Book contents
- Frontmatter
- Contents
- Preface
- Acknowledgements
- A note on units
- 1 Introduction
- 2 Fundamentals of macromolecular crystallography
- 3 Fundamentals of macromolecular structure
- 4 Sources and properties of SR
- 5 SR instrumentation
- 6 Monochromatic data collection
- 7 The synchrotron Laue method
- 8 Diffuse X-ray scattering from macromolecular crystals
- 9 Variable wavelength anomalous dispersion methods and applications
- 10 More applications
- 11 Conclusions and future possibilities
- Appendix 1 Summary of various monochromatic diffraction geometries
- Appendix 2 Conventional X-ray sources
- Appendix 3 Fundamental data
- Appendix 4 Extended X-ray absorption fine structure (EXAFS)
- Appendix 5 Synchrotron X-radiation laboratories: addresses and contact names (given in alphabetical order of country)
- Bibliography
- References
- Glossary
- Index
2 - Fundamentals of macromolecular crystallography
Published online by Cambridge University Press: 23 November 2009
- Frontmatter
- Contents
- Preface
- Acknowledgements
- A note on units
- 1 Introduction
- 2 Fundamentals of macromolecular crystallography
- 3 Fundamentals of macromolecular structure
- 4 Sources and properties of SR
- 5 SR instrumentation
- 6 Monochromatic data collection
- 7 The synchrotron Laue method
- 8 Diffuse X-ray scattering from macromolecular crystals
- 9 Variable wavelength anomalous dispersion methods and applications
- 10 More applications
- 11 Conclusions and future possibilities
- Appendix 1 Summary of various monochromatic diffraction geometries
- Appendix 2 Conventional X-ray sources
- Appendix 3 Fundamental data
- Appendix 4 Extended X-ray absorption fine structure (EXAFS)
- Appendix 5 Synchrotron X-radiation laboratories: addresses and contact names (given in alphabetical order of country)
- Bibliography
- References
- Glossary
- Index
Summary
X-rays are used to probe the atomic or molecular structure of matter because the wavelength of the radiation is of approximately the same dimension as an atom. Similarly longer wavelength visible light is appropriate for studying larger structures, e.g. cell organelles. However, since there is no known X-ray lens the equivalent function of a glass lens for visible light in a conventional microscope has to be performed by computational transformation of X-ray diffraction patterns.
The basic steps in a macromolecular crystal structure analysis involve:
(i) crystallisation;
(ii) space group and cell parameter determination;
(iii) data collection;
(iv) phase determination;
(v) electron density map interpretation;
(vi) refinement of the molecular model.
Figure 2.1 (a)—(f) illustrates some of these steps showing, as an example, the structure determination of human erythrocyte purine nucleoside phosphorylase (PNP) (Ealick et al (1990)). A list of general texts on crystallography is given in the bibliography, section 1.
CRYSTALLISATION, CRYSTALS AND CRYSTAL PERFECTION, SYMMETRY
Crystallisation is a process involving precipitation of the dissolved protein from solution. This is achieved by decreasing the protein solubility, decreasing any repulsive forces between individual protein molecules and/or increasing the attractive forces. The crystals that might be produced need to be of ‘X-ray diffraction quality’.
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- Publisher: Cambridge University PressPrint publication year: 1992