Abstract
We have examined the effects of adding cis- and trans-unsaturated lipid to a fully interdigitated membrane using differential scanning calorimetry (DSC) and x-ray diffraction. For the interdigitated lipid, we used a monofluorinated analog of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). The single fluorine atom on the end of the sn-2 chain allows 1-palmitoyl-2-(16-fluoropalmitoyl)sn-glycero-3-phosphocholine (F-DPPC) to spontaneously form the interdigitated gel phase (LβI) below the main transition temperature (Tm). Both the cis 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and the equivalent trans lipid 1,2-dielaidoyl-sn-glycero-3-phosphocholine (DEPC) are strongly disfavored to form the LβI phase. There is a large degree of phase segregation between interdigitated and non-interdigitated lipid in DOPC/F-DPPC and DEPC/F-DPPC. The DSC thermograms reveal low miscibility and that both unsaturated lipids broaden and lower the main transition corresponding to the F-DPPC-rich component. Our WAXS data demonstrate that the unsaturated lipids progressively disrupt the intermolecular packing at higher concentrations. Furthermore, the SAXS data show that as the ratio of unsaturated lipid increases, the amount of interdigitated lipid decreases. The interdigitated gel phase formed by F-DPPC is resilient in the sense that the interdigitated phase disappears only at very high fractions of the unsaturated lipid. However, at the same concentration of unsaturated lipid, a greater percentage of the membrane remains interdigitated with DEPC than with DOPC. Therefore, the cis isomer is more disruptive and inhibits interdigitation more effectively than the trans isomer. This behavior supports the general conclusion that lipids with trans fatty acids have properties that are intermediate between saturated and cis-unsaturated lipid.
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
