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31.
Helena C. Kraemer Byron Alexander Cathy Clark Curt Busse David Riss 《Primates; journal of primatology》1977,18(4):825-833
A method is suggested to evaluate on an empirical basis sampling plans for the longitudinal study of primate behavior in those
very common situations in which the mathematical structure of behavior is unknown. The method is based on a randomization
procedure applied to a pilot sample of the behavior organized so that cost of implementation of a sampling plan can be evaluated
vis á vis the sampling error intrinsic to the plan. 相似文献
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Unprecedented 34S‐enrichment of pyrite formed following microbial sulfate reduction in fractured crystalline rocks 下载免费PDF全文
Henrik Drake Martin J. Whitehouse Christine Heim Peter W. Reiners Mikael Tillberg K. Johan Hogmalm Mark Dopson Curt Broman Mats E. Åström 《Geobiology》2018,16(5):556-574
In the deep biosphere, microbial sulfate reduction (MSR) is exploited for energy. Here, we show that, in fractured continental crystalline bedrock in three areas in Sweden, this process produced sulfide that reacted with iron to form pyrite extremely enriched in 34S relative to 32S. As documented by secondary ion mass spectrometry (SIMS) microanalyses, the δ34Spyrite values are up to +132‰V‐CDT and with a total range of 186‰. The lightest δ34Spyrite values (?54‰) suggest very large fractionation during MSR from an initial sulfate with δ34S values (δ34Ssulfate,0) of +14 to +28‰. Fractionation of this magnitude requires a slow MSR rate, a feature we attribute to nutrient and electron donor shortage as well as initial sulfate abundance. The superheavy δ34Spyrite values were produced by Rayleigh fractionation effects in a diminishing sulfate pool. Large volumes of pyrite with superheavy values (+120 ± 15‰) within single fracture intercepts in the boreholes, associated heavy average values up to +75‰ and heavy minimum δ34Spyrite values, suggest isolation of significant amounts of isotopically light sulfide in other parts of the fracture system. Large fracture‐specific δ34Spyrite variability and overall average δ34Spyrite values (+11 to +16‰) lower than the anticipated δ34Ssulfate,0 support this hypothesis. The superheavy pyrite found locally in the borehole intercepts thus represents a late stage in a much larger fracture system undergoing Rayleigh fractionation. Microscale Rb–Sr dating and U/Th–He dating of cogenetic minerals reveal that most pyrite formed in the early Paleozoic era, but crystal overgrowths may be significantly younger. The δ13C values in cogenetic calcite suggest that the superheavy δ34Spyrite values are related to organotrophic MSR, in contrast to findings from marine sediments where superheavy pyrite has been proposed to be linked to anaerobic oxidation of methane. The findings provide new insights into MSR‐related S‐isotope systematics, particularly regarding formation of large fractions of 34S‐rich pyrite. 相似文献
35.
Chromatin plays a fundamental role in eukaryotic genomic regulation, and the increasing awareness of the importance of epigenetic processes in human health and disease emphasizes the need for understanding the structure and function of the nucleosome. Recent advances in chromatin structural studies, including the first structures of nucleosomes containing the Widom 601 sequence and the structure of a chromatin protein-nucleosome assembly, have provided new insight into stretching of nucleosomal DNA, nucleosome positioning, binding of metal ions, drugs and therapeutic candidates to nucleosomes, and nucleosome recognition by nuclear proteins. These discoveries ensure promising future prospects for unravelling structural attributes of chromatin. 相似文献
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Rudolph DA Dvorak CA Dvorak L Nepomuceno D Bonaventure P Lovenberg TW Carruthers NI 《Bioorganic & medicinal chemistry letters》2011,21(1):42-44
The synthesis and SAR for a novel series of tetrahydropyrido[3,2-c]pyrroles is described. Optimization of the pendant aryl ring lead to high binding affinity at the 5-HT7 receptor when small lipophilic groups were placed in the para position. Modification of the N-benzyl group and secondary amine were not well tolerated. A representative set of compounds was shown to be functional antagonists of the 5-HT7 receptor. 相似文献
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Aurore Gelin Modesto Redrejo-Rodríguez Jacques Laval Olga S. Fedorova Murat Saparbaev Alexander A. Ishchenko 《PloS one》2010,5(8)
Background
Human apurinic/apyrimidinic endonuclease 1 (APE1) is a key DNA repair enzyme involved in both base excision repair (BER) and nucleotide incision repair (NIR) pathways. In the BER pathway, APE1 cleaves DNA at AP sites and 3′-blocking moieties generated by DNA glycosylases. In the NIR pathway, APE1 incises DNA 5′ to a number of oxidatively damaged bases. At present, physiological relevance of the NIR pathway is fairly well established in E. coli, but has yet to be elucidated in human cells.Methodology/Principal Finding
We identified amino acid residues in the APE1 protein that affect its function in either the BER or NIR pathway. Biochemical characterization of APE1 carrying single K98A, R185A, D308A and double K98A/R185A amino acid substitutions revealed that all mutants exhibited greatly reduced NIR and 3′→5′ exonuclease activities, but were capable of performing BER functions to some extent. Expression of the APE1 mutants deficient in the NIR and exonuclease activities reduced the sensitivity of AP endonuclease-deficient E. coli xth nfo strain to an alkylating agent, methylmethanesulfonate, suggesting that our APE1 mutants are able to repair AP sites. Finally, the human NIR pathway was fully reconstituted in vitro using the purified APE1, human flap endonuclease 1, DNA polymerase β and DNA ligase I proteins, thus establishing the minimal set of proteins required for a functional NIR pathway in human cells.Conclusion/Significance
Taken together, these data further substantiate the role of NIR as a distinct and separable function of APE1 that is essential for processing of potentially lethal oxidative DNA lesions. 相似文献40.