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The harsh environmental conditions in alpine tundra exert a significant influence on soil macro-arthropod communities, yet few studies have been performed regarding the effects of vegetation heterogeneity on these communities. In order to better understand this question, a total of 96 soil macro-arthropod samples were collected from four habitats in the Changbai Mountains in China, namely, the Vaccinium uliginosum habitat, Sanguisorba sitchensis habitat, Rhododendron aureum habitat, and Deyeuxia angustifolia habitat. The results revealed that the taxonomic composition of the soil macro-arthropods varied among the habitats, and that dissimilarities existed in these communities. The abundance, richness and diversity in the D. angustifolia habitat were all at their maximum during the sampling period. The vegetation heterogeneity affected the different taxa of the soil macro-arthropods at various levels. In addition, the vegetation heterogeneity had direct effects not only on soil macro-arthropod communities, but also indirectly impacted the abundance, richness and diversity by altering the soil fertility and soil texture. Overall, our results provide experimental evidence that vegetation heterogeneity can promote the abundance, richness and diversity of soil macro-arthropods, yet the responses of soil macro-arthropods to vegetation heterogeneity differed among their taxa.

Sodium (Na) metal anodes stand out with their remarkable capacity and natural abundance. However, the dendritic Na growth, infinite dimensional changes, and low Coulombic efficiency (CE) present key bottlenecks plaguing practical applications. Here, heteroatom-doped (nitrogen, sulfur) hollow carbon fibers (D-HCF) are rationally synthesized as a nucleation-assisting host to enable a highly reversible Na metal. The "sodiophilic" functional groups introduced by the heteroatom-doping and large surface area (≈1052 m 2 g -1 ) synchronously contribute to a homogenous plating morphology with dissipated local current density. High "sodiophilicity" of the D-HCF is confirmed by first-principle calculations and experimental results, where strong adsorption energy of -3.52 eV with low Na + nucleation overpotential of 3.2 mV at 0.2 mA cm -2 is realized. As such, highly reversible plating/stripping is achieved at 1.0 mA cm -2 with average CE approximating 99.52% over 600 cycles. The as-assembled Na@D-HCF symmetric cells exhibit a prolonged lifetime for 1000 h. A full-cell paired with Na 3 V 2 (PO 4 ) 3 cathode further demonstrates stable electrochemical behavior for 200 cycles at 1 C along with excellent rate performance (102 mAh g -1 at 5 C). The results clearly show the effectiveness of the D-HCF in manipulating Na + deposition and thus the significance of nucleation control in realizing dendrite-free metal anodes., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A new series of hyperbranched polymers consisting of fluorene- alt -carbazole as the branches and the three-dimensional-structured spiro[3.3]heptane-2,6-dispirofluorene (SDF) as the core were designed and synthesized by one-pot Suzuki coupling polycondensation. A phosphor group with broad full width at half maximum (FWHM) bis(1-phenyl-isoquinoline)(acetylacetonato)iridium(iii) (Ir(Brpiq) 2 acac, 0.08 mol%) as the red-light emitting unit and bis(2-(4-bromophenyl)-1-[6-(9-carbazolyl)hexyl]-imidazole)(2-(5-(4-fluorinated phenyl)-1,3,4-triazole)pyridine)iridium(iii) ((CzhBrPI) 2 Ir(fpptz)) as the green-light emitting unit were introduced into the backbones to obtain sunlight-style white-light emission by adjusting the feeding ratios of (CzhBrPI) 2 Ir(fpptz) (0.08 to 0.32 mol%). The results indicate the synthesized polymers show high thermal stabilities and good amorphous film morphology because of the hyperbranched structures. Besides, the lowest unoccupied molecular orbital (LUMO) levels of polymers were reduced and the electron injection was improved because of excellent electron-transporting ability of the triazole unit in the green group. The hyperbranched structures can effectively suppress the polymers' chain distortion and aggregation, and promote the incomplete Förster resonance energy transfer (FRET) efficiency from fluorene- alt -carbazole segments to Ir complex units. As a result, the devices with hyperbranched polymer light-emitting layers realize white light emission, and the optimized device also exhibits good electroluminescent (EL) performance with Commission Internationale de l'Eclairage (CIE) coordinates at (0.32, 0.31), a maximum luminance of 9054 cd m -2 , a maximum current efficiency of 3.59 cd A -1 and a maximum Color Rendering Index (CRI) of 91. The hyperbranched polymers based on fluorene- alt -carbazole branches and a SDF core and high-efficiency phosphor groups with broad full width at half maximum are attractive candidates for sunlight-style white polymer light-emitting device., Competing Interests: The authors declare no competing financial interest., (This journal is © The Royal Society of Chemistry.)

