ETFIG 1: Philips Technai 20 transmission electron microscope is used for electron tomography.

This microscope (available from FEI, Portland, OR) has an excellent tilting goniometer to control views of the sample at many angles, and a bottom-mounted digital camera for data collection. The microscope can be programmed to collect images for many hours automatically, achieving the correct focus, magnification, tilt, and image framing on its own, and by comparison to previously collected images.

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