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Biotech / Medical : Xenogen (XGEN) -- Ignore unavailable to you. Want to Upgrade?

To: tuck who wrote (25)	6/22/2005 12:56:51 PM
From: tuck	Read Replies (1) \| Respond to of 45

[Reversible single-molecule photoswitching in the GFP-like fluorescent protein Dronpa] >>Published online before print June 22, 2005 Proc. Natl. Acad. Sci. USA, 10.1073/pnas.0500489102 OPEN ACCESS ARTICLE Biophysics Reversible single-molecule photoswitching in the GFP-like fluorescent protein Dronpa ( photochromism \| protonation/deprotonation \| fluorescence microscopy ) Satoshi Habuchi , Ryoko Ando , Peter Dedecker , Wendy Verheijen , Hideaki Mizuno , Atsushi Miyawaki , and Johan Hofkens ¶ Department of Chemistry, Katholieke Universiteit Leuven, Celestijnenlaan 200F, 3001 Heverlee, Belgium; Laboratory for Cell Function and Dynamics, Advanced Technology Development Group, Brain Science Institute, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan; and Unité Chimie des Matériaux Inorganiques et Organiques, Université Catholique de Louvain, Bâtiment Lavoisier Place L. Pasteur 1, 1348 Louvain-la-Neuve, Belgium Edited by J. Woodland Hastings, Harvard University, Cambridge, MA, and approved May 3, 2005 (received for review January 19, 2005) Reversible photoswitching of individual molecules has been demonstrated for a number of mutants of the green fluorescent protein (GFP). To date, however, a limited number of switching events with slow response to light have been achieved at the single-molecule level. Here, we report reversible photoswitching characteristics observed in individual molecules of Dronpa, a mutant of a GFP-like fluorescent protein that was cloned from a coral Pectiniidae. Ensemble spectroscopy shows that intense irradiation at 488 nm changes Dronpa to a dim protonated form, but even weak irradiation at 405 nm restores it to the bright deprotonated form. Although Dronpa exists in an acid-base equilibrium, only the photoinduced protonated form shows the switching behavior. At the single-molecule level, 488- and 405-nm lights can be used to drive the molecule back and forth between the bright and dim states. Such reversible photoswitching could be repeated >100 times. The response speed to irradiation depends almost linearly on the irradiation power, with the response time being in the order of milliseconds. The perfect reversibility of the Dronpa photoswitching allows us to propose a detailed model, which quantitatively describes interconversion among the various states. The fast response of Dronpa to light holds great promise for following fast diffusion or transport of signaling molecules in live cells.<< This is way early, and thus not really a threat, but sure is interesting. Full text freebie: pnas.org Cheers, Tuck