In order to study molecular dynamics and cell interactions successfully, scientists need a way to track the movements of specific cells and cell components. Currently, proteins isolated from jellyfish that emit fluorescent green light are widely used for this purpose. Now researchers have isolated a molecule from a common coral species that fluoresces in three colors. They described the protein in a report published online this week by the Proceedings of the National Academy of Sciences.

Ryoko Ando of the Institute of Physical and Chemical Research in Japan and colleagues cloned from the stony coral Trachyphyllia geoffroyi a gene whose protein product, dubbed Kaede, emits green, yellow and red light. The researchers determined that short bursts of ultraviolet light induced the shift from green to red, the conversion that most interested them. What is more, once the light emitted by the protein turned color, it glowed red for months, unlike signals given off by other proteins, whose fluorescence is fleeting. To test the protein's tracking capabilities, the scientists used it to label densely packed neurons in culture. When they shined UV light on a portion of a single cell, they could follow the red molecules' movements throughout the remainder of the neuron and better visualize contact sites between neighboring neurons (see image).