Selenium nanovirus and its cytotoxicity in selenite-exposed higher living organisms

Selenium (Se) is an essential micronutrient in living organisms, having a narrow margin between essential and potentially toxic intake/exposure. Thus, the biochemistry of Se in living organisms must be studied in-depth to determine the underlying mechanism of Se cytotoxicity. In this study, we report the emergence of selenium nanovirus (SeNVs) in selenite-exposed fish (freshwater and saltwater) and plants (dryland) and its toxicity in them. SeNVs were found in both the abdomen and tail of Oryzias melastigma and saltwater Rhodeus ocellatus, which led to their death. The occurrence of the intracellular assembly of SeNVs was observed in the roots and leaves of corn Zea mays, but not in those of Limnobium laevigatum. SeNVs led to the death of Z. mays but caused chronic toxicity in L. laevigatum. SeNVs should be a system or structure that dissipates the intracellular redox gradients of the host cells, with simple information consisting Se–O, Se–N, or Se–S bond, that would ensure elemental Se ligand binding with nearly specific biomolecules in host cells, thereby maintaining their composition and stabilizing their structure. The multiple toxic effects of Se, therefore, could be the consequence of increase of entropy in the host cells caused by the intracellular assembly of SeNVs. This study may provide an insight into the underlying mechanism of Se in environmental toxicology and its applications in human health.     

Structure of plant photosystem I−light harvesting complex I supercomplex at 2.4 Å resolution

Photosystem I (PSI) is one of the two photosystems in photosynthesis, and performs a series of electron transfer reactions leading to the reduction of ferredoxin. In higher plants, PSI is surrounded by four light-harvesting complex I (LHCI) subunits, which harvest and transfer energy efficiently to the PSI core. The crystal structure of PSI-LHCI supercomplex has been analyzed up to 2.6 Å resolution, providing much information on the arrangement of proteins and cofactors in this complicated supercomplex. Here we have optimized crystallization conditions, and analyzed the crystal structure of PSI-LHCI at 2.4 Å resolution. Our structure showed some shift of the LHCI, especially the Lhca4 subunit, away from the PSI core, suggesting the indirect connection and inefficiency of energy transfer from this Lhca subunit to the PSI core. We identified five new lipids in the structure, most of them are located in the gap region between the Lhca subunits and the PSI core. These lipid molecules may play important roles in binding of the Lhca subunits to the core, as well as in the assembly of the supercomplex. The present results thus provide novel information for the elucidation of the mechanisms for the light-energy harvesting, transfer and assembly of this supercomplex.     

Microwave‐assisted aqueous synthesis of new quaternary‐alloyed CdSeTeS quantum dots; and their bioapplications in targeted imaging of cancer cells

In this study, we report for the first time a one‐pot approach for the synthesis of new CdSeTeS quaternary‐alloyed quantum dots (QDs) in aqueous phase by microwave irradiation. CdCl₂ was used as a Cd precursor during synthesis, NaHTe and NaHSe were used as Te and Se precursors and mercaptopropionic acid (MPA) was used as a stabilizer and source of sulfur. A series of quaternary‐alloyed QDs of different sizes were prepared. CdSeTeS QDs exhibited a wide emission range from 549 to 709 nm and high quantum yield (QY) up to 57.7 %. Most importantly, the quaternary‐alloyed QDs possessed significantly long fluorescence lifetimes > 100 ns as well as excellent photostability. Results of high‐resolution transmission electron microscopy (HRTEM), energy dispersive X‐ray spectroscopy (EDX) and powder X‐ray diffraction (XRD) spectroscopy showed that the nanocrystals possessed a quaternary alloy structure with good crystallinity. Fluorescence correlation spectroscopy (FCS) showed that QDs possessed good water solubility and monodispersity in aqueous solution. Furthermore, CdSeTeS QDs were modified with alpha‐thio‐omega‐carboxy poly(ethylene glycol) (HS‐PEG‐COOH) and the modified QDs were linked to anti‐epidermal growth factor receptor (EGFR) antibodies. QDs with the EGFR antibodies as labeling probes were successfully applied to targeted imaging for EGFR on the surface of SiHa cervical cancer cells. We believe that CdSeTeS QDs can become useful probes for in vivo targeted imaging and clinical diagnosis. Copyright © 2012 John Wiley & Sons, Ltd.     

The History and Advances of Reversible Terminators Used in New Generations of Sequencing Technology

DNA sequencing using reversible terminators, as one sequencing by synthesis strategy, has garnered a great deal of interest due to its popular application in the second-generation high-throughput DNA sequencing technology. In this review, we provided its history of development, classification, and working mechanism of this technology. We also outlined the screening strategies for DNA polymerases to accommodate the reversible terminators as substrates during polymerization; particularly, we introduced the "REAP" method developed by us. At the end of this review, we discussed current limitations of this approach and provided potential solutions to extend its application.     

Tangshenosides from Codonopsis lanceolata roots

A new symmetrical phenylpropanoid glycoside, tangshenoside VIII (1), together with six known tangshenosides (2–7) were isolated from the roots of Codonopsis lanceolata (Campanulaceae). Their structures were established on the basis of spectroscopic data, including two-dimensional NMR analyses. Tangshenosides have chemotaxonomic significance.