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An amber map of Salmonella phage P22 总被引:2,自引:0,他引:2
Summary Forty five amber mutants of Salmonella phage P22 were assigned to 12 complementation groups. Two amber mutants could not be classified into any one particular group.Ten of the complementation groups were mapped by two-factor crosses. The map is circular and about 65 units long.The remaining two complementation groups each consist of a single member which form very small plaques. Attempts to map these two mutants by two-factor crosses were unsuccessful. 相似文献
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A. M. Harvey P. Hava A. B. Oppenheim H. H. Prell J. Soska 《Molecular & general genetics : MGG》1981,181(1):74-81
Summary Using SDS-polyacrylamide gel electrophoresis to study the early expression of P22 genes we show that early expression of the ant-gene (imm I region) is turned off after 6–8 min, independent of the late acting mnt-repressor. A semi-clear mutant called cir5 is defective for this early ant turn-off. The mutation cir5 maps in the imm I region of P22 between genes mnt and ant. P22 cir5 mutants are defective for a repressor which acts in trans to regulate early ant synthesis. There appears to be no absolute requirement of the cir5 allele for the establishment of lysogeny. The overproduction of ant in the P22 cir5 mutant leads to a marked increase in abortive infections, killing the infected cells. The cir5-phenotype can be suppressed by an ant
- mutation. 相似文献
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Plastic waste disposal is a huge ecotechnological problem and one of the approaches to solving this problem is the development of biodegradable plastics. This review summarizes data on their use, biodegradability, commercial reliability and production from renewable resources. Some commercially successful biodegradable plastics are based on chemical synthesis (i.e. polyglycolic acid, polylactic acid, polycaprolactone, and polyvinyl alcohol). Others are products of microbial fermentations (i.e. polyesters and neutral polysaccharides) or are prepared from chemically modified natural products (e.g., starch, cellulose, chitin or soy protein). 相似文献
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Caroline Schmutz Alison Cartwright Helen Williams Oliver Haworth John HH Williams Andrew Filer Mike Salmon Christopher D Buckley Jim Middleton 《Arthritis research & therapy》2010,12(4):R161
Introduction
Monocytes/macrophages accumulate in the rheumatoid (RA) synovium where they play a central role in inflammation and joint destruction. Identification of molecules involved in their accumulation and differentiation is important to inform therapeutic strategies. This study investigated the expression and function of chemokine receptor CCR9 in the peripheral blood (PB) and synovium of RA, non-RA patients and healthy volunteers. 相似文献8.
Degradation Pathway of Bisphenol A: Does ipso Substitution Apply to Phenols Containing a Quaternary α-Carbon Structure in the para Position? 下载免费PDF全文
B. Kolvenbach N. Schlaich Z. Raoui J. Prell S. Zühlke A. Schffer F. P. Guengerich P. F. X. Corvini 《Applied microbiology》2007,73(15):4776-4784
The degradation of bisphenol A and nonylphenol involves the unusual rearrangement of stable carbon-carbon bonds. Some nonylphenol isomers and bisphenol A possess a quaternary α-carbon atom as a common structural feature. The degradation of nonylphenol in Sphingomonas sp. strain TTNP3 occurs via a type II ipso substitution with the presence of a quaternary α-carbon as a prerequisite. We report here a new degradation pathway of bisphenol A. Consequent to the hydroxylation at position C-4, according to a type II ipso substitution mechanism, the C-C bond between the phenolic moiety and the isopropyl group of bisphenol A is broken. Besides the formation of hydroquinone and 4-(2-hydroxypropan-2-yl)phenol as the main metabolites, further compounds resulting from molecular rearrangements consistent with a carbocationic intermediate were identified. Assays with resting cells or cell extracts of Sphingomonas sp. strain TTNP3 under an 18O2 atmosphere were performed. One atom of 18O2 was present in hydroquinone, resulting from the monooxygenation of bisphenol A and nonylphenol. The monooxygenase activity was dependent on both NADPH and flavin adenine dinucleotide. Various cytochrome P450 inhibitors had identical inhibition effects on the conversion of both xenobiotics. Using a mutant of Sphingomonas sp. strain TTNP3, which is defective for growth on nonylphenol, we demonstrated that the reaction is catalyzed by the same enzymatic system. In conclusion, the degradation of bisphenol A and nonylphenol is initiated by the same monooxygenase, which may also lead to ipso substitution in other xenobiotics containing phenol with a quaternary α-carbon. 相似文献
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Free radical formation in the cochlea plays a key role in the development of noise-induced hearing loss (NIHL). The amount, distribution, and time course of free radical formation have been defined, including a clinically significant formation of both reactive oxygen species and reactive nitrogen species 7-10 days after noise exposure. Reduction in cochlear blood flow as a result of free radical formation has also been described. Here we report that the antioxidant agents vitamins A, C, and E act in synergy with magnesium to effectively prevent noise-induced trauma. Neither the antioxidant agents nor the magnesium reliably reduced NIHL or sensory cell death with the doses we used when these agents were delivered alone. In combination, however, they were highly effective in reducing both hearing loss and cell death even with treatment initiated just 1 h before noise exposure. This study supports roles for both free radical formation and noise-induced vasoconstriction in the onset and progression of NIHL. Identification of this safe and effective antioxidant intervention that attenuates NIHL provides a compelling rationale for human trials in which free radical scavengers are used to eliminate this single major cause of acquired hearing loss. 相似文献
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Dominik Hartl Matthias Griese Thomas Nicolai Gernot Zissel Christine Prell Dietrich Reinhardt Dolores J Schendel Susanne Krauss-Etschmann 《Respiratory research》2005,6(1):1-12