April 25, 2011

Sometimes you read a sentence in a paper and it feels like Babe Ruth’s “called shot” in the 1932 World Series. There’s my favorite line from Watson and Crick’s 1953 Nature paper describing the DNA double helix:

It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material.

While reading a recent paper on a new EM technique from Roger Tsien’s lab, I stopped in my tracks when I read the following:

MiniSOG may do for EM what Green Fluorescent Protein did for fluorescence microscopy.

The power of electron microscopy (EM) comes from its ability to visualize structures that are smaller than the limit of resolution in light microscopy. However, the EM techniques used for optimal visualization require such heavy-duty fixation that antibodies and gold particles, both used to label target proteins, can’t get very far in the cell. A recent paper introduces “miniSOG,” a very small protein that can be genetically fused to nearly any protein of interest. After illumination by blue light and fixation of a tissue, miniSOG generates singlet oxygen which results in the creation of a precipitate that can be clearly imaged at high resolution using EM. MiniSOG can also be visualized using fluorescent light microscopy techniques, allowing for correlative fluorescent AND EM visualization. Images above show the fluorescent and EM images of miniSOG being used to label different proteins, such as α-actinin (an actin cross-linker, top), histone 2B (a protein used for packaging DNA, middle), and mitochondria (bottom).

ResearchBlogging.orgShu, X., Lev-Ram, V., Deerinck, T., Qi, Y., Ramko, E., Davidson, M., Jin, Y., Ellisman, M., & Tsien, R. (2011). A Genetically Encoded Tag for Correlated Light and Electron Microscopy of Intact Cells, Tissues, and Organisms PLoS Biology, 9 (4) DOI: 10.1371/journal.pbio.1001041

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