An Upside Down View of Cholesterol's Condensing Effect: Does Surface Occupancy Play a Role?

Janout, Vaclav
Türkyılmaz, Serhan
Wang, Minghui
Wang, Yao
Manaka, Yuichi
Regen, Steven L.
The condensing action or cholesterol has been compared with that of a structural isomer having its hydroxyl group located at the C-25 position (i.e., 25-OH'), that is, an isomer favoring an "upside down" orientation in lipid membranes. Surface pressure area isotherms of mixed monolayers made from 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DM PC)/cholesterol and DM PC/25-OH' have established that 25-OH' has a weaker condensing effect than cholesterol. Nearest-neighbor recognition measurements in liposomes made from 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) have also shown that 25-OH' has a weaker condensing effect in the physiologically relevant fluid bilayer state. These findings provide support for surface occupancy playing a role in the condensing action of cholesterol.


Tamoxifen Increases Membrane Fluidity at High Concentrations
Severcan, Feride; Kazanci, Nadide; Zorlu, Faruk (Portland Press Ltd., 2000-6-1)
There are contradictory results in the literature relating to the effect of tamoxifen on membrane fluidity. The present work investigates the effect of tamoxifen on membrane dynamics to find out whether the concentration of tamoxifen can be one of the factors in this discrepancy. Turbidity (absorbance at 440 nm) and Fourier transform infrared spectroscopic studies reveal that tamoxifen causes opposite effects on membrane fluidity at low (1 mol.%) and high (30 mol.%) tamoxifen concentrations. Low tamoxifen c...
The Effect of 15-lipoxygenase-1 (15-LOX-1) on angiogenesis in colorectal and prostate cancer
Çolakoğlu, Melis; Banerjee, Sreeparna; Department of Biology (2017)
15-lipoxygenase-1 (15-LOX-1) is one of the lipoxygenases (LOX) that are important for the generation of inflammatory bioactive lipids, which then result in the initiation and resolution of inflammation. The enzyme mainly metabolizes the omega-6 fatty acid, linoleic acid, to 13-(S)-HODE. In colorectal carcinoma, the tumor suppressive role of 15-LOX-1 is highlighted with decreased proliferation, induction of apoptosis, reduced motility and invasion. Oppositely, the expression of 15-LOX-1 was reported to have ...
Investigation of phase inversion behavior of cellulose- ionic liquid solutions in relationship with membrane formation
Durmaz, Elif Nur; Çulfaz Emecen, Pınar Zeynep; Department of Chemical Engineering (2017)
Cellulose membranes were produced from ionic liquid solutions by phase inversion technique and thermodynamic and kinetic aspects of the process were investigated to relate these to membrane morphology and performance. In thermodynamics part, polymer-solvent, polymer-nonsolvent and polymer-solvent-nonsolvent interactions were examined experimentally, together with Hansen solubility parameter estimations. Kinetics part consisted of measuring phase inversion rate. Obtained membranes were characterized by their...
The effect of different solvents on the performance of zeolite-filled composite pervaporation membranes
Sener, Tansel; Okumus, Emin; Gurkan, Turker; Yılmaz, Levent (2010-10-15)
The aim of this research is to study effect of different solvents on the membrane morphology and on the performance of zeolite-filled composite pervaporation membranes. PAN (polyacrylonitrile) was used as a base polymer and zeolite 13x (32 wt.%) was used as the filler. The solvents considered were DMF (dimethyl formamide), DMSO (dimethyl sulfoxide), DMAc (dimethyl acedamide) and THF (tetrahydrofuran). The cross-sectional morphology of manufactured membranes shows three layers: a zeolite-free polymer layer, ...
Modelling of long-term photoresponse of bacteriorhodopsin immobilized on cellulose acetate membranes
Sediroglu, V; Aydemir, A; Gündüz, Ufuk; Yucel, M; Turker, L; Eroglu, I (1996-05-01)
Purple membrane fragments with its integrated protein bacteriorhodopsin were immobilized on lipid impregnated and lipid free cellulose acetate membranes. Two mathematical models were suggested to simulate the photoresponse curves of these membranes which were obtained by measuring the pH variation independently in each chamber of a specifically designed photoactivity cell for long periods of illumination. The first order model suggested was mainly based on the existence of light phase deprotonation and dark...
Citation Formats
V. Janout, S. Türkyılmaz, M. Wang, Y. Wang, Y. Manaka, and S. L. Regen, “An Upside Down View of Cholesterol’s Condensing Effect: Does Surface Occupancy Play a Role?,” LANGMUIR, pp. 5316–5318, 2010, Accessed: 00, 2020. [Online]. Available: