Synthesis of Amides with Remote Stereocenters by Catalytic Asymmetric γ-Alkynylation of α,ß-Unsaturated Amides.

An iridium-catalyzed enantioselective hydroalkynylation of α,ß-unsaturated amides was described. The selectivity of this reaction is distinct from that observed in many catalytic hydroalkynylations of α,ß-unsaturated carbonyl compounds. It occurs selectively at the γ instead of the ß position. Preliminary mechanistic studies suggest that the reaction proceeds through alkene isomerization followed by hydroalkynylation. This method provides a straightforward route for the synthesis of amides with a remote stereocenter at the γ position.

Knockdown of Dynamitin in testes significantly decreased male fertility in Drosophila melanogaster.

Dynamitin (Dmn) is a major component of dynactin, a multiprotein complex playing important roles in a variety of intracellular motile events. We previously found that Wolbachia bacterial infection resulted in a reduction of Dmn protein. As Wolbachia may modify sperm in male hosts, we speculate that Dmn may have a function in male fertility. Here we used nosGal4 to drive Dmn knock down in testes of Drosophila melanogaster to investigate the functions of Dmn in spermatogenesis. We found that knockdown of Dmn in testes dramatically decreased male fertility, overexpression of Dmn in Wolbachia-infected males significantly rescued male fertility, indicating an important role of Dmn in inducing male fertility defects following Wolbachia infection. Some scattered immature sperm with late canoe-shaped head distributed in the end of Dmn knockdown testis and only about half mature sperm were observed in the Dmn knockdown testis relative to those in the control. Transmission electron microscopy (TEM) exhibited fused spermatids in cysts and abnormal mitochondrial derivatives. Immunofluorescence staining showed significantly less abundance of tubulin around the nucleus of spermatid and scattered F-actin cones to different extents in the individualization complex (IC) during spermiogenesis in Dmn knockdown testes, which may disrupt the nuclear condensation and sperm individualization. Since dynein-dynactin complex has been shown to mediate transport of many cellular components, including mRNAs and organelles, these results suggest that Dmn may play an important role in Drosophila spermiogenesis by affecting transport of many important cytoplasmic materials.

[Study on the formaldehyde-induced DNA damage with comet assay].

Formaldehyde is known as a genotoxic substance. Numerous studies have shown that formaldehyde could induce DNA-DNA and DNA-protein crosslinks. However, scholars have disagreed with each other on the formaldehyde-induced DNA strand breaks. We chose buccal cells as materials to evaluate the genotoxicity of formaldehyde with comet assay--especially for DNA strand breaks. The results showed that formaldehyde of low concentration induced DNA strand breaks, while formaldehyde of high concentration induced DNA-DNA and DNA-protein crosslinks. According to our experimental results, we proposed the concept of the "peak point of break" at which formaldehyde induced DNA strand breaks most.