One of the main assumptions in protein X-ray crystallography is,that proteins (for that matter all other biological macromoleculesas well) in their crystalline state have folding topologiesidentical to those of the proteins in solutions or in their naturalcellular environment. Several lines of evidence support thisnotion. Which one of the following is the most compelling to you?(Rate A trough F from most to less compelling and give yourreasoning.
A) Except in some isolated cases, the structures of the sameprotein determined by X-ray crystallography and NMR methods aresimilar.
B) A crystalline protein can be essentially considered as insolution, because the solvent molecules, e.g. hydration water andsolutes co-crystallize with the protein.
C) Proteins are generally resistant against unwanted sideeffects when subjected to the X-ray irradiation; therefore theymaintain their overall physical state.
D) Enzymes usually retain their catalytic activity in thecrystalline state.
E) Electron density maps can be obtained at high, atomicresolution and assigned with high accuracy.
