Tuning the Color Palette of Fluorescent Copper Sensors through Systematic Heteroatom Substitution at Rhodol Cores

Abstract

Copper is an essential nutrient for sustaining life, and emerging data have expanded the roles of this metal in biology from its canonical functions as a static enzyme cofactor to dynamic functions as a transition metal signal. At the same time, loosely bound, labile copper pools can trigger oxidative stress and damaging events that are detrimental if misregulated. The signal/stress dichotomy of copper motivates the development of new chemical tools to study its spatial and temporal distributions in native biological contexts such as living cells. Here, we report a family of fluorescent copper sensors built upon carbon-, silicon-, and phosphorus-substituted rhodol dyes that enable systematic tuning of excitation/emission colors from orange to near-infrared. These probes can detect changes in labile copper levels in living cells upon copper supplementation and/or depletion. We demonstrate the ability of the carbon-rhodol based congener, Copper Carbo Fluor 1 (CCF1), to identify elevations in labile copper pools in the Atp7a fibroblast cell model of the genetic copper disorder Menkes disease. Moreover, we showcase the utility of the red-emitting phosphorus-rhodol based dye Copper Phosphorus Fluor 1 (CPF1) in dual-color, dual-analyte imaging experiments with the green-emitting calcium indicator Calcium Green-1 to enable simultaneous detection of fluctuations in copper and calcium pools in living cells. The results provide a starting point for advancing tools to study the contributions of copper to health and disease and for exploiting the rapidly growing palette of heteroatom-substituted xanthene dyes to rationally tune the optical properties of fluorescent indicators for other biologically important analytes.

Gasotransmitter Regulation of Phosphatase Activity in Live Cells Studied by Three‐Channel Imaging Correlation

“…In the range of pH 5–9, the probe itself remained almost non‐fluorescent; however, its three products formed by reaction with H 2 S, phosphatase, and both of them (Figure a) exhibited strong and stable fluorescence (Figure S11). Similar to the previously reported probe, the protonation of the piperazine group slightly decreased the green fluorescent signal from phosphatase at pH 5.…”

Cu2+selective chelators relieve copper-induced oxidative stressin vivo

“…S31 † and 8 ). 57 ATP7A is a P-type ATPase required for copper export. Loss of ATP7A function causes copper hyper-accumulation, 41 , 87 and previous ICP-MS studies have shown that the Atp7a –/– mouse embryonic fibroblast cells accumulate 6-fold more copper in the cytoplasm compared to isogenic wildtype cells.…”

“…Loss of ATP7A function causes copper hyper-accumulation, 41 , 87 and previous ICP-MS studies have shown that the Atp7a –/– mouse embryonic fibroblast cells accumulate 6-fold more copper in the cytoplasm compared to isogenic wildtype cells. 57 Higher Cu levels would induce oxidative stress provided the excess Cu ions are bound to cellular ligands that promote redox cycling leading to Cu ion catalyzed ROS production. Therefore, we decided to check the level of ROS in the Atp7a –/– mouse embryonic fibroblast cells.…”

“…These novel molecules suppress Cu 2+ triggered oxidative stress both in live cells and in vivo . Importantly, the chelators were also able to suppress Cu-induced oxidative stress in Menkes disease model Atp7a –/– cells 57 which have endogenously high levels of Cu ions. Hence, our ligands stand out not only in affording exquisite selectivity for Cu 2+ but also for their applicability to biological systems which we have proven all the way from in cell disease models to a live multicellular vertebrate system.…”

From Phosphaphenalenes to Diphosphahexaarenes: An Overview of Linearly Fused Six‐Membered Phosphorus Heterocycles

“…In a different approach, Chang et al reported in 2018 the phospharhodol 32 (Figure ) and compared its properties with the carbon and silicon analogs . 32 possesses a thioether fragment linked to the 10‐position of the central backbone for the selective coupling with Cu + ions.…”