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951.
Markovic O Cederlund E Griffiths WJ Lipka T Jörnvall H 《Cellular and molecular life sciences : CMLS》2002,59(3):513-518
The most alkaline form of pectin methylesterase was purified from ripe carrot roots and used for structural analysis. Determination
of an N-terminal blocking group and of the primary structure allowed comparisons with other forms, and facilitated crystallographic
determination of the three-dimensional structure. The mature enzyme has 319 residues and the N-terminal blocking group was
shown to be a pyroglutamyl residue derived from a glutaminyl cyclization. Few other methylesterases have been isolated and
assigned to exact mature forms, and together with the present enzyme, only two have been analyzed in three-dimensional structure.
However, comparison of 39 forms, mainly from GenBank data, reveals clear relationships and identifies sub-groups of this enzyme
type, deviating in structure but centering around two functionally important and conserved Asp residues at positions 136 and
157 in the carrot enzyme.
Received 2 January 2002; accepted 4 January 2002 相似文献
952.
Coghill EL Hugill A Parkinson N Davison C Glenister P Clements S Hunter J Cox RD Brown SD 《Nature genetics》2002,30(3):255-256
The construction of parallel archives of DNA and sperm from mice mutagenized with ethylnitrosurea (ENU) represents a potentially powerful and rapid approach for identifying point mutations in any gene in the mouse genome. We provide support for this approach and report the identification of mutations in the gene (Gjb2) encoding connexin 26, using archives established from the UK ENU mutagenesis program. 相似文献
953.
Frequent somatic mutations in PTEN and TP53 are mutually exclusive in the stroma of breast carcinomas 总被引:19,自引:0,他引:19
We have recently shown that loss of heterozygosity of specific markers, including those at 10q23, 17p13-p15 and 16q24, can occur in the stromal and epithelial compartments of primary invasive breast carcinomas. Here, we demonstrate high frequencies of somatic mutations in TP53 (encoding tumor protein p53) and PTEN (encoding phosphate and tensin homolog) in breast neoplastic epithelium and stroma. Mutations in TP53 and PTEN are mutually exclusive in either compartment. In contrast, mutations in WFDC1 (16q24, encoding WAP four-disulfide core domain 1) occur with low frequency in the stroma. 相似文献
954.
Most research into genomics and other related biotechnologies is concerned with the priorities of industrialized nations, and yet a limited number of projects have shown that these technologies could help improve health in developing countries. To encourage the successful application of biotechnology to global health, we carried out a study in which we asked an international group of eminent scientists with expertise in global health issues to identify the top ten biotechnologies for improving health in developing countries. The results offer concrete guidance to those in a position to influence the direction of research and development, and challenge common assumptions about the relevance and affordability of biotechnology for developing countries. 相似文献
955.
Mice heterozygous for mutation in Atm,the gene involved in ataxia-telangiectasia,have heightened susceptibility to cancer 总被引:11,自引:0,他引:11
Spring K Ahangari F Scott SP Waring P Purdie DM Chen PC Hourigan K Ramsay J McKinnon PJ Swift M Lavin MF 《Nature genetics》2002,32(1):185-190
Ataxia-telangiectasia is characterized by radiosensitivity, genome instability and predisposition to cancer. Heterozygous carriers of ATM, the gene defective in ataxia-telangiectasia, have a higher than normal risk of developing breast and other cancers. We demonstrate here that Atm 'knock-in' (Atm-Delta SRI) heterozygous mice harboring an in-frame deletion corresponding to the human 7636del9 mutation show an increased susceptibility to developing tumors. In contrast, no tumors are observed in Atm knockout (Atm(+/-)) heterozygous mice. In parallel, we report the appearance of tumors in 6 humans from 12 families who are heterozygous for the 7636del9 mutation. Expression of ATM cDNA containing the 7636del9 mutation had a dominant-negative effect in control cells, inhibiting radiation-induced ATM kinase activity in vivo and in vitro. This reduces the survival of these cells after radiation exposure and enhances the level of radiation-induced chromosomal aberrations. These results show for the first time that mouse carriers of a mutated Atm that are capable of expressing Atm have a higher risk of cancer. This finding provides further support for cancer predisposition in human ataxia-telangiectasia carriers. 相似文献
956.
Long-range chromatin regulatory interactions in vivo 总被引:19,自引:0,他引:19
957.
The discreteness of charge in units of e led Schottky in 1918 to predict that the electrical current in a vacuum tube fluctuates even if all spurious noise sources are eliminated carefully. This phenomenon is now widely known as shot noise. In recent years, shot noise in mesoscopic conductors, where charge motion is quantum-coherent over distances comparable to the system size, has been studied extensively. In those experiments, charge does not propagate as an isolated entity through free space, as for vacuum tubes, but is part of a degenerate and quantum-coherent Fermi sea of charges. It has been predicted that shot noise in mesoscopic conductors can disappear altogether when the system is tuned to a regime where electron motion becomes classically chaotic. Here we experimentally verify this prediction by using chaotic cavities where the time that electrons dwell inside can be tuned. Shot noise is present for large dwell times, where the electron motion through the cavity is 'smeared' by quantum scattering, and it disappears for short dwell times, when the motion becomes classically deterministic. 相似文献
958.
Antagonistic coevolution between the sexes in a group of insects 总被引:16,自引:0,他引:16
In coevolutionary 'arms races' between the sexes, the outcome of antagonistic interactions may remain at an evolutionary standstill. The advantage gained by one sex, with any evolutionary exaggeration of arms, is expected to be matched by analogous counteradaptations in the other sex. This fundamental coevolutionary process may thus be hidden from the evolutionist's eye, and no natural examples are known. We have studied the effects of male and female armament (clasping and anti-clasping morphologies) on the outcome of antagonistic mating interactions in 15 species of water strider, using a combination of experimental and phylogenetic comparative methods. Here we present, by assessing the independent effects of both species-specific level of arms escalation and small imbalances in the amounts of arms between the sexes within species, the consequences of a sexual arms race. Evolutionary change in the balance of armament between males and females, but not in the species-specific level of escalation, has resulted in evolutionary change in the outcome of sexually antagonistic interactions such as mating rate. 相似文献
959.
960.
Brain potential and functional MRI evidence for how to handle two languages with one brain 总被引:7,自引:0,他引:7
Bilingual individuals need effective mechanisms to prevent interference from one language while processing material in the other. Here we show, using event-related brain potentials and functional magnetic resonance imaging (fMRI), that words from the non-target language are rejected at an early stage before semantic analysis in bilinguals. Bilingual Spanish/Catalan and monolingual Spanish subjects were instructed to press a button when presented with words in one language, while ignoring words in the other language and pseudowords. The brain potentials of bilingual subjects in response to words of the non-target language were not sensitive to word frequency, indicating that the meaning of non-target words was not accessed in bilinguals. The fMRI activation patterns of bilinguals included a number of areas previously implicated in phonological and pseudoword processing, suggesting that bilinguals use an indirect phonological access route to the lexicon of the target language to avoid interference. 相似文献