Local anesthetic-bovine serum albumin interactional behaviour: Characterization by volumetric, calorimetric, and spectroscopic methods

Abstract

The main aim of the current work is to figure out the effect of concentrations of local anesthetics on globular protein's molecular and functional properties. For this, volumetric parameters i.e. partial specific volume (V), expansibility (E°), and adiabatic compressibility (Ks) of bovine serum albumin (BSA) have been calculated in buffered solutions of two local anesthetics: procaine hydrochloride (PC) and tetracaine hydrochloride (TC) using density and sound velocity meter at different temperatures. The variation in V, E°, and Ks with temperature and drug concentrations indicate the larger polar interactions/dehydration phenomenon in the interaction of TC with BSA at both lower and higher concentrations of TC whereas polar interactions at lower and non-polar interactions at higher concentrations of PC have been observed in the association of PC with BSA. Both drugs interacts via hydrophobic/hydration phenomenon at intermediate concentrations. These observations have also been supported by microcalorimetry. In addition to ionic, hydrogen bonding, hydrophobic, and π-π interactions, additional cation–π interactions have been addressed in case of PC-BSA from NMR. Due to the higher hydrophobicity of PC cation, it partially occupies the binding cavity of protein. The absorption spectroscopic measurements indicate the higher affinity constant for PC-BSA as compared to TC-BSA. The chromophoric environment of protein has not been disturbed by the interaction of PC and TC.