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The effects of Brij 35 micelles, CTABr micelles, and mixed Brij 35-CTABr micelles on the acid-base behavior of phenyl salicylate (PST) have been studied in aqueous solution containing 2% v/v acetonitrile. The apparent pK(b) (pK(app)(b)) of PST is decreased by 1.5 pK units with the increase in [Brij 35] from 0 to 0.02 M which is attributed to micellar medium effect. The values of pK(app)(b) remain almost independent of [CTABr] within its range 0.01-0.03 M. The increase in [CTABr] from 0 to 0.03 M in aqueous solution containing 0.02 M Brij 35 has not resulted in a change in pK(app)(b). This shows that the characeristic structural features of nonionic Brij 35 micelles remain essentially unchanged on addition of CTABr under the present experimental conditions. Copyright 1999 Academic Press.
Fiber-like gold particles were prepared by irradiation of HAuCl(4) solutions at 253.7 nm in the presence of alkyltrimethylammonium chlorides (C(n)TAC: n=10, 12, 14, and 16). Fiber-like gold particles were obtained above a threshold concentration of C(n)TAC. The length of fiber-like gold particles increases with increasing alkyl chain length of C(n)TAC. Copyright 2001 Academic Press.
The components of Na and K flux across the plasma membrane have been investigated in the Ehrlich ascites tumor cell. At intracellular K levels of approximately 100 mM, unidirectional K influx is composed of a ouabain-sensitive component, a ouabain-insensitive, nondiffusional component and a diffusional component. Unidirectional K efflux is composed of an external K-dependent component and a diffusional component. Upon reduction of intracellular K to approximately 50 mM, the external K-dependent component becomes maximal and diminishes upon further reduction of intracellular K. Unidirectional Na efflux is composed of a ouabain-sensitive component, a diffusional component and a saturable, external Na-dependent, ouabain-insensitive component. Unidirectional Na influx may be accounted for by a diffusional component, based on estimates of membrane permeability to Na, membrane potential and Na distribution. This would suggest that the ouabain-insensitive, external Na-dependent Na efflux is not Na--Na exchange. The origin of the cell membrane potential has not been previously established in the Ehrlich ascites cell. From the diffusional components of Na and K flux determined in these experiments, the membrane permeabilities to Na and K have been estimated. These permeabilities, in conjunction with the Na and K distributions across the plasma membrane, predict a cell membrane potential of - 18mV (inside negative). Passive Cl distributions in these cells predict a cell membrane potential of - 21 mV, which is in agreement with previous microelectrode measurements and dibenzyldimethylammonium distributions. The results are therefore consistent with the conclusion that the magnitude and polarity of the cell membrane potential in the Ehrlich ascites cell is dictated primarily by Na and K.
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Freshly prepared human red blood cells incubated with 5 mM ferricyanide, 0.2 mM iodoacetate and 2 mM adenosine in the presence of 5 mM EGTA demonstrate comparable increases in Na+ and K+ permeability (ferricyanide effect). This effect is unrelated to the Ca2+-activated K+ channel (Gardos effect) since influx of Ca2+ from outside the cell is excluded. Also this effect is different from the non-specific Na+ and K+ permeability change elicited by PCMBS. These differences become obvious by using various reagents. For example, A23187 and quinidine exert opposite effects in Gardos and ferricyanide experiments, where A23187 and atebrin react oppositely in the latter and in PCMBS experiments. The ferricyanide effect described here does not involve formation of nonspecific channels. The change in Na+ permeability separately from K+ permeability under certain circumstances suggests a more specific effect.
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