Magnetic Resonance Studies of Aqueous Manganese (II)-Phosphatidylserine-Adenosine Triphosphate Solutions

Abstract

IT has recently been proposed by Maas and Colburn¹ that certain solubility and pH observations made on aqueous solutions containing phosphatidylserine (PS), bivalent and trivalent metal cations (that is, cupric, magnesium and ferrous ion), and adenosine triphosphate (ATP) can be explained in terms of the following model. In concentrated solutions PS exists in the form of a colloidal micelle, with the polar end of the molecule lying in the aqueous phase (oil in water conformation); on addition of bivalent or trivalent metal cation, these bind to the polar end of the PS (that is, to the COO⁻) and produce, as a consequence, another colloidal form. It is proposed that this form has a water in oil conformation, that is, the polar group–metal complex points inwards and the aliphatic chains point outwards. The proximity of complexing metal cations to one another in this situation suggests a possible means of testing this hypothesis, for if the metal cations in question are paramagnetic, then it is possible that their electron paramagnetic resonance spectra should demonstrate the effects of dipolar and exchange interaction.