Protein structures determined by electron crystallography Electron crystallography

electron microscopy image of inorganic tantalum oxide, fourier transform, inset. notice how appearance changes upper thin region thicker lower region. unit cell of compound 15 25 Ångström. outlined @ centre of figure, inside result image processing, symmetry has been taken account. black dots show tantalum atoms. diffraction extends 6 orders along 15 Å direction , 10 orders in perpendicular direction. resolution of em image 2.5 Å (15/6 or 25/10). calculated fourier transform contain both amplitudes (as seen) , phases (not displayed).



electron diffraction pattern of same crystal of inorganic tantalum oxide shown above. notice there many more diffraction spots here in diffractogram calculated em image above. diffraction extends 12 orders along 15 Å direction , 20 orders in perpendicular direction. resolution of ed pattern 1.25 Å (15/12 or 25/20). ed patterns not contain phase information, clear differences between intensities of diffraction spots can used in crystal structure determination.