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- Claesson, PM, et al.
(författare)
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Interactions between hydrophilic mica surfaces in triolein: Triolein surface orientation, solvation forces, and capillary condensation
- 1997
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Ingår i: Langmuir. - 0743-7463 .- 1520-5827. ; 13, s. 1682-1688
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Tidskriftsartikel (refereegranskat)abstract
- Results obtained from surface force measurements using hydrophilic mica surfaces in triolein are presented. The forces were determined for different water activities in the triglyceride sample. With anhydrous triolein two oscillations in the force curve are observed. They appear at a separation of 60-50 Å and 30-20 Å. An interfacial ordering of triolein, allowing two molecular layers between the surfaces at the position of the outer oscillation and one molecular layer at the inner one is proposed. This structure at the interface is different from the triglyceride conformation suggested for the bulk system. A dramatic effect of water content on the structural forces is observed. The number and amplitude of the oscillations are dependent on the water content. The oscillations completely disappear when the triolein sample is satured with water, and the force becomes purely attractive. These data are interpreted in terms of preferential adsorption of water molecules onto the hydrophilic mica surface and in terms of a changing water adsorption with surface separation. The adhesion force between the surfaces is strongly increased when the water content is close to its saturation value. The strong adhesion is attributes to the presence of a water capillary around the contact position.
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- Dedinaite, A, et al.
(författare)
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Interactions between modified mica surfaces in triglyceride media
- 1998
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Ingår i: Langmuir. - 0743-7463 .- 1520-5827. ; 14, s. 5546-5554
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Tidskriftsartikel (refereegranskat)abstract
- Results obtained from surface force measurements using modified nonpolar mica surfaces immersed in triolein are presented. The force vs distance curves were determined for different water activities in the interaction medium. Two oscillations with a periodicity of 20 Å were observed in the force curve measured across anhydrous triolein. The force barriers appear at separations of 45-40 and 20-30 Å. It is suggested that triolein has no clear preferential orientation of the oleic acid chains outside a nonpolar surface. This is different from outside a polar mica surface where triolein adopts conformations with the three oleic acid residues directed toward the bulk. At high water contents the triolein molecules outside nonpolar surfaces suddenly change their orientation when a high compressive force is applied. The forces acting between mica surfaces were measured in triolein solutions containing phospholipids at different water activities. It was shown that the phospholipid self-assembled onto the mica surfaces and rendered them nonpolar. The forces between such surfaces in anhydrous triolein are similar to those observed between mica hydrophobized using the Langmuir-Blodgett technique. In addition, at high water activities a weak long range repulsive force was observed. This force was interpreted as being due to weakly adsorbed phospholipid aggregates. We discuss the implications of the results for the stability and physical properties of colloidal particle dispersions in nonpolar media. Adsorption isotherms for the phospholipid from refined vegetable oil at low water activity on mica and sucrose crystals are presented. They show that the phospholipid adsorbs in a monolayer on mica. On sucrose more than monolayer coverage is observed, which we interpret in terms of a phase separation of phospholipid into crevices and cracks.
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- Dedinaite, A, et al.
(författare)
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Interactions between modified mica surfaces in triglyceride media
- 1998
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Ingår i: LANGMUIR. - : AMER CHEMICAL SOC. - 0743-7463. ; 14:19, s. 5546-5554
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Results obtained from surface force measurements using modified nonpolar mica surfaces immersed in triolein are presented. The force vs distance curves were determined for different water activities in the interaction medium. Two oscillations with a perio
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- Palmqvist, K, et al.
(författare)
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Photosynthetic capacity in relation to nitrogen content and its partitioning in lichens with different photobionts
- 1998
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Ingår i: Plant, Cell and Environment. - : Wiley. - 0140-7791 .- 1365-3040. ; 21:4, s. 361-372
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Tidskriftsartikel (refereegranskat)abstract
- We tested the hypothesis that lichen species with a photosynthetic CO2-concentrating mechanism (CCM) use nitrogen more efficiently in photosynthesis than species without this mechanism. Total ribulose bisphosphate carboxylase-oxygenase (Rubisco; EC 4.1.1.39) and chitin (the nitrogenous component of fungal cell walls), were quantified and related to photosynthetic capacity in eight lichens. The species represented three modes of CO2 acquisition and two modes of nitrogen acquisition, and included one cyanobacterial (Nostoc) lichen with a CCM and N2 fixation, four green algal (Trebouxia) lichens with a CCM but without N2 fixation and three lichens with green algal primary photobionts (Coccomyxa or Dictyochloropsis) lacking a CCM. The latter have N2-fixing Nostoc in cephalodia. When related to thallus dry weight, total thallus nitrogen varied 20-fold, chitin 40-fold, Chl a 5-fold and Rubisco 4-fold among the species. Total nitrogen was lowest in three of the four Trebouxia lichens and highest in the bipartite cyanobacterial lichen. Lichens with the lowest nitrogen invested a larger proportion of this into photosynthetic components, while the species with high nitrogen made relatively more chitin. As a result, the potential photosynthetic nitrogen use efficiency was negatively correlated to total thallus nitrogen for this range of species. The cyanobacterial lichen had a higher photosynthetic capacity in relation to both Chl a and Rubisco compared with the green algal lichens. For the range of green algal lichens both Chl a and Rubisco contents were linearly related to photosynthetic capacity, so the data did not support the hypothesis of an enhanced photosynthetic nitrogen use efficiency in green-algal lichens with a CCM.
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- Zabel, B A, et al.
(författare)
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Human G protein-coupled receptor GPR-9-6/CC chemokine receptor 9 is selectively expressed on intestinal homing T lymphocytes, mucosal lymphocytes, and thymocytes and is required for thymus-expressed chemokine-mediated chemotaxis
- 1999
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Ingår i: Journal of Experimental Medicine. - 1540-9538. ; 190:9, s. 1241-1256
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Tidskriftsartikel (refereegranskat)abstract
- TECK (thymus-expressed chemokine), a recently described CC chemokine expressed in thymus and small intestine, was found to mediate chemotaxis of human G protein-coupled receptor GPR-9-6/L1.2 transfectants. This activity was blocked by anti-GPR-9-6 monoclonal antibody (mAb) 3C3. GPR-9-6 is expressed on a subset of memory alpha4beta7(high) intestinal trafficking CD4 and CD8 lymphocytes. In addition, all intestinal lamina propria and intraepithelial lymphocytes express GPR-9-6. In contrast, GPR-9-6 is not displayed on cutaneous lymphocyte antigen-positive (CLA(+)) memory CD4 and CD8 lymphocytes, which traffic to skin inflammatory sites, or on other systemic alpha4beta7(-)CLA(-) memory CD4/CD8 lymphocytes. The majority of thymocytes also express GPR-9-6, but natural killer cells, monocytes, eosinophils, basophils, and neutrophils are GPR-9-6 negative. Transcripts of GPR-9-6 and TECK are present in both small intestine and thymus. Importantly, the expression profile of GPR-9-6 correlates with migration to TECK of blood T lymphocytes and thymocytes. As migration of these cells is blocked by anti-GPR-9-6 mAb 3C3, we conclude that GPR-9-6 is the principal chemokine receptor for TECK. In agreement with the nomenclature rules for chemokine receptors, we propose the designation CCR-9 for GPR-9-6. The selective expression of TECK and GPR-9-6 in thymus and small intestine implies a dual role for GPR-9-6/CCR-9, both in T cell development and the mucosal immune response.
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