An N-N linked dimeric indole alkaloid from the marine sponge-associated rare actinomycetes Kocuria sp. S42.

Marine derived rare actinomycetes is emerging as one of the new sources for various natural products for further drug discovery. Dimeric indole alkaloids represent a group of structurally diverse natural products and N-N linkage is a special dimerization mode. Here, we report the isolation of 1,1'-([1,1'-biindole]-3,3'-diyl) bis (ethane-1,2-diol), a new tryptophan-derived indole alkaloid from the marine sponge-derived Kocuria sp. S42. The structure was established based on extensive spectroscopic analyses, including nuclear magnetic resonance (NMR) and high-resolution electrospray ionization mass (HR-ESI-MS) spectrometry. The new dimeric indole alkaloid via N-N linkage exhibits moderate antimicrobial activity.

A Semi-Synthetic Diet and the Potential Important Chemicals for Mythimna separata (Lepidoptera: Noctuidae).

Armyworm feeding in large, destructive groups is hugely difficult to control and the oriental armyworm, Mythimna separata (Walk), is one such pest. In this study, we reported a semisynthetic artificial diet for the oriental armyworm. This diet is based on Ritter's diet, a formula developed for Heliothis zea. The survival of M. separata was extremely low and only around 2% insects can reach the adult stage on Ritter's diet. But, it can reach up to 100% if corn leaf powder (CLP) was mixed, and insects grew faster and gained more mass. After testing a set of mixtures of Ritter's diet and CLP, we found that 14.3% was the optimal proportion of CLP for making the artificial diet. We then used chloroform to extract CLP. Insect performance was still much better on Ch-extracted CLP diets than that on Ritter's diet, but it was poorer than that on the diets containing unprocessed CLP, suggesting that the essential factor(s) was only partially extracted from corn leaf. We then used methanol and dichloromethane, two solvents differing in their polarity, to process the extractions and analyzed the extracted chemicals using gas chromatography-mass spectrometry (GC-MS). Insects had a better performance on dichloromethane-extracted CLP diet in comparison to methanol-extracted one, indicating that the important factor(s) is more prone to methanol extraction. The reported recipe here is useful for the research on M. separata and possibly other grain-crop eating armyworms. The functions of the chemicals extracted from corn leaf tissue can be investigated in the future studies.

Fabrication of hybridized nanoparticles with aggregation-induced emission characteristics and application for cell imaging.

Fluorescent nanoparticles used to detect important biological events in living cells or animals are in increasing demand in the biological and biomedical fields, and have attracted much attention from chemists and biologists in the past decade. Here, one aggregation-induced emission (AIE) bioconjugate, tetraphenylethene labelled chitosan (TPE-CS), is synthesized, which could be strongly emissive in the solid state. TPE-CS is used as a coating agent for negatively charged hydroxyapatite (HA) nanoparticles, and TPE-CS/HA nanocomposites with positive charges are well dispersed in their aqueous solution with a diameter of 111.9 nm. MTT assay indicates that the fluorescent TPE-CS/HA nanoparticles have good cytocompatibility. 293T cells are imaged by TPE-CS/HA nanoparticles. First, the nanoparticles are adhered to the cell membrane, and then many more particles are endocytosed through phagocytotic vesicles by culturing for a long time, resulting in a much stronger fluorescence emission. TPE-CS/HA bioprobes could strongly bind the cell cytoplasmic region, and might have promising applications in tumor diagnosis, long-term cell tracing, drug metabolism and drug delivery systems.

Monitoring layer-by-layer self-assembly process of natural polyelectrolytes by fluorescent bioconjugate with aggregation-induced emission characteristic.

A novel chitosan-based fluorescent bioconjugate (TPE-CS) with aggregation-induced emission (AIE) characteristic is synthesized and used as a fluorescent probe for monitoring layer-by-layer self-assembly process of natural polyelectrolytes. QCM results and contact angle measurement indicate that this AIE active TPE-CS bioconjugate can be assembled with alginate (ALG) through layer-by-layer deposition. Ellipsometry and fluorescence (FL) spectroscopy show an exponential growth of the TPE-CS/ALG multilayer films. Moreover, the exponential relationship between the FL intensity and the number of bilayers, which is in accordance with the thickness variation of multilayer films, provides solid evidence for its capacity to monitor the layer-by-layer self-assembly process.