Stretchable and conformable synapse memristors that can emulate the behaviour of the biological neural system and well adhere onto the curved surfaces simultaneously are desirable for the development of imperceptible wearable and implantable neuromorphic computing systems. Previous synapse memristors have been mainly limited to rigid substrates. Herein, a stretchable and conformable memristor with fundamental synaptic functions including potentiation/depression characteristics, long/short-term plasticity (STP and LTP), "learning-forgetting-relearning" behaviour, and spike-rate-dependent and spike-amplitude-dependent plasticity is demonstrated based on highly elastic Ag nanoparticle-doped thermoplastic polyurethanes (TPU : Ag NPs) and polydimethylsiloxane (PDMS). The memristor can be well operated even at 60% strain and can be well conformed onto the curved surfaces. The formed conductive filament (CF) obtained from the movement of Ag nanoparticle clusters under the locally enhanced electric field gives rise to resistance switching of our memristor. These results indicate a feasible strategy to realize stretchable and conformable synaptic devices for the development of new-generation artificial intelligence computers.

In this paper, urea-doped ZnO (U-ZnO) is investigated as a modified electron transport layer (ETL) in inverted polymer solar cells (PSCs). Using a blend of Poly{4,8-bis[(2-ethylhexyl)oxy] benzo [1,2-b:4,5-b'] dithiophene-2,6-diyl-alt-3-fluoro-2-[(2-ethylhexyl)carbonyl] thieno [3,4-b] thiophene-4,6-diyl}(PTB7), and [6,6]-phenyl-C71-butyric acid methyl ester (PC 71 BM) as light absorber, a champion power conversion efficiency (PCE) of 9.15% for U-ZnO ETL based PSCs was obtained, which is 15% higher than that of the pure ZnO ETL based PSCs (7.76%). It was demonstrated that urea helps to passivate defects in ZnO ETL, resulting in enhanced exciton dissociation, suppressed charge recombination and efficient charge extraction efficiency. This work suggests that the utilization of the U-ZnO ETL offer promising potential for achieving highly efficient PSCs.

Hybrid organic-inorganic perovskite, well-known as light-absorbing materials in solar cells, have recently attracted considerable interest for applications in resistive switching (RS) memory. A better understanding of the role of interface state in hybrid perovskite materials on RS behavior is essential for the development of practical devices. Here, we study the influence of interface state on the RS behavior of an Au/CH 3 NH 3 PbI 3 /FTO memory device using a simple air exposure method. We observe a transition of RS hysteresis behavior with exposure time. Initially no hysteresis is apparent, but air exposure induces bipolar RS and a negative differential resistance (NDR) phenomenon. The reductions of I/Pb atomic ratio and work function on the film surface are examined using XPS spectra and Kelvin probe technique, verifying the produce of donor-type interface states (e.g., iodine vacancies) during CH 3 NH 3 PbI 3 film degradation. Studies on complex impedance spectroscopy confirm the responsibility of interface states in NDR behavior. Eventually, the trapping/detrapping of electrons in bulk defects and at interface states accounts for the bipolar RS behavior accompanied with the NDR effect.

