Bio-EXAFS

Extended X-ray Absorption Fine Structure (EXAFS) is important to the study of biological molecules as a powerful tool for probing the atomic environment around the active metal sites in metalloprotein molecules which either elude crystallisation or yield poor crystal diffraction. EXAFS is element specific and requires tuneable X-ray energies. These macromolecular systems have low concentrations of metal elements thus EXAFSdata are acquired in fluorescence mode. The biological samples can be in any physical state: solution, amorphous as well as single crystal. Structural information around the excited metal atoms from EXAFSinclude bond distances (accuracy better than 0.1 Å for first-shell neighbouring atoms in macromolecules), coordination numbers, element identities, disorder, chemical valence state and spin state.

Kinetics:
Structure and function, catalysis and drug delivery are best studied with biological molecules in their native physical state (aqueous). Time-resolved fluorescence EXAFSon ligand binding, redox reactions and photolysis are possible by using special sample handling or solution mixing apparatus such as a stopped-flow unit. Atomic co-ordinates: 3-D refinement protocols in EXAFSanalysis, combining crystallographic data on known crystal structures, can yield refined atomic coordinates on related but unknown crystal structures.

Single crystal EXAFS:
By exploiting the interaction of crystal orientations with the polarisation of the synchrotron light, challenging analysis of heavily convoluted EXAFScontributions can be differentiated and thus made possible. This demands the highest performance instrumentation for fluorescence EXAFSand for crystallography, which are (uniquely) both available on the North West Structural Genomics Centrebeamline 10.1at the SRS.

station 16.5 station 10.1 station 9.2station 7.1