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

• Published in: ChemMedChem Vol. 12; no. 3; pp. 271 - 277
• Main Authors: Jennings, Laura, Waters, Ryan S., Pal, Robert, Parker, David
• Format: Journal Article
• Language: English
• Published: 03.02.2017
• Subjects: chirality; CPL; drug binding; europium; luminescence
• ISSN: 1860-7179; 1860-7187
• DOI: 10.1002/cmdc.201600571

Alpha‐1‐acid glycoprotein (α1‐AGP) is an important blood plasma glycoprotein. Following an acute‐phase reaction such as stress, inflammation, burn, or infection, the bloodstream concentration of α1‐AGP can increase up to 400 % of its normal concentration. A wide range of drugs is known to bind α1‐AGP. Increased binding of pharmacologically active compounds to α1‐AGP moderates their clinical effect by decreasing the amount of unbound drug in the bloodstream. This has important clinical ramifications for such applications as the duration of anesthesia and in determining dosage for drug therapy. In this study, the competitive binding to α1‐AGP of a dynamically racemic europium(III) complex with seven pharmacologically active drugs absorbing in the range λ 250–290 nm was monitored by following changes in europium total emission and in induced circularly polarized luminescence (CPL). Binding affinities corresponding to Kd values in the range 0.5–100 μm were measured, in good agreement with published data. This is the first time that a drug binding to a protein has been studied quantitatively by using changes in circularly polarized luminescence (CPL). With α1‐acid glycoprotein (α1‐AGP) as an example, we show that the competitive binding of selected pharmacologically active compounds can be assessed quickly and easily by observing the total emission and CPL spectral changes of a chiral europium(III) complex [Eu⋅L1]+.