Cell Penetrating Peptide (CPP)
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"My research aims to label proteins inside living cells with fluorescent molecules. By doing so, we can study a protein’s biological function using a fluorescence microscope. Unfortunately, many fluorescent molecules will not pass through the cell’s outer membrane. Therefore, to overcome this limitation, we linked a fluorescent terbium complex, Lumi4-Tb, to a short peptide consisting of nine arginine amino acids. This peptide has the remarkable ability of being able to pass through the cell’s membrane without damaging the cell, and importantly, it will carry along other molecules that are attached to it. At left is shown a representation of peptide-Lumi4-Tb entering a cell (not to scale). The upper right panel shows a microscope image of healthy epithelial cells that were incubated for 15 minutes in culture medium containing peptide-Lumi4-Tb (scale bar = 20 μm). The lower right panel shows the same cells imaged in fluorescence mode, where ultraviolet light was shined on the cells, causing the Lumi4-Tb to emit a green glow. The uniform pattern of fluorescence seen throughout the cells shows that our peptide delivery strategy was a success. These results set the stage for future studies of protein function in living cells."