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1.
Glucose oxidase (GOD) was covalently immobilized onto Fe3O4/SiO2 magnetic nanoparticles (FSMNs) using glutaraldehyde (GA). Optimal immobilization was at pH 6 with 3-aminopropyltriethoxysilane
at 2% (v/v), GA at 3% (v/v) and 0.143 g GOD per g carrier. The activity of immobilized GOD was 4,570 U/g at pH 7 and 50°C.
The immobilized GOD retained 80% of its initial activity after 6 h at 45°C while free enzyme retained only 20% activity. The
immobilized GOD maintained 60% of its initial activity after 6 cycles of repeated use and retained 75% of its initial activity
after 1 month at 4°C whereas free enzymes retained 62% of its activity. 相似文献
2.
Zoccarato F Miotto C Cavallini L Alexandre A 《Journal of bioenergetics and biomembranes》2011,43(4):359-366
In brain mitochondria succinate activates H2O2 release, concentration dependently (starting at 15 μM), and in the presence of NAD dependent substrates (glutamate, pyruvate,
β-hydroxybutyrate). We report that TCA cycle metabolites (citrate, isocitrate, α-ketoglutarate, fumarate, malate) individually
and quickly inhibit H2O2 release. When they are present together at physiological concentration (0.2, 0.01, 0.15, 0.12, 0.2 mM respectively) they
decrease H2O2 production by over 60% at 0.1–0.2 mM succinate. The degree of inhibition depends on the concentration of each metabolite.
Acetoacetate is a strong inhibitor of H2O2 release, starting at 10 μM and acting quickly. It potentiates the inhibition induced by TCA cycle metabolites. The action
of acetoacetate is partially removed by β-hydroxybutyrate. Removal is minimal at 0.1 mM acetoacetate, and is higher at 0.5 mM
acetoacetate. We conclude that several inhibitors of H2O2 release act jointly and concentration dependently to rapidly set the required level of H2O2 generation at each succinate concentration. 相似文献
3.
Selective effects of H<Subscript>2</Subscript>O<Subscript>2</Subscript> on cyanobacterial photosynthesis 总被引:3,自引:0,他引:3
The sensitivity of phytoplankton species for hydrogen peroxide (H2O2) was analyzed by pulse amplitude modulated (PAM) fluorometry. The inhibition of photosynthesis was more severe in five tested
cyanobacterial species than in three green algal species and one diatom species. Hence the inhibitory effect of H2O2 is especially pronounced for cyanobacteria. A specific damage of the photosynthetic apparatus was demonstrated by changes
in 77 K fluorescence emission spectra. Different handling of oxidative stress and different cell structure are responsible
for the different susceptibility to H2O2 between cyanobacteria and other phytoplankton species. This principle may be potentially employed in the development of new
agents to combat cyanobacterial bloom formation in water reservoirs. 相似文献
4.
It was shown that tobacco leaf treatment with 100 mM H2O2 increased their content of endogenous H2O2 and activities of catalase and hydrolases (acid phosphatase, proteases, and RNase) and also caused various changes in the cell structure. In this case, programmed cell death (PCD) occurred in some cells, which was observed as chromatin condensation, cytoplasm collapse, etc. In the meantime, many cells displayed organelle activation rather than PCD. It is suggested that cells that undergo H2O2-dependent PCD release signaling molecules inducing protective mechanisms against oxidative stress in neighboring cells not exhibiting PCD. 相似文献
5.
S. R. Sampson E. Bucris M. Horovitz-Fried A. Parnas S. Kahana G. Abitbol M. Chetboun T. Rosenzweig C. Brodie S. Frankel 《Apoptosis : an international journal on programmed cell death》2010,15(10):1165-1176
Insulin resistance results, in part, from impaired insulin signaling in insulin target tissues. Consequently, increased levels of insulin are necessary to control plasma glucose levels. The effects of elevated insulin levels on pancreatic beta (β) cell function, however, are unclear. In this study, we investigated the possibility that insulin may influence survival of pancreatic β cells. Studies were conducted on RINm, RINm5F and Min-6 pancreatic β-cells. Cell death was induced by treatment with H2O2, and was estimated by measurements of LDH levels, viability assay (Cell-Titer Blue), propidium iodide staining and FACS analysis, and mitochondrial membrane potential (JC-1). In addition, levels of cleaved caspase-3 and caspase activity were determined. Treatment with H2O2 increased cell death; this effect was increased by simultaneous treatment of cells with insulin. Insulin treatment alone caused a slight increase in cell death. Inhibition of caspase-3 reduced the effect of insulin to increase H2O2-induced cell death. Insulin increased ROS production by pancreatic β cells and increased the effect of H2O2. These effects were increased by inhibition of IR signaling, indicative of an effect independent of the IR cascade. We conclude that elevated levels of insulin may act to exacerbate cell death induced by H2O2 and, perhaps, other inducers of apoptosis. 相似文献
6.
