5336partitioning in the case of this relatively small hydrophilic monocation compared to the distinct binding observed with the larger, more hydrophobic C B P underlines the role of hydrophobic factors and once again reinforces the idea that these cations as well as probably many other polar organic molecules are solubilized or J. Am. Chem. SOC. 1981, 103, 5336-5341 interact with micelles by binding at hydrophobic-hydrophilic interfaces.Abstract: A simple theory based on electrochemical principles is presented which predicts some of the catalytic properties of the widely used colloidal metal dispersions. The theory has been specifically applied to the case of photocatalytic water reduction to H2. The model assumes that the kinetic properties of the system are governed by the current-potential curves of the half-reactions and that the reaction velocity can be determined by finding the common potential at which the current attributable to the mediator (e.g., methyl viologen) oxidation is equal to that for proton reduction at the metal surface. The effects of pH, mediator potential, and colloid size and composition can be predicted. These predictions have been experimentally verified with methyl viologen radical cation generated electrochemically and photochemically (via the Ru(bpy)?+-N-phenylglyche system) and with other mediators at colloidal dispersions of several metals.
The role of HLA-DR+ cells in NK activity against CMV-infected FS4 foreskin fibroblasts and K562 erythroleukemia cells was examined. When nonadherent PBMC were depleted of either HLA-DR+ or Leu-11b+ cells by treatment with mAbs plus C, NK activity against CMV-FS4 target cells was markedly reduced. In contrast, depletion of HLA-DR+ cells had no effect on NK activity against K562 target cells. When HLA-DR-depleted cells were added to Leu-11b-depleted cells, NK activity against CMV-FS4 was restored. Negative selection experiments indicated that the HLA-DR+ cells contributing to NK activity against CMV-FS4 are not B or T cells, while negative and positive selection experiments excluded a role for monocytes. Experiments in which HLA-DR- and Leu-11b- cells were mixed in varying proportions indicated that NK(CMV-FS4) is mediated by Leu-11b+ cells, while HLA-DR+ cells provide an accessory function. Irradiation (50 GY) abolished the NK effector function of Leu-11b+ cells, but not the accessory function of HLA-DR+ cells. The NK activity against CMV-FS4 of HLA-DR- cells was restored by the addition of rIFN-alpha or of cell-free supernatants generated by coculturing PBMC or Leu-11b- cells with CMV-FS4. The ability of these supernatants to restore NK activity of HLA-DR- cells was completely abrogated by the addition of neutralizing amounts of antibody to IFN-alpha. In related experiments, neutralization of IFN-alpha in NK assays had little or no effect on NK activity against CMV-FS4, suggesting that the accessory function of HLA-DR+ cells might be mediated by alternative mechanisms in addition to the secretion of extracellular IFN-alpha.
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