Samantha Walker, UoA 17, LS

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I enrolled at the University of Westminster as a mature student in 1999 and graduated with a First Class BSc (Honours) Biochemistry and Microbiology degree. I have always wanted to do a PhD but it was difficult to find an interesting project that was compatible with bringing up three young children. In 2008 I won a four-year University Scholarship to investigate pharmaceuticals as environmental pollutants. During my time here I also completed a Postgraduate Certificate in Supporting Learning and have enjoyed teaching undergraduate students in tutorials and laboratory practicals. It has been a challenge to undertake a PhD with a young family but Westminster has always been very understanding and supportive. The teaching is excellent and the staff are always helpful and willing to make time to assist students. Pharmaceuticals have emerged as pollutants of the environment. The major decline of vultures in Asia caused by the veterinary drug diclofenac, and the endocrine disruption of fish due to human contraceptives are well documented examples of these adverse effects.

Pharmaceuticals are different to other chemical pollutants in that they are designed to have a specific biological effect. Metabolic pathways and drug target proteins may be highly conserved in nontarget species suggesting that similar modes of action may occur. The aim of this work was to establish whether molecular docking is a potential tool to predict the effects of pharmaceutical compounds on non-target organisms using two drugs as examples. Diclofenac and ibuprofen are highly prescribed analgesics that ubiquitously pollute the aquatic environment. Molecular docking experiments were run with these drugs and primary drug target (cyclooxygenase, COX) homologues of four species: Salmo salar, Danio rerio, Oncorhynchus mykiss and Daphnia pulex. The results show that COX enzymes are highly conserved in these organisms. S.salar, D.rerio and O.mykiss COX enzymes bind these drugs in the same way and are likely to have a similar mode of action as in humans. This will probably lead to reduced COX enzyme function and reduced prostaglandin production. Binding interaction was not found for D.pulex due to differences in the 3D COX protein structure. Chronic ecotoxicological effects of these drugs reported in the literature support these findings. Although still in its infancy, the ever growing database of protein sequences for aquatic organisms may be probed to select vulnerable species as relevant targets for ecotoxicity testing. Incorporating the mechanism of action of human drugs into an intelligent approach for ecotoxicity tests also may help to select relevant chronic test end points in environmental risk assessments and reduce scientific uncertainty surrounding the effects of pharmaceuticals on aquatic ecosystems.

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