Front Cover: One Scaffold, Different Organelle Sensors: pH‐Activable Fluorescent Probes for Targeting Live Microglial Cell Organelles (ChemBioChem 9/2022)**

Abstract

One scaffold – different organelle sensors: The structure‐organelle relationship (SOR) of an important synthetic intermediate targeting the nucleus and its transformation into other pH‐activable fluorescent probes is demonstrated. The fluorescent probes were synthesized using a single synthetic route. As shown in the cover picture, the assembly line illustrates that a common synthetic intermediate (rectangle shape) was transformed into another molecule (triangle or hexagonal shape) in a one‐step reaction to target specific cell organelles in live microglial cells. The common intermediate targets the cell nucleus, the cationic probe targets mitochondria, whereas the amine‐containing probe with pH‐activable property targets acidic lysosomes. The graphic was created by Ryann Davis. More information can be found in the Communication by G. Chopra et al.

Mitochondrial Targeting and Imaging with Small Organic Conjugated Fluorophores: A Review

“…In this regard, the largest Stokes shift, Δλ=3006.2 cm −1 for a BODIPY system was reported for 30 , an architecture bearing pyridinium mitochondrial targeting unit on position 1 and no meso substitution [58] . Similarly, increments in Stokes shifts were accessed for 31 and 32 , both bearing terminal triphenylphosphonium units [56,77] . These systems indicate that greater Stokes shifts can also be accessed via larger peripheral substitutions on other than the meso position.…”

“…Synthetically, the way this class of materials is afforded is dictated by the overall symmetry of the molecule. Symmetric systems [34,55–67] can be accessed by reaction of the desired substituted pyrrole with an aldehyde or an acid chloride/anhydride [68–72] . In both cases, the first synthetic step is the generation of the relevant dipyrromethene intermediate [69] .…”