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- Cárdenas, Marité, et al.
(författare)
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Human Saliva Forms a Complex Film Structure on Alumina Surfaces
- 2007
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 8:1, s. 65-69
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Tidskriftsartikel (refereegranskat)abstract
- Films formed from saliva on surfaces are important for the maintenance of oral health and integrity by protection against chemical and/or biological agents. The aim of the present study was to investigate adsorbed amounts, thickness, and structure of films formed from human whole saliva on alumina surfaces by means of in situ ellipsometry, neutron reflectivity, and atomic force microscopy. Alumina (Al2O3, synthetic sapphire) is a relevant and interesting substrate for saliva adsorption studies as it has an isoelectric point close to that of tooth enamel. The results showed that saliva adsorbs rapidly on alumina. The film could be modeled in two layers: an inner and dense thin region that forms a uniform layer and an outer, more diffuse and thicker region that protrudes toward the bulk of the solution. The film morphology described a uniformly covering dense layer and a second outer layer containing polydisperse adsorbed macromolecules or aggregates.
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| 3. |
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| 4. |
- Vacklin, H P, et al.
(författare)
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Composition of supported model membranes determined by neutron reflection
- 2005
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 21:7, s. 2827-2837
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the formation of supported bilayers by coadsorption of dipalmitoyl phosphatidylcholine (DPPC) with the nonionic surfactant P-D-dodecyl maltoside. The adsorption of mixed phospholipid-surfactant micelles on hydrophilic silica surfaces at 25 degrees C was followed as a function of bulk concentration by neutron reflection. Using chain-deuterated d(25)-beta-D-dodecyl maltoside and d(62)-DPPC, we demonstrate that it is possible to determine the composition of the bilayers at each stage of a sequential dilution process, which enriches the adsorbed layer in phospholipid and leads to complete elimination of the surfactant. The final supported bilayers have thicknesses of 51 +/- 3 angstrom and are stable to heating to 37 degrees C once all surfactant has been removed, and the structures agree well with other published data on DPPC supported bilayers. The coadsorption of cholesterol in a DPPC-surfactant mixture was also achieved, and the location and volume fraction of cholesterol in the DPPC bilayer was determined. Cholesterol is located in a 18 +/- 1 angstrom thick layer below the lipid headgroup region and leads to an increased bilayer thickness of 58 +/- 2 angstrom at 26 mol % of cholesterol.
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| 5. |
- Vacklin, H P, et al.
(författare)
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Phospholipase A(2) hydrolysis of supported phospholipid bilayers: A neutron reflectivity and ellipsornetry study
- 2005
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Ingår i: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 44:8, s. 2811-2821
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the phospholipase A(2) catalyzed hydrolysis of supported phospholipid bilayers using neutron reflection and ellipsometry. At the hydrophilic silica-water interface, hydrolysis of phosphatidy1choline bilayers by phospholipase A(2) from Naja mossambica mossambica venom is accompanied by destruction of the bilayer at an initial rate, which is comparable for DOPC and DPPC but is doubled for POPC. The extent of bilayer destruction at 25 degreesC decreases from DOPC to POPC and is dramatically reduced for DPPC. Neutron reflectivity measurements indicate that the enzyme penetrates into the bilayers in increasing order for DOPC, POPC, and DPPC, while the amount of enzyme adsorbed at the interface is smallest for DPPC and exhibits a maximum for POPC. Penetration into the hydrophobic chain region in the bilayer is further supported by the fact that the enzyme adsorbs strongly and irreversibly to a hydrophobic monolayer of octadecyltrichlorosilane. These results are rationalized in terms of the properties of the reaction products and the effect of their accumulation in the membrane on the kinetics of enzyme catalysis.
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