Interfacial Organizations of Gel Phospholipid and Cholesterol in Bovine Lung Surfactant Films

Abstract

Pulmonary surfactants stabilize the lung by way of reducing surface tension at the air-lung interface of the alveolus. 31P NMR, thin-layer chromatography, and electrospray ionization mass spectroscopy of bovine lipid extract surfactant (BLES) confirmed dipalmitoylphosphatidylcholine (DPPC) to be the major phospholipid species, with significant amounts of palmitoyl-oleoylphosphatidylcholine, palmitoyl-myristoylphosphatidylcholine, and palmitoyl-oleoylphosphatidylglycerol. BLES and DPPC spread at the air-water interface were studied through surface pressure area, fluorescence, and Brewster angle microscopy measurements. Langmuir-Blodgett films of monomolecular films, deposited on mica, were characterized by atomic force microscopy. BLES films displayed shape, size, and vertical height profiles distinct from those of DPPC alone. Calcium ions in the subphase altered BLES film domain structure. The addition of cholesterol (4 mol %) resulted in the destabilization of compressed BLES films at higher surface pressures (>40 mN m-1) and the formation of multilayered structures, apparently consisting of stacked monolayers. The studies suggested potential roles for individual surfactant lipid components in supramolecular arrangements, which could be the contributing factors in pulmonary surfactant to attain low surface tension at the air-water interface.

Physicochemical studies on ion-pair amphiphiles: Solution and interfacial behaviour of systems derived from sodium dodecylsulfate and n-alkyltrimethylammonium bromide homologues

“…[18][19][20] Besides atomic force microscopic measurements of the transferred monolayer and Langmuir-Blodgett (LB) technique have been used to understand their microstructural information. 21,22 Although physicochemical studies have been made on the bulk as well as the interfacial properties of IPAs, still the efforts are considered fragmentary in nature. 4,5,[23][24][25] Although the said coacervates can mimic phospholipids, still their surface activity, aqueous solubility, vesicle forming capability, etc.…”

The anatomy, physics, and physiology of gas exchange surfaces: is there a universal function for pulmonary surfactant in animal respiratory structures?

“…One possibility is that they represent higher order condensed DPPCcholesterol regions, in which the cholesterol intercalates between the acyl chains inducing further rigidity, thereby, further reducing the tilt of the acyl chains relative to the plane of the liquid-expanded film and in turn increasing the height profile. Alternatively, addition of cholesterol may cause other structural anomalies such as formation of stacked layers, as recently reported in a study where cholesterol was added to BLES, an exogenous clinical surfactant formulation (Nag et al 2007).…”

Properties of Lipid Models of Lung Surfactant Containing Cholesterol and Oxidized Lipids: A Mixed Experimental and Computational Study

“…8 Furthermore, we observe similar structures in the imaging of the cholesterol-depleted poractant alpha, and similar structures were obtained previously for poractant alpha and other cholesterol-depleted lung surfactant extracts. 40,41 It suggests that the immiscibility is caused by the lack of cholesterol. This is supported by previous studies where addition of cholesterol to cholesterol-depleted lung surfactant extracts led to reduction of film inhomogeneities.…”