Vanadium is an environmentally toxic metal with peculiar and sometimes contradictory cellular effects. It is insulin-mimetic,
it can either stimulate cell growth or induce cell death, and it has both mutagenic and antineoplastic properties. However,
the mechanisms involved in those effects are poorly understood. Several studies suggest that H2O2 is involved in vanadate-induced cell death, but it is not known whether cellular sensitivity to vanadate is indeed related
to H2O2 generation. In the present study, the sensitivity of four cell lines from different origins (K562, K562-Lucena 1, MDCK, and
Ma104) to vanadate and H2O2 was evaluated and the production of H2O2 by vanadate was analyzed by flow cytometry. We show that cell lines very resistant to H2O2 (K562, K562-Lucena 1, and Ma104 cells) are much more sensitive to vanadate than MDCK, a cell line relatively susceptible
to H2O2, suggesting that vanadate-induced cytotoxicity is not directly related to H2O2 responsiveness. In accordance, vanadate concentrations that reduced cellular viability to approximately 60–70% of the control
(10 μmol/L) did not induce H2O2 formation. A second hypothesis, that peroxovanadium (PV) compounds, produced once vanadate enters into the cells, are responsible
for the cytotoxicity, was only partially confirmed because MDCK cells were resistant to both vanadate and PV compounds (10 μmol/L
each). Therefore, our results suggest that vanadate toxicity occurs by two distinct pathways, one dependent on and one independent
of H2O2 production. 相似文献
7.
Hossein Salehizadeh Elham Hekmatian Meisam Sadeghi Kevin Kennedy 《Journal of nanobiotechnology》2012,10(1):3
Background
Fe3O4-gold-chitosan core-shell nanostructure can be used in biotechnological and biomedical applications such as magnetic bioseparation, water and wastewater treatment, biodetection and bioimaging, drug delivery, and cancer treatment. 相似文献8.
Changes in tyrosine phosphorylation of soluble polypeptides of pea (Pisum sativum L.) roots were revealed under the action of exogenous hydrogen peroxide in situ and in vitro. The polypeptides whose tyrosine phosphorylation in situ was vanadate-sensitive were identified. A thiol agent dithiothreitol and the antioxidant ascorbic acid reversed the effect of hydrogen peroxide in vitro. The results indicate that tyrosine phosphorylation of pea proteins is a subject to redox regulation. 相似文献
9.
Barley seedlings were pre-treated with 1 and 5 μM H2O2 for 2 d and then supplied with water or 150 mM NaCl for 4 and 7 d. Exogenous H2O2 alone had no effect on the proline, malondialdehyde (MDA) and H2O2 contents, decreased catalase (CAT) activity and had no effect on peroxidase (POX) activity. Three new superoxide dismutase
(SOD) isoenzymes appeared in the leaves as a result of 1 μM H2O2 treatment. NaCl enhanced CAT and POX activity. SOD activity and isoenzyme patterns were changed due to H2O2 pre-treatment, NaCl stress and leaf ageing. In pre-treated seedlings the rate of 14CO2 fixation was higher and MDA, H2O2 and proline contents were lower in comparison to the seedlings subjected directly to NaCl stress. Cl− content in the leaves 4 and 7 d after NaCl supply increased considerably, but less in pre-treated plants. It was suggested
that H2O2 metabolism is involved as a signal in the processes of barley salt tolerance. 相似文献
10.
Density functional theory (DFT) calculations were used to study the effect of scandium doping on the structural, energetic, electronic, linear and nonlinear optical (NLO) properties of Be12O12, Mg12O12 and Ca12O12 nanoclusters. Scandium (Sc) doping on nanoclusters leads to narrowing of their E g, which enhances their conductance greatly. Also, the polarizability (α) and first hyperpolarizability (β0) of nanoclusters were dramatically increased as Be, Mg or Ca atoms are substituted with a Sc atom. Among all clusters, α and β0 values for Sc-doped Ca12O12 were the largest. Consequently, the effect of the doping atom, as well as of cluster size, on electronic and optical properties was explored. Time dependent (TD)-DFT calculations were also carried out to confirm the β0 values; the results show that the higher value of first hyperpolarizability belongs to Sc-doped Ca12O12, which has the smallest transition energy (ΔEgn). The results obtained show that these clusters can be candidates for using in electronic devices and NLO materials in industry. 相似文献
11.
