Model Lipid Membrane Permeability to ATP

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Abstract
A model phospholipid membrane separating two aqueous compartments was measured for permeability to 3H-ATP by diffusion. No diffusion lag time was demonstrated but the permeability coefficient was dependent on the ionic composition of the aqueous medium. In 0.1 M NaCl and distilled water the permeability coefficient was 6.78 × 10−7 cm/s and 1.41 × 10−7 cm/s, respectively, while in 0.5 mM MgCl2 it varied from a minimum of 0.25 × 10−7 cm/s to a maximum of 6.87 × 10−7 cm/s, depending on the concentration difference of 3H-ATP across the membrane.In 0.1 M NaCl the diffusion process had an activation energy of 1 kcal/mol while in 0.5 mM MgCl2 it exhibited a saturation characteristic which was attributed to space charge effects within the membrane. In 0.5 mM 2,4-dinitrophenol the permeability of the membrane to 3H-ATP was inhibited.

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