Abstract:
:Crystals of magnetite (Fe(3)O(4)) and periclase (MgO) in Fe-Mg-Ca carbonate in the Martian meteorite Allan Hills 84001 were studied by using transmission electron microscopy to understand their origin and evaluate claims that the magnetites were made by Martian microorganisms. In magnesian carbonate, periclase occurs as aggregates of crystals (grain size approximately equal to 3 nm) that are preferentially oriented with respect to the carbonate lattice. Larger periclase crystals approximately equal to 50 nm in size are commonly associated with voids of similar size. Periclase clearly formed by precipitation from carbonate as a result of partial decomposition and loss of CO(2). Magnetite occurs in more ferroan carbonate, and, like periclase, it is associated with voids and microfractures and the two oxides may be intermixed. Magnetite nanocrystals that are commonly euhedral and entirely embedded in carbonate are topotactically oriented with respect to the carbonate lattice, showing that they formed as solid-state precipitates. Magnetites in Fe-rich carbonate rims are not well oriented. These magnetites are generally more irregular in shape and diverse in size than the euhedral variety. All occurrences of magnetite and periclase are entirely consistent with in situ growth by solid-state diffusion as a result of carbonate decomposition during impact heating. Biogenic sources should not be invoked for any magnetites.
journal_name
Proc Natl Acad Sci U S Aauthors
Barber DJ,Scott ERdoi
10.1073/pnas.102045799keywords:
subject
Has Abstractpub_date
2002-05-14 00:00:00pages
6556-61issue
10eissn
0027-8424issn
1091-6490pii
99/10/6556journal_volume
99pub_type
杂志文章abstract::We report the use of engineered ribozymes to shuffle exon cassettes in vitro. Specifically, we have designed derivatives of a group II intron that insert into selected sites in the human tissue plasminogen activator (t-PA) mRNA. The insertion reaction links t-PA sequences to the group II intron sequences so that trans...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.93.15.7486
更新日期:1996-07-23 00:00:00
abstract::A mutation in RPB5 (rpb5-9), an essential RNA polymerase subunit assembled into RNA polymerases I, II, and III, revealed a role for this subunit in transcriptional activation. Activation by GAL4-VP16 was impaired upon in vitro transcription with mutant whole-cell extracts. In vivo experiments using inducible reporter ...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.95.26.15281
更新日期:1998-12-22 00:00:00
abstract::Oil spills can lead to irreversible environmental degradation and are a potential hazard to human health. We study how onshore oil spills affect neonatal and infant mortality by combining spatial data from the Nigerian Oil Spill Monitor with Demographic and Health Surveys. To identify a causal effect, we compare sibli...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1818303116
更新日期:2019-03-19 00:00:00
abstract::Several overlapping chromosomal deletions spanning the albino locus in the mouse cause perinatal lethality when homozygous and a block in the transcriptional induction of various unlinked hepatocyte-specific genes. Studies of such lethal albino deletion homozygotes in perinatal stages revealed a deficiency in the tran...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.89.14.6540
更新日期:1992-07-15 00:00:00
abstract::Three lines of evidence indicate that RNA-dependent RNA synthesis occurs in mouse erythroleukemia cells. The first involves labeling studies with [3H]uridine and shows a greater initial labeling rate of globin RNA in the cytoplasm than in the nucleus. Labeled globin RNA found in the cytoplasm after a very short pulse ...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.83.5.1208
更新日期:1986-03-01 00:00:00
abstract::Rapid North Atlantic cooling events during the last deglaciation caused atmospheric reorganizations on global and regional scales. Their impact on Asian climate has been investigated for monsoonal domains, but remains largely unknown in westerly wind-dominated semiarid regions. Here we generate a dust record from sout...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.2004071117
更新日期:2020-08-04 00:00:00
abstract::Heterogeneity of heart failure (HF) phenotypes indicates contributions from underlying common polymorphisms. We considered polymorphisms in the beta(1)-adrenergic receptor (beta(1)AR), a beta-blocker target, as candidate pharmacogenomic loci. Transfected cells, genotyped human nonfailing and failing ventricles, and a ...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.0509937103
更新日期:2006-07-25 00:00:00
abstract::We recently reported the hemochromatosis-like phenotype observed in our Usf2 knockout mice. In these mice, as in murine models of hemochromatosis and patients with hereditary hemochromatosis, iron accumulates in parenchymal cells (in particular, liver and pancreas), whereas the reticuloendothelial system is spared fro...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.072632499
更新日期:2002-04-02 00:00:00
abstract::We have developed a modified rhodamine (Rho) staining procedure to study uptake and efflux in murine hematopoietic stem cells. Distinct populations of Rho++ (bright), Rho+ (dull), and Rho- (negative) cells could be discriminated. Sorted Rho- cells were subjected to a second Rho staining procedure with the P-glycoprote...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.92.19.8901
更新日期:1995-09-12 00:00:00
abstract::Tumor necrosis factor alpha (TNF-alpha) stimulated the phosphorylation of a 28-kDa protein (p28) in the ME-180 line of human cervical carcinoma cells. The effect of TNF-alpha on the phosphorylation state of p28 was rapid (4-fold increase within 15 min) and persistent, remaining above the basal level for at least 2 hr....
