A suppressor of a yeast splicing mutation (prp8-1) encodes a putative ATP-dependent RNA helicase

Five small nuclear RNAs (snRNAs) are required for nuclear pre-messenger RNA splicing: U1, U2, U4, U5 and U6. The yeast U1 and U2 snRNAs base-pair to the 5' splice site and branch-point sequences of introns respectively. The role of the U5 and U4/U6 small nuclear ribonucleoprotein particles (snRNPs) in splicing is not clear, though a catalytic role for the U6 snRNA has been proposed. Less is known about yeast splicing factors, but the availability of genetic techniques in Saccharomyces cerevisiae has led to the identification of mutants deficient in nuclear pre-mRNA splicing (prp2-prp27). Several PRP genes have now been cloned and their protein products characterized. The PRP8 protein is a component of the U5 snRNP and associates with the U4/U6 snRNAs/snRNP to form a multi-snRNP particle believed to be important for spliceosome assembly. We have isolated extragenic suppressors of the prp8-1 mutation of S. cerevisiae and present here the preliminary characterization of one of these suppressors, spp81. The predicted amino-acid sequence of the SPP81 protein shows extensive similarity to a recently identified family of proteins thought to possess ATP-dependent RNA helicase activity. The possible role of this putative helicase in nuclear pre-mRNA splicing is discussed.     

Structural and temporal requirements for geomagnetic field reversal deduced from lava flows

Reversals of the Earth's magnetic field reflect changes in the geodynamo--flow within the outer core--that generates the field. Constraining core processes or mantle properties that induce or modulate reversals requires knowing the timing and morphology of field changes that precede and accompany these reversals. But the short duration of transitional field states and fragmentary nature of even the best palaeomagnetic records make it difficult to provide a timeline for the reversal process. 40Ar/39Ar dating of lavas on Tahiti, long thought to record the primary part of the most recent 'Matuyama-Brunhes' reversal, gives an age of 795 +/- 7 kyr, indistinguishable from that of lavas in Chile and La Palma that record a transition in the Earth's magnetic field, but older than the accepted age for the reversal. Only the 'transitional' lavas on Maui and one from La Palma (dated at 776 +/- 2 kyr), agree with the astronomical age for the reversal. Here we propose that the older lavas record the onset of a geodynamo process, which only on occasion would result in polarity change. This initial instability, associated with the first of two decreases in field intensity, began approximately 18 kyr before the actual polarity switch. These data support the claim that complete reversals require a significant period for magnetic flux to escape from the solid inner core and sufficiently weaken its stabilizing effect.     

GC/MS法追踪摇头丸杂质体系

本文运用GS/MS的总离子流法,选择离子法,对南京地区常见的几种摇头丸进行全面分析,找出与合成途径相关的痕量杂质,根据杂质情况初步确定其合成途径.     

鲁克沁构造带稠油成藏机制研究

吐哈盆地台南凹陷鲁克沁构造带中的北西走向断层受挤压强烈 ,封闭性好 ;而北东走向断层封闭性差 ,常成为油气运移的良好通道。由于本区断块圈闭的有效性差 ,故不具备大规模聚集稀油的条件 ,但对稠变到一定程度的稠油能起较好的封堵作用。鲁克沁构造带高粘重质油的形成是原油运移和成藏阶段双重稠变作用的结果 ,并且油气的聚集是一个动态的过程。随着原油的逐渐稠变 ,所需要的封堵条件逐渐降低 ,油气的聚集过程才趋于稳定。鲁克沁构造带构造后期变革主要表现在构造幅度的增大 ,而未发生强烈的断裂作用 ,因此 ,前侏罗系油藏得以完好地保存     

A yeast gene (BEM1) necessary for cell polarization whose product contains two SH3 domains.

Cell polarization requires that a cellular axis or cell-surface site be chosen and that the cytoskeleton be organized with respect to it. Details of the link between the cytoskeleton and the chosen axis or site are not clear. Cells of the yeast Saccharomyces cerevisiae exhibit cell polarization in two phases of their life cycle, during vegetative growth and during mating, which reflects responses to intracellular and extracellular signals, respectively. Here we describe the isolation of two mutants defective specifically in cell polarization in response to peptide mating pheromones. The mutants carry special alleles (denoted bem1-s) of the BEM1 gene required for cell polarization during vegetative growth. Unlike other bem1 mutants, the bem1-s mutants are normal for vegetative growth. Complete deletion of BEM1 leads to the defect in polarization of vegetative cells seen in bem1 mutants. The predicted sequence of the BEM1 protein (Bem1p) reveals two copies of a domain (denoted SH3) that is found in many proteins associated with the cortical cytoskeleton and which may mediate binding to actin or some other component of the cell cortex. The sequence of Bem1p and the properties of mutants defective in this protein indicate that it may link the cytoskeleton to morphogenetic determinants on the cell surface.     

Rate of respiration in relation to autogamy inParamecium aurelia

Zusammenfassung Die Atmung einzelner Pantoffeltierchen (Paramecium aurelia) aus Serien-isolierten Kulturen wurde mit Hilfe eines Cartesischen Tauchers gemessen. Die Messungen an Individuen vor und nach Autogamie (Selbstbefruchtung) zeigten, dass die Atmung nach Autogamie in signifikanter Weise ansteigt.Da die Autogamie für das überleben der Kulturen eine grosse Wichtigkeit besitzt, ergeben sich Parallelen zwischen den Stoffwechselveränderungen beiParamecium und der Alterung der somatischen Zellen von Metazoen.     

求取剩余油饱和度的一种实用方法

分析了水驱油田地质、测井及开发动态特征，提出了用生产井含水率资料结合测井资料求取产层平均剩余油饱和度的方法。阐述了该方法的基本模型和计算过程，并以实例计算说明了这种方法的实际应用效果。结果表明，该方法操作简便、实用性强、计算结果可靠，且能准确反映储层的剩余油分布特征。这种方法也避免了水淹层混合液电阻率、岩电系数和水淹层电阻率求取值失真的影响。     

渤海湾盆地早第三纪构造样式与油气藏的关系

渤海湾盆地早第三纪构造样式可归结为５种基本类型和３个演化序列。研究结果表明,构造样式及其演化控制着烃源岩的发育,决定着油气藏的类型和展布,制约着含油气系统的范围。综合考虑含油气系统的各个要素,在渤海湾盆地可划分出６个大的含油气系统,分别位于各个坳陷中,并受坳陷的限制。进一步考虑坳陷内凸起构造单元的分割作用,可划分出１３个小的含油气系统。     

临清坳陷莘县凹陷油气勘探远景评价

对莘县凹陷的构造、沉积、盆地模拟及油气勘探远景等进行了深入研究。结果表明,该凹陷具有浅、中、深３个勘探层次,浅层馆陶组和沙一段以储集次生油及低成熟油气为主;中层沙二段、沙三段以自生自储型油藏为主;深层孔二段以储集高成熟油气、石炭－二迭系以煤成气为主。此地区有着极广阔的勘探远景。