Graphene oxide (GO)-based resistive-switching (RS) memories offer the promise of low-temperature solution-processability and high mechanical flexibility, making them ideally suited for future flexible electronic devices. The RS of GO can be recognized as electric-field-induced connection/disconnection of nanoscale reduced graphene oxide (RGO) conducting filaments (CFs). Instead of operating an electrical FORMING process, which generally results in high randomness of RGO CFs due to current overshoot, a TiO 2 -assisted photocatalytic reduction method is used to generate RGO-domains locally through controlling the UV irradiation time and TiO 2 concentration. The elimination of the FORMING process successfully suppresses the RGO overgrowth and improved RS memory characteristics are achieved in graphene oxide-TiO 2 (Go-TiO 2 ) nanocomposites, including reduced SET voltage, improved switching variability, and increased switching speed. Furthermore, the room-temperature process of this method is compatible with flexible plastic substrates and the memory cells exhibit excellent flexibility. Experimental results evidence that the combined advantages of reducing the oxygen-migration barrier and enhancing the local-electric-field with RGO-manipulation are responsible for the improved RS behaviors. These results offer valuable insight into the role of RGO-domains in GO memory devices, and also, this mild photoreduction method can be extended to the development of carbon-based flexible electronics., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Color-tunable light-emitting devices (LEDs) have a great impact on our daily life. Herein, LEDs with tunable electroluminescence (EL) color were achieved via introducing Ag nanowires surface plasmons into p-GaN/n-ZnO film heterostructures. By optimizing the surface coverage density of coated Ag nanowires, the EL color was changed continuously from yellow-green to blue-violet. Transient-state and temperature-variable fluorescence emission characterizations uncovered that the spontaneous emission rate and the internal quantum efficiency of the near-UV emission were increased as a consequence of the resonance coupling interaction between Ag nanowires surface plasmons and ZnO excitons. This effect induces the selective enhancement of the blue-violet EL component but suppresses the defect-related yellow-green emission, leading to the observed tunable EL color. The proposed strategy of introducing surface plasmons can be further applied to many other kinds of LEDs for their selective enhancement of EL intensity and effective adjustment of the emission color.

In this work, we report the effort to develop high-efficiency inverted polymer solar cells (PSCs) by applying a solution-processable bilayer ZnO/carbon quantum dots (C-QDs) electron extraction layer (EEL). It is shown that the use of the bilayer EEL helps to suppress the exciton quenching by passivating the ZnO surface defects in the EEL, leading to an enhanced exciton dissociation, reduced charge recombination and more efficient charge extraction probability, and thereby achieving high power conversion efficiency (PCE). The inverted PSCs, based on the blend of poly{4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl-alt-3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophene-4,6-diyl} and [6,6]-phenyl C71-butyric acid methyl ester, possess a significant improvement in PCE of ∼9.64%, which is >27% higher than that of a control cell (∼7.59%). The use of a bilayer ZnO/C-QD EEL offers a promising approach for attaining high-efficiency inverted PSCs.

Two spiroannulated molecular structures with dithiafulvenyl units functionalized at the 2,2',7,7'- (SFX-DTF1) and 2,3',6,'7- (SFX-DTF2) positions of a spiro[fluorene-9,9'-xanthene] core were synthesized. Studies revealed the hole mobility was significantly influenced by the dithiafulvenyl functionalized positions in the molecular structure. To explore their primary applications as hole-transporting materials in perovskite solar cells, SFX-DTF1-based devices exhibited a power conversion efficiency of 10.67% without the use of p-type dopants, yielding good air stability.

Combination therapy with different functional drugs has been proved to be an effective strategy for cancer treatments by achieving cooperative therapeutic efficacy and reducing drug side effects. In this study, a novel combination anticancer system was designed by coating silver nanoparticles in the poly(aspartic acid) (PAsp) shell of polymer micelle via the in situ reduction of silver ions and encapsulating doxorubicin (DOX) into the micellar poly( ε -caprolactone) (PCL) core through hydrophobic interaction. This combination system not only avoided aggregation of the silver nanoparticles but also improved the bioavailability of DOX. As a result, it exhibited enhanced antitumor activity against HepG2 tumor cells compared with single silver-coated or DOX-loaded nanoparticles because of the combined anticancer effects of nanosilver and DOX. Therefore, this combination therapeutic system could be a potential candidate for enhanced anticancer therapy.

