The interactions of divalent metal cations with phospholipid membranes are important in many physiological processes and disease states. Exploring the molecular level details of cation-lipid interactions have become important to fully understand the physiological consequences of such interactions. Amidst numerous techniques to probe lipid membrane-analyte interactions, vibrational sum frequency generation spectroscopy (VSFS) has proven to be extremely powerful, due to its inherent interface specificity. We used a Langmuir monolayer of phospholipid molecules at the air/water interface as a model system for the lipid membrane. Our VSFS experiments demonstrated that transition and non-transition metal ions such as Cu2+ and Ca2+ can bind to negatively charged lipid membranes and disrupt the ordering of interfacial water molecules. The binding site of different ions were probed by monitoring the vibrational stretches of the lipid headgroup moieties. Moreover, the changes in the sum frequency response of interfacial water reflected the changes in surface charge of the lipid monolayers. Our results indicate that VSFS can be used as a powerful tool to understand the structural changes of biological membranes upon the binding of metal ions.

Probing the interactions of divalent cations with lipid membranes using vibrational sum frequency spectroscopy

254th National Meeting (2017)

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