A chiral probe for the acute phase proteins alpha-1-acid glycoprotein and alpha-1-antitrypsin based on europium luminescence

Abstract

Reversible and selective binding of a dynamically racemic europium(III) complex to α(1)-acid glycoprotein and α(1)-antitrypsin is characterised by a significant change in the europium total emission spectral fingerprint and the switching on of a large circularly polarised luminescence (CPL) signal from the metal centre. Observation of an induced CD into the ligand chromophore in the presence of α(1)-AGP allows a structure for the protein-bound complex to be postulated. A direct determination of elevated α(1)-AGP levels in human serum was achieved by monitoring changes in the intensity ratio of Eu emission bands.

Induced Europium Circularly Polarized Luminescence Monitors Reversible Drug Binding to Native α1‐Acid Glycoprotein

“…The racemic europium complex [Eu⋅L 1 (OH 2 )] + has been shown to bind reversibly to α 1 ‐AGP {log K =5.73 (0.06)} (Scheme ) . Addition of α 1 ‐AGP to [Eu⋅L 1 (OH 2 )] + caused displacement of the bound water molecule and gave rise to major changes in the intensity and form of the europium emission spectrum, consistent with a significant change in the coordination environment, notably involving loss of the axial donor ligand.…”

“…Binding to α 1 ‐AGP was characterized by a switching on of a large induced europium circularly polarized luminescence (CPL) . The parent complex is dynamically racemic and shows no CPL.…”

Lanthanide Probes for Bioresponsive Imaging

“…While this work was limited to detection of various amino acids, probes have recently emerged that bind to proteins, and by doing so, induce fingerprint signals. 78,81,147 …”

“…147 Protein binding occurs through hydrophobic interactions with the azaxanthone or azathioxanthone antenna units and coordinative interactions between the Eu(III) center and a glutamate side chain. The protein alters the chirality of the chelate, inducing a change in CPL signal profile and intensity.…”

Synthesis, Structural Characterization, and Chiroptical Studies of Bidentate Salen‐Type Lanthanide (III) Complexes

“…Chiral lanthanide complexes are interesting for their applications including enantioselective catalysis, detection of bio‐analytes, circularly polarized light emitting devices, and metal organic frameworks . The organic ligands define the Ln 3+ coordination sphere, modulating the access of further chemical species to the ion and making it soluble, stable, and persistent in various environments.…”