Role of Tail−Tail Interactions versus Head-Group−Subphase Interactions in Pressure−Area Isotherms of Fatty Amines at the Air−Water Interface. 2. Time Dependence

Langmuir ◽  
1997 ◽  
Vol 13 (20) ◽  
pp. 5440-5446 ◽  
Author(s):  
P. Ganguly ◽  
D. V. Paranjape ◽  
K. R. Patil ◽  
Murali Sastry ◽  
F. Rondelez
Keyword(s):  
Time Dependence ◽  
Head Group ◽  
Water Interface ◽  
Fatty Amines ◽  
Air Water Interface ◽  
Pressure Area

Specific ion adsorption at the air/water interface: The role of hydrophobic solvation

2009 ◽  
Vol 479 (4-6) ◽  
pp. 173-183 ◽  
Author(s):  
Dominik Horinek ◽  
Alexander Herz ◽  
Lubos Vrbka ◽  
Felix Sedlmeier ◽  
Shavkat I. Mamatkulov ◽  
...  
Keyword(s):  
Ion Adsorption ◽  
Water Interface ◽  
Air Water Interface ◽  
Specific Ion Adsorption ◽  
Hydrophobic Solvation

scholarly journals Cholesterol provides nonsacrificial protection of membrane lipids from chemical damage at air–water interface

2018 ◽  
Vol 115 (13) ◽  
pp. 3255-3260 ◽  
Author(s):  
Xinxing Zhang ◽  
Kevin M. Barraza ◽  
J. L. Beauchamp
Keyword(s):  
Lipid Membranes ◽  
Membrane Lipids ◽  
Oh Radicals ◽  
Significant Finding ◽  
Water Interface ◽  
Unsaturated Lipids ◽  
Air Water Interface ◽  
Liquid Ordered ◽  
Ester Linkage

The role of cholesterol in bilayer and monolayer lipid membranes has been of great interest. On the biophysical front, cholesterol significantly increases the order of the lipid packing, lowers the membrane permeability, and maintains membrane fluidity by forming liquid-ordered–phase lipid rafts. However, direct observation of any influence on membrane chemistry related to these cholesterol-induced physical properties has been absent. Here we report that the addition of 30 mol % cholesterol to 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) or 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1′-rac-glycerol) (POPG) monolayers at the air–water interface greatly reduces the oxidation and ester linkage cleavage chemistries initiated by potent chemicals such as OH radicals and HCl vapor, respectively. These results shed light on the indispensable chemoprotective function of cholesterol in lipid membranes. Another significant finding is that OH oxidation of unsaturated lipids generates Criegee intermediate, which is an important radical involved in many atmospheric processes.

scholarly journals Nighttime oxidation of surfactants at the air–water interface: effects of chain length, head group and saturation

2018 ◽  
Vol 18 (5) ◽  
pp. 3249-3268 ◽  
Author(s):  
Federica Sebastiani ◽  
Richard A. Campbell ◽  
Kunal Rastogi ◽  
Christian Pfrang
Keyword(s):  
Oleic Acid ◽  
Double Bond ◽  
Methyl Ester ◽  
Reaction Kinetics ◽  
Chain Length ◽  
Rate Coefficients ◽  
Head Group ◽  
Water Interface ◽  
Organic Monolayers ◽  
Air Water Interface

