Effects of solvent environment on the spectroscopic properties of tylosin, an experimental and theoretical approach

Authors: Avramenko, Aleksandr; Spiehs, Mindy

Submitted to: Water Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/9/2022
Publication Date: 6/1/2023
Citation: Avramenko, A.G., Spiehs, M.J. 2023. Effects of solvent environment on the spectroscopic properties of tylosin, an experimental and theoretical approach. Water Science and Technology. 87(11):2597-2606. https://doi.org/10.2166/wst.2023.155.
DOI: https://doi.org/10.2166/wst.2023.155

Interpretive Summary: Tylosin is a commonly used antibiotic in veterinary medicine. However, only a fraction of the administered dose is metabolized by the animal, and it remains unclear how this antibiotic impacts the broader ecosystem, with one of the main concerns being that it can lead to the development of antibiotic resistance. Using ultraviolet radiation to break down the tylosin molecule is one possible way to remove it from the ecosystem. However, to facilitate efficient light induced degradation of a molecule it is first necessary to understand the physical properties of the molecule being irradiated. In this study steady state spectroscopy and density functional theory were used to explore the spectral properties of a tylosin molecule. It was found that the strong absorption of tylosin in the ultraviolet region stems from two nearly degenerate transitions of similar energy. Moreover, these transitions lie in a particularly electronegative portion of the molecule which can be impacted by solvent polarity. Finally, a cavity polariton model is proposed in which visible light may be used to initiate the photodegradation of tylosin.

Technical Abstract: Tylosin is a commonly used antibiotic in animal medicine. However, it remains unclear how tylosin impacts the broader ecosystem once the host animal has excreted it. One of the main concerns is that it can lead to the development of antibiotic resistance. Therefore, there exists a need to develop systems that remove tylosin from the environment. Utilizing UV irradiation to destroy pathogens is one technique often deployed by scientists and engineers. However, for light-based techniques to be efficient, it is necessary to understand the spectral properties of the material being removed. Steady-state spectroscopy and density functional theory were used to analyze the electronic transitions of tylosin responsible for its strong absorbance in the mid-UV region. It was observed that the absorbance peak of tylosin stems from two transitions in the conjugated region of the molecule. Moreover, these transitions stem from an electronegative region of the molecule, which would allow them to be manipulated by changing solvent polarity. Finally, a polariton model has been proposed, which can be used to initiate the photodegradation of tylosin without the need for direct irradiation of the molecule with UV-B light.