Fluorescence Correlation Spectroscopy in Drug Discovery: Study of Alexa532-Endothelin 1 Binding to the Endothelin ET_A Receptor to Describe the Pharmacological Profile of Natural Products

Table 1

FCS binding studies with Alexa532-ET1 on endothelin ET_A receptor.

Binding of Alexa532-ET1 to A10 cells	Free L with 𝐷free [%]	R-L with 𝐷bound1 [%]	R-L with 𝐷bound2 [%]
Control^(a)	56.5±8.5	16.0±5.2	27.5±7.0
Displacement with 1 μM BQ-123 after 30 min^(a)	92±2	5±2	3±1
Displacement with 1 μg/mL fungal extract after 30 min^(b)	78±6	N.D.	22±6

L indicates Alexa532-ET1 14.3 nM^(a), 7.4 nM^(b); R-L: the receptor-ligand complex; N.D.: not detectable.