Practice question

X-ray diffraction requires coherent amplification of scattering from many molecules arranged identically. This condition is satisfied only by crystalline state where molecules occupy periodic lattice positions with long-range order. Solution-phase molecules randomly orient, canceling coherent interference, gases have too low scattering density, gels lack periodic repetition. Proteins are crystallized using vapor diffusion with precipitants like polyethylene glycol and salts, growing ordered lattices several hundred micrometers in size. These crystals, despite high solvent content, provide repeating unit cells essential for collecting high-quality diffraction patterns and solving three-dimensional structures.