Blue fluorescent proteins

Inouye, S. (2004). Blue fluorescent protein from the calcium-sensitive photoprotein aequorin is a heat resistant enzyme, catalyzing the oxidation of coelenterazine. FEBS Lett. 577 105-110. 

Koda, P., and Lee, J. (1979). Separation and structure of the prosthetic group of the blue fluorescence protein from the bioluminescent bacterium Photobacterium phosphoreum. Proc. Natl. Acad. Sci. USA 76 3068-3072. 

Ai F1W, Shaner NC, Cheng Z, Tsien RY, Campbell RE (2007) Exploration of new chromo-phore structures leads to the identification of improved blue fluorescent proteins. Biochemistry 46 5904-5910... 

Mena, M. A., Treynor, T. P., Mayo, S. L. and Daugherty, P. S. (2006). Blue fluorescent proteins with enhanced brightness and photostability from a structurally targeted library. Nat. Biotechnol. 24, 1569-71. 

Some cellular assays also present the ability to measure kinase activation using recombinantly expressed intracellular sensor molecules that fluoresce in response to phosphorylation. These sensors are reviewed by Lawrence et al. (2007). The most interesting versions use yellow and blue fluorescent proteins to create a FRET through phosphorylation-induced folding with an intramolecular SH2 domain. SH2 domains are known to bind tightly to phosphotyrosine molecules and have been successfully shown to serve as phosphotyrosine detectors. In this type of assay, imaging is not necessary because the total fluorescence can be measured in a population of cells using a standard plate reader. 

Fig. 29 A barcode of three different chemical functionalities formed in a silica capillary via spatially-selective polymerization. It consists of segments of poly(bis-SorbPC) doped with Rhodamine-capped DPPE (red), poly(bis-SorbPC) doped with NBD-capped DOPE (green), and DOPC doped with Ni2+-charged DOGS-NTA. After the lipid pattern was formed, 6xHis-tagged Cerulean, a blue fluorescent protein, was injected into the capillary and bound selectively to the immobilized Ni2+ (blue). The capillary inner diameter is 50 pm. Reprinted with permission from [96]. Copyright 2007, American Chemical Society...

Paralogues of eubacterial riboflavin synthase (designated as lumazine protein, yellow fluorescent protein, and blue fluorescent protein) without enzymatic activity have been isolated from several luminescent bacteria. These proteins are highly fluorescent and are believed to modulate to serve as optical transponders that modulate the spectral characteristics of bacterial bioluminescence.Energy is believed to be transferred from activated bacterial luciferase to the fluorescent proteins by radiation-less transfer. 

For biotechnological applications it has been possible to generate fluorescent proteins with different properties by site-directed mutagenesis of GFP (Figure 14). Blue fluorescent proteins have been designed, which contain as the critical feature the substitution of histidine for tyrosine as the middle amino acid residue in the chromophore tripeptide sequence. The critical mutation in cyan fluorescent proteins is the substitution of tryptophan for tyrosine as the middle amino acid residue in the tripeptide sequence, which causes the chromophore to form with an indole rather than phenol component. ... 

All blue fluorescent proteins known today are derivatives of Aequorea GFP. The first member of these class of proteins was obtained by intentional introduction of a single point mutation... 

Clearly, the usability of the blue-fluorescent proteins as reporters is limited by their high bleaching rates. Whether further improvement of the properties of theses proteins by means of molecular evolution is possible remains to be seen. 

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