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Thermotropic phase behavior and headgroup interactions of the nonbilayer lipids phosphatidylethanolamine and monogalactosyldiacylglycerol in the dry state.

Popova AV, Hincha DK - BMC Biophys (2011)

Bottom Line: Similarly, the ethanolamine moiety of EPE was H-bonded to the carbonyl and choline groups of PC and probably interacted through charge pairing with the phosphate group.This study provides a comprehensive characterization of dry membranes containing the two most important nonbilayer lipids (PE and MGDG) in living cells.These data will be of particular relevance for the analysis of interactions between membranes and low molecular weight solutes or soluble proteins that are presumably involved in cellular protection during anhydrobiosis.

View Article: PubMed Central - HTML - PubMed

Affiliation: Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, D-14476 Potsdam, Germany. hincha@mpimp-golm.mpg.de.

ABSTRACT

Background: Although biological membranes are organized as lipid bilayers, they contain a substantial fraction of lipids that have a strong tendency to adopt a nonlamellar, most often inverted hexagonal (HII) phase. The polymorphic phase behavior of such nonbilayer lipids has been studied previously with a variety of methods in the fully hydrated state or at different degrees of dehydration. Here, we present a study of the thermotropic phase behavior of the nonbilayer lipids egg phosphatidylethanolamine (EPE) and monogalactosyldiacylglycerol (MGDG) with a focus on interactions between the lipid molecules in the interfacial and headgroup regions.

Results: Liposomes were investigated in the dry state by Fourier-transform Infrared (FTIR) spectroscopy and Differential Scanning Calorimetry (DSC). Dry EPE showed a gel to liquid-crystalline phase transition below 0°C and a liquid-crystalline to HII transition at 100°C. MGDG, on the other hand, was in the liquid-crystalline phase down to -30°C and showed a nonbilayer transition at about 85°C. Mixtures (1:1 by mass) with two different phosphatidylcholines (PC) formed bilayers with no evidence for nonbilayer transitions up to 120°C. FTIR spectroscopy revealed complex interactions between the nonbilayer lipids and PC. Strong H-bonding interactions occurred between the sugar headgroup of MGDG and the phosphate, carbonyl and choline groups of PC. Similarly, the ethanolamine moiety of EPE was H-bonded to the carbonyl and choline groups of PC and probably interacted through charge pairing with the phosphate group.

Conclusions: This study provides a comprehensive characterization of dry membranes containing the two most important nonbilayer lipids (PE and MGDG) in living cells. These data will be of particular relevance for the analysis of interactions between membranes and low molecular weight solutes or soluble proteins that are presumably involved in cellular protection during anhydrobiosis.

No MeSH data available.


Related in: MedlinePlus

νOH of the galactose headgroups of MGDG in pure MGDG and in the indicated binary mixtures (compare Fig. 7) as a function of temperature. The peak positions determined from the two binary mixtures were almost identical at all temperatures and therefore only the symbols for one lipid composition are visible.
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Figure 8: νOH of the galactose headgroups of MGDG in pure MGDG and in the indicated binary mixtures (compare Fig. 7) as a function of temperature. The peak positions determined from the two binary mixtures were almost identical at all temperatures and therefore only the symbols for one lipid composition are visible.

Mentions: MGDG contains a galactose moiety that is able to H-bond to other headgroups through the sugar OH groups. The νOH presents a broad peak in the FTIR spectrum from about 3600 cm-1 to 3100 cm-1 (Figure 7), indicating a wide variety of H-bonding lengths and strengths. In pure, dry amorphous sucrose νOH is centered at 3370 cm-1 and this band is shifted to about 3320 cm-1 for sucrose fully H-bonded to EPC membranes in the dry state [40,58]. In pure, dry MGDG νOH was centered at 3448 cm-1 (Figure 7), indicating only a low degree of H-bonding between MGDG molecules. In membranes containing 50% of either EPC or DMPC, νOH was shifted by more that 100 wavenumbers to around 3310 cm-1, emphasizing the strong intermolecular H-bonding between MGDG and PC noted above (Figure 4 and 5). The exceptional strength of these bonds is also indicated by the complete absence of a temperature dependence in νOH in the mixed membranes, while the low level of H-bonding in pure MGDG was further decreased at higher temperatures (Figure 8).


