Flashcards in Lecture 8 - RH Deck (14):
What are the ways of examining 3D structures of proteins?
Nuclear Magnetic Resonance Imaging
Solution scattering (laser, X-ray and neutron)
Circular Dichroism (CD)
Homology modeling and ligand fitting
What limits NMR?
Size of the molecule must be small
How does solution scattering work?
Laser, X-ray and neutron beam are shined through a protein structure and the scattering pattern can be measured
What is Circular Dichroism useful for?
Finding the secondary structures in a solution
How does X-ray crystallography work?
Electron clouds weakly diffract X-rays in a way that is proportional to the number or density of electrons. Position of atoms are determined by interpretting the diffraction pattern.
What is required for crystallisation to occur?
How are crystals generated in the lab?
Crystals form when protein solution is slowly dehydrated (water is removed) under controlled conditions that favour the production of ordered crystal lattices rather than disordered aggregates
How are crystals of high throughput produced?
Via the use of multi-well plates
What kind of crystals are used for X-ray crystallography?
Large single crystals
Rotate plane polarised light (Rainbow structures should show)
Have few if any growth defects
What are some common growth defects with crystals?
Twins are formed when 2 crystal lattices intersect making it difficult to collect X-ray data relating to a single lattice
Cusps or clefts in crystals occur when protein solution is depleted locally in a droplet
Crystalline aggregates are when multiple crystals form as clusters
What are the 7 crystal classes found in nature?
Are lattices completely occupied by molecules?
Yes, solvent occupies the gaps between proteins.
How are crystals prepared for X-ray diffraction experiments?
Single crystals are isolated from drops and mounted into a capillary or nylon loop.
Capillaries are used for X-ray diffraction at ambient temperatures
Nylon loops are used for X-ray diffraction at low temperatures by cooling with N2 or He