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1.
2.
The packing of lipids into different aggregates, such as spheres, rods, or bilayers, is dependent on the hydrophobic volume, the hydrocarbon-water interfacial area, and the hydrocarbon chain length of the participating molecules, according to the self-assembly theory [Israelachvili, J. N., Marcelja, S., & Horn, R. G. (1980) Q. Rev. Biophys. 13, 121-200]. The origin of the participating molecules should be of no importance with respect to their abilities to affect the above-mentioned parameters. In this investigation, Acholeplasma laidlawii, with a defined acyl chain composition of the membrane lipids, has been grown in the presence of three different classes of foreign molecules, known to partition into model and biological membranes. This results in an extensive metabolic alteration in the lipid polar head group composition, which is expressed as changes in the molar ratio between the lipids monoglucosyldiglyceride (MGDG) and diglucosyldiglyceride (DGDG), forming reversed hexagonal and lamellar phases in excess water, respectively. The formation of nonlamellar phases by A. laidlawii lipids depends critically upon the MGDG concentration [Lindblom, G., Brentel, I., Sj?lund, M., Wikander, G., & Wieslander, A. (1986) Biochemistry (preceding paper in this issue)]. The foreign molecules tested belong to the following groups: nonpolar organic solvents, alcohols, and detergents. Their effects on the gel to liquid crystalline phase transition temperature (Tm), on the order parameter of the acyl chains, and on the phase equilibria between lamellar and nonlamellar liquid crystalline phases in lipid-water model systems are known in several instances.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
3.
Thermotropic phase properties of 1,2-di-O-tetradecyl-3-O-(3-O-methyl- beta-D-glucopyranosyl)-sn-glycerol.
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T P Trouard D A Mannock G Lindblom L Rilfors M Akiyama R N McElhaney 《Biophysical journal》1994,67(3):1090-1100
The hydration properties and the phase structure of 1,2-di-O-tetradecyl-3-O(3-O-methyl-beta-D-glucopyranosyl)-sn-glycerol (3-O-Me-beta-D-GlcDAIG) in water have been studied via differential scanning calorimetry, 1H-NMR and 2H-NMR spectroscopy, and x-ray diffraction. Results indicate that this lipid forms a crystalline (Lc) phase up to temperatures of 60-70 degrees C, where a transition through a metastable reversed hexagonal (Hll) phase to a reversed micellar solution (L2) phase occurs. Experiments were carried out at water concentrations in a range from 0 to 35 wt%, which indicate that all phases are poorly hydrated, taking up < 5 mol water/mol lipid. The absence of a lamellar liquid crystalline (L alpha) phase and the low levels of hydration measured in the discernible phases suggest that the methylation of the saccharide moiety alters the hydrogen bonding properties of the headgroup in such a way that the 3-O-Me-beta-D-GlcDAIG headgroup cannot achieve the same level of hydration as the unmethylated form. Thus, in spite of the small increase in steric bulk resulting from methylation, there is an increase in the tendency of 3-O-Me-beta-D-GlcDAIG to form nonlamellar structures. A similar phase behavior has previously been observed for the Acholeplasma laidlawii A membrane lipid 1,2-diacyl-3-O-(6-O-acyl-alpha-D-glucopyranosyl)-sn-glycerol in water (Lindblom et al. 1993. J. Biol. Chem. 268:16198-16207). The phase behavior of the two lipids suggests that hydrophobic substitution of a hydroxyl group in the sugar ring of the glucopyranosylglycerols has a very strong effect on their physicochemical properties, i.e., headgroup hydration and the formation of different lipid aggregate structures. 相似文献
4.
Distinct and overlapping ligand specificities of the alpha 3A beta 1 and alpha 6A beta 1 integrins: recognition of laminin isoforms. 总被引:7,自引:1,他引:6
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G O Delwel A A de Melker F Hogervorst L H Jaspars D L Fles I Kuikman A Lindblom M Paulsson R Timpl A Sonnenberg 《Molecular biology of the cell》1994,5(2):203-215
The ligand specificity of the alpha 3A beta 1 integrin was analyzed using K562 cells transfected with full-length alpha 3A cDNA and was compared with that of alpha 6A beta 1 in similarly transfected K562 cells. Clones were obtained that showed comparable surface expression of either alpha 3A beta 1 or alpha 6A beta 1 integrins. Those expressing alpha 3A beta 1 attached to and spread on immunopurified human kalinin and cellular matrices containing human kalinin, which is a particular isoform of laminin. In addition, alpha 3A transfectants adhered to bovine kidney laminins possessing a novel A chain variant. Binding to kalinin was blocked by a monoclonal antibody against the A chain constituent of kalinin and adhesion to both kalinin and kidney laminins by anti-alpha 3 and beta 1 monoclonal antibodies. The alpha 3A transfected cells bound more strongly to kalinin and bovine kidney laminins after treatment with the beta 1 stimulatory antibody TS2/16. A distinctly weaker and activation-dependent adhesion of alpha 3A transfectants was observed on human placental laminins possessing the Am chain variant (merosin), and no adhesion occurred on bovine heart laminins and murine EHS tumor laminin. Further inactive substrates were fibronectin, nidogen, and collagen types IV and VI, indicating that the alpha 3A beta 1 integrin is a much less promiscuous receptor than thought before. By contrast, alpha 6A transfected cells adhered to all laminin isoforms when stimulated with TS2/16. Adhesion also occurred only on bovine kidney laminins in the absence of TS2/16. These results demonstrate that both alpha 3A beta 1 and alpha 6A beta 1 integrins are typical laminin receptors but that their affinity and activation dependence for binding to various laminin isoforms differ considerably. 相似文献
5.
