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Efficient tools for controlling molecular functions with exquisite spatiotemporal resolution are much in demand to investigate biological processes in living systems. Here we report an easily synthesized caged dexamethasone for photo‐activating cytoplasmic proteins fused to the glucocorticoid receptor. In the dark, it is stable in vitro as well as in vivo in both zebrafish (Danio rerio) and Xenopus sp, two significant models of vertebrates. In contrast, it liberates dexamethasone upon UV illumination, which has been harnessed to interfere with developmental steps in embryos of these animals. Interestingly, this new system is biologically orthogonal to the one for photo‐activating proteins fused to the estrogen ERT receptor, which brings great prospect for activating two distinct proteins down to the single cell level. [ABSTRACT FROM AUTHOR]

The zebrafish is one of the most widely adopted animal models in both basic and translational research. This popularity of the zebrafish results from several advantages such as a high degree of similarity to the human genome, the ease of genetic and chemical perturbations, external fertilization with high fecundity, transparent and fast-developing embryos, and relatively low cost-effective maintenance. In particular, body translucency is a unique feature of zebrafish that is not adequately obtained with other vertebrate organisms. The animal's distinctive optical clarity and small size therefore make it a successful model for optical modulation and observation. Furthermore, the convenience of microinjection and high embryonic permeability readily allow for efficient delivery of large and small molecules into live animals. Finally, the numerous number of siblings obtained from a single pair of animals offers large replicates and improved statistical analysis of the results. In this review, we describe the development of opto-chemical tools based on various strategies that control biological activities with unprecedented spatiotemporal resolution. We also discuss the reported applications of these tools in zebrafish and highlight the current challenges and future possibilities of opto-chemical approaches, particularly at the single cell level. [ABSTRACT FROM AUTHOR]

The study presents a report on gold colloids, which are covalently derivatized with hydrophilic polymer brushes. A description on the preparation and properties of gold colloids is provided.

Homeoproteins of the Engrailed family are involved in the patterning of mesencephalic boundaries through a mechanism classically ascribed to their transcriptional functions. In light of recent reports on the paracrine activity of homeoproteins, including Engrailed, we asked whether Engrailed intercellular transfer was also involved in brain patterning and boundary formation. Using time-controlled activation of Engrailed combined with tools that block its transfer, we show that the positioning of the diencephalic-mesencephalic boundary (DMB) requires Engrailed paracrine activity. Both zebrafish Eng2a and Eng2b are competent for intercellular transfer in vivo, but only extracellular endogenous Eng2b, and not Eng2a, participates in DMB positioning. In addition, disruption of the Pbx-interacting motif in Engrailed, known to strongly reduce the gain-of-function phenotype, also downregulates Engrailed transfer, thus revealing an unsuspected participation of the Pbx interaction domain in this pathway. [ABSTRACT FROM AUTHOR]

The small and synthetically easily accessible coumarinylmethyl backbone has been modified to generate a family of photolabile protecting groups with redshifted absorption. We relied on introducing electron-donating groups in the 7 position and electron-withdrawing groups in the 2-, and 2- and 3 positions. In particular, we showed that the diethylamino-thiocoumarylmethyl and the diethylamino-coumarylidenemalononitrilemethyl are relevant for uncaging with cyan light. They both exhibit a significant action cross section for uncaging in the 470-500 nm wavelength range and a low light absorption between 350 and 400 nm. These attractive features are favorable to perform chromatic orthogonal photoactivation with UV and blue-cyan light sources, respectively. [ABSTRACT FROM AUTHOR]

Three procedures that rely on photoactivation are introduced to accurately analyze the disassembly kinetics of a collection of self-immolative spacer groups within the window 10−2-103 s. Our results are relevant for deriving quantitative structure-property relationships. In particular, we have been able to access 20 ms temporal resolution, which made possible the measurement of the shortest ever reported disassembly time for an activated self-immolative spacer. [ABSTRACT FROM AUTHOR]

Studies rigid tetrahedral molecules considered as models of Onsager molecular crosses. Design of molecular shape to avoid compact packing in the solid state; Strategy for bypassing crystallization and promoting solubility of organic compounds in many solvents; Advantages of extremely concave molecular architecture.