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101.
Z Cerovac J Ban A Morinville K Yaccato A Shaver D Maysinger 《Neurochemistry international》1999,34(4):337-344
Potassium bisperoxo(1,10-phenantroline)oxovanadate (V) [bpV(phen)] is a potent protein tyrocine phosphatase inhibitor which mediates a variety of biological effects. The aim of these studies was to examine the role(s) of mitogen activated protein kinase (MAPK) pathways in PC12 cell proliferation and toxicity by bpV(phen). BpV(phen) exerts a bimodal effect in PC12 cells: proliferation at low and cell death at higher micromolar concentrations. Activation of MAPK by bpV(phen) depends on time and concentration. The phosphorylation pattern of extracellular regulated kinases (ERK 1/2), c-jun N-terminal activated kinases (JNK) and p38 in PC12 cells is strikingly different. Activation of JNK is sustained in PC12 cells. In contrast, ERK 1/2 activation is transient and treatment with PD98059 indicates that ERK activation by bpV(phen) is partly independent from the ras-MEK pathway. Stability studies of bpV(phen) in DMEM and PBS showed linear relationship with T1/2 about 6 h and 10 days in DMEM and PBS, respectively. Comparison between the time courses of MAPK activation and kinetics of bpV(phen) decomposition as assessed by 51V-NMR analysis show that the initial and maximal phosphorylation signals are produced in the presence of the complex bpV(phen) and not caused by the decomposition products of bpV(phen). 相似文献
102.
The average height of 31-aged Robinia pseudoacacia plantation in west mountain of Beijing is 7 in and the mean breastheight diameter of tree is 8.3 cm. The number of tree per hectare appears 1750. The canopy coverage of plantation shows 0.5. Using tile diameter square at tree breast height times tree height (D2H), as an independing variable, to estimate the dry weight of various parts of trees, between them the significient correlations occur. According to the modle of Wstem=58.88(D2H)0.88 (WBranch)=e7.77+0.001(D2H) (Wleaf)=e5.71+0.0008(D2H) (Wroot)=e7.67+0.0009(D2H) 28.45 t/ha of the stem biomass, 11.6 t/ha of the branch biomass. 0.97 t/ha of the leaf biomass, 7.6 t/ha of the root biomass are estimated in arbor layer. The aboveground and belowground biomass of shrub and herb layers axe 13.71 t/ha and 10.72 t/ha respectively in September, the biomass of shrub and herb layer is 24.43 t/ha. 73.05 t/ha of the total biomass in Robinia pseudoacacia plantation is obtained. 相似文献
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104.
The complete structure of the chloroplast 70S ribosome in complex with translation factor pY
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Philipp Bieri Marc Leibundgut Martin Saurer Daniel Boehringer Nenad Ban 《The EMBO journal》2017,36(4):475-486
Chloroplasts are cellular organelles of plants and algae that are responsible for energy conversion and carbon fixation by the photosynthetic reaction. As a consequence of their endosymbiotic origin, they still contain their own genome and the machinery for protein biosynthesis. Here, we present the atomic structure of the chloroplast 70S ribosome prepared from spinach leaves and resolved by cryo‐EM at 3.4 Å resolution. The complete structure reveals the features of the 4.5S rRNA, which probably evolved by the fragmentation of the 23S rRNA, and all five plastid‐specific ribosomal proteins. These proteins, required for proper assembly and function of the chloroplast translation machinery, bind and stabilize rRNA including regions that only exist in the chloroplast ribosome. Furthermore, the structure reveals plastid‐specific extensions of ribosomal proteins that extensively remodel the mRNA entry and exit site on the small subunit as well as the polypeptide tunnel exit and the putative binding site of the signal recognition particle on the large subunit. The translation factor pY, involved in light‐ and temperature‐dependent control of protein synthesis, is bound to the mRNA channel of the small subunit and interacts with 16S rRNA nucleotides at the A‐site and P‐site, where it protects the decoding centre and inhibits translation by preventing tRNA binding. The small subunit is locked by pY in a non‐rotated state, in which the intersubunit bridges to the large subunit are stabilized. 相似文献
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Honda T Tajima H Kaneko Y Ban M Inaba T Takeno Y Okamoto K Aono H 《Bioorganic & medicinal chemistry letters》2008,18(9):2939-2943
We found 4-pyridylmethylthio derivative 1 to be very effective in using antiangiogenesis activity to prevent proliferation of HUVECs (Human Umbilical Vein Endothelial Cells), which was induced by vascular endothelial growth factor (VEGF). Compound 1 was equally effective in inhibiting VEGF receptor2 tyrosine kinase (KDR, IC50 = 26 nM). We deduced that the inhibition was the result of binding the catalytic domain of VEGF receptor2 tyrosine kinase in a similar fashion to both phthalazine derivative PTK787 2 and anthranylamide derivative AAL993 3. In this report, we will describe the conformational analyses, from ab initio MO calculation and X-ray crystallographic analyses, of compound 1 and the analogs, which include non-active 9, all in comparison with 2 and 3. The conformation–activity relationships suggest that a nonbonded intramolecular interaction between the sulfur and the carbonyl oxygen of 1 was very important in inhibiting KDR. 相似文献
108.