Propionic acid (PA) is a specialty chemical; its calcium salt is widely used as food preservative. Soy molasses (SM), a low-value byproduct from soybean refinery, contains sucrose and raffinose-family oligosaccharides (RFO), which are difficult to digest for most animals and industrial microorganisms. The feasibility of using SM for PA production by P. acidipropionici, which has genes encoding enzymes necessary for RFO hydrolysis, was studied. With corn steep liquor as the nitrogen source, stable long-term PA production from SM was demonstrated in sequential batch fermentations, achieving PA productivity of >0.8 g/L h and yield of 0.42 g/g sugar at pH 6.5. Economic analysis showed that calcium propionate as the main component (63.5%) in the product could be produced at US $1.55/kg for a 3000-MT plant with a capital investment of US $10.82 million. At $3.0/kg for the product, the process offers attractive 40% return of investment and is promising for commercial application., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Short-wavelength LEDs, a hot research topic in modern optoelectronics, have attracted tremendous attention in recent years because of their great application potential in both civil and military domains. Compared to conventional metallic surface-plasmons (SPs), carbon nanodot (CD) SPs with less optical loss and low cost, broader SP resonant frequency and good biocompatibility are expected to provide more prominent luminescence enhancement for light emitters. Herein, SP-enhanced near-UV emission quantum dot LEDs (Q-LED) were fabricated via introducing CDs into p-GaN/Al 2 O 3 /ZnO Q-LEDs by optimizing the molar ratio of ZnO quantum dots to CDs and a significant enhancement (∼20-fold) of the near-UV electroluminescence (EL) intensity from the ZnO-based Q-LEDs was achieved. Time-resolved spectroscopy studies reveal that the observed luminescence enhancement arises due to the resonant coupling between ZnO excitons and CD SPs. The current study not only demonstrates a feasible way to acquire near-UV emission from all-inorganic Q-LEDs, but also provides an effective strategy to enhance the EL intensity of these QD light emitters, which can further be extended to other types of light-emitting devices to improve EL efficiency.

It is very important to obtain a deeper understand of the carrier dynamics for indirect-bandgap multilayer MoS 2 and to make further improvements to the luminescence efficiency. Herein, an anomalous luminescence behavior of multilayer MoS 2 is reported, and its exciton emission is significantly enhanced at high temperatures. Temperature-dependent Raman studies and electronic structure calculations reveal that this experimental observation cannot be fully explained by a common mechanism of thermal-expansion-induced interlayer decoupling. Instead, a new model involving the intervalley transfer of thermally activated carriers from Λ/Γ point to K point is proposed to understand the high-temperature luminescence enhancement of multilayer MoS 2 . Steady-state and transient-state fluorescence measurements show that both the lifetime and intensity of the exciton emission increase relatively to increasing temperature. These two experimental evidences, as well as a calculation of carrier population, provide strong support for the proposed model., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Bacteria identification plays a vital role in the field of clinical diagnosis, food industry, and environmental monitoring, which is in great demand of point of care detection methods. In this paper, in order to discriminate the source of nosiheptide product, a plasmonic filter was fabricated to filtrate, capture and identify Streptomycete spores with Surface enhanced Raman Scattering (SERS). Since the plasmonic filter was derived from self-assembled photonic crystal coated with silver, the plasmonic "hot spots" on the filter surface was distributed evenly in a fare good density and the SERS enhancement factor was 7.49 × 10 7 . With this filter, a stain- and PCR-free detection was realized with only 5 μL sample solution and 5 min in a manner of "filtration and measure". Comparison to traditional Gram stain method and silver-plated nylon filter membrane, the plasmonic filter showed good sensitivity and efficiency in the discrimination of nosiheptide prepared with chemical and biological methods. It is anticipated that this simple SERS detection method with plasmonic filter has promising potentials in food safety, environmental, or clinical applications.

