Imaging and Visualization Welcoming an improved blue fluorescent protein Though a rainbow of genetically encodable fluorescent proteins are available for biological imaging applications, existing blue fluorescent protein (BFP) variants were rather dim, had low quantum yields and underwent rapid photobleaching. By repacking the BFP core to make the chromophore more rigid, Mena et al. have developed a new BFP named Azurite with greatly improved properties for biological imaging in both bacterial and mammalian systems.
Mena, M.A. et al. Nat. Biotechnol.; published online (19 November 2006).
Proteomics A quantitative picture of the synaptic vesicle Using a battery of proteomics, biophysical, imaging and modeling technologies, Takamori et al. have constructed the first detailed, quantitative model of a trafficking organelle—the synaptic vesicle. They determined its size, density and mass, its full protein and lipid composition, and the copy numbers of major constituents. This complete model sets the stage for future quantitative trafficking studies.
Stem Cells Small-molecule stem-cell maintenance There is currently much to learn about the molecular cues that cause embryonic stem cells (ESCs) to remain in an undifferentiated state. Normally, when ESCs are grown in vitro, feeder cells are used to help them remain undifferentiated. Using high-throughput screening of chemical libraries, Chen et al>. identified a new small molecule that can be used to maintain mouse ESCs in an undifferentiated state, even in the absence of feeder cells.
Spectroscopy Elementary insights into an enzyme mechanism Using a combination of colloidal probe atomic force microscopy and a quartz crystal microbalance, Suzuki et al. obtained an extremely detailed picture of the specific elementary interactions taking place in an enzymatic reaction. For the first time, they were able to investigate the complex interactions between the heptaprenyl disphosphate synthase enzyme subunits, a cofactor and a substrate.
Protein Biochemistry A method for selective sulfation Tyrosine sulfation is a common post-translational modification found in eukaryotic proteins, yet tools to probe the biological function of this modification have been lacking. Liu and Schultz now describe a method for the selective, recombinant incorporation of sulfotyrosines into proteins by an orthogonal tRNA–aminoacyl-tRNA synthetase pair assigned to the amber nonsense codon. They expressed sulfo-hirudin in Escherichia coli, which previously could not be made using recombinant methods.
