Studying Membrane Behavior

Biological membranes are delicate structures that assemble as a result of the amphiphilic properties of lipid molecules in an aqueous environment, they will form lipid bilayers. To investigate the properties of a lipid 

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Reverse micelles can also act as a convenient membrane mimetic medium for studying membrane interactions of bioactive peptides [329,330]. Fluorescence behavior of piroxicam in AOT-RMs and Triton X-100 microemulsions was investigated by Andrade and Costa [331].Dutta etal. [332] studied the interactions of an antileprotic drug dapson in dipalmitoyl phosphotidyl choline (DPPC)-RMs in chloroform. The DPPC was found to form RMs just beyond 6 mmol 1" concentration, which is relatively low compared to conventional AOT concentration. 

Liquid crystals are widely believed to be closely related to membranes of living cells and have been used as model systems in studies to understand membrane behavior. Among dynamic processes of interest here are transport of various species across membranes and various motions and deformations of membranes. 

In the model membrane studies discussed here, results from experiments using bovine brain ceramides differed from those using epidermal ceramides in the presence of a solid phase in the former, i.e. a lipid organization in which molecular motion is less than in a gel, and similar to that observed in an anhydrous powder. Model membranes composed of epidermal ceramides are clearly an advantage in studying the behavior of SC intercellular membranes, and appropriate NMR studies to detect such a phase will resolve this issue. One possible explanation is found by considering the kinetics of the formation of the solid phase In the bovine brain ceramide mixtures it was very slow to form, on the order of days to weeks, and was even more sluggish at pH 7.4... 

Demir I. (1988) Studies of smectite membrane behavior electrokinetic, osmotic, and isotopic fractionation processes at elevated pressures. Geochim. Cosmochim. Acta 52, 727-737. 

Haydon P. R. and Graf D. L. (1986) Studies of smectite membrane behavior Temperature dependence, 20-180°C. Geochim. Cosmochim. Acta 50, 115-122. 

A way to analyze different distributions of dipoles at the membrane interface is by studying the behavior of the surface potential as a function of the group esterified to the phosphate (Diaz et al., 2001 Disalvo et al., 2002). 

The membrane or interfacial potential, particularly in biological applications, is often determined from the change in fluorescence of added carbocyanine dyes (12, 13). The fluorescence intensity of the dyes depends on the solvent in which the dyes are present. When the dyes are used as potential-sensitive probes, their fluorescent intensity is a function of the interfacial potential across the membrane. We studied the behavior of dye transport on a phase boundary between water and nitrobenzene to better understand the principles of the potential dye partitioning as a function of interfacial potential (141... 

Structural changes in the lipid bilayer upon insertion of the transmembrane domain of the membrane-bound protein phospholamban (PLB) were studied using P and solid state NMR. Phospholamban is a 52-amino acid integral membrane protein that regulates the flow of Ca " ions in cardiac muscle cells. Solid state NMR experiments were carried out to study the behavior of lipid bilayers in the presence of the hydrophobic PLB at different temperatures. P NMR was used to study the different phases formed by phospholipid membranes. Simulations of the P NMR spectra were carried out to reveal the formation of different vesicle sizes upon PLB insertion. Molecular order parameters were calculated by performing solid state NMR studies on deuterated phospholipid bilayers. 

Similarly, Shukla and Cheryan [18], studying the behavior of the permeation of 18 UF membranes, found that 15 of these membranes agree with the Darcy model, in which the permeate flux decreased in linear correlation with the increasing viscosity of the permeation solvent, indicating that in these 15 UF membranes, the transport phenomenon of the solvent was affected by viscosity. 

In order to study the behavior of the pores it is assumed that all other transport processes in the membrane apart from the K antiport are switched off. The equations for the fluxes are... 

As already mentioned, an important feature of the membrane assisted fluidized bed to be elucidated is the effect of membranes (and permeation through them) on the bubble behavior (and hence on mass/heat transfer). A DPM can be used in combination with an immersed boundary method to study the behavior of the gas in the immediate vicinity of the membrane. With this... 

Two other media that offer promise for further studies of this sort are membranes and sol -gel glasses. Showalter and colleagues (Winston et al., 1991) studied the behavior of waves on the surface of a Nafion membrane impregnated... 

The behavior of alkyl-chained pyrogaUol[4]arenes in membranes as assayed by the planar bilayer method is described in Section 4. The compounds to which those studies refer aU had hnear alkyl chains. The fact that branched chain compounds, especially tetra-3-pentylpyrogallol[4]arene, differed in some respects in their behavior from those having hnear chains, suggested that different transport activity might be observed in the membrane. We determined to compare the membrane behavior of the 3-pentyl- and 4-heptylpyrogallol[4]arenes. As noted earher, the former crystalhzes as a unique nanombe and the latter forms bilayers in the solid state [30]. 

In order to correlate chemical surface nature of the studied membranes with their structures and electrical behavior, values of some of these parameters are presented in the next section. Equipments and experimental procedures have been reported in the literature [13,19,24,34-35]. 

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