Interfacial Reactions of Ozone with Surfactant Protein B in a Model Lung Surfactant System

Abstract

Oxidative stresses from irritants such as hydrogen peroxide and ozone (O3) can cause dysfunction of the pulmonary surfactant (PS) layer in the human lung, resulting in chronic diseases of the respiratory tract. For identification of structural changes of pulmonary surfactant protein B due to the heterogeneous reaction with O3, field induced droplet ionization (FIDI) mass spectrometry is utilized. FIDI is a soft ionization method in which ions are extracted from the surface of microliter-volume droplets. We report the structurally specific oxidative changes of SP-B1-25 (a shortened version of human surfactant protein B) at the air-liquid interface. We also present studies of the interfacial oxidation of SP-B1-25 in a non-ionizable 1-palmitoyl-2-oleoyl-sn-glycerol (POG) surfactant layer as a model PS system, where the competitive oxidation of the two components is observed. Our results indicate that the heterogeneous reaction of SP-B1-25 at the interface is quite different from that in the solution phase. Compared to the nearly complete homogeneous oxidation of SP-B1-25, only a subset of the amino acids known to react with ozone is oxidized by direct ozonolysis in the hydrophobic interfacial environment, both with and without the lipid monolayer. Combining these experimental observations with the results of molecular dynamics simulations provides an improved understanding of the interfacial structure and chemistry of a model lung surfactant system when subject to oxidative stress.

Time resolved study of hydroxyl radical oxidation of oleic acid at the air-water interface

“…In earlier FIDI studies of the oxidation of lipid mixtures by ozone it was observed that eventually the products from oxidized unsaturated lipids were dissolved back into solution, leaving a surface layer dominated by unreactive saturated lipids. 26 are much lower than other products discussed above (Figures 1 and 4) where no bond cleavage occurs; they amount to approximately 4% of the total product yield. The major m/z 171 peak is a result of the C=C bond cleaved into an aldehyde group, and the peaks at higher m/z can be accounted for as oxidation products of the nascent aldehyde product.…”

Stability of an amphipathic helix-hairpin surfactant peptide in liposomes

“…Exposure of mixed monolayers composed of POPC and DPPC to ozone does not lead to a loss of DPPC from the air-water interface, but surface activity changes significantly secondary to oxidative damage of the unsaturated POPC [32]. Similar findings have been reported for the shorter SP-B mimic SP-B 1–25 in unsaturated 1-palmitoyl-2-oleoyl-sn-glycerol [33]. Both components were affected by exposure to ozone resulting in reduced surface activity at the air-water interface.…”

Studying Interfacial Reactions of Cholesterol Sulfate in an Unsaturated Phosphatidylglycerol Layer with Ozone Using Field Induced Droplet Ionization Mass Spectrometry

“…Field-induced droplet ionization mass spectrometry (FIDI-MS) employs a soft ionization technique to sample ions from the surface of microliter liquid droplets to a mass analyzer [12][13][14][15]. Utilizing FIDI-MS, several studies of time-resolved heterogeneous reactions at air-liquid interfaces have been reported [14,15].…”

“…Utilizing FIDI-MS, several studies of time-resolved heterogeneous reactions at air-liquid interfaces have been reported [14,15]. For example, the location and orientation of SP-B 1-25 (a shortened version of human surfactant protein B) in a lipid surfactant layer has been deduced from experimentally observed reactivity with ozone (O 3 ) using a FIDI-MS methodology [14].…”

“…Utilizing FIDI-MS, several studies of time-resolved heterogeneous reactions at air-liquid interfaces have been reported [14,15]. For example, the location and orientation of SP-B 1-25 (a shortened version of human surfactant protein B) in a lipid surfactant layer has been deduced from experimentally observed reactivity with ozone (O 3 ) using a FIDI-MS methodology [14]. In addition, detailed mechanistic studies of the heterogeneous oxidation of unsaturated phospholipids as well as the alteration of phospholipid compositions resulting from reaction with O 3 at the air-liquid interface have also been reported [15].…”