Kun Yang Xiao-Fang Chen Jian-Yong Liu Wei-Peng Lai Bo-Zhou Wang 《Journal of molecular modeling》2011,17(5):1017-1027
Nitrosation reactions of malononitrile by three nitrosating agents, HONO, ClNO, and N2O3, have been theoretically investigated at the B3LYP/cc-pVTZ and MP2/cc-pVDZ levels. Two possible competitive paths for nitrosation
of malononitrile to give 2-nitroso-malononitrile were proposed: (a) direct C-nitrosation and (b) N-nitrosation and subsequent
nitroso transfer from N to C atom. The calculations show that at both B3LYP and MP2 levels, path b is kinetically favored
over path a for nitrosations by HONO and N2O3. In the case of ClNO, the B3LYP predicts preference of path b, while the MP2 calculations suggest that both paths have similar
rate-determining barriers. The data suggest that N2O3 is the preferred nitrosating agent for the nitrosation of malononitrile in aqueous solution. Transformation of 2-nitroso-malononitrile
to form malononitrileoxime via intramolecular proton transfer has also been explored, and it is found that inclusion of an
assistant water molecule can drastically accelerate the tautomerization. 相似文献
12.
13.
Ashok Kumar In-Won Kim Sanjay K. S. Patel Jung-Kul Lee 《Indian journal of microbiology》2018,58(1):100-104
In the present study, a method for easy and rapid synthesis of lipase nanohybrids was evaluated using cobalt chloride as an encapsulating agent. The synthesized nanohybrids exhibited higher activity (181%) compared to free lipase and improved catalytic properties at higher temperature and in harsh conditions. The nanohybrids retained 84% of their residual activity at 25 °C after 10 days. In addition, these nanohybrids also exhibited high storage stability and reusability. Collectively, the synthesis of carrier-free immobilized biocatalysts was performed rapidly within 24 h at 4 °C. Their high reusability and catalytic activities highlight the broad applicability of this method for catalysis in organic and aqueous media. 相似文献
14.
Zhi-Sheng Zhu Ming-Jun Zhu Wan-Xia Xu Lei Liang 《Biotechnology and Bioprocess Engineering》2012,17(2):316-325
In this study, we investigated the production of bioethanol from sugarcane bagasse (SCB) using an NH4OH-H2O2 pretreatment and simultaneous saccharification and co-fermentation (SScF). Response surface methodology and a 23 Box-Behnken design were used to evaluate the effect of different liquid mixture concentrations, liquid-to-solid ratios (LSRs)
and pretreatment temperatures on the production of ethanol. The liquid mixture concentration and LSR significantly influenced
the fermentation efficiency. Based on ridge max analysis, the following pretreatment conditions resulted in a fermentation
efficiency of 95.79 ± 0.01%: liquid mixture concentration 53%, LSR 28, and a temperature of 63°C. A morphological analysis
performed using scanning electron microscopy (SEM) and chemical characterization revealed that these pretreatment conditions
were effective in disrupting the sugarcane fibers and removing lignin. Ethanol fermentation with the pretreated SCB using
SScF in yeast SHY 07-1 resulted in an ethanol concentration of 14.65 ± 0.17 g/L, an ethanol yield of 0.48 ± 0.01 g/g, and
an ethanol productivity of 0.12 ± 0.01 g/(L/h), which represents increases of 106.02, 89.98, and 107.02%, respectively, over
the values obtained from SScF with untreated SCB. 相似文献
15.
This study examined the effects of carbon dioxide (CO2)-, ozone (O3)-, and genotype-mediated changes in quaking aspen (Populus tremuloides) chemistry on performance of the forest tent caterpillar (Malacosoma disstria) and its dipteran parasitoid (Compsilura concinnata) at the Aspen Free-Air CO2 Enrichment (FACE) site. Parasitized and non-parasitized forest tent caterpillars were reared on two aspen genotypes under elevated levels of CO2 and O3, alone and in combination. Foliage was collected for determination of the chemical composition of leaves fed upon by forest tent caterpillars during the period of endoparasitoid larval development. Elevated CO2 decreased nitrogen levels but had no effect on concentrations of carbon-based compounds. In contrast, elevated O3 decreased nitrogen and phenolic glycoside levels, but increased concentrations of starch and condensed tannins. Foliar chemistry also differed between aspen genotypes. CO2, O3, genotype, and their interactions altered forest tent caterpillar performance, and differentially so between sexes. In general, enriched CO2 had little effect on forest tent caterpillar performance under ambient O3, but reduced performance (for insects on one aspen genotype) under elevated O3. Conversely, elevated O3 improved forest tent caterpillar performance under ambient, but not elevated, CO2. Parasitoid larval survivorship decreased under elevated O3, depending upon levels of CO2 and aspen genotype. Additionally, larval performance and masses of mature female parasitoids differed between aspen genotypes. These results suggest that host-parasitoid interactions in forest systems may be altered by atmospheric conditions anticipated for the future, and that the degree of change may be influenced by plant genotype. 相似文献
16.
