Membrane Studies

Permeation process of small molecules across lipid membranes studied by molecular dynamics simulations. J. Phys. Chem. 100 (1996) 16729-16738. 

Marrink, S.J., Jahnig, F., Berendsen, H.J.C. Proton transport across transient single-file water pores in a lipid membrane studied by molecular dynamics simulations. Biophys. J. 71 (1996) 632-647. 

M2irrink et al., 1998] Marrink, S.-J., Berger, O., Tieleman, R, and Jahnig, F. Adhesion forces of lipids in a phospholipid membrane studied by molecular dynamics dimulations. Biophys. J. 74 (1998) 931-943... 

Alphaviruses, such as Sindbis virus and Semliki Forest virus, are a group of mosquito-borne, enveloped RNA viruses that can cause encephalitis, fever, arthritis and rashes in mammals. These viruses have two protein shells—an outer glycoprotein layer and an inner core— which are separated by a lipid bilayer, a membrane. Studies by cryoelectron microscopy have shown that... 

With the adequacy of lipid bilayer membranes as models for the basic structural motif and hence for the ion transport barrier of biological membranes, studies of channel and carrier ion transport mechanisms across such membranes become of central relevance to transport across cell membranes. The fundamental principles derived from these studies, however, have generality beyond the specific model systems. As noted above and as will be treated below, it is found that selective transport... 

Fig. 27 a and b. Schematic representation of the molecular structure of a side chain polymeric liquid crystals b polymer model membranes studied by 2H NMR... 

Gruszecki, W.I., A. Sujak, K. Strzalka, A. Radunz, and G.H. Schmid. 1999. Organisation of xanthophyll-lipid membranes studied by means of specific pigment antisera, spectrophotometry and monomolecular layer technique lutein versus zeaxanthin. Z. Naturforsch. C 54 517-525. 

A number of speculations can arise from the photo-physical data presented earlier. The major carotenoids that protect the macular are the XANs, ZEA, and LUT, yet, at least in the model membranes studies, these are rather poor 02 quenchers (compared, e.g., with P-CAR and LYC). However, free... 

Sklar, L. A., Hudson, B. S. and Simoni, R. D. (1977). Conjugated polyene fatty-acids as fluorescent-probes - Synthetic phospholipid membrane studies. Biochemistry (Mosc). 16, 819-828. 

With their newly accorded significance in signal transduction and membrane studies, the increase in knowledge about phospholipases has been remarkable. 

Hutcheson SW, Buchanan BB. Polyphenol oxidation by Viciafaba chloroplast membranes studies on the latent membrane-bound polyphenol oxidase and on the mechanism of photochemical polyphenol oxidation. Plant Physiol 1966 66 1150-1154. 

Zachariasse K. A., Kozankiewicz B. and Kuhnle W. (1983) Micelles and Biological Membranes Studied by Probe Molecules, in Zewail A. H. (Ed.), Photochemistry and Photobiology, Vol. II, Harwood, London, pp. 941-960. 

Another series of probes which has attracted much interest in membrane studies has been the 2-A-(4-nitrobenzo-2-oxa-l,3-diazole) (NBD)-labeled lipids. These have been used for studies of the lipid trafficking in intact cells using mainly fluorescence microscopic techniques(77), for fluorescence quenching 78-791 and for studies of phospholipase A2 activities in membranes.(80) To date, they have received less attention in the study of lipid dynamics. 

D. Schachter, U. Cogan, and R. E. Abbot, Asymmetry of lipid dynamics in human erythrocyte membranes studied by permeant fluorophores, Biochemistry 21, 2146-2150 (1982). 

D. Axelrod, Carbocyanine dye orientation in red cell membrane studied by microscopic fluorescence polarization, Biophys. J. 26, 557-573 (1979). 

Patri, M., Hande, V. R., Phadnis, S. and Deb, P. C. 2004. Radiation-grafted solid polymer electrolyte membrane Studies of fluorinated ethylene propylene (PEP) copolymer-g-acrylic acid grafted membranes and their sulfonated derivatives. Polymers for Advanced Technologies 15 485-489. 

