Summary of lecture at biophysics and structural biology at synchrotrons workshop Crystallography 101: diffraction theory and space groups
- 37 Downloads
To determine the three-dimensional structures of proteins, we need to ‘look’ at them using electromagnetic radiation which has a similar wavelength to the interatomic distances in the molecule. These are typically around 1.5 × 10−10 m (= 0.15 nm =1.5 Å) but visible light has wavelengths between 400 and 700 nm which is far too long to enable us to visualise the detailed structures of proteins and viruses. We thus usually use X-rays, neutrons or electrons of much shorter wavelength: for X-rays between 0.7 and 1.7 Å which are ideal for this. However, unlike in a light microscope, we do not have any lenses that can form an image from X-rays scattering from such small objects. We have to rely on the interference patterns (so-called ‘diffraction’) formed between the X-rays as they scatter elastically (no energy loss in the sample) from crystals of the macromolecule. We then deconvolute these patterns using the tools of Mathematics (Fourier transforms) and some extra information...
This is a very short summary of a 2.5-h lecture which has evolved over many years of teaching crystallography. It contains input from Martin Noble and Airlie McCoy, and I am very grateful to both of them for continued discussions on improving our teaching of these topics, which are conceptually challenging.
The funding for the Workshop came from the GCRF START (Synchrotron Techniques for African Research and Technology), IUPAB and the SA National Research Foundation (NRF).
Compliance with ethical standards
Conflict of interest
Elspeth F. Garman declares that she has no conflict of interest.
This article does not contain any studies with human participants or animals performed by the author.