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We isolated a 2-alkenal reductase (AaAER) gene from Artemisia annua L. cDNA library through homologous cloning strategy. Enzymatic properties of AaAER, including substrate selectivity, enzyme kinetics, and key factors affecting enzyme activity, were characterized in vitro. We found that AaAER mainly functions in catalyzing the reduction of adjacent straight chain “C = C” double bond in the carbonyl group. This suggests the possibility of its participation in downstream events of the HPL (hydroperoxide lyase) pathway and contribution to cell detoxification in plants. Although, AaAER shares some substrates with AaDbr 1 and AaDbr 2, which are involved in artemisinin biosynthesis, AaAER was unable to reduce the adjacent double bond of carbonyl group in artemisinic aldehyde. We also analyzed the possible causes for highly homologous reductases with different types of substrates and non-homologous enzymes sharing the same substrate. The identification of a novel double bond reductase in A. annua provides an opportunity to explore the mechanism underlying the detoxification of aldehyde ketone molecules, which are generated by HPL downstream pathway and the redox process in the metabolic pathway of artemisinin synthesis.

Artemisinin, an effective drug against Plasmodium species that cause malaria, is a sesquiterpene lactone isolated from Artemisia annua. The yield of artemisinin in plants is relatively low, and it is influenced by various environmental growing conditions. In Arabidopsis, cryptochrome 1 (CRY1) is one of the key receptors that perceive light signals, and its overexpression promotes accumulation of secondary metabolites. In this study, overexpression of Arabidopsis CRY1 in A. annua resulted in increased accumulation of both artemisinin and anthocyanins. Under blue light, transgenic plants expressing high level of AtCRY1 showed a variety of blue light-induced responses, including inhibition of hypocotyl elongation and cotyledon expansion, dwarfism, and purpuring of aerial organs. Reverse transcription polymerase chain reaction analysis revealed that expression levels of the phenylalanine ammonia-lyase- and chalcone synthase-encoding genes were elevated and that anthocyanin accumulation was increased. Expression analysis of genes encoding farnesyl diphosphate synthase (FPS), amorpha-4,11-diene synthase (ADS), and CYP71AV1, three important enzymes in artemisinin biosynthesis, indicated that transcript abundance of all three genes, FPS, ADS, and CYP71AV1, increased in AtCRY1 plants. Based on high performance liquid chromatography analysis, artemisinin content in these plants increased by 30∼40%, when compared to control. These results have demonstrated that alteration of light signaling components could provide a viable approach for enhancing production of the secondary metabolite artemisinin.

Wurtzite stalactite-like quasi-one-dimensional ZnS nanoarrays with ZnO protuberances were synthesized through a thermal evaporation route. The structure and morphology of the samples are studied and the growth mechanism is discussed. X-ray diffraction (XRD) results show both the ZnS stem and the ZnO protuberances have wurtzite structure and show preferred [001] oriented growth. The photoluminescence and field emission properties have also been investigated. Room temperature photoluminescence result shows it has a strong green light emission, which has potential application for green light emitter. Experimental results also show that the stalactite arrays have a good field emission property, with turn-on field of 11.4 V/mu m, and threshold field of 16 V/mu m. The ZnO protuberances on the ZnS stem might enhance the field emission notably.

Two neuropeptides were isolated from synganglia (central nervous system) of the hard tick, Ixodes sinensis. Their primary sequences were established as Leu-Val-Val-Tyr-Pro-Trp-Thr-Lys and Trp-Glu-Lys-Leu-Gly-Ser-Met-Glu-Thr-Leu. By hot plate bioassay, neuropeptide a displayed strong antinociceptive effect in mice by a dose-dependent behavior, while neuropeptide b had some relaxant effects on the isolated rat strip. These neuropeptides might be involved in down-regulating the host’s defensive reaction.

Photoluminescence studies on porous silicon show that there are luminescence centers present in the surface states. By taking photoluminescence spectra of porous silicon with respect to temperature, a distinct peak can be observed in the temperature range 100–150 K. Both linear and nonlinear relationships were observed between excitation laser power and the photoluminescence intensity within this temperature range. In addition, there was a tendency for the photoluminescence peak to red shift at low temperature as well as at low excitation power. This is interpreted as indicating that the lower energy transition becomes dominant at low temperature and excitation power. The presence of these luminescence centers can be explained in terms of porous silicon as a mixture of silicon clusters and wires in which quantum confinement along with surface passivation would cause a mixing of Γ andX band structure between the surface states and the bulk. This mixing would allow the formation of luminescence centers.

Nature 459, 796–801 (2009) In this Letter, the scale bars in Fig. 5c are incorrectly listed as 1 mm, the correct size of the scale bars is 1 μm.