All membranes studied in this work were flat sheets. Samples of approximately eight square inches were rolled into cylinders of 1 inch diameter and 2.5 inches long. Details of test chambers and gas injection equipment are shown in Figure 1. 

Dense Membrane Studies. The weight of water sorbed by SPSF-Na membranes at 100% relative humidity is plotted as a function of time in Figure 1. Water uptake increased with Increasing D.S.. The same trend was observed for the K salt membranes. The results are summarized in Table III. The point to be noted here is that the absolute amount of water sorbed by the SPSF-Na membranes is greater (by a factor of two) than that of the SPSF-K membranes. It is clear that hydrophillcity increases with increasing D.S. and is dependent on the nature of the counter ion. 

Asymmetric Membrane Studies. In light of the results presented in the preceding two sections, plus those found in the literature (21-26,28), the decision was made to commence the asymmetric membrane studies with SPSF-Na(0.A2). The selection of the sodium salt polymer was based on the desire to limit ion exchange in desalination. The selection of D.S. of 0.A2 represents a compromise of hydrophilic/hydrophobic balance and structural stability. The exploration of asymmetric membranes cast from the pol3rmers of other salts and various D.S. values is planned for the future. 

ESCA was employed to analyze membranes before and after use in the desalination cell. Wide scan ESCA spectra were obtained on the last two membranes listed in Table VII. Table IX lists the binding energies (B.E.) and the atomic fractions (A.F.) for the membranes studied. In addition to the expected carbon, oxygen, sodium, and sulfur peaks, two small peaks were attributed to nitrogen and silicon, which may be due to the contamination in the air (silicon grease). A smaller photo peak was observed at 51.3 eV and remains unasslgned. Overall, there is no significant surface contamination of the membranes. 

After completing initial mass spectrometric studies, it was quickly found, much to the authors delight, that sapphyrin 3, when protonated, acts as an efficient receptor and carrier for chloride and fluoride anions (as judged from the U-tube model membrane studies) vide infra Further, using visible absorption and fluorescence spectroscopic analyses, it proved possible to derive a binding constant (K ) of ca. 9.6 X lO for fluoride anion in methanol. For comparison, chloride anion was found to be bound with much lower affinity in this same solvent (K 10 M ), whereas bromide anion hardly formed a complex at all < 10 M ). 

For similar solvent polymeric membranes (78 wt.% dicresyl butyl phosphate in polyvinyl chloride) self-diffusion coefficients of the order of 10-7 cm2s 1 have been reported.12 These diffusion coefficients, as well as measurements of rotational mobilities,14 indicate that the solvent polymeric membranes studied here are indeed liquid membranes. This liquid phase is so viscous, however, that convective flow is virtually absent. This contrasts with pure solvent membranes where an organic solvent is interposed between two aqueous solutions either by sandwiching it between two cellophane sheets or by fixing it in a hole of a Teflon sheet separating the aqueous solutions.15 The extremely high convective flow is one of the reasons why the term membrane for extraction systems... 

Reverdin EC, Weingart R Electrical properties of the gap junctional membrane studied in rat liver cell... 

In this section we shall consider the simplest model problem for the locally electro-neutral stationary concentration polarization at an ideally permselective uniform interface. The main features of CP will be traced through this example, including the breakdown of the local electro-neutrality approximation. Furthermore, we shall apply the scheme of 4.2 to investigate the effect of CP upon the counterion selectivity of an ion-exchange membrane in a way that is typical of many membrane studies. Finally, at the end of this section we shall consider briefly CP at an electrically inhomogeneous interface (the case relevant for many synthetic membranes). It will be shown that the concentration and the electric potential fields, developing in the course of CP at such an interface, are incompatible with mechanical equilibrium in the liquid electrolyte, that is, a convection (electroconvection) is bound to arise. 

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