Preservation of Photoreceptor Nanostructure for Electron Tomography Using Transcardiac Perfusion Followed by High-Pressure Freezing and Freeze-Substitution.

The phototransductive membrane disks of a vertebrate photoreceptor outer segment (OS) are highly susceptible to perturbations during preservation for electron microscopy. To optimize their preservation for nanostructural studies, such as with electron tomography (ET), we developed a protocol, using a combination of chemical and physical fixation approaches, including transcardiac perfusion, high-pressure freezing, and freeze-substitution.