LAUSR

Abstract The mechanism of interaction between anesthetic drug procaine with model serum protein bovine serum albumin (BSA) was seen by means of various spectroscopic and molecular docking methods. The spectroscopic techniques used in the study were UV visible, fluorescence quenching, 3-d fluorescence, circular dichroism (CD), and Forster resonance energy transfer (FRET). Formation of the ground state complex between procaine and BSA was evidenced from the UV–visible spectrophotometry. Due to the strong absorption of procaine at the excitation wavelength, inner filter effect was corrected for the fluorescence analyses. There was 1:1 cooperative binding between BSA and procaine which was taken place via static mechanism. Procaine was found to slightly induce the secondary structure of BSA by increasing its α-helical contents. Thermodynamic parameters revealed that hydrogen bonding and hydrophobic forces played important role in the binding. From the competitive binding measurements it was shown that the principal binding site for the procaine in BSA was site 1, located in the hydrophobic cavity of subdomain IIA. Both these experimental observations i.e., thermodynamic parameters analysis and site specific studies were supported by theoretical molecular docking analysis according to which procaine binds to the vicinity of His67, Glu100 via hydrogen bonding and Asn99, Pro96, Ser65, Glu6, His246, Glu243, Asp248, and Glu251 via hydrophobic interactions. The most favorable site of the procaine was located near the Sudlow's site 1.