Probing the interaction of cephalosporin with bovine serum albumin: A structural and comparative perspective

Cephalosporins belong the largest class of antibiotics used in the treatment of a wide range of infectious diseases caused by susceptible organisms. In the present study, we chose two typical antibiotics cefalexin/cefixime based on their structure, and investigated the interaction of cephalexin/cefixime with bovine serum albumin (BSA) using UV–vis absorption spectra, fluorescence spectroscopy, circular dichroism (CD) spectroscopy and molecular modeling approaches. Spectroscopic experiments revealed the formation of a BSA ? cefalexin/cefixime complex. The binding parameters calculated using a modified Stern ? Volmer method and the Scatchard method reached 10³–10⁴ L·mol^?1. Thermodynamic parameter studies revealed that binding characteristics by negative enthalpy and positive entropy changes, and electrostatic interactions play a major role. Site marker competitive displacement experiments and molecular modeling approaches demonstrated that cefalexin and cefixime bind with appropriate affinity to site I (subdomain IIA) of BSA. Furthermore, synchronous fluorescence spectra, CD spectra and molecular modeling results indicated that the secondary structure of BSA was changed in the presence of cefalexin and cefixime. Additionally, the effects of metal ions on the BSA ? cefalexin/cefixime system were also assessed.     

Comparative study of two cephalosporin antibiotics binding to calf thymus DNA by multispectroscopy,electrochemistry, and molecular docking

The over‐use of antibiotics has caused a number of problems such as contamination of antibiotic residues and virus resistance, and therefore has attracted global attention. In this study, spectroscopic techniques and molecular docking were employed to predict conformational changes and binding interaction between two cephalosporins (cefaclor and cefixime) and calf thymus DNA (ctDNA). Fluorescence and UV–vis spectra suggested that static quenching was predominant and cephalosporin bound to the groove region of ctDNA. Binding parameters calculated by the Stern–Volmer and Scatchard equations showed that cephalosporin bound to ctDNA with a binding affinity in the order of 10³ L mol^?1. Thermodynamic parameters further indicated that the reaction was a spontaneous process driven by enthalpy and entropy, and that the main binding force was an electrostatic force. The effects of iodide, denaturant, thermal denaturation and pH on a cephalosporin–Hoechst–DNA complex were also studied, and the results confirmed that cephalosporin bound to the groove area of DNA. Finally, these results were further confirmed by molecular docking and electrochemical studies.     

A sensitive fluorescent sensor based on the photoinduced electron transfer mechanism for cefixime and ctDNA

Cefixime is a third generation orally administered cephalosporin that is frequently used as a broad spectrum antibiotic against various gram‐negative and gram‐positive bacteria. In this study, a simple and sensitive fluorescent sensor for the determination of the cefixime and ctDNA was established based on the CdTe:Zn²⁺ quantum dots (QDs). The fluorescence of CdTe:Zn²⁺ QDs can be effectively quenched by cefixime in virtue of the surface binding of cefixime on CdTe:Zn²⁺ QDs and the subsequent photoinduced electron transfer process from CdTe:Zn²⁺ QDs to cefixime, in particular, the high sensitivity of QDs fluorescence emission to cefixime at the micromole per liter level, which render the cefixime‐CdTe:Zn²⁺ QDs system into fluorescence “OFF” status, then turn on in the presence of ctDNA. Furthermore, the Fourier transform infrared (FTIR) spectra of characteristic bands of C–N and N–H groups of cefixime endow evidence for the interaction of cefixime with CdTe:Zn²⁺ QDs. The relative electrochemical behavior of the affinity of CdTe:Zn²⁺ QDs for cefixime and ctDNA reveals the potential molecular binding mechanism.     

Comparison of Neisseria gonorrhoeae MICs obtained by Etest and agar dilution for ceftriaxone,cefpodoxime, cefixime and azithromycin

We evaluated Neisseria gonorrhoeae Etest minimum inhibitory concentrations (MICs) relative to agar dilution MICs for 664 urethral isolates for ceftriaxone (CRO) and azithromycin (AZM), 351 isolates for cefpodoxime (CPD) and 315 isolates for cefixime (CFM). Etest accurately determined CPD, CFM and AZM MICs, but resulted in higher CRO MICs.     

Comparative studies on the interaction of cefixime with bovine serum albumin by fluorescence quenching spectroscopy and synchronous fluorescence spectroscopy

Under simulated physiological conditions, the reaction mechanism between cefixime and bovine serum albumin at different temperatures (293, 303 and 310 K) was investigated using a fluorescence quenching method and synchronous fluorescence method, respectively. The results indicated that the fluorescence intensity and synchronous fluorescence intensity of bovine serum albumin decreased regularly on the addition of cefixime. In addition, the quenching mechanism, binding constants, number of binding sites, type of interaction force and energy‐transfer parameters of cefixime with bovine serum albumin obtained from two methods using the same equation were consistent. The results indicated that the synchronous fluorescence spectrometry could be used to study the binding mechanism between drug and protein, and was a useful supplement to the conventional method. Copyright © 2014 John Wiley & Sons, Ltd.