Thermotropic phase behavior and headgroup interactions of the nonbilayer lipids phosphatidylethanolamine and monogalactosyldiacylglycerol in the dry state.

Popova AV, Hincha DK - BMC Biophys (2011)

νOH of the galactose headgroups of MGDG in pure MGDG and in the indicated binary mixtures (compare Fig. 7) as a function of temperature. The peak positions determined from the two binary mixtures were almost identical at all temperatures and therefore only the symbols for one lipid composition are visible.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3116483&req=5

Figure 8: νOH of the galactose headgroups of MGDG in pure MGDG and in the indicated binary mixtures (compare Fig. 7) as a function of temperature. The peak positions determined from the two binary mixtures were almost identical at all temperatures and therefore only the symbols for one lipid composition are visible.
Mentions: MGDG contains a galactose moiety that is able to H-bond to other headgroups through the sugar OH groups. The νOH presents a broad peak in the FTIR spectrum from about 3600 cm-1 to 3100 cm-1 (Figure 7), indicating a wide variety of H-bonding lengths and strengths. In pure, dry amorphous sucrose νOH is centered at 3370 cm-1 and this band is shifted to about 3320 cm-1 for sucrose fully H-bonded to EPC membranes in the dry state [40,58]. In pure, dry MGDG νOH was centered at 3448 cm-1 (Figure 7), indicating only a low degree of H-bonding between MGDG molecules. In membranes containing 50% of either EPC or DMPC, νOH was shifted by more that 100 wavenumbers to around 3310 cm-1, emphasizing the strong intermolecular H-bonding between MGDG and PC noted above (Figure 4 and 5). The exceptional strength of these bonds is also indicated by the complete absence of a temperature dependence in νOH in the mixed membranes, while the low level of H-bonding in pure MGDG was further decreased at higher temperatures (Figure 8).

Bottom Line: Similarly, the ethanolamine moiety of EPE was H-bonded to the carbonyl and choline groups of PC and probably interacted through charge pairing with the phosphate group.This study provides a comprehensive characterization of dry membranes containing the two most important nonbilayer lipids (PE and MGDG) in living cells.These data will be of particular relevance for the analysis of interactions between membranes and low molecular weight solutes or soluble proteins that are presumably involved in cellular protection during anhydrobiosis.

View Article: PubMed Central - HTML - PubMed

Affiliation: Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, D-14476 Potsdam, Germany. hincha@mpimp-golm.mpg.de.

ABSTRACT

Background: Although biological membranes are organized as lipid bilayers, they contain a substantial fraction of lipids that have a strong tendency to adopt a nonlamellar, most often inverted hexagonal (HII) phase. The polymorphic phase behavior of such nonbilayer lipids has been studied previously with a variety of methods in the fully hydrated state or at different degrees of dehydration. Here, we present a study of the thermotropic phase behavior of the nonbilayer lipids egg phosphatidylethanolamine (EPE) and monogalactosyldiacylglycerol (MGDG) with a focus on interactions between the lipid molecules in the interfacial and headgroup regions.

Results: Liposomes were investigated in the dry state by Fourier-transform Infrared (FTIR) spectroscopy and Differential Scanning Calorimetry (DSC). Dry EPE showed a gel to liquid-crystalline phase transition below 0°C and a liquid-crystalline to HII transition at 100°C. MGDG, on the other hand, was in the liquid-crystalline phase down to -30°C and showed a nonbilayer transition at about 85°C. Mixtures (1:1 by mass) with two different phosphatidylcholines (PC) formed bilayers with no evidence for nonbilayer transitions up to 120°C. FTIR spectroscopy revealed complex interactions between the nonbilayer lipids and PC. Strong H-bonding interactions occurred between the sugar headgroup of MGDG and the phosphate, carbonyl and choline groups of PC. Similarly, the ethanolamine moiety of EPE was H-bonded to the carbonyl and choline groups of PC and probably interacted through charge pairing with the phosphate group.

Conclusions: This study provides a comprehensive characterization of dry membranes containing the two most important nonbilayer lipids (PE and MGDG) in living cells. These data will be of particular relevance for the analysis of interactions between membranes and low molecular weight solutes or soluble proteins that are presumably involved in cellular protection during anhydrobiosis.

No MeSH data available.


Related in: MedlinePlus