Effects of surface pressure on the structure of the monolayer formed at the air/water interface by a non-ionic surfactant

The effect of neutral helper lipids on the structure of cationic lipid monolayers

“…approx. 42 [27,34]. Reassuringly, the isotherm measured for DODAB/cholesterol in the present study is similar to that reported for the same lipid mixture by Hac-Wydro et al [27].…”

“…In order to determine the hydration of the lipids as described by Ma et al [42], the number densities of the components of the monolayer were calculated in the z-direction (data not shown). At each point in the z-direction, z i , the quotient of the number densities, n, of the two components, n S (z i )/n L (z i ), where n S and n L are the number of solvent and lipid molecules, respectively, gives the number of water molecules associated with the DODAB molecule at that position in the monolayer.…”

Structure of vesicles formed from non-ionic dialkylglycerol poly(oxyethylene) ether surfactants: effect of electrolyte and cholesterol

“…With no tilt and no intermixing of headgroup and hydrophobe the 2C 18 E 12 bilayer thickness would, therefore, be ∼80Å. As the thin bilayer for 2C 18 E 12 has been attributed, by neutron reflectivity and neutron scattering (Barlow et al, 1997;Ma et al, 2008), to the mixing of some of the oxyethylene groups with the hydrophobic chains it is not unreasonable to assume the same explanation for the thin bilayers of 2C 16 E 12 and 2C 18 E 16 , although an alternative explanation may of course may be that there is interdigitation of the hydrocarbon chains as reported for bilayers formed solely from the anionic PEG lipid, prepared from distearoylphosphatidylethanolamine and polyoxyethylene glycol of molecular weight 350 (corresponding to approximately 8 ethyl oxide units) (Kenworthy et al, 1995a). However, given the absence of ionic species in the head groups of the lipids studied here (in contrast to those studied by Kenworthy et al which involved anionic phosphate groups) there would be less need for interdigitation as a means to reduce electrostatic repulsion.…”

“…Previous freeze fracture electron microscopy (FFEM) and small angle neutron scattering (SANS) measurements, particularly small angle neutron scattering and neutron specular reflection, in combination with isotopic substitution have been used successfully to characterize the monolayers and vesicle bilayers formed by the lead surfactant in the series, namely 2C 18 E 12 (Harvey et al, 2004;Ma et al, 2008). Surprisingly, it was found that there was considerable intermixing of the hydrophilic polyoxyethylene chains with the hydrophobic alkyl chains in the mono and bilayers prepared by 2C 18 E 12 (Barlow et al, 1997;Ma et al, 2008).…”

“…Surprisingly, it was found that there was considerable intermixing of the hydrophilic polyoxyethylene chains with the hydrophobic alkyl chains in the mono and bilayers prepared by 2C 18 E 12 (Barlow et al, 1997;Ma et al, 2008). This intermixing was thought to be the reason for the poor encapsulation of water-soluble materials by the 2C 18 E 12 vesicles (Harvey et al, 2007).…”