Measurement of glucose exclusion from the fully hydrated DOPE inverse hexagonal phase

Abstract

The degree of exclusion of glucose from the inverse hexagonal H II phase of fully hydrated DOPE is determined using contrast variation small angle neutron scattering and small angle X-ray scattering. The presence of glucose is found to favour the formation of the non-lamellar H II phase over the fluid lamellar phase, over a wide range of temperatures, while having no significant effect on the structure of the H II phase. Glucose is preferentially excluded from the lipid-water interface resulting in a glucose concentration in the H II phase of less than half that in the coexisting aqueous phase. The degree of exclusion is quantified and the results are consistent with a hydration layer of pure water adjacent to the lipid head groups from which glucose is excluded. The osmotic gradient created by the difference in glucose concentration is determined and the influence of glucose on the phase behaviour of non-lamellar phase forming lipid systems is discussed.

Phospholipid Membrane Protection by Sugar Molecules during Dehydration—Insights into Molecular Mechanisms Using Scattering Techniques

“…Additional information in the shape and relative intensities of higher order peaks, n > 1, allows the reconstruction of the electron density profiles. Calculations of the electron density profile found that the electron density in the head group region is not altered by the presence of sugars in the aqueous phase [40]. This finding reinforces the conclusion that sugars are not preferentially located at the lipid head groups in partially dried samples.…”

Disordered Cold Regulated15 Proteins Protect Chloroplast Membranes during Freezing through Binding and Folding, But Do Not Stabilize Chloroplast Enzymes in Vivo

“…These rings are radially averaged to produce intensity versus scattering vector data, as shown in Figure 9. The analysis is similar to that reported previously for interactions between membranes and sugars (Lenné et al, 2009Kent et al, 2010;Garvey et al, 2013). The peaks are fit with a Gaussian function to determine the repeat spacings that are further illustrated in Supplemental Figure S2.…”

Reconciliation of opposing views on membrane–sugar interactions

“…This ubiquitous correlation is explained by a preferential expulsion or exclusion that increases the interfacial free energy and thus promotes the stability of lipid phases with low water accessible areas. The exclusion hypothesis has been supported by some spectroscopic evidence (28), and recently both small-angle scattering studies (36,38) and vapor pressure measurements (39) have provided direct evidence for a partial depletion of sugar in the hydration zone of lipid bilayers. Several aspects of the exclusion hypothesis were recently discussed by Lenné et al (40) who concluded that "sugars partition away from the phospholipid headgroups, rather than inserting between the headgroups.…”

“…Conversely, the exclusion hypothesis is supported by a multitude of studies on the phase behavior of fully hydrated phospholipids showing that the addition of sugars and other kosmotropic solutes consistently stabilize the phase with the smallest surface area (34,35). For example, the gel phase is stabilized over the fluid phase (25, 27), hexagonal phases are favored over lamellar phases (34,36), and the lateral expansion associated with interdigitation is strongly disfavored (37). This ubiquitous correlation is explained by a preferential expulsion or exclusion that increases the interfacial free energy and thus promotes the stability of lipid phases with low water accessible areas.…”