Quantitative studies of science a current bibliography

Schubert, András

doi:10.1007/bf02026419

Cited by 1 publication

(1 citation statement)

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“…Furthermore, the added Nachol aggregated and located at boundaries between the aqueous medium and the hydrophobic edges of PC membranes when either perforated vesicles with transient holes or intermediates such as discoidal and rod-like mixed micelles were formed. 7,10,33) We thought that this boundary formation may be caused by electrostatic repulsion between the anionic charges on the surfaces of the vesicles and that the boundary would protect the hydrophobic edges of the phospholipid from exposure to the aqueous medium. Eventually, the addition of Na-chol to PC SUV caused at first a decrease in membrane fluidity, followed by aggregation of Na-chol in the PC membranes and the separation of two immiscible phases.…”

Section: )mentioning

confidence: 99%

Physical Properties of Phosphatidylcholine Vesicles Containing Small Amount of Sodium Cholate and Consideration on the Initial Stage of Vesicle Solubilization.

Sun

Kashiwagi

Ueno

2002

CHEMICAL & PHARMACEUTICAL BULLETIN

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Sodium cholate (Na-chol) is a physiological detergent. Its solubilizing properties are important in several fundamental biophysical and biochemical processes. This includes disintegration of biomembranes to mixed micelles, 1) reconstitution of membrane proteins and lipids to functional supramolecular structures (vesicles in most cases) 2,3) and preparation of homogeneous lipid vesicles of controlled sizes. 4,5) The vesicle destruction mechanism has been studied in connection with the reconstitution of membrane proteins after purification in detergent solutions. Concerning the disintegration from mixed vesicles to mixed micelles by Nachol, many studies have concentrated on the variation in morphology and properties of mixed aggregates.6,7) Consequently, the solubilization process of phosphatidylcholine (PC) vesicles is summarized as follows; addition of very small amounts of Na-chol to vesicles results in the partitioning of Na-chol between the water and lipid phases. At a further increased detergent concentration, vesicles containing a large amount of Na-chol are formed, whose behavior, such as fusion of small vesicles to larger ones, is found to be different from that of PC vesicles containing large amounts of nonionic detergents (i.e. octylglucoside).5) At a still further increased detergent concentration, the Na-chol-containing vesicles disintegrate into intermediate structures, and finally into mixed micelles. 8,9) As far as intermediate structures are concerned, structural changes from vesicles to perforated vesicles, to discoidal sheets, 10) or to rod-like structures 11) have been reported. As described above, the incorporation of Na-chol into vesicular membranes remarkably influences the structures and properties of PC vesicles. However, little is known about the effects of the incorporation of Na-chol on the behavior of membranes at a molecular level, although it is important for further detailed studies on the mechanism of vesicle disintegration. The present report deals with the influence of addition of small amounts (insufficient to destroy vesicles) of Na-chol on several physicochemical properties of PC small unilamellar vesicles (SUV). Similar to the previous reports, 12-14) ESR spectra of a spin label 12-doxylstearic acid (12-DS) are applied to monitor the variation in properties and structures of the mixed PC SUV. Differential scanning calorimetry (DSC) and z potentials measured with electrophoretic light scattering methods were also employed for observing the variation in the properties of PC SUV induced by Na-chol. The obtained results will be considered in connection with the initial stage of the solubilization of PC vesicular membranes. ExperimentalMaterials Phosphatidylcholine isolated from egg yolk (EPC) (purity approximately 98.8%) was purchased from Nihon Yushi (Tokyo, Japan). Sodium cholate and cholesterol of guaranteed degree were obtained from Nacalai Tesque (Kyoto, Japan). Synthetic dimyristoylphosphatidylcholine (DMPC) (purity ca. 99%) as well as 5-, 12-, and 16-DS were purchased from...

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Section: )mentioning

confidence: 99%