Metallomembranes: Exploring the Interactions of Metal Ions with Lipid Bilayers

Seminar | January 24 | 4-5 p.m. |  Pitzer Auditorium, 120 Latimer Hall

 Prof. Paul Cremer, Department of Chemistry and BMB, Penn State University

 College of Chemistry

Phosphatidylserine (PS) and phosphatidylethanolamine (PE) are major components of numerous cellular membranes. Both these lipids contain amine moieties in their head groups that can strongly interact with first row transition metal ions such as Cu2+. This is significant because copper is a redox active metal ion and causes lipid oxidation in the presence of an oxidant such as hydrogen peroxide. To explore both the binding and oxidation chemistry of these systems, we have employed a combination of spectroscopic techniques (e.g. vibrational sum frequency and infrared spectroscopy), microfluidic platforms, fluorescence microscopy, as well as monolayer and planar supported bilayer architectures. This includes the development of a novel analytical tool that employs fluorescence quenching upon resonance energy transfer from a fluorophore to Cu2+ to quantitatively monitor metal ion binding at the bilayer surface. Both thermodynamic and molecular level details of these systems have been obtained. The results reveal that Cu2+ binding can be highly dependent on the concentration of PS within the membrane, the pH of the bulk solution, as well the ionic strength of the solution. Moreover, the presence or absence of various charged lipids can also greatly influence the binding properties. The interactions of transition metals with lipid membranes may play a role in neurodegenerative diseases such as Alzheimer’s as well as in Autism, where metal ion homeostasis is not maintained.

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