Embryogenesis is the process by which a fertilized egg develops into a fetus. It starts with a single zygote cell that multiplies through rapid division (mitosis) into stem cells that subsequently differentiate into the specific types of cells that make up organs and tissues. Biologists need non-invasive imaging techniques to capture in detail such developments at the molecular as well as the cellular levels. Glycans play a central role in the signaling that takes place between cells during embryogenesis, which makes them appealing targets for molecular imaging. However, prior to Bertozzi's research, glycans were difficult to visualize using the standard tools of molecular imaging.
In 2007, Bertozzi and her research group announced the first copper-free variant of a chemical reaction known as "click chemistry," one of the most proficient methods for attaching probes to biological molecules. Conventional click chemistry requires a copper catalyst to accelerate the reaction of alkynes with azides - functional groups featuring three nitrogen atoms that can be integrated into biomolecules by metabolic labeling. However, because of copper's toxicity, the original click chemistry reactions could only be used on fixed cells or cells in a test-tube. Bertozzi and her group extended click chemistry to living cells and organisms by developing a difluorinated cyclooctyne or DIFO reagent that reacts with azides at physiological temperatures, eliminating the need for the toxic catalyst.
"It is a two-step chemical strategy for labeling glycans with imagi
|Contact: Lynn Yarris|
DOE/Lawrence Berkeley National Laboratory