As a two-dimensional (2D) material, molybdenum disulfide (MoS2) exhibits unique electronic and optical properties useful for a variety of optoelectronic applications including light harvesting. In this article, we review recent progress in the synthesis, properties and applications of MoS2 and related heterostructures. Heterostructured materials are developed to add more functionality or flexibility compared to single component materials. Our focus is on their novel properties and functionalities as well as emerging applications, especially in the areas of light energy harvesting or conversion. We highlight the correlation between structural properties and other properties including electronic, optical, and dynamic. Whenever appropriate, we also try to provide fundamental insight gained from experimental as well as theoretical studies. Finally, we discuss some current challenges and opportunities in technological applications of MoS2.

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In mammals, follicular atresia can be partially triggered by granulosa cell apoptosis. However, very little is known about the functions of miRNAs in granulosa cell apoptosis. We previously reported that hsa-mir-23a (miR-23a) and hsa-mir-27a (miR-27a) were highly expressed in the plasma of patients with premature ovarian failure, but the action of these two miRNAs in follicular development was unclear. In this study, we explored the roles of miR-23a and miR-27a in the granulosa cells of women undergoing in vitro fertilization/embryo transfer. Using Hoechst staining, we found that miR-23a and miR-27a promoted apoptosis in human granulosa cells. In addition, the Western blotting results suggested that the miR-23a/miR-27a-mediated apoptosis occurred via the FasL-Fas pathway. Based on the results of a luciferase-reporter assay and quantitative RT-PCR and Western blotting analyses, we found that SMAD5 is a target gene of both miR-23a and miR-27a. Furthermore, knocking down SMAD5 expression increased the rate of apoptosis, as well as the levels of Fas, FasL, cleaved caspase-8, and cleaved caspase-3 protein. Taken together, these data suggest that miR-23a and miR-27a target SMAD5 and regulate apoptosis in human granulosa cells via the FasL-Fas pathway. These findings provide an improved understanding of the mechanisms underlying granulosa cell apoptosis, which could potentially be used for future clinical applications.

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Tn5397 is a novel conjugative transposon, originally isolated from Clostridium difficile. This element can transfer between C. difficile strains and to and from Bacillus subtilis. It encodes a conjugation system that is very similar to that of Tn916. However, insertion and excision of Tn5397 appears to be dependent on the product of the element encoded gene tndX, a member of the large resolvase family of site-specific recombinases. To test the role of tndX, the gene was cloned and the protein was expressed in Escherichia coli. The ability of TndX to catalyze the insertion and excision of derivatives (minitransposons) of Tn5397 representing the putative circular and integrated forms, respectively, was investigated. TndX was required for both insertion and excision. Mutagenesis studies showed that some of the highly conserved amino acids at the N-terminal resolvase domain and the C-terminal nonconserved region of TndX are essential for activity. Analysis of the target site choices showed that the cloned Tn5397 targets from C. difficile and B. subtilis were still hot spots for the minitransposon insertion in E. coli.Conjugative transposons are gene transfer elements that can move from the genomes of donor cells to those of recipients, sometimes across large phylogenetic distances. They are one of the major vectors responsible for the spread of antibiotic resistance among bacterial pathogens (for recent reviews, see references 32, 37, and 39). The most intensely studied of the conjugative transposons is Tn916. This 18.3-kb element was originally isolated from the chromosome of Enterococcus faecalis DS16, where it mediated tetracycline resistance via the tet(M) gene (11). The complete DNA sequence of this element has been obtained (10). Open reading frames have been identified that have the potential to encode polypeptides with sequence similarity to proteins known to be involved in conjugation (e.g., the antirestriction protein Ard of plasmid Collb-P9 and the MbeA mobilization protein of plasmid ColE1). A functional oriT site has also been located (19), and there is evidence that this site is involved in single-stranded DNA transfer to the recipient (35,40).Tn5397 is a 21-kb tetracycline resistance-encoding conjugative transposon originally found in Clostridium difficile (24,25). Tn5397 was shown to be transferred by a conjugation-like process from C. difficile strain 630 to Bacillus subtilis strain CU2189 and back to C. difficile, and between C. difficile strains (24). Furthermore, Tn5397 has also been shown to be capable of transfer in a model oral biofilm community, indicating that the element is likely to be able to transfer in natural environments (33). Tn5397 is related to Tn916; the central regions that are involved in conjugation of these two elements are very similar (14,24,25). However, Tn5397 can be distinguished from Tn916 in at least two important characteristics: first, Tn5397 contains a group II intron inserted into a gene almost identical to orf14 from Tn916 (25), and second, the DNA sequences of the...

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