Scientists discover a new fluorescent protein at the ESRF


Scientists from the Institut de Biologie Structurale (IBS, Institut mixte CEA-CNRS-Université Joseph Fourier), the ESRF, the University of Ulm (Germany) and the University of Southampton (United Kingdom) have just developed a new fluorescent protein derived from the GFP (green fluorescent protein). The new protein, called Iris-FP, should allow scientists to monitor the spatio-temporal dynamics of proteins with super-resolution optical microscopy. These results bring new perspectives to nanoscopy and biophotonics, and they have just been published online by the journal Proceedings of the National Academy of Sciences (PNAS).

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Nanoscopy, which is being developed in recent years, defines the microscopy techniques which allow a spatial resolution of some tenths of nanometers. This is a much higher resolution than that of traditional optical microscopy.

One of these techniques is based on the use of new fluorescent proteins derived from the natural protein GFP, the fluorescence of which can be controlled. With the aim of improving this principle, many structural biology teams are trying to develop new fluorescent proteins. Among those, some can be « switched » on or off. Others have the capacity of changing colour in a controlled way when they are excited by a laser light. 

In the PNAS publication, the scientists show the development of a new protein, Iris-FP, which combines these two properties. The X-rays of the ESRF allowed the team to obtain its structure and to characterise each of its colour-states.

Iris-FP is a very flexible marker and a tool which will allow the improvement of microscopy techniques. When genetically fused with a protein of interest, Iris-FP could let scientists monitor the movements of this protein in the cell with unprecedented resolution.


The fluorescent protein IrisFP described here undergoes multiple color changes, which makes it a powerful tool for bio-imaging and bio-technological applications. The X-ray structure of IrisFP is shown in the center (gray ribbons) and the green and red rays represent multi-color light-emission by the protein. Pictures of crystals of IrisFP in its different color states are shown around the central image, linked by arrows representing the colors of the lasers needed to operate the color changes.

Further to its use in microscopy, the development of these new fluorescent probes opens new perspectives in the domain of nanotechnology. New applications can be envisaged, such as the development of high-density mass storage media based on the changing of colours of these proteins, thus giving the possibility of storing a large amount of information in nanometric-sized structures.


Adam et al., Structural characterization of IrisFP, an optical highlighter undergoing multiple photo-induced transformations, PNAS published online before print November 18, 2008, doi:10.1073/pnas.0805949105.