and neurofilaments in the neuronal cytoskeleton: quick-freeze, deep-etch immunoelectron microscopy and reconstitution studies”
N Hirokawa et al. Journal of Neuroscience, 8:6, 2769–2779 (1988).
Deep-etch image of cytoskeleton, with origami inset (upper left)
N Morone et al. JCB, 174:6, 851–862 (2006).
PWK Rothemund,Nature, 440:297–302 (2006). [pdf]
In an earlier post I mentioned that researchers have been hampered by difficulties with imaging 3D DNA nanostructures (a technology pioneered by Nadrian Seeman). Faster progress in this area would be valuable, since structural DNA nanotechnology looks like an excellent way to organize complex, atomically precise components in composite nanosystems. I asked Paul Rothemund about current applications of electron microscopy in SDN, but the examples he knew of involved structures stained and flattened on surfaces.
The images posted here show the results of a very different technique: quick-freezing a sample, then letting a layer of the water leave by sublimation, thereby exposing macromolecular structures which are then coated with metal (with further processing [pdf]). As you can see in the images here, electron microscopy then shows 3D nanoscale structures. Note that these are thickened by the metal, like twigs coated with sticky snow, and so the finest filaments visible in the images represent structures that are even slimmer. (The pdf I just cited says that “Typical resolutions are 2 nm for platinum/carbon and 0.6 nm for tantalum/tungsten.”) [Updated]
As the inset origami AFM image suggests, the “quick-freeze, deep-etch” technique would give a relatively coarse image, yet would offer enough resolution to provide useful information about objects of this size — information that could enable a designer to recognize failures, and perhaps gain enough confidence about an apparent success to take a few more steps before pausing to collect more detailed information.
If this has already been tried, I’d like to hear about the results, but if not, is it likely to work? The technique exposes and images biomolecular structures that are on the same scale as some of the recent SDN structures, and made of reasonably similar materials, so it seems likely. If you have a friend who does electron microscopy, you might suggest trying this technique on some SDN samples. I expect that researchers would be glad to offer them.
About the previous post: the comment-giveaway thread will close soon, as scheduled. I’ll be away for a few days, so the drawing may be later in the week.
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http://www.zsgenetics.com/
may be of interest. Their goal is to use terahertz waves to directly read DNA sequence. As I understand it, the imaging works just fine, but the DNA won’t sit still for the photo shoot.
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