Peatlands are organic-matter-rich but nitrogen-limited natural systems, the carbon/nitrogen (C/N) status of which are subject to increasing exposure from long-term nitrate (NO 3 - ) fertilizer inputs and atmospheric nitrogen (N) deposits. To manage and protect these unique environments, an improved understanding of denitrification-dependent anaerobic oxidation of methane (DAMO) in peatlands is needed. In this study, we used stable isotope measurements and incubation with NO 3 - additions to facilitate an investigation and comparison of the potential DAMO rates in a paddy-peatland that has been influenced by N fertilizer over 40 years and an undisturbed peatland in northeast China. Monitoring of 13 CO 2 production confimed DAMO did occur in both the paddy-peatland and the undisturbed peatland, the rates of which increased with NO 3 - additions, but decreased logarithmically with time. When NO 3 - was added, there were no significant differences between the CH 4 oxidation in the paddy-peatland and peatland samples after 36 hours of incubation (97.08 vs. 143.69 nmol g -1 dry peat) and the potential DAMO rate after incubation for 1 hour (92.53 vs. 69.99 nmol g -1  h -1 ). These results indicate that the occurrence of DAMO in peatlands might be controlled by the amount of NO 3 - applied and the depth to which it penetrates into the anoxic layer.

Ultraviolet light-emitting devices (LEDs) were fabricated on the basis of Au/MgO/ZnO metal/insulator/semiconductor (MIS) heterostructures. By introducing a thermally oxidized p-type Cu 2 O hole-injection layer into this MIS structure, enhanced ultraviolet electroluminescence (EL) and random lasing with reduced threshold injection current are achieved. The enhancement mechanism is attributed to effective hole transfer from p-Cu 2 O to i-MgO under forward bias, which increases the initial carrier concentration of MgO dielectric layer and further promotes "impact-ionization" effect induced carrier generation and injection. The current study proposes a new and effective route to improve the EL performance of MIS junction LEDs via introducing extrinsic hole suppliers.

Reversible and nonvolatile modulation of magnetization switching characteristic in ferromagnetic materials is crucial in developing spintronic devices with low power consumption. It is recently discovered that strain engineering can be an active and effective approach in tuning the magnetic/transport properties of thin films. The primary method in strain modulation is via the converse piezoelectric effect of ferroelectrics, which is usually volatile due to the reliance of the required electric field. Also the maximum amount of deformation in ferroelectrics is usually limited to be less than 1%, and the corresponding magnetoelastic strain energy introduced to ferromagnetic films is on the order of 10(4) J/m(3), not enough to overcome magnetocrystalline anisotropy energy (Ku) in many materials. Different from using conventional strain inducing substrates, this paper reports on the significantly large, reversible, and nonvolatile lattice strain in the L10-FePt films (up to 2.18%) using nonelectrically controlled shape memory alloy substrates. Introduced lattice strain can be large enough to effectively affect domain structure and magnetic reversal in FePt. A noticeable decrease of coercivity field by 80% is observed. Moreover, the coercivity field tunability using such substrates is nonvolatile at room temperature and is also reversible due to the characteristics of the shape memory effect. This finding provides an efficient avenue for developing strain assisted spintronic devices such as logic memory device, magnetoresistive random-access memory, and memristor.

Tuning the lattice strain (εL) is a novel approach to manipulate the magnetic, electronic, and transport properties of spintronic materials. Achievable εL in thin film samples induced by traditional ferroelectric or flexible substrates is usually volatile and well below 1%. Such limits in the tuning capability cannot meet the requirements for nonvolatile applications of spintronic materials. This study answers to the challenge of introducing significant amount of elastic strain in deposited thin films so that noticeable tuning of the spintronic characteristics can be realized. Based on subtle elastic strain engineering of depositing L10-FePt films on pre-stretched NiTi(Nb) shape memory alloy substrates, steerable and nonvolatile lattice strain up to 2.18% has been achieved in the L10-FePt films by thermally controlling the shape memory effect of the substrates. Introduced strains at this level significantly modify the electronic density of state, orbital overlap, and spin-orbit coupling (SOC) strength in the FePt film, leading to nonvolatile modulation of magnetic anisotropy and magnetization reversal characteristics. This finding not only opens an efficient avenue for the nonvolatile tuning of SOC based magnetism and spintronic effects, but also helps to clarify the physical nature of pure strain effect.

