Using a TEM Electron Energy Loss Spectrometer to Eliminate Offensive Carbon “halos” from Platinum Replicas of Quick-Frozen, Deep-Etched Biological Samples

A significant improvement in image quality can be achieved, when imaging deepetch replicas via TEM, by using an electron energy loss spectrometer in a rather unorthodox manner. Microscopes equipped with true imaging spectrometers, such as the Zeiss EM 902, permit the viewer to subtract the offensive carbon “background halo” which is characteristic of all deep-etch replicas. Heretofore, this “halo” has been an unavoidable consequence of the need to “back” or physically support the otherwise extremely delicate platinum replica. In fact, much thicker carbon supports would be desirable, since fragmentation of platinum replicas during their cleaning represents the single greatest impediment to successful use of the deep-etch technique. Until now, such thick carbon has created hopeless “halos” and excessive blurring of replicas in the TEM. Amazingly, such imaging problems can be circumvented, regardless of the thickness of the carbon “backing”, by “dialing out” the carbon signal from the TEM image!