IsoSTED microscopy

IsoSTED microscopy is a clever combination of STED and 4Pi microscopy and reduces the (cigar-shaped) confocal volume to a sphere of only 30 nm diameter. This corresponds to a reduction of the focal volume by three orders of magnitude [Schmidt et al., 2009].
The coherent use of two opposing objective lenses (4Pi-configuration) renders an almost isotropic resolution in all three spatial dimensions.

	Comparison of the confocal focus (left) and the spherical isoSTED focus (right). (Image: Schmidt & Egner / MPIbpc)

This “3D-nanosope” was the first light microscope to unravel the interior of mitochondria (the cellular power plants) in intact cells [Schmidt et al., 2008]. Therefore it was possible to image the distribution of two proteins, one forming clusters on the mitochondrial membrane, the other being distributed in the interior of the organelle, with unprecedented resolution.
		Distribution of proteins Tom20 (red) and mtHsp70 (green) in mitochondria. (Image: Schmidt & Egner / MPIbpc)

Further information:

Schmidt, R., C. A. Wurm, S. Jakobs, J. Engelhardt, A. Egner, S. W. Hell (2008):
"Spherical nanosized focal spot unravels the interior of cells"
Nature Meth. 5 (6), 539 - 544

Schmidt, R., C. A. Wurm, A. Punge, A. Egner, S. Jakobs, S. W. Hell (2009):
"Mitochondrial Cristae Revealed with Focused Light"
Nano Lett. 9 (6), 2508-2510

Hell, S. W., R. Schmidt, A. Egner (2009):
"Diffraction-unlimited three-dimensional optical nanoscopy with opposing lenses"
Nature Photonics 3, 381 - 387