Specificity of Ca2+ and Mg2+ binding to phosphatidylserine vesicles and resultant phase changes of bilayer membrane structure

Further aspects of the Ca2+-dependent polymorphism of bovine heart cardiolipin

“…It is also observed with this negatively charged phospholipid that above a threshold concentration of 1-2 mM Ca 2+ an 1 : 2 Ca 2+ phosphatidylserine complex is formed resulting in a large structural change [35,36]. However, the organization of the Ca-phosphatidylserine complex is markedly different from that of the Ca-cardiolipin complex, in that the phosphatidylserine is organized in a closely packed cochleated lamellar arrangement in which the acyl chains are in the gel state [35,36]. The Ca-phosphatidylserine complex formation is an exothermic reaction with a AH of -4.7 _ 0.5 kcal/mol [37,38 ] in agreement with a chain crystallization process.…”

“…It is of interest to compare these data with those obtained for bovine brain phosphatidylserine. It is also observed with this negatively charged phospholipid that above a threshold concentration of 1-2 mM Ca 2+ an 1 : 2 Ca 2+ phosphatidylserine complex is formed resulting in a large structural change [35,36]. However, the organization of the Ca-phosphatidylserine complex is markedly different from that of the Ca-cardiolipin complex, in that the phosphatidylserine is organized in a closely packed cochleated lamellar arrangement in which the acyl chains are in the gel state [35,36].…”

The exothermic reaction of calcium with unilamellar phosphatidylserine vesicles

“…At this stage, Cazc has formed an anhydrous complex with the PS, accompanied by a transformation of the phospholipid acyl chains (mostly 18:O and 18: I [ 141) from a hexagonal packing to a crystalline orthorhombic perpendicular packing [7,8,17L19]. The total heat released during the titration, 4.7 + 0.5 kcal/mol, is similar to the enthalpy of the liquidcrystalline-gel transition of multilamellar dispersions of PS in NaCl(4.5 + 0.5 kcal/mol) determined by differential scanning calorimetry [7,19] and may reflect the crystallization of the acyl chains. It is also likely, however, that part of this heat is due to the release of the strain in the highly curved membrane during fusion.…”

“…Small unilamellar PS vesicles have a similar instability in the presence of Ca*+ in that they fuse [5], leak their contents [3], and eventually form cochlear cylinders [6]. PS also exhibits a specificity for the binding of Ca*+, and the gel to liquid crystalline transition temperature of the phospholipid is shifted to above 100°C when Ca*' is added [7,8]. The binding of divalent ions to PS appears to be correlated with their ability to fuse sonicated vesicles made of this phospholipid [8-l I].…”

In vitro and in vivo effect of Escherichia coli endotoxin on mitochondrial phospholipase A2 activity

“…It is also known that calcium influences the structure of membranes containing acidic phospholipids [24-321 through fusion [24,25], lateral phase separation [26-291 and permeability changes; the release of bound calcium accompanies a phospholipid structural reorganization [30] mainly dependent upon calcium concentration, ionic strength and phospholipid molecular species [29][30][31][32]331. In spite of these observations it is not possible to predict the structural or organizational impact of calcium on any native biological membrane [34].…”