Propionibacteria are widely used in industry for manufacturing of Swiss cheese, vitamin B₁₂, and propionic acid. However, little is known about their genetics and only a few reports are available on the metabolic engineering of propionibacteria aiming at enhancing fermentative production of vitamin B12 and propionic acid. n-Propanol is a common solvent, an intermediate in many industrial applications, and a promising biofuel. To date, no wild-type microorganism is known to produce n-propanol in sufficient quantities for industrial application purposes. In this study, a bifunctional aldehyde/alcohol dehydrogenase (adhE) was cloned from Escherichia coli and expressed in Propionibacterium freudenreichii. The mutants expressing the adhE gene converted propionyl- coenzyme A, which is the precursor for propionic acid biosynthesis, to n-propanol. The production of n-propanol was limited by NADH availability, which was improved significantly by using glycerol as the carbon source. Interestingly, the improved propanol production was accompanied by a significant increase in propionic acid productivity, indicating a positive effect of n-propanol biosynthesis on propionic acid fermentative production. To our best knowledge, this is the first report on producing n-propanol by metabolically engineered propionibacteria, which offers a novel route to produce n-propanol from renewable feedstock, and possibly a new way to boost propionic acid fermentation.

Background: Enterovirus 71 (EV71), one of the most important neurotropic EVs, has caused death and long-term neurological sequelae in hundreds of thousands of young children in the Asia-Pacific region in the past decade. The neurological diseases are attributed to infection by EV71 inducing an extensive peripheral and central nervous system (CNS) inflammatory response with abnormal cytokine production and lymphocyte depletion induced by EV71 infection. In the absence of specific antiviral agents or vaccines, an effective immunosuppressive strategy would be valuable to alleviate the severity of the local inflammation induced by EV71 infection., Presentation of the Hypothesis: The complement system plays a pivotal role in the inflammatory response. Inappropriate or excessive activation of the complement system results in a severe inflammatory reaction or numerous pathological injuries. Previous studies have revealed that EV71 infection can induce complement activation and an inflammatory response of the CNS. CR2-targeted complement inhibition has been proved to be a potential therapeutic strategy for many diseases, such as influenza virus-induced lung tissue injury, postischemic cerebral injury and spinal cord injury. In this paper, a mouse model is proposed to test whether a recombinant fusion protein consisting of CR2 and a region of Crry (CR2-Crry) is able to specifically inhibit the local complement activation induced by EV71 infection, and to observe whether this treatment strategy can alleviate or even cure the neurogenic inflammation., Testing the Hypothesis: CR2-Crry is expressed in CHO cells, and its biological activity is determined by complement inhibition assays. 7-day-old ICR mice are inoculated intracranially with EV71 to duplicate the neurological symptoms. The mice are then divided into two groups, in one of which the mice are treated with CR2-Crry targeted complement inhibitor, and in the other with phosphate-buffered saline. A group of mice deficient in complement C3, the breakdown products of which bind to CR2, are also infected with EV71 virus. The potential bioavailability and efficacy of the targeted complement inhibitor are evaluated by histology, immunofluorescence staining and radiolabeling., Implications of the Hypothesis: CR2-Crry-mediated targeting complement inhibition will alleviate the local inflammation and provide an effective treatment for the severe neurological diseases associated with EV71 infection.

