Abstract
The thermodynamic and structural behaviors of lamellar dimyristoylphosphatidylcholine-alkanol(abbreviation DMPC–CnOH, n = 8–18 is the even number of carbons in the alkyl chain) systemswere studied by using DSC and SAXD/WAXD methods at a 0–0.8 CnOH : DMPC molar ratio range. Up to n ≤ 10 a significant biphasic effect depending on the main transition temperature tm on the CnOH concentration was observed. Two breakpoints were revealed: turning point (TP), corresponding to theminimum, and threshold concentration (cT), corresponding to the end of the biphasic tendency. Thesebreakpoints were also observed in the alkanol concentration dependent change in the enthalpy of themain transition DHm. In the case of CnOHs with n > 10 we propose a marked shift of TP and cT to verylow concentrations; consequently, only increase of tm is observed. A partial phase diagram wasconstructed for a pseudo-binary DMPC–C12OH system. We suggest a fluid–fluid immiscibility of the DMPC–C12OH system above cT with a consequent formation of domains with different C12OH contents. At a constant CnOH concentration, the effects of CnOHs on DHm and bilayer repeat distancewere found to depend predominantly on the mismatch between CnOH and lipid chain lengths. Observed effects are suggested to be underlined by a counterbalancing effect of interchain van der Waals interactions and headgroup repulsion.
Original language | English |
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Journal | Physical Chemistry Chemical Physics |
Volume | 23 |
Issue number | 14 |
Pages (from-to) | 8598-8606 |
Number of pages | 9 |
ISSN | 1463-9076 |
DOIs | |
Publication status | Published - 2021 |