H. Mitomo et al., STRUCTURAL-CHANGES IN PHOSPHATIDYLSERINE SALTS BY HYDRATION AND ADDITION OF CALCIUM-ION, Journal of the Physical Society of Japan, 62(6), 1993, pp. 2174-2179
Hydrations and phase transitions of ammonium, sodium and potassium sal
ts of phosphatidylserines (PS) were investigated by small-angle X-ray
scattering (SAXS) and differential scanning calorimetry (DSC). The inc
rease in long spacings for NH4+-PS by addition of water was slightly s
maller than those for the other PS salts, implying that a small amount
of water penetrated into the hydrocarbon regions. The long spacings f
or PS salts and water system were reduced by addition of CaCl2. A mixt
ure of phosphatidylcholine (PC) and PS in KCl aqueous solution gave a
long spacing of 59 angstrom, while it separated into two long spacings
at 65 and 55 angstrom in 1 mol CaCl2 solution. This SAXS result shows
that Ca2+ ion induces not only two dimensional, but three dimensional
phase separation of the mixture of PC and PS. The phase transition te
mperature of the anhydrous NH4+-PS was lowest among those of the three
PS salts, but fully hydrated NH4+-PS had the highest transition tempe
rature among them.