Proteomics

Automating phosphoproteomics

One of the most powerful applications of mass spectrometry–based proteomics is the ability to identify and map post-translational modifications. As data sets grow larger, however, the manual validation of such sites becomes nearly impossible. Beausoleil et al. have devised an automated scoring tool they call 'Ascore' that, using the intensities of site-determining ions from tandem mass spectrometry data, measures the probability of correct phosphorylation site localization.

Beausoleil, S.A. et al. Nat. Biotechnol. 24, 1285–1292 (2006).

Cell biology

Visualizing disulfide reduction

Yang et al. present a FRET-based strategy to image disulfide-bond cleavage in live cells. Using the folate receptor as an example to probe the endocytic pathway, they created a FRET reporter consisting of folate, rhodamine and BODIPY. When the disulfide bond between folate and rhodamine is cleaved, the fluorescence switches from red to green, providing a visual readout of cellular location.

Yang, J. et al. Proc. Natl. Acad. Sci. USA 103, 13872–13877 (2006).

Chemical biology

Reversing reactions to make new sugars

Sugar-based natural products with therapeutic activities are notoriously difficult to make using organic synthesis alone. With the discovery that several glycosyltransferase enzymes can catalyze reversible reactions, Zhang et al. describe a powerful tool to synthesize exotic natural product variants and to incorporate chemical handles onto sugar scaffolds.

Zhang, C. et al. Science 313, 1291–1294 (2006).

Microbilogy

Identification of parasite genes silenced to evade host immunity

A Vibrio cholerae strain expressing a Tet repressor–sensitive GFP and a transposon carrying the repressor permits the identification of genes that are silenced as the parasite adapts from the surface-water environment to its mammalian host. Transposon-containing bacteria clones turn green only when adapting from in vitro culture to the infection of infant mice, allowing identification of genes that are silenced to escape host immunity.

Hsiao, A. et al. Proc. Natl. Acad. Sci. USA 103, 14542–14547 (2006).

Imaging and visualization

Improving FLAsH

The fluorogenic, membrane-permeable biarsenical dye called FlAsH has been indispensable for the chemical labeling of proteins in cells, requiring only that the protein be engineered with a tetracysteine motif. Spagnuolo et al. have developed a new biarsenical dye they name F2FlAsH, which exhibits higher absorbance, quantum yield and photostability, with a reduced dependence on pH as compared to the original FlAsH.

Spagnuolo, C.C. et al. J. Am. Chem. Soc. 128, 12040–12041 (2006).