Light and electron microscopy of QD-immuno-labeled microtubules from rat lung fibroblast. Upper: Mosaic of light micrographs depicting the microtubule assemblages of six fibroblasts, each labeled with a unique size/color of QD-conjugated antibodies. Lower: Electron micrograph of preparation illustrating the electron-dense QDs decorating individual microtubules (QD diameter approx. 5 nm).
Quantum Dots allow NCMIR
scientists image cellular and subcellular detail from a single
preparation..
Cell biologists at UCSD’s National Center for Microscopy and Imaging Research (NCMIR) demonstrate the suitability of Quantum dots (QDs) for determining the specific location of endogenous proteins in cells and tissues—using correlated light and electron imaging techniques. Ben Giepmans and colleagues recently reported in Nature Methods (vol 2 (10);743-749, October 2005, on a study of QD-immuno-labeling technique for optimal imaging of cell preparations from the millimeter down to the nanometer size ranges.
While light microscopy is regularly used to map protein localization inside of cells, many investigators also need the nano-scale imaging capabilities provided by electron microscopy. Typically, researchers used one set of sample preparation and labeling protocols for mapping endogenous proteins with light microscopy (LM) and another for electron microscopy (EM). The team of NCMIR researchers illustrate how Quantum dots may be applied as a label for both LM and EM, in the same specimen.
Quantum dots, originating with the semiconductor industry of the 1970s, have intrigued physicists with their unique properties. These tiny crystals of luminescent semiconductor material exhibit unique optical properties. Biologists are busy exploiting QD’s novel properties in order to develop new tools for cellular and molecular biology. The color of light emitted by QDs with light microscopy corresponds to the dimension of the electron-dense nanocrystals observed with electron microscopy. The NCMIR team exploited this physical relationship in developing labeling protocols--with up to four contemporaneous labels--for building QD-conjugated labels to locate endogenous proteins at the cellular scale with LM and the nano-scale with EM.
Mark Ellisman, Director of NCMIR and a co-author on this paper, explains:
“Demonstrating the practicality of using multiple ‘Quantum dot’-conjugated labels to locate multiple proteins—from a single sample using light and electron microscopy—creates a powerful tool for elucidating phenomena and processes spanning multiple scales.”
