35 MHz quartz crystal microbalance and surface plasmon resonance studies on the binding of angiotensin converting enzyme with lisinopril.

Abstract Angiotensin converting enzyme (ACE) plays a pivotal role in blood pressure regulation, and its interaction with an ACE inhibitor (ACEI) is an important research topic for treatment of hypertension. Herein, a low reagent consumption, multiparameter and highly sensitive quartz crystal microbalance (QCM) at 35-MHz fundamental frequency was utilized to monitor in situ the binding process of solution lisinopril (LIS, a carboxylic third-generation ACEI) to ACE adsorbed at a 1-dodecanethiol (C12SH)-modified Au electrode. From the QCM data, the binding molar ratio ( r ) of LIS to adsorbed ACE was estimated to be 2.3:1, and the binding and dissociation rate constants ( k 1 and k −1 ) and the binding equilibrium constant ( K a ) were estimated to be k 1  = 4.1 × 10 6  L mol −1  s −1 , k −1  = 7.3 × 10 −3  s −1 and K a  = 5.62 × 10 8  L mol −1 , respectively. Comparable qualitative and quantitative results were also obtained from separate experiments of cyclic voltammetry, electrochemical impedance spectroscopy and surface plasmon resonance measurements.