Marked small molecule libraries: a truncated approach to molecular probe design.

A truncated approach to the design of molecular probes from small molecule libraries is outlined, based upon the incorporation of a bioorthogonal marker. The applicability of this strategy to small molecule chemical genetics screens has been demonstrated using analogues of the known stress activated protein kinase (SAPK) pathway activator, anisomycin. Compounds marked with a propargyl group have shown activation of the SAPK pathways comparable to that induced by their parent structures, as demonstrated by immunoblot assays against the downstream target JNK1/2. The considerable advantages of this new approach to molecular probe design have been illustrated through the rapid development of a functionally active fluorescent molecular probe, through coupling of the marked analogues to fluorescent azides using the copper(i)-catalyzed Huisgen 1,3-dipolar cycloaddition reaction. Active molecular probes generated in this study were used to investigate cellular uptake through FACS analysis and confocal microscopy.