A new infrared spectroscopoic marker for cochleate phases in phosphatidylserine-containing model membranes

Abstract

Fourier transform-infrared (IR) spectroscopic and electron microscopic studies are reported for 1,2-dimyristoylphosphatidylserine (DMPS) and for DMPS/1,2-dimyristoylphosphatidylcholine mixtures in the presence and absence of Ca2+ ion. The frequency of the methyl symmetric deformation mode near 1,378 cm-1, previously assumed insensitive to changes in lipid morphology, has been found to respond to cochleate phase formation by undergoing an approximately 8 cm-1 increase. The new IR spectroscopic marker at 1,386 cm-1 has been used to identify and verify structures suggested from the phase diagram of J. R. Silvius and J. Gagné (1984. Biochemistry. 23:3241-3247) for this system. In addition, the ability of Mg2+ ion to induce cochleate formation has been demonstrated. Higher Mg2+ than Ca2+ levels are required for this process. Finally, IR spectroscopy has been used to monitor dehydration of the lipid surface through changes in the asymmetric PO2- stretching mode. Dehydration precedes cochleate phase formation (i.e., occurs at a lower Ca2+/phosphatidylserine level).

Infrared studies of protein-induced perturbation of lipids in lipoproteins and membranes

“…, that was assumed to be insensitive to changes in lipid morphology, was later found as sensitive to cochleate phase formation in phosphatidylserine-containing model membranes (Flach and Mendelsohn, 1993). Full or partial isotopic substitution of the acyl chains can be used to avoid interference with other components, i.e.…”

The Role of Lateral Tension in Calcium-Induced DPPS Vesicle Rupture

“…Previous studies have reported that the addition of Ca 2+ to DPPS liposomes results in the formation of cochleate structures. 35, 36 One characteristic of the cochleates is dehydration of the PS lipids upon complexation with Ca 2+ . 36, 37 A solid precipitate was observed to form upon increased addition of Ca 2+ to our DPPS vesicles, which may indicate formation of these structures following rupture at high Ca 2+ concentrations.…”

“…35, 36 One characteristic of the cochleates is dehydration of the PS lipids upon complexation with Ca 2+ . 36, 37 A solid precipitate was observed to form upon increased addition of Ca 2+ to our DPPS vesicles, which may indicate formation of these structures following rupture at high Ca 2+ concentrations. LTS is only sensitive to vesicles remaining in suspension and did not detect cochleate particles; had cochleate structures formed, we would have expected to see cigar shaped clumps rather than large terraces in the AFM image.…”

Lipid complexes with cationic peptides and OAKs; their role in antimicrobial action and in the delivery of antimicrobial agents

“…FT-IR spectroscopy was used to identify an absorption band characteristic for cochleate phases made with PS and Ca 2? , which undergoes an 8 cm -1 increase upon cochleate formation, from 1,386 cm -1 to 1,344 cm -1 [46]. Laurdan fluorescence has also been developed to successfully characterize cochleates [45,52].…”

“…Other cations, like Mg 2? for example, or cationic antimicrobial OAKs, cause water entrapment into the structure leading to the formation of larger-size cochleates in some systems [20,45,46]. Cochleate structures made with PS and Ca 2?…”