Efficient and flexible synthesis of new photoactivatable propofol analogs.

Propofol is a widely used general anesthetic, which acts by binding to and modulating several neuronal ion channels. We describe the synthesis of photoactivatable propofol analogs functionalized with an alkyne handle for bioorthogonal chemistry. Such tools are useful for detecting and isolating photolabeled proteins. We designed expedient and flexible synthetic routes to three new diazirine-based crosslinkable propofol derivatives, two of which have alkyne handles. As a proof of principle, we show that these compounds activate heterologously expressed Transient Receptor Potential Ankyrin 1 (TRPA1), a key ion channel of the pain pathway, with a similar potency as propofol in fluorescence-based functional assays. This work demonstrates that installation of the crosslinkable and clickable group on a short nonpolar spacer at the para position of propofol does not affect TRPA1 activation, supporting the utility of these chemical tools in identifying and characterizing potentially druggable binding sites in propofol-interacting proteins.

Sites Contributing to TRPA1 Activation by the Anesthetic Propofol Identified by Photoaffinity Labeling.

In addition to inducing anesthesia, propofol activates a key component of the pain pathway, the transient receptor potential ankyrin 1 ion channel (TRPA1). Recent mutagenesis studies suggested a potential activation site within the transmembrane domain, near the A-967079 cavity. However, mutagenesis cannot distinguish between protein-based and ligand-based mechanisms, nor can this site explain the complex modulation by propofol. Thus more direct approaches are required to reveal potentially druggable binding sites. Here we apply photoaffinity labeling using a propofol derivative, meta-azipropofol, for direct identification of binding sites in mouse TRPA1. We confirm that meta-azipropofol activates TRPA1 like the parent anesthetic, and identify two photolabeled residues (V954 and E969) in the S6 helix. In combination with docking to closed and open state models of TRPA1, photoaffinity labeling suggested that the A-967079 cavity is a positive modulatory site for propofol. Further, the photoaffinity labeling of E969 indicated pore block as a likely mechanism for propofol inhibition at high concentrations. The direct identification of drug-binding sites clarifies the molecular mechanisms of important TRPA1 agonists, and will facilitate drug design efforts to modulate TRPA1.

Internet suicide in Japan: a qualitative content analysis of a suicide bulletin board.

Netto shinju, or Internet group suicide, is a contemporary form of Japanese suicide where strangers connect on the Internet and make plans to commit suicide together. In the past decade, numerous incidents have occurred whereby young Japanese make contact on the Internet, exchange tips on suicide methods, and make plans to meet offline for group/individual suicide. A systematic qualitative content/thematic analysis of online communications posted on a popular Japanese suicide bulletin board yielded a textured, thematic understanding of this phenomenon. Themes identified reflected Shneidman's theory of suicide but with an emphasis on interpersonal concerns that are embedded in Japanese culture.