Electrochemical tuning of the optical properties of nanoporous gold.

Using optical in-situ measurements in an electrochemical environment, we study the electrochemical tuning of the transmission spectrum of films from the nanoporous gold (NPG) based optical metamaterial, including the effect of the ligament size. The long wavelength part of the transmission spectrum around 800 nm can be reversibly tuned via the applied electrode potential. The NPG behaves as diluted metal with its transition from dielectric to metallic response shifted to longer wavelengths. We find that the applied potential alters the charge carrier density to a comparable extent as in experiments on gold nanoparticles. However, compared to nanoparticles, a NPG optical metamaterial, due to its connected structure, shows a much stronger and more broadband change in optical transmission for the same change in charge carrier density. We were able to tune the transmission through an only 200 nm thin sample by 30%. In combination with an electrolyte the tunable NPG based optical metamaterial, which employs a very large surface-to-volume ratio is expected to play an important role in sensor applications, for photoelectrochemical water splitting into hydrogen and oxygen and for solar water purification.

Comparative sequence and expression analysis of tapetum specific male sterility related genes in Medicago truncatula.

Heterosis, or enhancement through outbreeding, is one of the most promising approaches for increasing crop yield. Male sterility (MS), which promotes heterosis, has been widely applied in hybrid crop production. Medicago truncatula is a model legume species and is closely related to M. sativa, an important legume forage plant. Although the molecular mechanisms of MS in M. truncatula and M. sativa remain unclear, several studies of MS have been conducted in Arabidopsis thaliana. Previous research has shown that MS is associated with the destruction of tapetal cell layers. Disruption of tapetum developmental processes may result in pollen abortion. In an effort to identify genes useful for breeding in M. sativa, we identified MS related genes in M. truncatula using BLAST and homology to A. thaliana genes. In this study, we identified 63 tapetum specific male sterility (TSMS) related genes. The length of TSMS genes varied from 225 to 3747 bp. We identified 15 conserved domains and 8 cis-elements associated with TSMS related genes. Analysis of the phylogenetic relationships among these genes allowed them to be classified into three groups, MtTsms A, MtTsms B, and MtTsms C. Expression analyses revealed that these genes may be involved in developmental processes and response to abiotic stress.

A new cell culture system for infection with hepatitis B virus that fuses HepG2 cells with primary human hepatocytes.

Hepatitis B virus (HBV) infection exhibits a very narrow host range and shows a strong tropism for liver parenchymal cells, however none of the previously established experimental models can reproduce the natural process of HBV infection. In the present study, primary human hepatocytes were fused with HepG2 cells to establish the hybrid HepCHLine-4 cell line with high susceptibility to HBV. The HepCHLine-4 cells expressed HBV-specific antigen when co-incubated with HBV-positive serum from a hepatitis B patient. Post-infection, HBV relaxed circular DNA and covalently closed circular DNA were detected in HepCHLine-4 cells using a nested polymerase chain reaction, and HBV-specific particles were visualized by electron microscopy of the culture media of HepCHLine-4 cells. HepG2 cells were not susceptible to HBV infection under the same conditions. The HepCHLine-4 cells can be sub-cultured for > 12 months while maintaining susceptibility to HBV and may, therefore, be useful for studying HBV infection and the viral life cycle in human hepatocytes.