Influence of Band-Gap Opening on Ballistic Electron Transport in Bilayer Graphene and Graphene Nanoribbon FETs

BACKGROUND: While silver nanoparticles (AgNPs) are widely used in consumer and medical products, the mechanism by which AgNPs cause pulmonary cytotoxicity is not clear. AgNP agglomerates are found in endo-lysosomal structures within the cytoplasm of treated cells. In this study, the functional role of lysosomes in AgNP-induced cellular damage was examined in A549 human lung alveolar epithelial cells. We evaluated the intracellular distribution of AgNPs, lysosomal pH, cellular viability, Ag dissolution, and metallothionein (MT) mRNA levels in AgNP-exposed A549 cells that were treated with bafilomycin A1, the lysosomal acidification inhibitor. FINDINGS: Exposure of A549 cells to citrate-coated AgNPs (20 nm diameter) for 24 h induced cellular damage and cell death at 100 and 200 μg Ag/ml, respectively. Confocal laser microscopic examination of LysoTracker-stained cells showed that AgNPs colocalized with lysosomes and their agglomeration increased in a dose-dependent manner (50–200 μg Ag/ml). In addition, the fluorescence signals of LysoTracker were reduced following exposure to AgNPs, suggesting the elevation of lysosomal pH. Treatment of A549 cells with 200 nM bafilomycin A1 and AgNPs (50 μg Ag/ml) further reduced the fluorescence signals of LysoTracker. AgNP-induced cell death was also increased by bafilomycin A1 treatment. Finally, treatment with bafilomycin A1 suppressed the dissolution of Ag and decreased the mRNA expression levels of MT-I and MT-II following exposure to AgNPs. CONCLUSIONS: The perturbation of lysosomal pH by AgNP exposure may play a role in AgNP agglomeration and subsequent cellular damage in A549 cells

The cyanobacterium Gloeobacter violaceus PCC 7421 uses bacterial-type phytoene desaturase in carotenoid biosynthesis

AbstractCarotenoid composition and its biosynthetic pathway in the cyanobacterium Gloeobacter violaceus PCC 7421 were investigated. β-Carotene and (2S,2′S)-oscillol 2,2′-di(α-l-fucoside), and echinenone were major and minor carotenoids, respectively. We identified two unique genes for carotenoid biosynthesis using in vivo functional complementation experiments. In Gloeobacter, a bacterial-type phytoene desaturase (CrtI), rather than plant-type desaturases (CrtP and CrtQ), produced lycopene. This is the first demonstration of an oxygenic photosynthetic organism utilizing bacterial-type phytoene desaturase. We also revealed that echinenone synthesis is catalyzed by CrtW rather than CrtO. These findings indicated that Gloeobacter retains ancestral properties of carotenoid biosynthesis

Angiotensin II alters the expression of duodenal iron transporters, hepatic hepcidin, and body iron distribution in mice

Purpose: Angiotensin II (ANG II) has been shown to affect iron metabolism through alteration of iron transporters, leading to increased cellular and tissue iron contents. Serum ferritin, a marker of body iron storage, is elevated in various cardiovascular diseases, including hypertension. However, the associated changes in iron absorption and the mechanism underlying increased iron content in a hypertensive state remain unclear. Methods: C57BL6/J mice were treated with ANG II to generate a model of hypertension. Mice were divided into 3 groups: (1) control, (2) ANG II-treated, and (3) ANG II-treated and ANG II receptor blocker (ARB)-administered (ANG II-ARB) groups. Results: Mice treated with ANG II showed increased serum ferritin levels compared to vehicle-treated control mice. In ANG II-treated mice, duodenal divalent metal transporter-1 (DMT1) and ferroportin (FPN) expression levels were increased and hepatic hepcidin mRNA expression and serum hepcidin concentration were reduced. The mRNA expression of bone morphogenetic protein 6 (BMP6) and CCAAT/enhancer binding protein alpha (C/EBPα), which are regulators of hepcidin, was also down-regulated in the livers of ANG II-treated mice. In terms of tissue iron content, macrophage iron content and renal iron content were increased by ANG II treatment, and these increases were associated with reduced expression of transferrin receptor 1 and FPN and increased expression of ferritin. These changes induced by ANG II treatment were ameliorated by administration of an ARB. Conclusions: ANG II altered the expression of duodenal iron transporters and reduced hepcidin levels, contributing to the alteration of body iron distribution

The secondary electron acceptor of photosystem I in Gloeobacter violaceus PCC 7421 is menaquinone-4 that is synthesized by a unique but unknown pathway

The secondary electron acceptor of photosystem (PS) I in the cyanobacterium Gloeobacter violaceus PCC 7421 was identified as menaquinone-4 (MQ-4) by comparing high performance liquid chromatograms and absorption spectra with an authentic compound. The MQ-4 content was estimated to be two molecules per one molecule of chlorophyll (Chl) a′, a constituent of P700. Comparative genomic analyses showed that six of eight men genes, encoding phylloquinone/MQ biosynthetic enzymes, are missing from the G. violaceus genome. Since G. violaceus clearly synthesizes MQ-4, the combined results indicate that this cyanobacterium must have a novel pathway for the synthesis of 1,4-dihydroxy-2-naphthoic acid