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91.
Angus R. Brown Maryanne Covington Robert C. Newton Robert Ramage Patricia Welch 《Journal of peptide science》1996,2(1):40-46
The affinity-based Nα-amino protecting group tetrabenzo [a,c,g,i]fluorenyl-17-methoxycarbonyl (Tbfmoc) has been utilized as a hydrophobic probe to allow the simple, quick and highly effective isolation of a 76 residue cysteine-containing protein (MCP-1). The base-labile Tbfmoc group can be removed under very mild conditions, which preserve the thiol-con taining protein in the reduced state. Oxidative folding was then used to furnish the biologically active β-chemokine MCP-1. 相似文献
92.
We used a previously described precipitation gradient in a tropical montane ecosystem of Hawai’i to evaluate how changes in
mean annual precipitation (MAP) affect the processes resulting in the loss of N via trace gases. We evaluated three Hawaiian
forests ranging from 2200 to 4050 mm year−1 MAP with constant temperature, parent material, ecosystem age, and vegetation. In situ fluxes of N2O and NO, soil inorganic nitrogen pools (NH4+ and NO3−), net nitrification, and net mineralization were quantified four times over 2 years. In addition, we performed 15N-labeling experiments to partition sources of N2O between nitrification and denitrification, along with assays of nitrification potential and denitrification enzyme activity
(DEA). Mean NO and N2O emissions were highest at the mesic end of the gradient (8.7±4.6 and 1.1±0.3 ng N cm−2 h−1, respectively) and total oxidized N emitted decreased with increased MAP. At the wettest site, mean trace gas fluxes were
at or below detection limit (≤0.2 ng N cm−2 h−1). Isotopic labeling showed that with increasing MAP, the source of N2O changed from predominately nitrification to predominately denitrification. There was an increase in extractible NH4+ and decline in NO3−, while mean net mineralization and nitrification did not change from the mesic to intermediate sites but decreased dramatically
at the wettest site. Nitrification potential and DEA were highest at the mesic site and lowest at the wet site. MAP exerts
strong control N cycling processes and the magnitude and source of N trace gas flux from soil through soil redox conditions
and the supply of electron donors and acceptors. 相似文献
93.
The survival of UV-irradiated phage T1 is much lower in excision repair-deficient than in excision repair-proficient E. coli cells, due to lack of “host cell reactivation” (HCR). An additional decrease in phage survival occurs when repair-deficient (HCR−) host cells have been exposed to UV doses from 3000–10 000 erg mm−2 of 254 nm UV-radiation prior to infection. The observed effect is attributed to loss of a minor phage recovery process, which requires neither the bacterial excision repair nor the bacterial REC repair system. This type of recovery is little affected by caffeine or acriflavine at concentrations that preclude HCR completely. Its full inhibition by UV-irradiation of the cells requires an approximately 8 times larger dose than complete inhibition of HCR.
In heavily preirradiated cells, the T1 burst size is extremely small and multiplicity reactivation is considerably less extensive than in unirradiated cells. Presumably the survival of singly infecting T1 in these cells reflects absence of any type of repair. The observed phage sensitivity and shape of the curve are compatible with the expectation for completely repairless conditions. The mechanism underlying the minor recovery is not known; theoretical considerations make a phage REC repair mechanism seem likely. 相似文献
94.
To show the relationship of the monodelphic species of Trichodoridae with the nominal taxa, the genus Monotrichodorus is redefined, with the addition of one new species. The new genus Allotrichodorus is proposed on the basis of new species found in Brazil; and one new species is described in the genus Paratrichodorus. 相似文献
95.
Gene therapy has converged with bone engineering over the past decade, by which a variety of therapeutic genes have been delivered to stimulate bone repair. These genes can be administered via in vivo or ex vivo approach using either viral or nonviral vectors. This article reviews the fundamental aspects and recent progresses in the gene therapy-based bone engineering, with emphasis on the new genes, viral vectors and gene delivery approaches. 相似文献
96.
Structural comparison of the two distinct sugar binding sites in wheat germ agglutinin isolectin II 总被引:12,自引:0,他引:12
C S Wright 《Journal of molecular biology》1984,178(1):91-104
97.
