ABSTRACT:We present a theoretical study of the structural evolution of small minimum energy platinum clusters, using density functional theory (DFT). Three growth pathways were identified. At the subnanoscale, clusters with triangular packing are energetically most favorable. At a cluster size of approximately n ϭ 19, a structural transition from triangular clusters to icosahedral clusters occurs. A less energetically favorable transition from triangular clusters to fcc-like clusters takes place at around n ϭ 38. Ionization potentials, electron affinities, and magnetic moments of the triangular clusters were also calculated. Understanding the structures and properties will facilitate studies of the chemical reactivity of Pt nanoclusters toward small molecules.

The main bottleneck of photocatalytic H2 evolution is the high recombination rate of photoexcited electrons and holes. Herein, a novel composite comprising p-type AgFeO2 nanoparticles loaded on the surface of n-type ZnIn2S4 microspheres was successfully synthesized via an ultrasound-assisted method. Because of the intimate interface between AgFeO2 and ZnIn2S4 and the formed internal electric field, the ZnIn2S4/AgFeO2 p–n heterojunction has more efficient separation and migration of photoexcited charge carriers, thereby significantly increasing the photocatalytic H2 evolution rate. Compared with pure ZnIn2S4, ZnIn2S4/AgFeO2-3 composite showed a 30-fold increase in H2 evolution rate (9.14 mmol h–1 g–1). Meanwhile, various characterization techniques provided powerful proof for the formation of the p–n heterojunction and the transport pathway of the charge carrier. The specific photocatalytic mechanism was discussed for the visible-light photocatalytic H2 evolution. This work offers a valuable guidance toward the design and fabricate other p–n heterojunctions having high photocatalytic performance for use in the energy and environment fields.

H2 sequential dissociative chemisorption on small palladium clusters was studied using density functional theory. The chosen clusters Pdn (n = 2-9) are of the lowest energy structures for each n. H2 dissociative chemisorption and subsequent H atom migration on the bare Pd clusters were found to be nearly barrierless. The dissociative chemisorption energy of H2 and the desorption energy of H atom in general decrease with the coverage of H atoms and thus the catalytic efficiency decreases as the H loading increases. These energies at full cluster saturation were identified and found to vary in small energy ranges regardless of cluster size. As H loading increases, the clusters gradually change their bonding from metallic character to covalent character. For the selected Pd clusters, the capacity to adsorb H atoms increases almost proportionally with cluster size; however, it was found that the capacity of Pd clusters to adsorb H atoms is, on average, substantially smaller than that of small Pt clusters, suggesting that the catalytic efficiency of Pt nanoparticles is superior to Pd nanoparticles in catalyzing dissociative chemisorption of H2 molecules.

MicroRNAs (miRNAs) are a group of small non-coding RNAs that modulate post-transcriptional gene expression. It has been demonstrated that various miRNAs may be expressed at different levels in different types of tumors. The present study assessed the role of microRNA-148a-3p (miR-148a-3p) in epithelial ovarian cancer (EOC). The results demonstrated that miR-148a-3p was decreased in EOC tissues and that a lower miRa-148-3p concentration was associated with a higher overall survival rate. Transfection of miR-148a-3p suppressed the invasive and proliferative capacity of SKOV3 cells. The induced overexpression of miR-148a-3p significantly inhibited the relative luciferase activity of the pmirGLO-c-Met-3′untranslated region compared with an empty vector. In addition, c-Met silencing led to a decrease in the invasive and proliferative capacity of EOC cells. The inhibition of miR-148a-3p did not increase the invasiveness of SKOV3 cells, even when c-Met was silenced. To the best of our knowledge, the present study is the first to demonstrate that miR-148a-3p expression is decreased in EOC cancer tissues and cell lines. The present study therefore demonstrated that miR-148a-3p may serve as a tumor suppressor in EOC by targeting c-Met.

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Hydrogen dissociative chemisorption and desorption on small lowest energy Ni(n) clusters up to n=13 as a function of H coverage was studied using density functional theory. H adsorption on the clusters was found to be preferentially at edge sites followed by 3-fold hollow sites and on-top sites. The minimum energy path calculations suggest that H(2) dissociative chemisorption is both thermodynamically and kinetically favorable and the H atoms on the clusters are mobile. Calculations on the sequential H(2) dissociative chemisorption on the clusters indicate that the edge sites are populated first and subsequently several on-top sites and hollow sites are also occupied upon full cluster saturation. In all cases, the average hydrogen capacity on Ni(n) clusters is similar to that of Pd(n) clusters but considerably smaller than that of Pt(n) clusters. Comparison of hydrogen dissociative chemisorption energies and H desorption energies at full H-coverage among the Ni family clusters was made.

The abnormal expression of microRNAs (miRNAs/miRs) has been widely reported in various tumor types. miR-217 was demonstrated to be aberrantly expressed in a number of tumors, including pancreatic adenocarcinoma and osteosarcoma; however, its specific expression pattern has never been investigated in cervical cancer cells. Compared with normal control, the level of Rho-associated protein kinase 1 (ROCK1) expression was markedly increased in cervical cancer tissues and cells compared with that in non-cancerous tissues and cells. The expression of miR-217 was significantly reduced in cervical cancer tissues and cell lines. Overexpression of miR-217 could suppress colony formation and the cell invasion capacity of SiHa and HeLa cells. Flow cytometry indicated that miR-217 significantly increased cell apoptosis in SiHa and HeLa cells. Dual-luciferase reporter assays demonstrated that ROCK1 was a target gene of miR-217. In addition, overexpression of ROCK1 also led to an increased invasion capacity in SiHa cells, even when miR-217 was inhibited, indicating that the anti-invasive effects of miR-217 were mediated through ROCK1. In summary, the results of the present study indicated that miR-217 functions as a tumor suppressor in cervical cancer cells, primarily by targeting ROCK1.