Binding of metal ions to monolayers of lecithins, plasmalogen, cardiolipin, and dicetyl phosphate

Modulation of phospholipase A2 by electrostatic fields and dipole potential of glycosphingolipids in monolayers

“…In addition, one cannot disregard electrostatically induced effects on the very mechanism of catalysis and it is interesting to consider how our results would compare to what is known about the postulated intrinsic mechanisms of the phosphohydrolytic reaction catalyzed by secretory class I/II PLA 2 s. Ca 2ϩ ions are essential for unifying enzyme binding to the phospholipid substrate and catalysis; the bivalent cation is responsible for oxygen-mediated binding of the sn-3 phosphate group and for the formation and localization of the nucleophilic attack on the sn-2 carbonyl of the ester linkage, with electrophilic stabilization of the tetrahedral intermediate (41,45). In the absence of applied electrostatic fields, Ca 2ϩ interacts with lipid polar head groups in monolayers of zwitterionic and anionic phospholipids and their mixtures with glycosphingolipids, as indicated by concentration-dependent changes of the surface (dipole) potential which may be accompanied by alteration of molecular packing depending on the condensed or expanded state of the monolayer (46,47). The increase of surface potential induced by Ca 2ϩ indicates that the ion contributes with an additional resultant dipole with a positive end pointing toward the air side of the monolayer interface; this suggested that the cation is located in the aqueous region in a plane displaced above that of the phospholipid phosphate group and toward the hydrocarbon side (46)(47)(48).…”

“…In the absence of applied electrostatic fields, Ca 2ϩ interacts with lipid polar head groups in monolayers of zwitterionic and anionic phospholipids and their mixtures with glycosphingolipids, as indicated by concentration-dependent changes of the surface (dipole) potential which may be accompanied by alteration of molecular packing depending on the condensed or expanded state of the monolayer (46,47). The increase of surface potential induced by Ca 2ϩ indicates that the ion contributes with an additional resultant dipole with a positive end pointing toward the air side of the monolayer interface; this suggested that the cation is located in the aqueous region in a plane displaced above that of the phospholipid phosphate group and toward the hydrocarbon side (46)(47)(48). The application of a negative potential to the surface electrode with respect to the reference in the subphase (or local lipid hyperpolarization) could drive Ca 2ϩ to a facilitated position for phosphate binding and the consequent nucleophilic attack to the sn-2 carbonyl.…”

Phospholipid-subclass-specific partitioning of lipophilic ions in membrane‒water systems

“…The membrane dipole potential calculated from the membrane-water partition coefficients was approximately 25 mV lower in membranes comprised of PlasCho than in membranes comprised of PhosCho or AlkCho (Table 2). This substantial difference in dipole potential in membrane bilayers comprised of different phospholipid subclasses can be explained by both the differential membrane conformation and the covalent structure of each phospholipid subclass near the membrane interface including : (i) the presence of an induced dipole in the double bond of the vinyl ether linkage of plasmalogens [8,9] ; (ii) the differences in both the conformation and dynamics of the phospholipid head groups in choline glycerophospholipid subclasses [32,33] ; and (iii) the alterations in the orientation of the carbonyl group at the sn-2 fatty acid chains [22][23][24]. It should be noted that previous workers have assumed that the sn-1 acyl chain in diacyl phospholipids does not contribute substantially to the membrane dipole potential since the dipole of carbonyl is oriented perpendicularly to the membrane director [24,34,35].…”

“…electrically active membranes), such as sarcolemma and sarcoplasmic reticulum, plasmalogen molecular species are the predominant phospholipid subclass [5][6][7]. Prior studies have demonstrated substantial differences in the dipole potential present in membranes comprised of plasmalogen compared with diacyl phospholipid molecular species [8,9]. Since alterations in membrane dipole potential change the free-energy profile of interactions between charged moieties and the host membranes, we anticipated that Abbreviations used : DiBAC 4 (3), bis-(1,3-dibutylbarbituric acid)trimethine oxonol ; diSC 3 (5), 3,3h-dipropylthiadicarbocyanine iodide ; PG, phosphatidylglycerol ; PS, phosphatidylserine ; AlkCho, plasmanylcholine ; PlasCho, plasmenylcholine ; PtdCho, phosphatidylcholine ; PA PlasCho, 1-O-(Z)hexadec-1h-enyl-2-eicosa-5h,8h,11h,14h-tetraenoyl-sn-glycero-3-phosphocholine ; PO AlkCho, 1-O-hexadecyl-2-octadec-9h-enoyl-sn-glycero-3-phosphocholine ; PO PhosCho, 1-hexadecanoyl-2-octadec-9h-enoyl-sn-glycero-3-phosphocholine ; PO PlasCho, 1-O-(Z)-hexadec-1h-enyl-2-octadec-9h-enoyl-sn -glycero-3-phosphocholine ; PO PS, 1-hexadecanoyl-2-octadec-9h-enoyl-sn-glycero-3-phosphoserine ; PO PG, 1-hexadecanoyl-2-octadec-9h-enoylsn-glycero-3-phosphoglycerol ; PA PhosCho, 1-hexadecanoyl-2-eicosa-5h,8h,11h,14h-tetraenoyl-sn-glycero-3-phosphocholine ; PA AlkCho, 1-Ohexadecyl-2-eicosa-5h,8h,11h,14h-tetraenoyl-sn-glycero-3-phosphocholine.…”

Iron Binding in an Ethylenediaminetetracetic Acid‐Based Gemini Surfactant Monolayer Film

“…The association of trivalent ions with surfactant molecules is more complex compared to most mono‐ or divalent ions (e.g., see (Aroti et al, 2004; Shah and Schulman, 1965) and the references therein) in part because of the potential for forming coordinate covalent bonds between the transition metal ions and surrounding ligand molecules in bulk solution (Tyrode and Corkery, 2018; Wang et al, 2014, 2016; Wen et al, 2016). More broadly, interactions between trivalent ions, and iron in particular, with charged surfactant interfaces is of interest because of their importance in membrane‐based biomineralization processes, as well as their relevance in controlling the interaction between metal‐based nanomaterials and self‐assembled ionic surfactants that comprise nanoparticle coatings (Arakaki et al, 2003; Kang et al, 2002).…”