Abstract: The direct method was applied to the image processing for [001] simulated high-r esolution electron microscope images of protein streptavidin.The image deconvolu tion was carried out for two images of different defocus values such that the st ructural information loss due to the zero crosses of contrast transfer function could be compensated.It is shown that the determined defocus values based on two images combined are closer to the true ones than those based on a single image. The phase extension was also carried out for this protein.The initial structure factors were calculated from the theoretical structure model,with the phases of 0.30nm resolution and amplitudes of 0.25nm resolution.Both the deconvoluted imag e of 0.30nm resolution and projected crystal structure of 0.25nm resolution obta ined are in agreement with the projected potential distribution maps of theoreti cal structure model.

Keywords: 
• high-resolution electron microscopy /
• direct method /
• image processing