Correlative Fluorescence Microscopy
A key advantage of X-ray microscopy is that it is relatively straightforward to combine it with fluorescence imaging of the same specimen. This can either be done by first performing fluorescence imaging of the specimen on a fluorescence microscope, then noting the position of the specimen of interest on the X-ray microscopy grid, and then transferring the sample to the X-ray microscope and finding the same position on the grid. Alternatively, many X-ray microscopes have built in fluorescence microscopes that allow imaging of the specimen by both X-ray and fluorescence all in the same cryo chamber.
Shown below are images of a cell infected with Herpes virus (from Kai Grünewald’s lab). Inverted X-ray contrast is used, such that the viral particles are white. On the right is the same cell but imaged in the same cryo chamber with fluorescence to detect a GFP-tagged viral protein. The asterisk indicates one of many regions where viral particles in X-ray correlate with the GFP fluorescence. Note also that red fluorescent beads can also be correlated. Scale bar = 2 um.