Design and synthesis of fluorescent ligands for selective detection of a target protein

NICOLÁS ARRUPE; ANA BELLOMO; LUCIANA GIORDANO

Villa Carlos Paz, Córdoba

Conferencia; XIII ELAFOT 2017; 2017

Screening is a key tool to find promising compounds in a large set able to modulate biological activity of specific therapeutic targets with the hypothesis that this will provide new drug leads[1]. Proteins are some of the major therapeutic targets. The relevant assays used as a sifting process must be reproducible, reliable, and robust. Fluorescent-based techniques are simple, economic, and sensitive methods widely used in screening. An active pocket of proteins/enzymes is used as target to design selective ligands/inihibitors. Such protein?ligand interactions have been utilized to develop selective protein sensing/imaging systems. The key issue represents how to transduce the ligand/protein recognition into readable detection signals. Fluorescence switch-on can be achieved upon the binding of the fluorescent probes to the active ligand-binding domain of the target protein [2]. Most of the ligand fluorescent switch-on probes are designed for monitoring enzyme activities so the design of fluorescence switchable probes for non-enzymatic protein targets is highly desirable. The fluorescent probes can be synthesized by conjugating a fluorophore with a protein-specific ligand. We focus on two representative detection concepts: (i) environmentally-sensitive probes exhibiting very weak fluorescence in a polar and/or protic environment but strong fluorescence in a hydrophobic surrounding, and (ii) molecular rotor probes, undergoing intramolecular charge transfer upon irradiation, relax via the nonradiative torsional relaxation pathway, and are thus sensitive to changes in viscosity.Our model system consists in 3-hydroxychromone (3HC)[3] as a small and highly environmentally sensitive fluorophore and BODIPY[4] as molecular rotor, which are conjugated to benzenesulfonamide, a ligand for carbonic anhydrase II (hCAII) as a target protein. HC derivatives show dual-color emission and thus a ratiometric response due to Excited-State Intramolecular Proton Transfer (ESIPT) and therefore constitute very versatile and sensitive probes of environmental properties such as polarity and hydrogen-bonding capacity.