Evolution can be observed in all living organisms, and pathogenic microorganisms are no exception. Almost before we had finished celebrating the discovery of penicillin and dozens of other antibiotics, we began to realise that pathogens are efficient at developing resistance to antimicrobial agents. Conventional antibiotics target the genetic machinery of the pathogens, such as DNA, RNA and ribosomes, and the processes they are involved in. A few decades ago, scientists realised the potential of small peptides produced by all higher living organisms. These are called defensins, and they make up part of their innate immunity. Defensins are antimicrobial peptides (AMPs) that target cell membranes – the ‘nanoboundaries’ of all cells – and in this case bacterial cells. Membranes are not extensively controlled by cell genetics, and may therefore be less prone to mutations.

In his PhD project, Vijay Shankar Balakrishnan studied membrane interactions of an AMP called Novicidin (Nc), which is derived from sheep defensins. He used different biophysical methods involving artificial membrane systems (liposomes) to study these interactions. Liposomes are made up of fat molecules known as phospholipids. Vijay Shankar Balakrishnan used physical techniques to understand the physicochemical nature of interactions between the peptide and the membranes. He used various spectroscopic and calorimetric methods to investigate the lipid-induced changes in the peptide due to membrane binding and vice versa. These interactions are very sensitive to the composition of the phospholipid – changes in the chemical composition and the electrostatic charge profoundly influence how Nc can bind to the membrane.

The PhD degree was completed at the Interdisciplinary Nanoscience Centre (iNANO), Science and Technology, Aarhus University.

Time: Monday 19 November 2012 at 12.30
Place: Lecture Theatre, iNANO House, building 1593, room 012, Aarhus University, Gustav Wieds Vej 14
Title of dissertation: Novicidin interactions with phospholipid membranes: a dossier
Contact information: Vijay Shankar Balakrishnan, vijay@inano.dk
Members of the assessment committee:
Associate Professor Chad Leidy, Department of Physics, University of the Andes, Colombia
Senior Researcher Thomas L. Andresen, DTU Nanotech, Technical University of Denmark
Professor Troels Skrydstrup (chair), iNANO and Department of Chemistry, Aarhus University
Main supervisor:
Professor Daniel Otzen, iNANO and Department of Molecular Biology and Genetics, Aarhus University
Language: The dissertation will be defended in English

The defence is public.
The dissertation is available for reading at the Graduate School of Science and Technology / GSST, Ny Munkegade 120, building 1521, room 112, 8000 Aarhus C.