Insights into the interactions between tetracycline, its degradation products and bovine serum albumin

Abstract

Tetracyclines (TCs) are the most widely used antibiotics in the world. Because antibiotics have low bioavailability and are difficult to completely remove using current sewage treatment facilities, residual TCs and their degradation products in the environment, animal and plant foodstuffs and personal care products may enter the body through the food chain, thus causing unpredictable effects on human health. We studied bovine serum albumin (BSA) (a functional protein) as a target of tetracycline-induced toxicity by examining its interactions with TC, anhydrotetracycline (ATC) and epitetracycline (ETC), based on a fluorescence spectroscopy and molecular docking method under simulated physiological conditions. The interaction mechanism was elucidated at the molecular level. The results show that TC, ATC and ETC bind at site II of BSA and interact mainly through hydrogen bonding interactions and van der Waals interactions. The binding affinities can be ranked in the order ATC > TC > ETC.

Keywords: BSA; Degradation products; Molecular docking; Spectroscopic method; Tetracycline.

Fig. 1

Structure of TC, ATC and ETC

Fig. 2

Effect of TC (a)/ATC (b)/ETC (c) on fluorescence spectra of BSA. Conditions: C_BSA = 2.0 × 10⁻⁶ mol L⁻¹; λ_ex = 285 nm; T = 298 K; pH = 7.40; C from 1–12: 0, 0.2, 0.4, 0.8, 1.2, 1.6, 2.0, 2.4, 2.8, 3.2, 3.6 and 4.0 (×10⁻⁵ mol L⁻¹)

Fig. 3

Stern–Volmer curves of TC and its degradation products on fluorescence intensity of BSA

Fig. 4

The Van’t Hoff curves

Fig. 5

Synchronous fluorescence spectra of TC and its degradation products on BSA. Conditions: CBSA = 2.0 × 10⁻⁶ mol L⁻¹; pH = 7.40; T = 298 K; a Δλ = 15 nm; b Δλ = 60 nm; C from 1–12: 0, 0.2, 0.4, 0.8, 1.2, 1.6, 2.0, 2.4, 2.8, 3.2, 3.6 and 4.0 (×10⁻⁵ mol L⁻¹)

Fig. 6

The combining model of TC (a)/ATC (b)/ETC (c) with BSA