X-ray radiation is superior for the structure investigation of macromolecules,
e.g. proteins, nucleic acids, carbohydrates, polymers and complex materials
in solution and, if available, in the crystallinic state. The X-ray photons
interact mainly with the electrons of the sample, which are mostly contributed
by carbon, oxygen, nitrogen, sulfur etc.. Thus the hydrogen atoms contribute
only scarcely to the signal X-ray, in contrast to neutron
scattering. Generally X-ray photons are required in structural biology
and polymer science for:
1. structure estimation of crystallized proteins with a monochromatic
beam (X-ray diffraction); atomar resolution (0.1-0.3 nm); static
2. structure investigation of protein or polymer solutions with
1 nm resolution by X-ray small angle scattering (SAXS); resolution 1 nm,
static comparing
3. estimation of molecular motion in protein or polymer solutions
by time-resolved X-ray small angle scattering (TR-SAXS); resolution 1 nm;
dynamic
4. structure estimation of crystallized small proteins with a
polychromatic beam (Laue diffraction); atomar resolution (0.1-0.3 nm);
static
5. estimation of molecular motion in crystals of small proteins
by time-resolved polychromatic beam diffraction (TR-Laue diffraction);
atomar resolution (0.1-0.3 nm); dynamic
6. precise estimation of ligand distances and motion in metal
proteins and complexes by X-ray absorption spectroscopy (EXAFS, TR-EXAFS);
subatomar resolution (0.001 nm); range 0.5 nm; static or dynamic
7. estimation of the distribution of special elements (metals,
sulfur, phosphorus, halogens) in proteins by energy dependent (anomalous)
X-ray scattering and diffraction (ASAXS, TR-ASAXS, MAD)
