Structure of IrisFP (2008)

Structural characterization of IrisFP, an optical highlighter undergoing multiple photo-induced transformations

Scientists from the Institut de Biologie Structurale (IBS, a mixed research unit of the CEA, CNRS and 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 GFP (green fluorescent protein). The new protein, called Iris-FP, will help scientists to monitor the spatio-temporal dynamics of proteins using super-resolution optical microscopy. The results, recently published online by the journal Proceedings of the National Academy of Sciences raises exciting prospects for nanoscopy and biophotonics.
Nanoscopy is an emerging field in microscopy that allows samples to be imaged at spatial resolutions on the order of a few tens of nanometers, considerably higher than that possible by traditional optical microscopy.
One set of nanoscopic techniques makes use of fluorescent proteins that are derived from the natural protein GFP and have fluorescent properties which can be altered in a controlled manner.
Many structural biology groups are trying to improve these techniques by developing a new generation of fluorescent proteins. Some of these proteins have the property of being "photocommutable" : they can be switched on or off at will. Others are capable of photoconversion : their colour can be altered by exciting them with laser light.
The PNAS study reports the development of a new protein, Iris-FP, which combines both properties. Using ESRF X-rays, the research team determined the protein’s atomic structure and characterized each of its colour-states. Iris-FP is a highly versatile tool which promises to considerably advance microscopy techniques. By genetically fusing Iris-FP to a protein of interest, scientists will be able to monitor the protein’s movements within the cell at unprecedented spatial and temporal resolution.
Besides microscopy, the development of new fluorescent probes raises exciting prospects for nanotechnology. Potential future applications include the development of high-density mass storage media that exploit changes in the colour of crystals of these proteins, allowing a large amount of information to be stored in a nanometric-sized structure.

Virgile Adam, Mickaël Lelimousin, Susan Boehme, Guillaume Desfonds, Karin Nienhaus, Martin J. Field, Joerg Wiedenmann, Sean McSweeney, G. Ulrich Nienhaus & Dominique Bourgeois, "Structural characterization of IrisFP, an optical highlighter undergoing multiple photo-induced transformations” PNAS(2008) , 105, 18343-48. DOI : 10.1073/pnas.0805949105

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