The Molecular Structure in Surface Films of Saturated Monoglycerides on Water as Related to Three-dimensional States¹

Abstract

The relationship of the molecular structure in monolayers of saturated 1-and 2-monoglycerides to three-dimensional states is discussed. Cross-sectional areas per molecule were calculated from density and X-ray data for the three-dimensional crystals and hypothetical liquid crystals. The areas for the latter were in agreement with the limiting areas obtained for the liquid condensed state of the monolayers. A correlation was found between the stabilities of the condensed monolayers and the stabilities of the three-dimensional crystals. The results indicate that the orientation of the molecules in the condensed monolayers approximates the orientation in the anhydrous three-dimensional crystals.

Studies on mixed monolayers of phospholipids and fusogenic lipids

“…For glyceryl mono-oleate and glyceryl monostearate, the limiting areas were 0.35 nm2 and 0.18 nm2 and the collapse pressures were 44.1 and 50.8mN-m'l respectively. These may be compared with the values of 0.37nm2 for glyceryl mono-oleate and 0.20-0.22nm2 for glyceryl monostearate, and collapse pressures between 45 and 50mN m-that have been reported by Merker & Daubert (1958. The isotherms of other lipids used were similar (within 0.04nm2) to the curves reported in the literature, and the reported collapse pressures were reproduced within 3mN m'1.…”

“…Gaines, 1966) with cholesterol and galactosylceramide (see below), and with all the phospholipids studied except for egg phosphatidylethanolamine, phosphatidylserine and dipalmitoylglycerylphosphorylethanolamine. Secondly, glyceryl monopalmitate was found to have a force-area curve that showed a transition between 6 and 10mN-m-1, from a liquid expanded to a liquid condensed state, in agreement with Merker & Daubert (1958). At pressures below lOmN m-1 thisnon-fusogeniclipidexhibitedamaximumnegative deviation of 13% in a mixed film with egg phosphatidylcholine; at higher surface pressures the observed deviation was smaller ( Table 1).…”

Lateral Intermolecular Forces between Biomembrane Lipids in Two Dimensions: 1,2-Dipalmitin at the Heptane/Water Interface Compared with Phospholipids

“…The molecular areas of long-chain n-alkanoyl glycerides spread at the air/water (A/W) interface in the close-packed state at temperatures at or close to 25 °C are given as between 0.19 and 0.21 nm 2 /molecule for 1-monoglycerides, 0.40 for 1,2-diglycerides, and 0.60 for triglycerides at high surface pressures near collapse. [35][36][37][38] 1,2n-alkanoyl phospholipids spread at the heptane/water interface show areas at high pressures close to 0.44 nm 2 /molecule. 1,4 For noninteracting hard discs, B 2 (T) will be approximately twice the close-packed area, giving ∼0.8 nm 2 /molecule for DP.…”

“…The value of B ‘ = B 2 ( T ) = 0.31 nm 2 /molecule for dipalmitin at 25 °C is definitely less than the close-packed area of ∼0.40 typical for a pair of long hydrocarbon chains. The molecular areas of long-chain n -alkanoyl glycerides spread at the air/water (A/W) interface in the close-packed state at temperatures at or close to 25 °C are given as between 0.19 and 0.21 nm 2 /molecule for 1-monoglycerides, 0.40 for 1,2-diglycerides, and 0.60 for triglycerides at high surface pressures near collapse. − 1,2- n -alkanoyl phospholipids spread at the heptane/water interface show areas at high pressures close to 0.44 nm 2 /molecule. , For noninteracting hard discs, B 2 ( T ) will be approximately twice the close-packed area, giving ∼0.8 nm 2 /molecule for DP. Calculations for 1,2- n -alkylphosphatidyl choline head groups, taken as hard circular discs or as rectangles mimicking the geometry of the zwittterion head groups, give values of B 2 ( T ) of 0.892 and 0.972 nm 2 /molecule, respectively, compared to the close-packed area of 0.446 nm 2 /molecule.…”