 Locating and Visualizing Crystals for X-Ray Diffraction Experiments
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    Chapter 7 Collection of X-Ray Diffraction Data from Macromolecular Crystals
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    Chapter 8 Identifying and Overcoming Crystal Pathologies: Disorder and Twinning
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    Chapter 9 Applications of X-Ray Micro-Beam for Data Collection
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    Chapter 10 Serial Synchrotron X-Ray Crystallography (SSX)
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    Chapter 11 Time-Resolved Macromolecular Crystallography at Modern X-Ray Sources
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    Chapter 12 Structure Determination Using X-Ray Free-Electron Laser Pulses
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    Chapter 13 Processing of XFEL Data
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    Chapter 14 Many Ways to Derivatize Macromolecules and Their Crystals for Phasing
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    Chapter 15 Experimental Phasing: Substructure Solution and Density Modification as Implemented in SHELX
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    Chapter 16 Contemporary Use of Anomalous Diffraction in Biomolecular Structure Analysis
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    Chapter 17 Long-Wavelength X-Ray Diffraction and Its Applications in Macromolecular Crystallography
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    Chapter 18 Acknowledging Errors: Advanced Molecular Replacement with Phaser
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    Chapter 19 Rosetta Structure Prediction as a Tool for Solving Difficult Molecular Replacement Problems
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    Chapter 20 Radiation Damage in Macromolecular Crystallography
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    Chapter 21 Boxes of Model Building and Visualization
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    Chapter 22 Structure Refinement at Atomic Resolution
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    Chapter 23 Low Resolution Refinement of Atomic Models Against Crystallographic Data
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    Chapter 24 Stereochemistry and Validation of Macromolecular Structures
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    Chapter 25 Validation of Protein–Ligand Crystal Structure Models: Small Molecule and Peptide Ligands
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    Chapter 26 Protein Data Bank (PDB): The Single Global Macromolecular Structure Archive
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    Chapter 27 Databases, Repositories, and Other Data Resources in Structural Biology
Attention for Chapter 23: Low Resolution Refinement of Atomic Models Against Crystallographic Data
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Chapter title
Low Resolution Refinement of Atomic Models Against Crystallographic Data
Chapter number 23
Book title
Protein Crystallography
Published in
Methods in molecular biology, January 2017
DOI 10.1007/978-1-4939-7000-1_23
Pubmed ID
Book ISBNs
978-1-4939-6998-2, 978-1-4939-7000-1
Authors

Robert A. Nicholls, Oleg Kovalevskiy, Garib N. Murshudov

Editors

Alexander Wlodawer, Zbigniew Dauter, Mariusz Jaskolski

Abstract

This review describes some of the problems encountered during low-resolution refinement and map calculation. Refinement is considered as an application of Bayes' theorem, allowing combination of information from various sources including crystallographic experimental data and prior chemical and structural knowledge. The sources of prior knowledge relevant to macromolecules include basic chemical information such as bonds and angles, structural information from reference models of known homologs, knowledge about secondary structures, hydrogen bonding patterns, and similarity of non-crystallographically related copies of a molecule. Additionally, prior information encapsulating local conformational conservation is exploited, keeping local interatomic distances similar to those in the starting atomic model. The importance of designing an accurate likelihood function-the only link between model parameters and observed data-is emphasized. The review also reemphasizes the importance of phases, and describes how the use of raw observed amplitudes could give a better correlation between the calculated and "true" maps. It is shown that very noisy or absent observations can be replaced by calculated structure factors, weighted according to the accuracy of the atomic model. This approach helps to smoothen the map. However, such replacement should be used sparingly, as the bias toward errors in the model could be too much to avoid. It is in general recommended that, whenever a new map is calculated, map quality should be judged by inspection of the parts of the map where there is no atomic model. It is also noted that it is advisable to work with multiple blurred and sharpened maps, as different parts of a crystal may exhibit different degrees of mobility. Doing so can allow accurate building of atomic models, accounting for overall shape as well as finer structural details. Some of the results described in this review have been implemented in the programs REFMAC5, ProSMART and LORESTR, which are available as part of the CCP4 software suite.

Mendeley readers

The data shown below were compiled from readership statistics for 9 Mendeley readers of this research output. Click here to see the associated Mendeley record.

Geographical breakdown

Country Count As %
Unknown 9 100%

Demographic breakdown

Readers by professional status Count As %
Researcher 4 44%
Student > Bachelor 1 11%
Student > Ph. D. Student 1 11%
Professor 1 11%
Student > Postgraduate 1 11%
Other 0 0%
Unknown 1 11%
Readers by discipline Count As %
Biochemistry, Genetics and Molecular Biology 3 33%
Chemistry 2 22%
Physics and Astronomy 1 11%
Medicine and Dentistry 1 11%
Unknown 2 22%