X-Ray   Crystallography

 

 

1. Image Formation

 

       Resolution  /  Wavelength (Amplitude, Phase) /  Light Microscopy / EM /  X-ray /  NMR

 

2. X-Ray Crystallography

 

            a) Crystal Growth –  Materials  / Methods

                        Batch / Hanging Drop / Standing Drop / Dialysis

            b) Crystal Lattices - Lattice Constants / Space Groups

                        Role of symmetry

            c) X-ray Sources – Sealed Tube / Rotation Anode / Synchrotron

                        Relative flux / advantages of tunable sources

            d)Theory of Diffraction – Bragg’s Law / Reciprocal Space

                        Bragg Equation -   nλ= 2 d sin(θ)

                        Real Space Lattice/cell  vs. Reciprocal Space Lattice / cell

            e) Data Collection – Methods / Detectors / Structure Factors

                        Observed SF from Intensities:      F(hkl) = SQRT [cI(hkl)]

 

                        Calculated Structure Factors –

 

 

 

 

 


            f) Structure Solution – Phase Problem: MIR / MR / MAD

                        Electron Density and Structure Factors

 

 

 

 

 


                        (MIR) = Multiple Isomorphous Replacement (Heavy Atom Method)

                        (MR) = Molecular Replacement ( Rotation and Translation of Model Structure)

                        (MAD) = Multi-Wavelength Anomolous Dispersion Methods – absorption edge

            h) Refinements and Models

                        Least-squares + Energy Refinement (restraints)

            i) Analysis and presentation of results

            Visualization programs (Cn3D / RasMol / SwissPDBV / etc)

                        SCOP – Structural Classification of Proteins

                        CATH – Classification / Arch / Topology