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121.
Primary structure, gene organization and polypeptide expression of poliovirus RNA   总被引:217,自引:0,他引:217  
The primary structure of the poliovirus genome has been determined. The RNA molecule is 7,433 nucleotides long, polyadenylated at the 3' terminus, and covalently linked to a small protein (VPg) at the 5' terminus. An open reading frame of 2,207 consecutive triplets spans over 89% of the nucleotide sequence and codes for the viral polyprotein NCVPOO. Twelve viral polypeptides have been mapped by amino acid sequence analysis and were found to be proteolytic cleavage products of the polyprotein, cleavages occurring predominantly at Gln-Gly pairs.  相似文献   
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Zusammenfassung Die Verteilung von aus 5-Hydroxy-Tryptophan entstandenem Serotonin in der Zirbeldrüse von Affen wird beschrieben.  相似文献   
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Zusammenfassung Vier verschiedene Methoden zur Gewinnung von Lochfolien für elektronenmikroskopische Belange werden beschrieben. Damit lassen sich unter anderem leicht Anzahl der Löcher pro Flächeneinheit und Lochdurchmesser variieren, so dass eine weitgehende Anpassung der Filmqualität an die sonstigen Versuchsbedingungen ermöglicht wird.  相似文献   
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Moy CM  Seltzer GO  Rodbell DT  Anderson DM 《Nature》2002,420(6912):162-165
The variability of El Ni?o/Southern Oscillation (ENSO) during the Holocene epoch, in particular on millennial timescales, is poorly understood. Palaeoclimate studies have documented ENSO variability for selected intervals in the Holocene, but most records are either too short or insufficiently resolved to investigate variability on millennial scales. Here we present a record of sedimentation in Laguna Pallcacocha, southern Ecuador, which is strongly influenced by ENSO variability, and covers the past 12,000 years continuously. We find that changes on a timescale of 2-8 years, which we attribute to warm ENSO events, become more frequent over the Holocene until about 1,200 years ago, and then decline towards the present. Periods of relatively high and low ENSO activity, alternating at a timescale of about 2,000 years, are superimposed on this long-term trend. We attribute the long-term trend to orbitally induced changes in insolation, and suggest internal ENSO dynamics as a possible cause of the millennial variability. However, the millennial oscillation will need to be confirmed in other ENSO proxy records.  相似文献   
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Anderson MJ  Dixson AF 《Nature》2002,416(6880):496
In animals with multiple-partner mating systems, the gametes of two or more males must compete to fertilize a given set of ova. Here we show that the volume of the midpiece in individual sperm is significantly greater in primate species in which the females mate with multiple partners, and in which males have larger testes in relation to their body weight, than in those species that mate with only one partner and have relatively small testes. Our results indicate that sexual selection by sperm competition has influenced the evolution of a specific component of male-gamete morphology, the volume of the sperm midpiece.  相似文献   
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Smith DE  Tans SJ  Smith SB  Grimes S  Anderson DL  Bustamante C 《Nature》2001,413(6857):748-752
As part of the viral infection cycle, viruses must package their newly replicated genomes for delivery to other host cells. Bacteriophage straight phi29 packages its 6.6-microm long, double-stranded DNA into a 42 x 54 nm capsid by means of a portal complex that hydrolyses ATP. This process is remarkable because entropic, electrostatic and bending energies of the DNA must be overcome to package the DNA to near-crystalline density. Here we use optical tweezers to pull on single DNA molecules as they are packaged, thus demonstrating that the portal complex is a force-generating motor. This motor can work against loads of up to 57 pN on average, making it one of the strongest molecular motors reported to date. Movements of over 5 microm are observed, indicating high processivity. Pauses and slips also occur, particularly at higher forces. We establish the force-velocity relationship of the motor and find that the rate-limiting step of the motor's cycle is force dependent even at low loads. Notably, the packaging rate decreases as the prohead is filled, indicating that an internal force builds up to approximately 50 pN owing to DNA confinement. Our data suggest that this force may be available for initiating the ejection of the DNA from the capsid during infection.  相似文献   
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