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Title: Exploring theoretical origins of the toxicity of organic quaternary ammonium salts towards Escherichia coli using machine learning approaches
Author: Naden, Alexandria Olessia
ISNI:       0000 0004 5364 0909
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2014
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Quaternary ammonium salts are surface active bactericides. A mechanism of their biological activity has been well studied experimentally, and it encompasses two stages. The first stage involves electrostatic interactions of polar functional groups of the salts with oppositely charged functional groups on a bacterial cell surface, and the second stage includes incorporation of their lipophilic groups into a bacterial cell membrane. However, despite numerous experimental studies, computational modelling of this mechanism with the aim to support experimental observations with theoretical conclusions, to the author's knowledge, has not yet been reported. In the current study, linear regression models correlating theoretical descriptors of lipophilicity and electronic properties of mono- and disubstituted imidazolium carboxylates with their biological activity towards Escherichia coli have been developed. These models established that biological activity of these salts is governed by the chemical structures of imidazolium cations, and that the centre of this biological activity is located in the long alkyl side chains of the cations. It was also found that these side chains have an intrinsic electronic potential to form internal C-H- -H-C electrostatic interactions when their lengths reach seven carbon atoms. Additionally, the nature of the C-H- -O-C inter-ionic electrostatic interactions in imidazolium carboxylates has been explored via a topological analysis of these interactions in 1-ethyl-3-methylimidazolium acetate. Thus, it was established that these electrostatic interactions are hydrogen bonds.
Supervisor: Goodacre, Roy Sponsor: BBSRC
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: quaternary ammonium salts ; QSAR ; hydrogen bond ; QTMS ; dipole ; agar diffusion test