In discussions of cellular permeability frequent reference is made to the peculiar sensitivity, of some mammalian erythrocytes to snmll traces of copper, observed in studies of the penetration of glycerol into these cells. The retarding effect of copper on hemolysis of human red cells in isosmotic glycerol solutions was first reported by Jacobs and Corson (1934); Jacobs and his group (1938) have subsequently demonstrated this action in the rat, rabbit, and guinea pig, though not in many other mammals tested. With suitable precautions against interference by extraneous protein, Jacobs and Stewart (1946) detected the inhibition of entry of glycerol into the human red cell by copper at concentrations around 10 --7 M. With 90 per cent inhibition, the amounts of copper required could not have covered more than about 1 per cent of the total cell surfaces involved; furthermore, no diminution in the effect was found when the ceils were quickly removed and replaced from a fresh suspension, so that only a small fraction of even this small amount of copper was actually removed in the inhibitory processes. These considerations clearly suggested a special mechanism for glycerol entry into these ceils, apparently localized in limited regions on the cell surfaces. Davson and Reiner (1942), in discussing the active transfer of sodium across the cat erythrocyte membrane, called attention to the evidence then at hand of an analogous active movement of glycerol in the human red cell.Such small quantities of copper as those found effective in this connection typically show inhibitory effects on certain types of enzymatic reactions (Hellerman, 1937;Rapkine, 1938). Enzymes whose activity depends on readily available sulfhydryl (thiol) groups are often interfered with by small traces of copper, as well as by various other oxidizing agents, and by alkylating or mercapfide-forming agents . Thus it seemed expedient to test the effect on glycerol hemolysis of some of these agents which resemble copper in their inhibitory effects on other systems. The results of these experiments suggested that the entrance of glycerol into the human erythrocyte might involve the activity of a sulfhydryl-containlng enzyme or at least of some sulfhydryl groups located at the cell surfaces.Later experiments in which volume changes were followed by the photo-505

The effects of slurry surfactant, abrasive size, abrasive content, wafer pressure, and sliding velocity on frictional and kinetics attributes of copper chemical mechanical planarization were studied. While abrasive content did not affect the tribological mechanism of the process, abrasive size was shown to be a significant factor. Surfactant-containing formulations were also shown to dramatically reduce coefficient of friction ͑COF͒. At low pressures and velocities, the removal rate was independent of surfactant content, abrasive diameter, and abrasive concentration, while at high pressures and velocities, surfactant-containing slurries caused an increase in removal rate. Slurries containing a larger abrasive increased removal rate. No correlation was observed between the removal rate and COF. Instead the removal rate was shown to loosely correlate with the variance of the frictional force, thus suggesting that the rapid formation and extinction of the copper oxide layer as captured by the variance of frictional forces ͑i.e., stick-slip͒ was the rate-determining step.

No abstract

The ‘carrier’ system in the surface of the human erythrocyte, facilitating passage of monosaccharides through the cell membrane, reacts preferentially with those sugars in which the pyranose ring tends to assume the particular ‘chair’ shape designated by Reeves as the ‘C1’ conformation. This novel type of steric specificity was revealed in a comparative study of fourteen aldoses (6 pentoses, 5 hexoses, and 3 deoxyhexoses), in which the dissociation constants of the carrier-sugar complexes were derived from the kinetics of the transfer process and of the competitive inhibition by phloretin. The sequence of increasing affinities thus determined paralleled the sequence of increasing relative stability in the C1 conformation as dictated by the distribution of substituent groups between axial and equatorial positions on the ring. Sugars predominantly stable in the other chair conformation (1C) showed extremely low affinity. Since no instance of biological utilization of the latter sugars has apparently yet been found, it is suggested that the necessity for the C1 ring-shape is basic in all enzymic reactions with pyranoses. However, most systems show further special requirements for particular side-group arrangements, which are superimposed on the primary ring specificity seen in the red cell's sugar transport system.