Isolated mitochondria that have been quick-frozen, fractured and deep-etched show some space between the inner and outer membranes. Arcs of tubules, where they are tangentially fractured, show the helically arrayed zipper on the outer margin of the curved tubular cristae. A pair of particles can be seen on the cross-fractured tubules. These may be bound to transmembrane subunits. Such complexes are thought to represent the F1F0 synthases. TEM taken on 5/11/88 by C. Schroeder with Zeiss 10A operating at 80kV. Neg. 40,500X. The raw negative was scanned with an Epson Perfection V750 Pro and this high resolution image is best used for quantitative analysis. Additional information available at (http://www5.pbrc.hawaii.edu/allen/). Published in J. Cell Biol. 108:2233-2240, 1989. Adapted with permission.