In this study, we performed small RNA library sequencing using human placental tissues to identify placenta-specific miRNAs. We also tested the hypothesis that human chorionic villi could secrete miRNAs extracellularly via exosomes, which in turn enter into maternal circulation. By small RNA library sequencing, most placenta-specific miRNAs (e.g., MIR517A) were linked to a miRNA cluster on chromosome 19. The miRNA cluster genes were differentially expressed in placental development. Subsequent validation by real-time PCR and in situ hybridization revealed that villous trophoblasts express placenta-specific miRNAs. The analysis of small RNA libraries from the blood plasma showed that the placenta-specific miRNAs are abundant in the plasma of pregnant women. By real-time PCR, we confirmed the rapid clearance of the placenta-specific miRNAs from the plasma after delivery, indicating that such miRNAs enter into maternal circulation. By using the trophoblast cell line BeWo in culture, we demonstrated that miRNAs are indeed extracellularly released via exosomes. Taken together, our findings suggest that miRNAs are exported from the human placental syncytiotrophoblast into maternal circulation, where they could target maternal tissues. Finally, to address the biological functions of placenta-specific miRNAs, we performed a proteome analysis of BeWo cells transfected with MIR517A. Bioinformatic analysis suggests that this miRNA is possibly involved in tumor necrosis factor-mediated signaling. Our data provide important insights into miRNA biology of the human placenta.

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Optically active phosphines play a most important role as the chiral ligands in various metal-catalyzed asymmetric reactions, and numerous chiral phosphines have been designed and synthesized over the past three decades. 1 Among them, some P-chiral phosphines such as (R,R)-1,2-bis[(o-methoxyphenyl)phenylphosphino]ethane (DIPAMP) were landmark discoveries at an early stage in the history of asymmetric hydrogenation reactions. 2,3 Thereafter, however, relatively less attention has been paid to P-chiral phosphine ligands in the field of asymmetric catalysis. 4 This is largely ascribed not only to the synthetic difficulty of highly enantiomerically enriched P-chiral phosphines but also to the fact that this class of phosphines, especially diaryl-and triarylphosphines, are configurationally unstable and gradually racemize at high temperatures. 5 On the other hand, optically active trialkylphosphines are known to hardly racemize even at considerably high temperature. 6 On the basis of this fact, we designed a new class of P-chiral phosphine ligands, 1,2-bis(alkylmethylphosphino)ethanes (alkyl ) tert-butyl, 1,1-diethylpropyl, 1-adamantyl, cyclopentyl, cyclohexyl) (abbreviated as BisP*) (Figure 1). 7 An important feature of these ligands is that a bulky alkyl group and the smallest alkyl S0002-7863(97)03423-9 CCC: $15.00

Cu is known as one of the most promising metallic catalysts for conversion of CO2 to hydrocarbons such as methane, ethylene, and ethanol by electrochemical reduction. The oxide-derived Cu (OD-Cu) moiety has been investigated as a candidate for enhancing the activity for CO2 electrochemical reduction to C2+ products. The reduction process is affected by catalytic grain boundary, local pH, residual oxygen atoms, and other features of the catalysts. In order to understand the detailed mechanism, we performed in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (in situ ATR-SEIRAS) measurements for CO2 reduction using several different Cu electrodes whose oxidation states are controlled. The spectroscopic investigations demonstrate that a copper oxide electrode (Cu2O) has low activity against CO2 reduction on the basis of low-level detection of CO as an intermediate of CO2 reduction. On the other hand, other Cu electrodes possessing an OH layer on the Cu surface (Cu­(OH)2/Cu) and metallic Cu exhibit higher CO2 reduction activity with significantly greater detection of produced CO. When the metallic Cu electrode is used, only one peak (2060 cm–1) assignable to CO bound to the atop site of Cu is observed. However, additional peaks are detected in the range of 1900–2100 cm–1 when the Cu­(OH)2/Cu electrode is used. To understand these findings, the adsorption energy of CO on a Cu­(OH)2/Cu electrode and the CO stretching frequency were evaluated by performing DFT calculations. The adsorption energy is enhanced and the CO stretching frequencies are shifted to lower energy in comparison with those using a metallic Cu electrode. These results indicate that it is predominantly favorable to adsorb some CO molecules near the OH moiety of the Cu­(OH)2/Cu electrode and to induce interactions of CO molecules with each other. This observation is consistent with the results of controlled potential electrolysis (CPE), which generates C2+ products as previously reported. When CPE is carried out in D2O solution, residual and/or adsorbed OD– groups on Cu are detected by ATR-SEIRAS and the surface of the Cu­(OH)2/Cu electrode is confirmed to be metallic Cu, as measured by in situ Raman and XPS. From the ATR-SEIRAS experiments when switching from under CO2 to Ar during the electrochemical reduction, the OH layer is suggested to prevent deactivation of the Cu electrode via formation of the CO layer, which is detected as a bridge-bounded form on the metallic Cu electrode. The above findings indicate that the OH layer provides the advantage of attracting CO molecules closer to each other while reducing them to C2+ products without any degradation during electrolysis.