Dually Labeled Neurotensin NTS₁R Ligands for Probing Radiochemical and Fluorescence-Based Binding Assays.

Area of Science:

• Pharmacology
• Biochemistry
• Medicinal Chemistry

Background:

• Ligand-receptor binding affinity is crucial for pharmaceutical development.
• Classical radiochemical assays use radioligands, while fluorescence assays use fluorescent probes.
• Discrepancies often exist between radio- and fluorescence-labeled ligands' structures and bioactivities.

Purpose of the Study:

• To directly compare radiochemical and fluorescence-based binding assays using identical ligand structures.
• To synthesize novel tritiated fluorescent neurotensin receptor ligands and their non-tritiated analogues.
• To evaluate the suitability of both assay types for drug screening and characterization.

Main Methods:

• Synthesis of tritiated fluorescent neurotensin receptor ligands ([3H]13, [3H]18) and their non-tritiated analogues (13, 18).
• Application of labeled probes in radiochemical and fluorescence-based binding assays.
• Utilized high-content imaging, flow cytometry, and fluorescence anisotropy for fluorescence-based assays.

Main Results:

• Equilibrium saturation binding experiments demonstrated well-comparable ligand-receptor affinities between the two assay types.
• The study confirmed that both radiochemical and fluorescence-based setups are suitable for screening new drug candidates.
• Kinetic binding behavior showed discrepancies, likely due to technical differences between the methods.

Conclusions:

• Direct comparison of radiochemical and fluorescence assays using identical ligands is feasible and valuable.
• Both assay formats provide reliable affinity data for drug screening.
• Further investigation is needed to understand the mechanistic basis of observed kinetic differences between assay types.