05 - xray1

05 - xray1 - X-ray crystallography What is in a Crystal?...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
What is in a Crystal? The same number of molecules is found in (almost) all unit cells. A molecule can crystallise in different forms. Different crystal forms may have different numbers of molecules in their unit cells. Billions of small identical three- dimensional units “Unit Cells” packed against each other. The Unit Cell may contain one or more molecules. X-ray crystallography A Pseudo-Crystal Two-dimensional “unit-cells” each containing two “molecules” packed against each other in a regular form. The two-fold symmetry in the unit cell is also common in proteins. A unit cell with two alanines Three-dimensional objects in three-dimensional unit cells packed in a three-dimensional lattice. Note two-fold symmetry. Crystals Are Mostly Solvent There may be channels through the crystal. Each molecule will be surrounded by solvent. Enzymes have been shown to be active in the crystal form. The crystal form (usually) represents a biologically relevant structure.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Making a Crystal – Hanging Drop Need a pure and homogeneous protein sample (>97%). A drop of protein solution in a buffer with a precipitant is brought slowly to supersaturation by loss of water to reservoir. Equilibrium between the reservoir and drop is reached by diffusion.
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 6

05 - xray1 - X-ray crystallography What is in a Crystal?...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online