Dehalogenation of halide precursors [ (olefin)RhCl], [olefin = ethylene, 1,5-cyclooctadiene (COD), norbornadiene (NBD), 2,3-dimethylbutadiene (DMB)] in water gave the respective cis-diolefin aqua ions, characterized by NMR spectroscopy in solution. Attempted isolation of the tosylate salt [(COD)Rh-(H20),]OTs yielded crystals of (COD)Rh(H20)(q'-OTs) characterized by X-ray structural analysis. [(NBD)Rh(H,0),]SbF6 in the presence of adventitious toluene decomposed into [(NBD)Rh(~f-toluene)]SbF, and [(NBD),Rh]SbF,, both complexes were isolated and structurally characterized. Ethylene exchange in [(C,H4)2Rh(H20)2]f is fast with k2 of the order of 104-105 s-l . M-'. The rate constant for water exchange in [CODRh(H20),]' is estimated a s lo4 s-' (AGf73 = 25 k J I mol) at 173 K. Scheme 1 X = BF,, OTs-, CF,SO,-1,2,4-7 for: 1 2 6 7 for: 4 5 Dehalogenation of Olefin Chloro Complexes Treatment of [(COD)RhC1I2 with AgOTs in water, water/ acetone, or watedethanol gave almost instantaneously a
The formation of bis(phosphino)nitrilimine 3 demonstrates the potential of tin diazo compounds as nitrilimines precursors and allows a clarification of the mechanism of the reaction of electrophiles with lithium diazo compounds. The first experimental evidence of an organic nitrilimine and its isolation were separated by 30 years. The crucial step was the stabilization of these 1,3-dipoles by heteroatom substituents. Experimental Procedure6: An acetonitrile solution (4 mL) of bis(trimethylstanny1)diazomethane (2) (278mg, 0.757mmol) was added dropwise to 2 equivalents of triphenylmethylchloride (421 mg, 1.51 mmol) in acetonitrile (6 mL) at -30 "C. The solution was stirred for 1 h at -30 "C, and 6 precipitated as a pale yellow solid which was washed several times with acetonitrile. Trimethylchlorostannane was removed under vacuum (ca. 15 h) at room temperature. Nitrilimine 6 was recrystallized from THF/Et,O (358 mg, 90%). Nitrilimine 6 is air stable in the solid state but slowly decomposes in solution above -20 "C. Cycloaddition reactions: A solution of the dipolarophile in THF was added to the stoichiometric amount of nitrilimine 6 in THF at -30 "C. The mixture was allowed to warm to room temperature, and the solvent was then removed at lo-, Torr. The solids 7-10 were washed several times with pentane and dried in vacuo.
Tritiated proline was administered to domestic cats during the development of their permanent premolars. The metabolic activity of collagen in the mature premolar dentin was determined by quantitating the amount of tritiated hydroxyproline in the dentin as a function of time. It has been demonstrated that the metabolic activity of the dentinal collagen was extremely low and remained within the experimental error for a period of 45 weeks.
Previously it has been suggested that Li+/Na+ exchange is a mode of operation of Na+/H+ exchange, with arguments pro and contra. In the present experiments this question was studied by measuring Li+ effluxes from Li+ loaded trout erythrocytes under various conditions. Trout erythrocytes were loaded with Li+ by incubation in a lithium carbonate-containing solution and the efflux of Li+ was determined in both Na+-free and 150 mM Na+-containing media. The presence of Na+ enhanced the Li+ efflux. The Na+ effect was neither sensitive to amiloride nor to 5-NN-dimethylamiloride (DMA), both inhibitors of the Na+/H+ exchanger. Activation of the Na+/H+ exchanger by isoproterenol was demonstrated by an increased Li+ efflux (Li+/H+ exchange mode of the Na+/H+ exchanger). This effect was eliminated by DMA and amiloride, and by the presence of O2 which also inhibits the Na+/H+ exchanger in trout erythrocytes. However, the activation of the Li+ efflux by Na+ was not affected by O2. The finding that the stimulating effect of Na+ on Li+ efflux persists to occur in the presence of amiloride, DMA, or O2, supports the idea that the trout erythrocyte possesses a Li+/Na+ exchanger that is different from the Na+/H+ exchanger.
Abstract. The protein responsible for the Na+/Li+ ex change activity across the erythrocyte membrane has not been cloned or isolated. It has been suggested that a Na'TH4' exchanger could be responsible for the Na+/Li+ exchange activity across the erythrocyte membrane. Pre viously, we reported that in the trout erythrocyte, the Li+/H+ exchange activity (mediated by the Na'VH* ex changer 3NHE) and the Na+/Li+ exchange activity re spond differently to cAMP, DMA (dimethyl-amiloride) and 0 2. We concluded that the DMA insensitive Na+/ Li+ exchange activity originates from a different protein.To further examine these findings, we measured Li+ ef flux in fibroblasts expressing the (3NHE as the only Na+/ H+ exchanger. Moreover, the internal pH of these cells was monitored with a fluorescent probe. Our findings indicate that acidification of fibroblasts expressing the Na+/H+ exchanger £NHE, induces a Na+ stimulated Li+ efflux activity in trout erythrocytes. This exchange ac tivity, however, is DMA sensitive and therefore differs from the DMA insensitive Na+/Li+ exchange activity. In these fibroblasts no significant DMA insensitive Na+/ Li* exchange activity was found. These results support the hypothesis that the trout erythrocyte NaVLi* ex change activity is not mediated by the Na+/H+ exchanger (pNHE) present in these membranes.
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