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.86.21.8417
更新日期:1989-11-01 00:00:00
abstract::DsRed, a brilliantly red fluorescent protein, was recently cloned from Discosoma coral by homology to the green fluorescent protein (GFP) from the jellyfish Aequorea. A core question in the biochemistry of DsRed is the mechanism by which the GFP-like 475-nm excitation and 500-nm emission maxima of immature DsRed are r...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.97.22.11990
更新日期:2000-10-24 00:00:00
abstract::The major protein extracted from anyloid deposits induced in mice by injection of either Candida albicans cells or sodium caseinate was found to have chromatographic and electrophoretic properties and an amino-acid compostiion characteristic of the AA class of amyloid proteins. The homology of the mouse protein with p...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.73.3.964
更新日期:1976-03-01 00:00:00
abstract::Language is classically thought to be supported by perisylvian cortical regions. Here we provide intracranial evidence linking the hippocampal complex to linguistic processing. We used direct recordings from the hippocampal structures to investigate whether theta oscillations, pivotal in memory function, track the amo...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1603312113
更新日期:2016-10-04 00:00:00
abstract::We have investigated the frequency of p53 mutations in B- and T-cell human lymphoid malignancies, including acute lymphoblastic leukemia, the major subtypes of non-Hodgkin lymphoma, and chronic lymphocytic leukemia. p53 exons 5-9 were studied by using genomic DNA from 197 primary tumors and 27 cell lines by single-str...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.88.12.5413
更新日期:1991-06-15 00:00:00
abstract::Chemical cross-linking mass spectrometry (CXMS) is being increasingly used to study protein assemblies and complex protein interaction networks. Existing CXMS chemical cross-linkers target only Lys, Cys, Glu, and Asp residues, limiting the information measurable. Here we report a "plant-and-cast" cross-linking strateg...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1813574115
更新日期:2018-10-30 00:00:00
abstract::Replication and transcription of viral RNA genomes rely on host-donated proteins. Qbeta virus infects Escherichia coli and replicates and transcribes its own genomic RNA by Qbeta replicase. Qbeta replicase requires the virus-encoded RNA-dependent RNA polymerase (beta-subunit), and the host-donated translational elonga...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1006559107
更新日期:2010-09-07 00:00:00
abstract::J-domain chaperones are involved in the efficient handover of misfolded/partially folded proteins to Hsp70 but also function independently to protect against cell death. Due to their high flexibility, the mechanism by which they regulate the Hsp70 cycle and how specific substrate recognition is performed remains unkno...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1914999116
更新日期:2019-10-22 00:00:00
abstract::The cat tongue is covered in sharp, rear-facing spines called papillae, the precise function of which is a mystery. In this combined experimental and theoretical study, we use high-speed film, grooming force measurements, and computed tomography (CT) scanning to elucidate the mechanism by which papillae are used to gr...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1809544115
更新日期:2018-12-04 00:00:00
abstract::Vascular endothelial growth factor C (VEGF-C) recently has been described to be a relatively specific growth factor for the lymphatic vascular system. Here we report that ectopic application of recombinant VEGF-C also has potent angiogenic effects in vivo. VEGF-C is sufficiently potent to stimulate neovascularization ...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.95.24.14389
更新日期:1998-11-24 00:00:00
abstract::Ras has achieved notoriety as an oncogene aberrantly activated in multiple human tumors. Approximately 30% of all human tumors express an oncogenic form of this GTPase that is locked in an active conformation as a result of being insensitive to Ras GTPase-activating proteins (GAPs), proteins that normally regulate the...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.0700153104
