Date of Award

Summer 1987

Degree Type

Thesis - Restricted

Degree Name

Master of Science (MS)

Department

Physics

First Advisor

Collins, Joseph M.

Second Advisor

Feldott, Jeanette

Third Advisor

Mendelson, Kenneth S.

Abstract

Interacting forces between 3-component mixed lipid bilayers, composed of DOPE: DOPC: cerebrosides in a 1:1:1 molar ratio, have been characterized by using X-ray diffraction and osmotic stress techniques. The mixed lipid system formed a single lamellar phase both in water and in 30 mM CaCl2 solution. The strength of the net force between the 3-component bilayers was found to be weaker and to decay at a slower rate than for DOPC alone. The decay parameter, A, for the net force is 3.22 ± 0.02A and that for the hydration force is 3.88 ± 0.15A. The strength of the van der Waals force for the 3-component system is also weaker (H = 10.7 x 10 - 14 ergs) than DOPC alone. The strength of the van der Waals force for the three lipids are in the order cerebrosides > DOPC > DOPE. The electrostatic force, due to Ca2+ binding on the bilayer surface, decayed more rapidly (A = 5.64 ± 0.14A) between the 3-component bilayers than for DOPC alone. The mixed system exhibits decreasing surface potential and increasing area per bound Ca2+ as a function of increasing bilayer separation in the region < 40A. We infer that the strength of the binding of Ca2+ to the 3-component bilayer surface is weaker than that for DOPC alone.

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