Copper(I) and copper(II) binding to β-amyloid 16 (Aβ16) studied by electrospray ionization mass spectrometry

Copper-β-amyloid 16 (Aβ16) complexes were investigated by electrospray ionization mass spectrometry (ESI-MS). Copper(i) and (ii) complexes were formed on-line in a microchip electrospray emitter by using a sacrificial copper electrode as the anode in positive ionization mode. In the presence of ascorbic acid in the peptide solution, the amount of Cu(i)-Aβ16 generated electrochemically was even higher. A kinetic model is proposed to account for the generation of copper complexes. The structure of Cu(i)-Aβ16 was investigated by tandem mass spectrometry (MS/MS), and the binding site of Cu(i) to Aβ16 was identified at the His13, His14 residues. Cu(ii)-Aβ16 was also investigated by MS/MS and, based on the unusual observations of a-ions, the two binding residues of His13 and His14 of Aβ16 to Cu(ii) were also confirmed. This approach provides direct information on Cu(i)-Aβ16 complexes generated in solution from metallic copper and gives evidence that both His13 and His14 are involved in the coordination of both Cu(i)- and Cu(ii)-Aβ16 complexes.     

Carbon nanotube powders as electrode modifier to enhance the activity of anodic biofilm in microbial fuel cells

Carbon nanotube (CNT) is a promising electrode material and has been used as an anode modifier in microbial fuel cells (MFCs). In this study, a new method of simultaneously adding CNT powders and Geobacter sulfurreducens into the anode chamber of a MFC was used, aiming to form a composite biofilm on the anode. The performance of MFCs such as startup time and steady-state power generation was investigated under conditions of different CNT powders dosages. Results showed that both the startup time and the anodic resistance were reduced. The optimal dosage of CNT powders pre-treated by acid was 4 mg/mL for the anode chamber with an effective volume of 25 mL. The anodic resistance and output voltage of the MFC with CNT powders addition were maintained around 180 Ω and 650 mV during 40 days operation, while those of the MFC without CNT powders addition increased from 250 Ω to 540 Ω and decreased from 630 mV to 540 mV, respectively, demonstrating that adding CNT powders helped stabilize the anodic resistance, thus the internal resistance and power generation during long-term operation. Based on cyclic voltammogram, the electrochemical activity of anodic biofilm was enhanced by adding CNT powders, though no significant increase of the biomass in anodic biofilm was detected by phospholipids analysis. There was no remarkable change of ohmic resistance with an addition of CNT powders revealed by current interrupt method, which indicated that the rate of mass transfer might be promoted by the presence of CNT powders.     

Expression of an Oncidium gene encoding a patatin-like protein delays flowering in Arabidopsis by reducing gibberellin synthesis

The involvement of lipase in flowering is seldom studied, and this research provides evidence that fatty acids produced by lipase affect flowering. OSAG78 encoding a patatin-like protein was isolated from Oncidium Gower Ramsey. OSAG78 fused with green fluorescent protein was found to localize at the cell membrane. Transgenic Arabidopsis overexpressing OSAG78 demonstrated higher lipase activity than the wild-type control. In addition, the amount of free linoleic acid and linolenic acid in transgenic Arabidopsis was found to be higher than that in the wild type. Transgenics overexpressing OSAG78 exhibited altered phenotypes, including smaller leaves and rounder flowers, and also demonstrated a late flowering phenotype that could be rescued by gibberellin A(3) (GA(3)) application. Several flowering-related genes were analyzed, indicating that the expression of gibberellin-stimulated genes was decreased in the plants overexpressing OSAG78. Also, the expression of AtGA2ox1, AtGA3ox1 and AtGA20ox1 genes encoding GA2-, GA3- and GA20-oxidases, respectively, which are mainly responsible for gibberellin metabolism, was decreased, and the level of GA(4), a bioactive gibberellin, measured by gas chromatography-mass spectrometry was also reduced in the overexpressing lines. Furthermore, the expression levels of AtGA3ox1 and AtGA20ox1 were significantly decreased in wild-type Arabidopsis treated with linoleic acid, linolenic acid or methyl jasmonate. The membrane-bound OSAG78 might hydrolyze phospholipids to release linoleic acid and linolenic acid, and then depress the expression of genes encoding GA3- and GA20-oxidase. These changes reduced the bioactive gibberellin level, and, finally, late flowering occurred. Our results indicate that a patatin-like membrane protein with lipase activity affects flowering through the regulation of gibberellin metabolism.     

Intraspecific variation of trunk segmentation in the oryctocephalid trilobite Duyunaspis duyunensis from the Cambrian (Stage 4, Series 2) of South China

A detailed exploration of growth and trunk segmentation of the oryctocephalid trilobite, Duyunaspis duyunensis Chang & Chien in Zhou et al. 1977, from the lower Cambrian (Stage 4, Series 2) Balang Formation in western Hunan Province, South China, is presented. Because of the excellent preservation, the complete post‐protaspid ontogenetic series from merapsid degree 0 to the holaspid phase is described. The ontogenetic series reveals new information on morphological changes such as the migration of the posterior branch of the facial sutures (from proparian to opisthoparian) and contraction of the posteromedial notch in the pygidium. The abundance of articulated specimens available from a narrow stratigraphical interval makes this material singularly useful for studying the morphogenesis and post‐embryonic growth of D. duyunensis in comparison with other oryctocephalids. Strong evidence that multiple numbers of pygidial segment are recognized in each meraspid degree as well as in the holaspid period showed unusual intraspecific variability in the rate of trunk segmentation, providing insights into how Cambrian subisopygous trilobites controlled their body patterning, including size, shape and trunk segment number in both thorax and caudal plate during growth.     

RNA激活效应研究

RNAa(RNA activation)即RNA激活效应,是指某些小分子非编码RNA(non-coding RNA,ncRNA)在转录水平上激活基因表达的现象,这种发挥激活作用的小RNA分子又叫激活小RNA(small activating RNA,saRNA)。saRNA与干扰小RNA(small interfer-ing RNA,siRNA)同属小分子双链非编码RNA家族,既有相似的分子特征,在靶序列、作用动力学和调控方式等方面又有显著差别。虽然RNAa的作用机制尚未完全明了,但其在肿瘤治疗中的应用前景吸引了人们的关注。本文就RNAa近年的研究进展进行了简要综述。     

Effect of recombinant Rv1009 protein on promoting the growth of Mycobacterium tuberculosis

Aims: To determine whether resuscitation-promoting factor (RPF) from Mycobacterium tuberculosis can promote mycobacterial growth and shorten culture time. Method and Results: We cloned, expressed and purified an RPF from M. tuberculosis, Rv1009 protein and subsequently studied the biological activity of the recombinant Rv1009 (rRv1009) in liquid and on solid media. Our results indicate that the molecular weight of rRv1009 protein expressed in Escherichia coli BL21 was approximately 39 kDa. At picomolar and micromolar concentrations, rRv1009 protein could increase the optical density of freeze-dried Mycobacterium bovis BCG three to fivefold in Middlebrook 7H9 medium, stimulate the growth of viable mycobacteria on solid medium, and shorten positive growth detection time of a small number of M. tuberculosis in BACTEC 960 medium. Conclusions: The rRv1009 could promote proliferation of mycobacteria. It may be useful for culture of mycobacteria presented in clinical samples. Significance and Impact of the Study: rRv1009 protein can be used as a growth-promoting reagent of mycobacteria in the medium to shorten the time of culture.