Lanthanides have been reported to induce apoptosis in cancer cell lines. Human cervical cancer cell line HeLa was found to be more sensitive to dicitratolanthanum (III) complex ([LaCit2]3−) than other cancer cell lines. However, the effect and mechanism of dicitratoytterbium (III) complex ([YbCit2]3−) on HeLa cells is unknown. Using biochemical and comparative proteomic analyses, [YbCit2]3− was found to inhibit HeLa cell growth and induce apoptosis. Similar to the effects of [LaCit2]3−, proteomics results from [YbCit2]3−-treated cells revealed profound changes in proteins relating to mitochondria and oxidative stress, suggesting that mitochondrial dysfunction plays a key role in [YbCit2]3−-induced apoptosis. This was confirmed by the decreased mitochondrial transmembrane potential and the increased generation of reactive oxygen species in [YbCit2]3−-treated cells. Western blot analysis showed that [YbCit2]3−-induced apoptosis was accompanied by the activation of caspase-9 and specific proteolytic cleavage of PARP, leading to an increase in the pro-apoptotic protein Bax and a decrease in the anti-apoptotic protein Bcl-2. These results suggest a mitochondrial pathway of cell apoptosis in [YbCit2]3−-treated cells, which will help us understand the molecular mechanisms of lanthanide-induced apoptosis in tumor cells. 相似文献
98.
Russell H. Messing Michelle N. Tremblay Edward B. Mondor Robert G. Foottit Keith S. Pike 《Biological invasions》2007,9(5):601-607
Invasive species have had devastating impacts on the fauna and flora of the Hawaiian Islands. While the negative effects of
some invasive species are obvious, other species are less visible, though no less important. Aphids (Homoptera: Aphididae)
are not native to Hawai’i but have thoroughly invaded the Island chain, largely as a result of anthropogenic influences. As
aphids cause both direct plant feeding damage and transmit numerous pathogenic viruses, it is important to document aphid
distributions and ranges throughout the archipelago. On the basis of an extensive survey of aphid diversity on the five largest
Hawaiian Islands (Hawai’i, Kaua’i, O’ahu, Maui, and Moloka’i), we provide the first evidence that invasive aphids feed not
just on agricultural crops, but also on native Hawaiian plants. To date, aphids have been observed feeding and reproducing
on 64 native Hawaiian plants (16 indigenous species and 48 endemic species) in 32 families. As the majority of these plants
are endangered, invasive aphids may have profound impacts on the island flora. To help protect unique island ecosystems, we
propose that border vigilance be enhanced to prevent the incursion of new aphids, and that biological control efforts be renewed
to mitigate the impact of existing species. 相似文献
99.
Pediatric phase I trials are usually carried out after the adult trial testing the same agent has started, but not completed yet. As the pediatric trial progresses, in light of the accrued interim data from the concurrent adult trial, the pediatric protocol often is amended to modify the original pediatric dose escalation design. In practice, this is done frequently in an ad hoc way, interrupting patient accrual and slowing down the trial. We developed a pediatric-continuous reassessment method (PA-CRM) to streamline this process, providing a more efficient and rigorous method to find the maximum tolerated dose for pediatric phase I oncology trials. We use a discounted joint likelihood of the adult and pediatric data, with a discount parameter controlling information borrowing between pediatric and adult trials. According to the interim adult and pediatric data, the discount parameter is adaptively updated using the Bayesian model averaging method. Numerical study shows that the PA-CRM improves the efficiency and accuracy of the pediatric trial and is robust to various model assumptions. 相似文献
100.
S K Gupta N Dhanasekaran L E Heasley G L Johnson 《Journal of cellular biochemistry》1991,47(4):359-368
The alpha subunit polypeptides of the G proteins Gs and Gi2 stimulate and inhibit adenylyl cyclase, respectively. The alpha s and alpha i2 subunits are 65% homologous in amino acid sequence but have highly conserved GDP/GTP binding domains. Previously, we mapped the functional adenylyl cyclase activation domain to a 122 amino acid region in the COOH-terminal moiety of the alpha s polypeptide (Osawa et al: Cell 63:697-706, 1990). The NH2-terminal half of the alpha s polypeptide encodes domains regulating beta gamma interactions and GDP dissociation. A series of chimeric cDNAs having different lengths of the NH2- or COOH-terminal coding sequence of alpha s substituted with the corresponding alpha i2 sequence were used to introduce multi-residue non-conserved mutations in different domains of the alpha s polypeptide. Mutation of either the amino- or carboxy-terminus results in an alpha s polypeptide which constitutively activates cAMP synthesis when expressed in Chinese hamster ovary cells. The activated alpha s polypeptides having mutations in either the NH2- or COOH-terminus demonstrate an enhanced rate of GTP gamma S activation of adenylyl cyclase. In membrane preparations from cells expressing the various alpha s mutants, COOH-terminal mutants, but not NH2-terminal alpha s mutants markedly enhance the maximal stimulation of adenylyl cyclase by GTP gamma S and fluoride ion. Neither mutation at the NH2- nor COOH-terminus had an effect on the GTPase activity of the alpha s polypeptides. Thus, mutation at NH2- and COOH-termini influence the rate of alpha s activation, but only the COOH-terminus appears to be involved in the regulation of the alpha s polypeptide activation domain that interacts with adenylyl cyclase. 相似文献