The crystal of NaCl having 2500 unit cells can diffract X-rays. X-rays are diffracted through atoms from their electrons. Why not then diffraction from a protein molecule?
It is not yet possible but when the X-ray laser beam will be operative at DESY then it would be possible to measure the X-ray scattering from a single protein molecule. You must note that the scattering from a 2500 unit cell of NaCl crystal will be concentrated on a relatively small number of diffraction peaks whereas the scattering from a similar volume protein molecule will be spread out in the reciprocal space rather than concentrated in a small number of spots and therefore measurement will be more difficult due to smaller peak/signal ratio. In case of NaCl crystal peak/background ratio will be much larger. If you have X-ray laser beam of high intensity then you can do coherent diffraction from a single protein molecule and you will also have phase information. Then you can solve the molecular structure by inverse Fourier transforming. You will of course destroy the molecule but the the diffraction pattern will be recorded before the destruction of the protein molecule. Well this will be a future technology and we as yet do not know all the technical difficulties that will arise. But they will be solved eventually. The X-ray laser beam has already been produced by the wavelength is still far too large.
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