Overview of the potent cyanobacterial neurotoxin β-methylamino-L-alanine (BMAA) and its analytical determination

Blue-green algae are responsible for the production of different types of toxins which can be neurotoxic, hepatotoxic, cytotoxic and dermatotoxic and that can affect both aquatic and terrestrial life. Since its discovery the neurotoxin β-methylamino-L-alanine (BMAA) has been a cause for concern, being associated with the neurodegenerative disease amyotrophic lateral sclerosis/Parkinsonism–dementia complex (ALS/PDC). The initial focus was on Guam where it was observed that a high number of people were affected by the ALS/PDC complex. Subsequently, researchers were surprised to find levels of BMAA in post mortem brains from Canadian patients who also suffered from ALS/PDC. Recent research demonstrates that BMAA has been found at different levels in the aquatic food web in the brackish waters of the Baltic Sea. There is emerging evidence to suggest that sand-borne algae from Qatar can also contain BMAA. Furthermore, there is now concern because BMAA has been found not only in warmer regions of the world but also in temperate regions like Europe. The aim of this review is to focus on the methods of extraction and analysis of the neurotoxic non-protein amino acid BMAA. We also consider the neurotoxicity, aetiology, and diverse sources and routes of exposure to BMAA. In recent years, different methods have been developed for the analysis of BMAA. Some of these use HPLC-FD, UPLC-UV, UPLC-MS and LC-MS/MS using samples that have been derivatised or underivatised. To date the LC-MS/MS approach is the most widely used analytical technique as it is the most selective and sensitive method for BMAA determination.     

Citrus-derived auraptene stimulates angiogenesis by activating the Erk- and PI3K/Akt/eNOS-dependent signaling pathways in human umbilical vein endothelial cells

Auraptene is a citrus-derived natural monoterpene that has been shown to exert anti-cancer, anti-bacterial, anti-inflammatory, and antioxidant roles. Since little is known about other biological functions of auraptene, we examined the efficacy of auraptene for stimulating angiogenesis in human umbilical vein endothelial cells (HUVECs). Treatment with low concentrations of auraptene stimulated endothelial cell proliferation, migration, and tube formation. Furthermore, auraptene activated Erk, Akt, and endothelial nitric oxide synthase (eNOS), and increased NO production. Auraptene also partially induced the phosphorylation of VEGFR2. Furthermore, auraptene-induced activation of Erk, Akt, and eNOS were significantly inhibited by the inhibitors PD98059, LY294002, and l-NIO dihydrochloride. These results suggest that auraptene stimulates angiogenesis by regulating the VEGFR2, Erk, and PI3K/Akt-eNOS signaling pathways.     

The effect of oxygen in resulfurized steels—Part II

Part I of this two-part paper, which appeared in the June issue, covered the effects of deoxidation with silicon, boron, aluminum, or carbon (under vacuum) on the machinability and microstructure of low-carbon resulfurized steels containing nominally 0.1%C-1.0%Mn-0.25%S. Deoxidation reduced machinability and it was concluded that the removal of oxygen was directly responsible. Deoxidation was found to suppress the formation of large random sulfide inclusions so that sufficiently strong deoxidation, such as with aluminum, caused the steel to solidify with a characteristic eutectic structure in which the inter dendritic sulfide inclusions were comparatively small. Consequently, the inclusions in the rolled steel were small and machinability was reduced.     

An electrochemically regenerative hydrogen-chlorine energy storage system: electrode kinetics and cell performance

The electrochemical oxidation and reduction of hydrogen and chlorine in hydrochloric acid has been investigated on graphite, ruthenized titanium and platinum electrodes. Both steady state and potentiostatic pulse methods were used. Cell studies were also carried out in cells with flow-by and flow-through chlorine electrodes. Results indicate that the electrode kinetics are fast and the electrolysis and fuel cell reactions can be carried out in the same cell with electric-to-electric efficiencies in excess of 75% at current densities of 300 mA cm^–2. Mass transfer limitations at the chlorine electrode during discharge can be eliminated by cell pressurization and the use of flow-through electrodes.This study was carried out under the auspices of the US Department of Energy.in the summers of 1976 and 1977     

Ultrafast switching in nanoscale phase-change random access memory with superlattice-like structures

Phase-change random access memory cells with superlattice-like (SLL) GeTe/Sb(2)Te(3) were demonstrated to have excellent scaling performance in terms of switching speed and operating voltage. In this study, the correlations between the cell size, switching speed and operating voltage of the SLL cells were identified and investigated. We found that small SLL cells can achieve faster switching speed and lower operating voltage compared to the large SLL cells. Fast amorphization and crystallization of 300 ps and 1 ns were achieved in the 40 nm SLL cells, respectively, both significantly faster than those observed in the Ge(2)Sb(2)Te(5) (GST) cells of the same cell size. 40 nm SLL cells were found to switch with low amorphization voltage of 0.9 V when pulse-widths of 5 ns were employed, which is much lower than the 1.6 V required by the GST cells of the same cell size. These effects can be attributed to the fast heterogeneous crystallization, low thermal conductivity and high resistivity of the SLL structures. Nanoscale PCRAM with SLL structure promises applications in high speed and low power memory devices.     

Transforming C60 molecules into graphene quantum dots

The fragmentation of fullerenes using ions, surface collisions or thermal effects is a complex process that typically leads to the formation of small carbon clusters of variable size. Here, we show that geometrically well-defined graphene quantum dots can be synthesized on a ruthenium surface using C(60) molecules as a precursor. Scanning tunnelling microscopy imaging, supported by density functional theory calculations, suggests that the structures are formed through the ruthenium-catalysed cage-opening of C(60). In this process, the strong C(60)-Ru interaction induces the formation of surface vacancies in the Ru single crystal and a subsequent embedding of C(60) molecules in the surface. The fragmentation of the embedded molecules at elevated temperatures then produces carbon clusters that undergo diffusion and aggregation to form graphene quantum dots. The equilibrium shape of the graphene can be tailored by optimizing the annealing temperature and the density of the carbon clusters.     

Paper-based microfluidic surface acoustic wave sample delivery and ionization source for rapid and sensitive ambient mass spectrometry

A surface acoustic wave-based sample delivery and ionization method that requires minimal to no sample pretreatment and that can operate under ambient conditions is described. This miniaturized technology enables real-time, rapid, and high-throughput analysis of trace compounds in complex mixtures, especially high ionic strength and viscous samples that can be challenging for conventional ionization techniques such as electrospray ionization. This technique takes advantage of high order surface acoustic wave (SAW) vibrations that both manipulate small volumes of liquid mixtures containing trace analyte compounds and seamlessly transfers analytes from the liquid sample into gas phase ions for mass spectrometry (MS) analysis. Drugs in human whole blood and plasma and heavy metals in tap water have been successfully detected at nanomolar concentrations by coupling a SAW atomization and ionization device with an inexpensive, paper-based sample delivery system and mass spectrometer. The miniaturized SAW ionization unit requires only a modest operating power of 3 to 4 W and, therefore, provides a viable and efficient ionization platform for the real-time analysis of a wide range of compounds.