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Noncovalent Interaction of Tilmicosin With Bovine Serum Albumin


Noncovalent Interaction of Tilmicosin With Bovine Serum Albumin

Beáta Lemli et al. Molecules.


Tilmicosin is a widely used antibiotic in veterinary applications. Its antimicrobial activity is ranged from Gram-positive and some Gram-negative bacteria towards activities against Mycoplasma and Chlamydia. Adsorption affinity of tilmicosin antibiotics towards bovine serum albumin was investigated by both spectroscopic (UV-vis, Photoluminescence) and calorimetric methods. The interaction was determined on the basis of quenching of albumin by tilmicosin. Results confirm noncovalent binding of tilmicosin on bovine serum albumin with 1:1 stoichiometry associated with pK = 4.5, highlighting possible removal of tilmicosin molecules from the albumin surface through exchange reactions by known competitor molecules. Calorimetric measurements have confirmed the weak interaction between tilmicosin and albumin and reflect enhanced denaturation of the albumin in the presence of tilmicosin antibiotic. This process is associated with the decreased activation energy of conformational transition of the albumin. It opens a new, very quick reaction pathway without any significant effect on the product by noncovalent binding the tilmicosin molecules to the protein molecules. Results highlight the medical importance of these investigations by considerable docking of the selected antibiotic molecules on serum albumins. Although the binding may cause toxic effects in living bodies, the strength of the binding is weak enough to find competitor molecules for effective removals from their surface.

Keywords: albumin-drug interaction; binding properties; macrolide antibiotic; thermal denaturation; veterinary drug.

Conflict of interest statement

The authors declare no conflict of interest.


Figure 1
Figure 1
Chemical structure of tilmicosin.
Figure 2
Figure 2
UV-vis absorption spectra of increasing TIL concentrations (0–15 μM) in the presence of 2 μM BSA.
Figure 3
Figure 3
Fluorescence emission spectra of 2.0 μM BSA in the absence and presence of TIL with increasing concentrations (0.5, 1.0, 2.0, 3.0, 5.0, 7.5, 10.0 and 15.0 μM) in PBS (pH 7.4) buffer and the Stern-Volmer plot of the interaction (λexc = 280 nm, λem = 350 nm).
Figure 4
Figure 4
Representative DSC curves of BSA in the absence and presence of TIL and the Kissinger’s plots of the kinetic parameters.

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