Correlative cryo-fluorescent and electron microscopy for biological applications.

Chemical fixation is a standard procedure used in preparation for optical microscopy of biological samples. Unfortunately, chemical fixation produces various artefacts and may destroy cellular ultrastructure. Cryo-fixation offers an alternative way of preserving a sample in a life-like state. While cryo-fixation poses challenges for subsequent imaging, it also allows for different imaging modalities. The photo-physical properties of fluorescent labels can be very different at low temperature, so the combination of fluorescent labels and light imaging methodology needs to be reevaluated.~ Furthermore, good ultrastructure preservation allows for subsequent high-quality electron microscopy imaging, thus permitting correlated optical and electron microscopy imaging. We will describe the instruments and methods we developed for preparation and imaging of cultured cells using cryo-fluorescent and electron microscopy.