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61.
A single U leads to G transversion in the 3' consensus sequence AAUAAA of the adenovirus early region 1A gene was constructed and the effect of this mutation on processing of the 3' end of the nuclear early region 1A RNAs was analysed. The results demonstrate that the intact AAUAAA is not required for RNA polyadenylation but is required for the cleavage step preceding polyadenylation to occur efficiently. 相似文献
62.
Summary The erythropoietic effects in exhypoxic polycythemic mice of two endoperoxide analogs were assessed and compared with PGE2. The 9a, 11a epoxymethano analog (U-44069) was found to be a much more potent erythropoietic stimulus than the 11a,9a analog (U-46619) or PGE2.This work was supported by a Senior Research Grant-in-Aid from the American Heart Association-Louisiana (DMG) and USPHS Grant No. AM 13211 (JWF). 相似文献
63.
J. C. Chabala V. B. Waits T. Ikeler A. A. Patchett L. Payne L. H. Peterson R. A. Reamer K. Hoogsteen M. Wyvratt W. L. Hanson M. H. Fisher 《Cellular and molecular life sciences : CMLS》1991,47(1):51-53
Summary 1-(Substituted)benzyl-5-aminoimidazole-4-carboxamides are potent orally active inhibitors ofTrypanosoma cruzi infections in mice. The most active compounds are the 1-(4-chlorobenzyl)- and 1-(3,4-dichlorobenzyl)-analogs (L-153,094 [2] and L-153,153 [4], resp.) which are approximately 7-fold more potent upon oral administration than nifurtimox (Lampit) in suppressing parasite levels in the blood of mice with acuteTrypanosoma cruzi infections. 相似文献
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66.
Lu DH Yi M Mo SK Erickson AS Analytis J Chu JH Singh DJ Hussain Z Geballe TH Fisher IR Shen ZX 《Nature》2008,455(7209):81-84
The recent discovery of superconductivity in the iron oxypnictide family of compounds has generated intense interest. The layered crystal structure with transition-metal ions in planar square-lattice form and the discovery of spin-density-wave order near 130 K (refs 10, 11) seem to hint at a strong similarity with the copper oxide superconductors. An important current issue is the nature of the ground state of the parent compounds. Two distinct classes of theories, distinguished by the underlying band structure, have been put forward: a local-moment antiferromagnetic ground state in the strong-coupling approach, and an itinerant ground state in the weak-coupling approach. The first approach stresses on-site correlations, proximity to a Mott-insulating state and, thus, the resemblance to the high-transition-temperature copper oxides, whereas the second approach emphasizes the itinerant-electron physics and the interplay between the competing ferromagnetic and antiferromagnetic fluctuations. The debate over the two approaches is partly due to the lack of conclusive experimental information on the electronic structures. Here we report angle-resolved photoemission spectroscopy (ARPES) of LaOFeP (superconducting transition temperature, T(c) = 5.9 K), the first-reported iron-based superconductor. Our results favour the itinerant ground state, albeit with band renormalization. In addition, our data reveal important differences between these and copper-based superconductors. 相似文献
67.
We investigated localities from which Eutamias atristriatus Bailey, 1913 (= Tamias minimus atristriatus ) and Zapus luteus Miller, 1911 (= Zapus hudsonius luteus ) were collected during a 1902 survey in the Sacramento Mountains, New Mexico, by the United States Biological Survey. The locality from which the holotype of Eutamias atristriatus was collected is restricted to James Canyon rather than the Rio Pe?asco. Locality records indicate that the historical distribution of Zapus hudsonius luteus and its obligate wetland habitat were broader than currently realized. 相似文献
68.
Badano JL Leitch CC Ansley SJ May-Simera H Lawson S Lewis RA Beales PL Dietz HC Fisher S Katsanis N 《Nature》2006,439(7074):326-330
Epistatic interactions have an important role in phenotypic variability, yet the genetic dissection of such phenomena remains challenging. Here we report the identification of a novel locus, MGC1203, that contributes epistatic alleles to Bardet-Biedl syndrome (BBS), a pleiotropic, oligogenic disorder. MGC1203 encodes a pericentriolar protein that interacts and colocalizes with the BBS proteins. Sequencing of two independent BBS cohorts revealed a significant enrichment of a heterozygous C430T mutation in patients, and a transmission disequilibrium test (TDT) showed strong over-transmission of this variant. Further analyses showed that the 430T allele enhances the use of a cryptic splice acceptor site, causing the introduction of a premature termination codon (PTC) and the reduction of steady-state MGC1203 messenger RNA levels. Finally, recapitulation of the human genotypes in zebrafish shows that modest suppression of mgc1203 exerts an epistatic effect on the developmental phenotype of BBS morphants. Our data demonstrate how the combined use of biochemical, genetic and in vivo tools can facilitate the dissection of epistatic phenomena, and enhance our appreciation of the genetic basis of phenotypic variability. 相似文献
69.
Sebastian SE Harrison N Batista CD Balicas L Jaime M Sharma PA Kawashima N Fisher IR 《Nature》2006,441(7093):617-620
Competition between electronic ground states near a quantum critical point (QCP)--the location of a zero-temperature phase transition driven solely by quantum-mechanical fluctuations--is expected to lead to unconventional behaviour in low-dimensional systems. New electronic phases of matter have been predicted to occur in the vicinity of a QCP by two-dimensional theories, and explanations based on these ideas have been proposed for significant unsolved problems in condensed-matter physics, such as non-Fermi-liquid behaviour and high-temperature superconductivity. But the real materials to which these ideas have been applied are usually rendered three-dimensional by a finite electronic coupling between their component layers; a two-dimensional QCP has not been experimentally observed in any bulk three-dimensional system, and mechanisms for dimensional reduction have remained the subject of theoretical conjecture. Here we show evidence that the Bose-Einstein condensate of spin triplets in the three-dimensional Mott insulator BaCuSi2O6 (refs 12-16) provides an experimentally verifiable example of dimensional reduction at a QCP. The interplay of correlations on a geometrically frustrated lattice causes the individual two-dimensional layers of spin-(1/2) Cu2+ pairs (spin dimers) to become decoupled at the QCP, giving rise to a two-dimensional QCP characterized by linear power law scaling distinctly different from that of its three-dimensional counterpart. Thus the very notion of dimensionality can be said to acquire an 'emergent' nature: although the individual particles move on a three-dimensional lattice, their collective behaviour occurs in lower-dimensional space. 相似文献
70.
During the 1930s and 1940s, American physical organic chemists employed electronic theories of reaction mechanisms to construct models offering explanations of organic reactions. But two molecular rearrangements presented enormous challenges to model construction. The Claisen and Cope rearrangements were predominantly inaccessible to experimental investigation and they confounded explanation in theoretical terms. Drawing on the idea that models can be autonomous agents in the production of scientific knowledge, I argue that one group of models in particular were functionally autonomous from the Hughes–Ingold theory. Cope and Hardy’s models of the Claisen and Cope rearrangements were resources for the exploration of the Hughes–Ingold theory that otherwise lacked explanatory power. By generating ‘how-possibly’ explanations, these models explained how these rearrangements could happen rather than why they did happen. Furthermore, although these models were apparently closely connected to theory in terms of their construction, I argue that partial autonomy issued in extra-logical factors concerning the attitudes of American chemists to the Hughes–Ingold theory. And in the absence of a complete theoretical hegemony, a degree of consensus was reached concerning modelling the Claisen rearrangement mechanism. 相似文献