This study examined the effects of season-long exposure of Chinese pine (Pinus tabulaeformis) to elevated carbon dioxide (CO2) and/or ozone (O3) on indole-3-acetic acid (IAA) content, activities of IAA oxidase (IAAO) and peroxidase (POD) in needles. Trees grown in
open-top chambers (OTC) were exposed to control (ambient O3, 55 nmol mol−1 + ambient CO2, 350 μmol mol−1, CK), elevated CO2 (ambient O3 + high CO2, 700 μmol mol−1, EC) and elevated O3 (high O3, 80 ± 8 nmol mol−1 + ambient CO2, EO) OTCs from 1 June to 30 September. Plants grown in elevated CO2 OTC had a growth increase of axial shoot and needle length, compared to control, by 20% and 10% respectively, while the growth
in elevated O3 OTC was 43% and 7% less respectively, than control. An increase in IAA content and POD activity and decrease in IAAO activity
were observed in trees exposed to elevated CO2 concentration compared with control. Elevated O3 decreased IAA content and had no significant effect on IAAO activity, but significantly increased POD activity. When trees
pre-exposed to elevated CO2 were transferred to elevated O3 (EC–EO) or trees pre-exposed to elevated O3 were transferred to elevated CO2 (EO–EC), IAA content was lower while IAAO activity was higher than that transferred to CK (EC–CK or EO–CK), the change in
IAA content was also related to IAAO activity. The results indicated that IAAO and POD activities in Chinese pine needles
may be affected by the changes in the atmospheric environment, resulting in the change of IAA metabolism which in turn may
cause changes in Chinese pine’s growth.
An erratum to this article can be found at 相似文献
17.
Jingjing Jia Ting Zhang Jieshan Chi Xiaoma Liu Jingjing Sun Qizhi Xie Sijia Peng Changyan Li Li Yi 《Neurochemical research》2018,43(7):1439-1453
18.
Osório H Moradas-Ferreira P Günther Sillero MA Sillero A 《Archives of microbiology》2004,181(3):231-236
As has been previously shown, Saccharomyces cerevisiae grown in 2% or 0.025% glucose uses this carbohydrate by the fermentative or oxidative pathways, respectively. Depending on the glucose concentration in the medium, the effect of the addition of H2O2 on the level of ATP and on glyceraldehyde-3-phosphate dehydrogenase (GAPDH) activity differed. In the presence of 2% glucose, ATP and GAPDH decreased sharply during the first few minutes of treatment, whereas in the presence of 0.025% glucose, GAPDH activity decreased similarly, but the ATP level remained practically unchanged. The addition of 3 mM glutathione to the culture media prevented the depletion of ATP levels and GAPDH activity in the presence of H2O2. Catalase and superoxide dismutase activities did not vary significantly when yeast cells were grown either in 2% or in 0.025% glucose. 相似文献
19.
Bortolami S Comelato E Zoccarato F Alexandre A Cavallini L 《Journal of bioenergetics and biomembranes》2008,40(1):9-18
Complex I is responsible for most of the mitochondrial H2O2 release, low during the oxidation of the NAD linked substrates and high during succinate oxidation, via reverse electron
flow. This H2O2 production appear physiological since it occurs at submillimolar concentrations of succinate also in the presence of NAD
substrates in heart (present work) and rat brain mitochondria (Zoccarato et al., Biochem J, 406:125–129, 2007). Long chain fatty acyl-CoAs, but not fatty acids, act as strong inhibitors of succinate dependent H2O2 release. The inhibitory effect of acyl-CoAs is independent of their oxidation, being relieved by carnitine and unaffected
or potentiated by malonyl-CoA. The inhibition appears to depend on the unbound form since the acyl-CoA effect decreases at
BSA concentrations higher than 2 mg/ml; it is not dependent on ΔpH or Δp and could depend on the inhibition of reverse electron transfer at complex I, since palmitoyl-CoA inhibits the succinate
dependent NAD(P) or acetoacetate reduction. 相似文献
20.
Qien Li Zhaofeng Wang Yanning Zhao Xiaochen Zhang Shuaijun Zhang Letao Bo Yao Wang Yingfeng Ding Lizhe An 《Plant cell reports》2016,35(5):1155-1168