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排序方式: 共有494条查询结果,搜索用时 31 毫秒
91.
zlem Alptekin S. Seyhan Tükel Deniz Yldrm Dilek Alagz 《Journal of Molecular Catalysis .B, Enzymatic》2009,58(1-4):124-131
Bovine liver catalase was covalently immobilized onto controlled pore glass (CPG) beads modified with 3-aminopropyltriethoxysilane (3-APTES) followed by treatment with glutaraldehyde. Coupling of catalase onto CPG was optimized to improve the efficiency of the overall immobilization procedure. The optimum coupling conditions: pore diameter of CPG, pH, buffer concentration, temperature, coupling time and initial catalase amount per grams of carrier were determined as 70 nm, 6.0, 75 mM, 5 °C, 7 h and 6 mg catalase, respectively. Catalytic efficiencies (kcat/Km) and thermal inactivation rate constants (ki) of ICPG1 were determined and compared with that of free catalase. Suitability of ICPG1 was also investigated by using it in batch and plug-flow type reactors. When the remaining activity of ICPG1 retained was about 50% of its initial activity the highest total productivity of ICPG1 was determined as 7.6 × 106 U g immobilized catalase−1 in plug-flow type reactor. However, the highest total productivity of ICPG1 was 6.2 × 105 U g immobilized catalase−1 in batch type reactor. ICPG1 may have great potentials as biocatalyst for the application in decomposition of hydrogen peroxide in plug-flow type reactor. 相似文献
92.
Huseyin Inceer Deniz Guney Sema Hayirlioglu-Ayaz Melahat Ozcan Ibrahim Turna Ali Omer Ucler 《Biologia》2009,64(6):1076-1084
Karyological studies have been investigated within 8 native Anatolian populations of oriental spruce (Picea orientalis (L.) Link) in Turkey. The somatic chromosome number of 2n = 2x = 24 has been observed in all accessions. The karyotypes are generally asymmetrical with most of the chromosomes having median
to median-submedian centromeres. Inter-population variability of the karyotype was summarized with cluster analysis. We found
that the karyotypes have positively correlated with the altitudes of the natural habitats. The high value of karyotype asymmetry
may be attributed to both microenvironment and natural regeneration methods used in oriental spruce. 相似文献
93.
Coding nucleotide sequences contain myriad functions independent of their encoded protein sequences. We present the COMIT
algorithm to detect functional noncoding motifs in coding regions using sequence conservation, explicitly separating nucleotide
from amino acid effects. COMIT concurs with diverse experimental datasets, including splicing enhancers, silencers, replication
motifs, and microRNA targets, and predicts many novel functional motifs. Intriguingly, COMIT scores are well-correlated to
scores uncalibrated for amino acids, suggesting that nucleotide motifs often override peptide-level constraints. 相似文献
94.
95.
Nitrogen and Phosphorus Limitation of Phytoplankton Growth in New Zealand Lakes: Implications for Eutrophication Control 总被引:6,自引:0,他引:6
We examine macronutrient limitation in New Zealand (NZ) lakes where, contrary to the phosphorus (P) only control paradigm,
nitrogen (N) control is widely adopted to alleviate eutrophication. A review of published results of nutrient enrichment experiments
showed that N more frequently limited lake productivity than P; however, stoichiometric analysis of a sample of 121 NZ lakes
indicates that the majority (52.9%) of lakes have a mean ratio of total nitrogen (TN) to total phosphorus (TP) (by mass) indicative
of potential P-limitation (>15:1), whereas only 14.0% of lakes have mean TN:TP indicative of potential N-limitation (<7:1).
Comparison of TN, TP, and chlorophyll a data between 121 NZ lakes and 689 lakes in 15 European Union (EU) countries suggests that at the national scale, N has a
greater role in determining lake productivity in NZ than in the EU. TN:TP is significantly lower in NZ lakes across all trophic
states, a difference that is driven primarily by significantly lower in-lake TN concentrations at low trophic states and significantly
higher TP concentrations at higher trophic states. The form of the TN:TP relationship differs between NZ and the EU countries,
suggesting that lake nutrient sources and/or loss mechanisms differ between the two regions. Dual control of N and P should
be the status quo for lacustrine eutrophication control in New Zealand and more effort is needed to reduce P inputs. 相似文献
96.
Emir Alper Türkoğlu Deniz Ekinci 《Journal of enzyme inhibition and medicinal chemistry》2017,32(1):74-77
Inhibitors of carbonic anhydrase (CA) have been carried out in many therapeutic applications, especially antiglaucoma activity. In this study, we investigated some uracil derivatives (4–12) to inhibit human CA I (hCA I) and II (hCA II) isoenzymes. The KI values of the compounds 4–12 are in the range of 0.085–428?µM for hCA I and of 0.1715–645?µM against hCA II, respectively. It is concluded from the kinetic investigations, all compounds used in the study act as competitive inhibitors with substrate, 4-NPA. Uracil derivatives are emerging agents for the inhibiton of carbonic anhydrase which could be used in biomedicine. 相似文献
97.
Hypolimnetic phosphorus and nitrogen dynamics in a small,eutrophic lake with a seasonally anoxic hypolimnion 总被引:4,自引:0,他引:4
In situ estimates of sediment nutrient flux are necessary to understand seasonal variations in internal loading in lakes.