Hans Lindblom U.-B. Axiö-Rredriksson Edward H. Cooper Ron Turner 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1983,273(1):107-116
Proteins excreted in urine due to renal failure were separated on Mono QTM, a new strong anion exchanger designed for fast high-resolution protein separations. The separation procedure was divided into two steps. The first step involved removal of low-molecular- weight substances by rapid desalting on a Sephadex G-25 Superfine column. In the second step, the total protein fraction (3–6 ml) was loaded onto the Mono Q column with the aid of a superloop. The proteins were adsorbed onto the top of the ion-exchanger column and gradually displaced by a combined pH and salt gradient in 40 min. The choice of ion exchanger and initial operating conditions were based on data obtained from electrophoretic titration curve experiments. Identification of separated proteins was achieved by fused rocket electrophoresis and sodium dodecyl sulphate-polyacrylamide gel electrophoresis, respectively. 相似文献
6.
Proton NMR spectra for gel and liquid crystalline samples, composed of dimyristoyl and/or dipalmitoyl lecithin, cholesterol and water, can be consistently interpreted in terms of mesophase symmetry and molecular diffusion according to a model proposed by Wennerstrom (Wennerstrom, H. (1973) Chem. Phys. Lett. 18, 41-44). It is shown by computer simulation that the characteristic "super-lorentzian" bandshape of the lamellar mesophase can be described by the superposition of three gaussian curves. The NMR signal of the gel phase can be simulated by the superposition of two gaussian curves with widths at half height of 2.5 kHz and 19 kHz. An upper limit of the lateral diffusion coefficient of the lecithin molecules in the gel phase is calculated to be about 5-10(-15) m-2/s. It is therefore concluded that the static intermolecular dipolar couplings average to zero in the lamellar mesophase. An estimation of the order parameter of the liquid crystalline phase is made from experimental data and a calculated "rigid lattice" linewidth. A two phase system is shown to exist in the temperature range 28-34 degrees C for a mesophase of a mixture of dimyristoyl and dipalmitoyl lecithin. The presence of cholesterol results in enhanced lateral diffusion of the lecithin molecules at temperatures below the Chapman transition point. 相似文献
7.
Leukotrienes and myometrial activity of the term pregnant uterus 总被引:1,自引:0,他引:1
Biopsies from different segments of the pregnant human uterus were superfused in organ chambers and contractile activity was registered. Leukotriene C4(LTC4) caused inhibition of spontaneous but not noradrenaline induced contractile activity in strips from the cervix. This effect occurred both in early pregnancy and at term. However, the lower and the upper uterine segment of the term pregnant uterus did not respond to LTC4. The results represent a documentation of the segmental differentiation in the uterine response to eicosanoids. 相似文献
8.
Sensibility and cutaneous reinnervation in free flaps 总被引:2,自引:0,他引:2
A Hermanson C J Dalsgaard C Arnander U Lindblom 《Plastic and reconstructive surgery》1987,79(3):422-427
Sensibility and sensory reinnervation were investigated in 19 free flaps, predominantly located on the lower extremities, between 2 months and 3 years after flap transfer. All patients showed deep pressure sensibility. In 10 of the patients, primarily those examined late after surgery, a heat pain threshold was obtained at about 50 degrees C. None of the patients had superficial sensibility of any other modality. No neurofilament-positive sensory nerve fibers were observed in the dermis or epidermis. In one patient nerve fibers were detected in the subcutaneous tissue. It is concluded that patients will have deep pressure sensibility of the flap area even early after the operation and that most patients will develop a heat pain sensitivity, probably due to subcutaneous reinnervation. 相似文献
9.
Christina T. Fuentes Catarina Runa Xenxo Alvarez Blanco Verónica Orvalho Patrick Haggard 《PloS one》2013,8(10)
Despite extensive research on face perception, few studies have investigated individuals’ knowledge about the physical features of their own face. In this study, 50 participants indicated the location of key features of their own face, relative to an anchor point corresponding to the tip of the nose, and the results were compared to the true location of the same individual’s features from a standardised photograph. Horizontal and vertical errors were analysed separately. An overall bias to underestimate vertical distances revealed a distorted face representation, with reduced face height. Factor analyses were used to identify separable subconfigurations of facial features with correlated localisation errors. Independent representations of upper and lower facial features emerged from the data pattern. The major source of variation across individuals was in representation of face shape, with a spectrum from tall/thin to short/wide representation. Visual identification of one’s own face is excellent, and facial features are routinely used for establishing personal identity. However, our results show that spatial knowledge of one’s own face is remarkably poor, suggesting that face representation may not contribute strongly to self-awareness. 相似文献
10.