Abstract. Reactions of the key atmospheric nighttime oxidant NO3 with organic monolayers at the air–water interface are used as proxies for the ageing of organic-coated aqueous aerosols. The surfactant molecules chosen for this study are oleic acid (OA), palmitoleic acid (POA), methyl oleate (MO) and stearic acid (SA) to investigate the effects of chain length, head group and degree of unsaturation on the reaction kinetics and products formed. Fully and partially deuterated surfactants were studied using neutron reflectometry (NR) to determine the reaction kinetics of organic monolayers with NO3 at the air–water interface for the first time. Kinetic modelling allowed us to determine the rate coefficients for the oxidation of OA, POA and MO monolayers to be (2.8±0.7) × 10−8, (2.4±0.5) × 10−8and (3.3±0.6) × 10−8 cm2 molecule−1 s−1 for fitted initial desorption lifetimes of NO3 at the closely packed organic monolayers, τd, NO3, 1, of 8.1±4.0, 16±4.0 and 8.1±3.0 ns, respectively. The approximately doubled desorption lifetime found in the best fit for POA compared to OA and MO is consistent with a more accessible double bond associated with the shorter alkyl chain of POA facilitating initial NO3 attack at the double bond in a closely packed monolayer. The corresponding uptake coefficients for OA, POA and MO were found to be (2.1±0.5) × 10−3, (1.7±0.3) × 10−3 and (2.1±0.4) × 10−3, respectively. For the much slower NO3-initiated oxidation of the saturated surfactant SA we estimated a loss rate of approximately (5±1) × 10−12 cm2 molecule−1 s−1, which we consider to be an upper limit for the reactive loss, and estimated an uptake coefficient of ca. (5±1) × 10−7. Our investigations demonstrate that NO3 will contribute substantially to the processing of unsaturated surfactants at the air–water interface during nighttime given its reactivity is ca. 2 orders of magnitude higher than that of O3. Furthermore, the relative contributions of NO3 and O3 to the oxidative losses vary massively between species that are closely related in structure: NO3 reacts ca. 400 times faster than O3 with the common model surfactant oleic acid, but only ca. 60 times faster with its methyl ester MO. It is therefore necessary to perform a case-by-case assessment of the relative contributions of the different degradation routes for any specific surfactant. The overall impact of NO3 on the fate of saturated surfactants is slightly less clear given the lack of prior kinetic data for comparison, but NO3 is likely to contribute significantly to the loss of saturated species and dominate their loss during nighttime. The retention of the organic character at the air–water interface differs fundamentally between the different surfactant species: the fatty acids studied (OA and POA) form products with a yield of  ∼ 20 % that are stable at the interface while NO3-initiated oxidation of the methyl ester MO rapidly and effectively removes the organic character ( ≤ 3 % surface-active products). The film-forming potential of reaction products in real aerosol is thus likely to depend on the relative proportions of saturated and unsaturated surfactants as well as the head group properties. Atmospheric lifetimes of unsaturated species are much longer than those determined with respect to their reactions at the air–water interface, so they must be protected from oxidative attack, for example, by incorporation into a complex aerosol matrix or in mixed surface films with yet unexplored kinetic behaviour.

Organization of Microgels at the Air–Water Interface under Compression: Role of Electrostatics and Cross-Linking Density

Langmuir ◽  
2017 ◽  
Vol 33 (32) ◽  
pp. 7968-7981 ◽  
Author(s):  
Christine Picard ◽  
Patrick Garrigue ◽  
Marie-Charlotte Tatry ◽  
Véronique Lapeyre ◽  
Serge Ravaine ◽  
...  
Keyword(s):  
Cross Linking ◽  
Water Interface ◽  
Air Water Interface

scholarly journals Interfacial Interactions and Nanostructure Changes in DPPG/HD Monolayer at the Air/Water Interface

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Huaze Zhu ◽  
Runguang Sun ◽  
Tao Zhang ◽  
Changchun Hao ◽  
Pengli Zhang ◽  
...  
Keyword(s):  
Lung Surfactant ◽  
Compression Modulus ◽  
Metabolic Energy ◽  
Excess Gibbs Free Energy ◽  
Valuable Insight ◽  
Water Interface ◽  
Force Microscopy ◽  
Lung Expansion ◽  
Air Water Interface ◽  
Pressure Area

Lung surfactant (LS) plays a crucial role in regulating surface tension during normal respiration cycles by decreasing the work associated with lung expansion and therefore decreases the metabolic energy consumed. Monolayer surfactant films composed of a mixture of phospholipids and spreading additives are of optional utility for applications in lung surfactant-based therapies. A simple, minimal model of such a lung surfactant system, composed of 1,2-dipalmitoyl-sn-glycero-3-[phosphor-rac-(1-gylcerol)] (DPPG) and hexadecanol (HD), was prepared, and the surface pressure-area (π-A) isotherms and nanostructure characteristics of the binary mixture were investigated at the air/water interface using a combination of Langmuir-Blodgett (LB) and atomic force microscopy (AFM) techniques. Based on the regular solution theory, the miscibility and stability of the two components in the monolayer were analyzed in terms of compression modulus (Cs-1) , excess Gibbs free energy (ΔGexcπ) , activity coefficients (γ), and interaction parameter (ξ). The results of this paper provide valuable insight into basic thermodynamics and nanostructure of mixed DPPG/HD monolayers; it is helpful to understand the thermodynamic behavior of HD as spreading additive in LS monolayer with a view toward characterizing potential improvements to LS performance brought about by addition of HD to lung phospholipids.

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