Oxidative Degradation of the Monolayer of 1-Palmitoyl-2-Oleoyl-sn-Glycero-3-Phosphocholine (POPC) in Low-Level Ozone

Abstract

Ambient ozone is a common pollutant in the atmosphere that has an extremely high oxidative ability, can dramatically change the structure and functionality of biomolecules, and is harmful to public health. However, the knowledge about the influence of low-level ozone is still very limited at a molecular level. In the present study, the monolayer of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC, 16:0-18:1 PC) as well as its binary mixed monolayer with 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC, 16:0 PC), which are widely found in many biological systems, have been systematically investigated in a low-level ozone environment (20 ± 10 ppb), by π-A isotherm, sum frequency generation (SFG) vibrational spectroscopy, and atomic force microscopy (AFM). Our results demonstrate that the POPC monolayer is unstable and the C═C moieties in the oleyl chain are selectively oxidized by the low-level ozone. The oxidized lipids from POPC initially remain and reorientate the hydrophilic portion to the water surface and gradually dissolve into the aqueous solution. One should take great caution when using unsaturated lipid molecules to avoid their possible oxidation in the ambient environment. The present study expands and deepens our insights into the oxidation mechanism of unsaturated lipids at a molecular level.

Mitigating oxygen loss to improve the cycling performance of high capacity cation-disordered cathode materials

“…Correspondingly, the spectral weight of the Ni L 2 -edge at ~873 eV increases upon charge and decreases upon discharge. This overall lineshape evolution of both the L 3 - and L 2 -edges is a typical sXAS evidence of Ni 2+ in the bulk of LNF15 particles oxidized to Ni 3+ and Ni 4+ upon charge, and reduced back to Ni 2+ on discharge 30, 31 . Overall, changes in the Ni L-edges are small compared with other Ni systems 31 , and the Ni 2+ signal remains strong even after charging to 4.6 V, suggesting that only a small portion of the Ni redox reservoir is utilized in LNF15 during cycling.…”

“…This overall lineshape evolution of both the L 3 - and L 2 -edges is a typical sXAS evidence of Ni 2+ in the bulk of LNF15 particles oxidized to Ni 3+ and Ni 4+ upon charge, and reduced back to Ni 2+ on discharge 30, 31 . Overall, changes in the Ni L-edges are small compared with other Ni systems 31 , and the Ni 2+ signal remains strong even after charging to 4.6 V, suggesting that only a small portion of the Ni redox reservoir is utilized in LNF15 during cycling. Additionally, because the main sXAS feature of Ni 4+ sits at higher energy compared with that of Ni 2+ and Ni 3+ 31 , the weak spectral weight above 855 eV indicates that most Ni has not been oxidized to Ni 4+ in LNF15.…”

“…8a) reveal that, prior to cycling, the Ni L 3 -edge region consists of a major peak at ~852.5 eV and a weak shoulder at ~855 eV. This is a typical lineshape of Ni 2+ -containing electrode samples 31 . Such Ni 2+ lineshape persists for all the electrodes in the surface-sensitive (~10 nm) TEY spectra (Fig.…”

“…Because TM L-edges correspond to the excitation of 2 p electrons to unoccupied 3 d orbitals, they are direct probes of TM -3d states and allow to monitor changes in oxidation states 30, 31 . In general, TM L-edge sXAS features can be divided into two regions: the L 3 -edge at lower excitation energy and the L 2 -edge at higher energy, separated by the 2 p core hole spin–orbit splitting 30, 31 .…”

Atmospheric chemistry of bioaerosols: heterogeneous and multiphase reactions with atmospheric oxidants and other trace gases

“…Several studies by Finlayson-Pitts and co-workers have shown that unsaturated phospholipids are readily oxidized by O 3 from the “top down” to generate secondary ozonides and a number of products. 122–124 The group of Ye 125,126 probed the structure and stability of phospholipids in low ozone concentration by a combination of π–A isotherms, vibrational spectroscopy, and force microscopy. Their results demonstrate that the CC moieties in the unsaturated lipids are selectively oxidized by a trace amount of ozone in the ambient environment.…”