Researches have shown that melatonin is neuroprotectant in ischemia/reperfusion-mediated injury. Although melatonin is known as an effective antioxidant, the mechanism of the protection cannot be explained merely by antioxidation. This study was devoted to explore other existing mechanisms by investigating whether melatonin protects ischemia/reperfusion-injured neurons through elevating autophagy, since autophagy has been frequently suggested to play a crucial role in neuron survival. To find it out, an ischemia/reperfusion model in N2a cells was established for examinations. The results showed that autophagy was significantly enhanced in N2a cells treated with melatonin at reperfusion onset following ischemia and greatly promoted cell survival, while autophagy blockage by 3-MA led to the shortened N2a cell survival as assessed by MTT, transmission electron microscopy, and laser confocal scanning microscopy. Besides, the protein levels of LC3II and Beclin1 were remarkably increased in ischemia/reperfusion-injured N2a in the presence of melatonin, whereas the expression of p-PKB, key kinase in PI3K/PKB signaling pathway, showed a decrease when compared with untreated subjects as accessed by immunoblotting. Taken together these data suggest that autophagy is possibly one of the mechanisms underlying neuroprotection of melatonin.

The protective effect of exogenous melatonin or 6-hydroxylmelatonin on neurons was examined in N2a cells following exposure to oxygen-glucose-serum deprivation insults. After N2a cells cultured in vitro were deprived of glucose, serum and oxygen for 90 min, the different concentrations of melatonin or 6-hydroxylmelatonin were added to the medium. Then, treated cells were cultured for different intervals. At the end of the treatment, the collected culture solution was used for the analysis of the activity of lactate dehydrogenase (LDH) and the cells were used for the examination of the following parameters: cell viability (MTT), DNA fragmentation, reactive oxygen species (ROS) production, mitochondrial transmembrane potential, cytochrome C and caspase 3 activity. The results show that melatonin and 6-hydroxylmelatonin both reduced oxygen-glucose-serum deprivation-mediated N2a cell apoptosis, but they could not completely inhibit the apoptosis of the cells and the inhibitory effect of melatonin was stronger than that of 6-hydroxylmelatonin. Both of them could inhibit LDH and cytochrome C release and caspase 3 activity. Although 6-hydroxylmelatonin could no longer maintain mitochondrial transmembrane potential 6 h after reperfusion, its inhibitory effect on cytochrome C release from mitochondria and the scavenging role of ROS were stronger than those of melatonin. Moreover, melatonin promoted ROS production at the 15th min of the reperfusion, and then it began to remove ROS from cells. Our study showed that melatonin and 6-hydroxylmelatonin can be used as supplements in the treatment of neurological disorders involving oxidative stress. Melatonin serves as more than a ROS scavenger and its other roles await further study.

To investigate the role of mitochondria in neuronal apoptosis, ischemia-reperfusion mediated neuronal cell injury model was established by depriving of glucose, serum and oxygen in media. DNA fragmentation, cell viability, cytochrome C releasing, caspase3 activity and mitochondrial transmembrane potential were observed after N2a cells suffered the insults. The results showed that N2a cells in ischemic territory exhibited survival damage, classical cell apoptosis change, DNA ladder and activation of caspase3. Apoptosis-related alterations in mitochondrial functions, including release of cytochrome C and depression of mitochondrial transmembrane potential (deltapsim) were testified in N2a cells after mimic ischemia-reperfusion. Moreover, activation of caspase3 occurred following the release of cytochrome C. However, the inhibitor of caspase3, Ac-DEVD-CHO, couldn't completely rescue N2a cells from apoptosis. Administration of cyclosporine A, an inhibitor of mitochondria permeability transition pore only partly inhibited caspase3 activity and reduced DNA damage. Interestingly, treatment of Z-IETD-FMK, an inhibitor of caspase8 could completely reverse DNA fragmentation, but can't completely inhibit caspase3 activity. It was concluded that there were caspase3 dependent and independent cellular apoptosis pathways in N2a cells suffering ischemia-reperfusion insults. Mitochondria dysfunction may early trigger apoptosis and amplify apoptosis signal.