The scientists at Carnegie Mellon University's Molecular Biosensor and Imaging Center said the FAPs can be used to monitor biological activities of individual proteins and other biomolecules within living cells in real time.

The FAPs emit fluorescent light only when bound to a fluorogen -- an otherwise non-fluorescent dye added by the scientists. This feature will allow biologists to track proteins on the cell surface and within living cells, eliminating cumbersome experimental steps.

Scientists said the fluorogen activating proteins are especially useful for developing molecular biosensors because FAPs allow researchers not only to see where the target protein is within the space of the cell, but also to see color changes when it becomes fluorescent. Color changes, they said, might reflect changes in the local environment of the protein, and allow quantitative sensing in real time of the biological activity of proteins and biomolecules that are in close proximity to each other.

The complex project is described in the February issue of Nature Biotechnology.