X-Ray Crystallography in Biology
An experimental biophysical technique determining the 3D atomic structure of biological macromolecules from X-ray diffraction patterns of crystallized proteins or nucleic acids.
Governing formula
n λ = 2 d sin θ (Bragg's Law for Macromolecules)
SI unit
Å or nm (Structural Resolution)
In depth
High-energy X-rays scatter off macromolecular crystal electron clouds. Analyzing diffracted beam intensities and solving the phase problem calculates electron density maps to resolve 3D protein structures.
Examples in the real world
Rosalind Franklin's 'Photo 51' X-ray diffraction image enabling Watson and Crick to discover the DNA double helix structure.