Interaction of short-chain lecithin with long-chain phospholipids: characterization of vesicles that form spontaneously

Abstract

Stable unilamellar vesicles formed spontaneously upon mixing aqueous suspensions of long-chain phospholipid (synthetic, saturated, and naturally occurring phosphatidylcholine, phosphatidylethanolamine, and sphingomyelin) with small amounts of short-chain lecithin (fatty acid chain lengths of 6-8 carbons) have been characterized by using NMR spectroscopy, negative staining electron microscopy, differential scanning calorimetry, and Fourier transform infrared (FTIR) spectroscopy. This method of vesicle preparation can produce bilayer vesicles spanning the size range 100 to greater than 1000 A. The combination of short-chain lecithin and long-chain lecithin in its gel state at room temperature produces relatively small unilamellar vesicles, while using long-chain lecithin in its liquid-crystalline state produces large unilamellar vesicles. The length of the short-chain lecithin does not affect the size distribution of the vesicles as much as the ratio of short-chain to long-chain components. In general, additional short-chain decreases the average vesicle size. Incorporation of cholesterol can affect vesicle size, with the solubility limit of cholesterol in short-chain lecithin micelles governing any size change. If the amount of cholesterol is below the solubility limit of micellar short-chain lecithin, then the addition of cholesterol to the vesicle bilayer has no effect on the vesicle size; if more cholesterol is added, particle growth is observed. Vesicles formed with a saturated long-chain lecithin and short-chain species exhibit similar phase transition behavior and enthalpy values to small unilamellar vesicles of the pure long-chain lecithin prepared by sonication. As the size of the short-chain/long-chain vesicles decreases, the phase transition temperature decreases to temperatures observed for sonicated unilamellar vesicles. FTIR spectroscopy confirms that the incorporation of the short-chain lipid in the vesicle bilayer does not drastically alter the gauche bond conformation of the long-chain lipids (i.e., their transness in the gel state and the presence of multiple gauche bonds in the liquid-crystalline state).

Ribosome-independent Regulation of Translocon Composition and Sec61α Conformation

“…These studies also noted that solubilization of membranes with such detergents preserves the structural organization of the bilayer in the mixed micelle (44,45). In contrast to digitonin, DHPC is a short-chain phosphatidylcholine derivative, which, because of its pronounced structural similarities to native membrane lipids and solubility in aqueous media, efficiently disperses biological membranes (34,46). In so doing, DHPC is remarkable in its ability to preserve native membrane protein structure and function in the solubilized state (34,35).…”

Characterization of the Surfaces Generated by Liposome Binding to the Modified Dextran Matrix of a Surface Plasmon Resonance Sensor Chip

“…The size of the bicelles increases with decreasing bicelle concentration. Presumably, the short-chain phospholipid is depleted from the bicelles because of its high solubility resulting in bicelle fusion as indicated by the larger size (10).…”

Preservation of the native structure and function of Ca2+-ATPase from sarcoplasmic reticulum: Solubilization and reconstitution by new short-chain phospholipid detergent 1,2-diheptanoyl-sn-phosphatidylcholine

“…The two detergents that are most widely used for SR Ca# + -ATPase study are C "# E ) and cholate. Gabriel and Roberts [41] first demonstrated the ability of short-chain phospholipids to disperse bilayers of long-chain phospholipids. It was subsequently shown by Kessi et al [24] that DHPC acts as an effective solubilizing agent for biological membranes.…”