更新日期:2007-07-24 00:00:00
abstract::Regulatory mechanisms for tissue repair and regeneration within damaged tissue have been extensively studied. However, the systemic regulation of tissue repair remains poorly understood. To elucidate tissue nonautonomous control of repair process, it is essential to induce local damage, independent of genetic manipula...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1523681113
更新日期:2016-02-16 00:00:00
abstract::We have found the two-dimensional electrophoretic technique of O'Farrell to be highly efficient in the detection of charge-change substitutions in a large number of proteins. We have applied this method to determine the level of heterozygosity of the most abundant proteins in Drosophila melanogaster adults from a natu...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.76.5.2381
更新日期:1979-05-01 00:00:00
abstract::The free energy difference between complexes of the restriction nuclease EcoRI with nonspecific DNA and with the enzyme's recognition sequence is linearly dependent on the water chemical potential of the solution, set using several very different solutes, ranging from glycine and glycerol to triethylene glycol and suc...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.93.22.12272
更新日期:1996-10-29 00:00:00
abstract::A paradigm of evolutionary biology is that adaptation and reproductive isolation are caused by a nearly infinite number of mutations of individually small effect. Here, we test this hypothesis by investigating the genetic basis of pollinator discrimination in two closely related species of monkeyflowers that differ in...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.96.21.11910
更新日期:1999-10-12 00:00:00
abstract::Femtosecond and subfemtosecond time scales typically rule electron dynamics at metal surfaces. Recent advance in experimental techniques permits now remarkable precision in the description of these processes. In particular, shorter time scales, smaller system sizes, and spin-dependent effects are current targets of in...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1008517107
更新日期:2011-01-18 00:00:00
abstract::A robust body of evidence supports the concept that phosphodiesterase 10A (PDE10A) activity in the basal ganglia orchestrates the control of coordinated movement in human subjects. Although human mutations in the PDE10A gene manifest in hyperkinetic movement disorders that phenocopy many features of early Huntington's...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1916398117
更新日期:2020-01-07 00:00:00
abstract::Normal rat mast cells were stimulated by antibodies against IgE receptors (anti-RBL) or by anti-IgE, and [3H]methyl group incorporation into phospholipids, 45Ca uptake, and histamine release were examined. Anti-RBL or its F(ab')2 fragments and anti-IgE induced an increase in the incorporation of [3H]methyl into phosph...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.77.4.1903
更新日期:1980-04-01 00:00:00
abstract::Biochemically, the syntrophic bacteria constitute the missing link in our understanding of anaerobic flow of carbon in the biosphere. The completed genome sequence of Syntrophus aciditrophicus SB, a model fatty acid- and aromatic acid-degrading syntrophic bacterium, provides a glimpse of the composition and architectu...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.0610456104
更新日期:2007-05-01 00:00:00
abstract::Cells have evolved complex regulatory networks that reorganize gene expression patterns in response to changing environmental conditions. These changes often involve redundant mechanisms that affect various levels of gene expression. Here, we examine the consequences of enhanced mRNA degradation in the galactose utili...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1111408109
更新日期:2011-12-27 00:00:00
abstract::The origin of highly magnetized white dwarfs has remained a mystery since their initial discovery. Recent observations indicate that the formation of high-field magnetic white dwarfs is intimately related to strong binary interactions during post-main-sequence phases of stellar evolution. If a low-mass companion, such...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1015005108
更新日期:2011-02-22 00:00:00