Electrostatic Charging of Lipid Membranes by ATP
Abstract
This work studies experimentally the effect of adenosine triphosphate (ATP) on the interaction of phospholipid multilayers. These are bioinspired materials with liquid crystalline properties that can have applications in technology. Two complementary methods, namely small-angle x-ray scattering (SAXS) and nuclear magnetic resonance (NMR) are used to perform measurements as a function of adenosine concentration and by varying three controlling parameters, namely the number of phosphate groups, choice of counterion, and pH value. X-ray measurements provide information on how ATP modifies the lattice spacing in lipid multilayers which is determined by a balance of forces that includes van der Waals and electrostatics. NMR measurements in turn give information on molecular orientations that can be used to interpret scattering measurements. The analysis of these measurements shows that ATP electrically charges the membrane surface causing increased repulsion that leads to unbinding of multilayers in some conditions. By measuring its competition with bromide ions, ATP is shown to create positive electrical charge on membrane surfaces which is explained by an overcharging effect due to counterions. In conclusion, this work has revealed unexpected effects of ATP on lipid interactions, and the body of experimental data produced in this work can inspire developments of new materials and it provides a solid basis for future theoretical development of membrane interaction models.
Degree
Ph.D.
Advisors
Petrache, Purdue University.
Subject Area
Physics|Materials science|Biophysics|Biochemistry
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