We investigated the sources and sinks of nutrients in the hypolimnion of a small (0.33 km2), relatively shallow (18 m max. depth), eutrophic lake (Lake Okaro, New Zealand) in order to determine changes in sediment
nutrient fluxes resulting from a whole lake sediment capping trial using a modified zeolite phosphorus inactivation agent
(Z2G1). Sediment nutrient fluxes in the hypolimnion were estimated as the residual term in a nutrient budget model that accounted
for mineralisation of organic nutrients, nutrient uptake by phytoplankton and mixing, nitrification, adsorption/desorption
and diffusion of dissolved nutrients at the thermocline. Of the total hypolimnetic phosphate and ammonium fluxes during one
period of seasonal stratification (2007–08), up to 60 and 50%, respectively, were derived from the bottom sediments, 18 and
24% were due to mineralisation of organic species, 36 and 28% were due to phytoplankton uptake and 9 and 6% were from diffusion
across the thermocline. Adsorption/desorption of phosphate to suspended solids and nitrification were of minor (<8%) importance
to the total fluxes. Any reduction in sediment nutrient release by Z2G1 was small compared with both the total sediment nutrient
flux and the sum of other hypolimnetic fluxes. Uneven sediment coverage of Z2G1 may have been responsible for the limited
effect of the sediment capping layer formed by Z2G1. 相似文献
98.
To assess the alternative responses to aluminum toxicity, maize (Zea mays L. cv Karadeniz y?ld?z?) roots were exposed to different concentrations of AlCl3 (150, 300 and 450 μM). Aluminum reduced the root elongation by 39.6% in 150 μM, 44.1% in 300 μM, 50.1% in 450 μM AlCl3 after 96 h period. To correlate the root elongation with the alternative stress responses including aluminum accumulation, lipid peroxidation, mitotic abnormalities, reduction of starch content, intracellular Ca2+ accumulation, callose formation, lignin deposition and peroxidase activity, cytochemical and biochemical tests were performed. The results indicated that aluminum accumulation and lipid peroxidation were observed more densely on the root cap and the outer cortex cells. In addition to morphological deformations, cytochemical analysis displayed cellular deformations. Furthermore, mitotic abnormalities were observed such as c-mitosis, micronuclei, bi- and trinucleated cells in aluminum treated root tips. Aluminum treatment induced starch reduction, callose formation, lignin accumulation and intracellular Ca2+ increase. Moreover, the peroxidase activity increased significantly by 3, 4.4 and 7.7 times higher than in that of control after 96 h, respectively. In conclusion, aluminum is significantly stressful in maize culminating in morphological and cellular alterations. 相似文献
99.
Deniz S Wersinger E Schwab Y Mura C Erdelyi F Szabó G Rendon A Sahel JA Picaud S Roux MJ 《Journal of neurochemistry》2011,116(3):350-362
Lateral interactions at the first retinal synapse have been initially proposed to involve GABA by transporter-mediated release from horizontal cells, onto GABA(A) receptors expressed on cone photoreceptor terminals and/or bipolar cell dendrites. However, in the mammalian retina, horizontal cells do not seem to contain GABA systematically or to express membrane GABA transporters. We here report that mouse retinal horizontal cells express GAD65 and/or GAD67 mRNA, and were weakly but consistently immunostained for GAD65/67. While GABA was readily detected after intracardiac perfusion, it was lost during classical preparation for histology or electrophysiology. It could not be restored by incubation in a GABA-containing medium, confirming the absence of membrane GABA transporters in these cells. However, GABA was synthesized de novo from glutamate or glutamine, upon addition of pyridoxal 5'-phosphate, a cofactor of GAD65/67. Mouse horizontal cells are thus atypical GABAergic neurons, with no functional GABA uptake, but a glutamate and/or glutamine transport system allowing GABA synthesis, probably depending physiologically from glutamate released by photoreceptors. Our results suggest that the role of GABA in lateral inhibition may have been underestimated, at least in mammals, and that tissue pre-incubation with glutamine and pyridoxal 5'-phosphate should yield a more precise estimate of outer retinal processing. 相似文献
100.
Elena Kurenova Deniz Ucar Jianqun Liao Michael Yemma Priyanka Gogate Wiam Bshara 《Cell cycle (Georgetown, Tex.)》2014,13(16):2542-2553
Melanoma has the highest mortality rate of all skin cancers and a major cause of treatment failure is drug resistance. Tumors heterogeneity requires novel therapeutic strategies and new drugs targeting multiple pathways. One of the new approaches is targeting the scaffolding function of tumor related proteins such as focal adhesion kinase (FAK). FAK is overexpressed in most solid tumors and is involved in multiple protein-protein interactions critical for tumor cell survival, tumor neovascularization, progression and metastasis. In this study, we investigated the anticancer activity of the FAK scaffold inhibitor C4, targeted to the FAK-VEGFR-3 complex, against melanomas. We compared C4 inhibitory effects in BRAF mutant vs BRAF wild type melanomas. C4 effectively caused melanoma tumor regression in vivo, when administered alone and sensitized tumors to chemotherapy. The most dramatic effect of C4 was related to reduction of vasculature of both BRAF wild type and V600E mutant xenograft tumors. The in vivo effects of C4 were assessed in xenograft models using non-invasive multimodality imaging in conjunction with histologic and molecular biology methods. C4 inhibited cell viability, adhesion and motility of melanoma and endothelial cells, specifically blocked phosphorylation of VEGFR-3 and FAK and disrupted their complexes. Specificity of in vivo effects for C4 were confirmed by a decrease in tumor FAK and VEGFR-3 phosphorylation, reduction of vasculogenesis and reduced blood flow. Our collective observations provide evidence that a small molecule inhibitor targeted to the FAK protein-protein interaction site successfully inhibits melanoma growth through dual targeting of tumor and endothelial cells and is effective against both BRAF wild type and mutant melanomas. 相似文献