The Investigation of the Interaction between Lomefloxacin and Human Serume Albumin by Specteroscopic Methods

Abstract

Mechanism of the binding of lomefloxacin (LMF) with human serum albumin has been studied at
physiological pH (7.4) using fluorescence spectroscopic technique. LMF is a third-generation fluoroquinolone
antibiotic that exhibits striking potency against a broad spectrum of Gram-negative and Gram-positive bacteria
through inhibition of DNA gyrase. Lomefloxacin is a drug that is excreted in urine and has very variable
systemic absorption. Human serum albumin (HSA) is the most important and abundant constituent of blood
plasma and serves as a protein storage component. Recently, the three-dimensional structure of HSA was
determined through X-ray crystallographic measurement. Fluorescence studies showed that (LMF) has an ability
to quench the intrinsic fluorescence of HSA through a static quenching procedure according to the Stern–
Volmer equation .LMF showed two types of binding sites, the first having a very high affinity (1/72 ×107M-1)
and a secondary binding site with an affinity two orders lower than the primary site. The number of binding sites
for complex: HSA-LMF at 280 nm was calculated 1and0.5. The microenvironment of tryptophan and tyrosin
residues and more hydrophobic of fluorophores microenvironment were changed and disturbed by the blue shift
in maximum wavelength and decreased in fluorescence intensity in the presence of lomefloxacin revealed
decreased polarity of the fluorophores. The binding site for LMF is in a hydrophobic pocket in the sub-domain II
A of HSA.