Enomoto H Morikawa Y Miyake Y Tsuji F Mizuchi M Suhara H Fujimura K Horiuchi M Ban M 《Bioorganic & medicinal chemistry letters》2008,18(16):4529-4532
We studied the synthetic modification of structurally similar N-mercaptoacyl-L-proline and (4R)-N-mercaptoacylthiazolidine-4-carboxylic acid to obtain potent leukotriene A(4) (LTA(4)) hydrolase inhibitors. An N-mercaptoacyl group, (2S)-3-mercapto-2-methylpropionyl group, was effective for both scaffolds. Additional introduction of a large substituent such as 4-isopropylbenzylthio (3f), 4-tert-butylbenzylthio (3l) or 4-cyclohexylbenzylthio group (3m) with (S)-configuration at the C(4) position of proline yielded much more potent LTA(4) hydrolase inhibitors (IC(50); 52, 31, and 34 nM, respectively) than captopril (IC(50); 630,000 nM). 相似文献
109.
The vertical distributions of planktonic bacteria, chroococcoid cyanobacteria, and heterotrophic nanoflagellates (HNF) were
examined in Lake Toya, an oligotrophic lake located in Hokkaido, the northern island of Japan, at monthly intervals from May
1993 to May 1994. The abundances of bacteria, cyanobacteria, and HNF during the study period ranged from 104 to 105,102 to 104, 10 to 102 cells ml−1, respectively. The range of bacterial abundances was among the lowest previously reported from other oligotrophic lakes.
The vertical distributions of both bacteria and cyanobacteria were influenced by thermal stratification: they were homogeneous
throughout the water column during the circulation period (January to April) and heterogeneous during the period of stratification
(June to November). During the period of stratification, the cyanobacterial abundance decreased toward the surface in the
euphotic zone while the frequency of diving cells (FDC) increased, suggesting that grazing pressure was high near the surface.
This hypothesis was supported by the relatively high abundance of HNF at the surface and the negative correlation between
HNF and cyanobacterial abundances in the euphotic zone (r = −0.503, n = 33, P < 0.05). On the other hand, multiple regression analysis revealed that 52% of the variation in bacterial abundance in the
stratified period can be explained by chlorophyll a concentration, water temperature, and HNF abundance (df = 3, 45; F = 16.2; P < 0.01), suggesting that both substrate limitation and grazing loss by HNF were important factors controlling bacterial abundance
in the lake.
Received: June 21, 2002 / Accepted: October 16, 2002
Present address: 5-2-2-18-805 Kikusui-motomachi, Shiroishi, Sapporo 003-0825, Japan
Present address: School of Environmental Science, University of Shiga Prefecture, 2500 Hassaka-cho, Hikone 522-8533, Japan Tel. +81-749-28-8307;
Fax +81-749-28-8463 e-mail: ban@ses.usp.ac.jp
Acknowledgments We thank Dr. H. Ueda for encouraging this study and Mr. Haruna and the members of the Plankton Laboratory, Hokkaido University,
for their help in sampling. We also thank two anonymous reviewers for their critical comments.
Correspondence to:S. Ban 相似文献
110.