Abstract:
:A calix[4]arene was designed to reversibly dimerize and form an egg-shaped enclosure. Adhesive interactions in the assembly were provided by four self-associating ureas, which form a cyclic array containing 16 hydrogen bonds. The synthesis was completed in four steps from the previously described O,O',O",O"'-tetrabenzylcalix[4]arene. Evidence for dimerization of the calixarene tetraurea was provided by H NMR, mass spectrometry, and the observation of encapsulated molecules. The resulting cavity was of sufficient size to capture guests such as ethyl benzene and p-xylene.
journal_name
Proc Natl Acad Sci U S Aauthors
Shimizu KD,Rebek J Jrdoi
10.1073/pnas.92.26.12403subject
Has Abstractpub_date
1995-12-19 00:00:00pages
12403-7issue
26eissn
0027-8424issn
1091-6490journal_volume
92pub_type
杂志文章abstract::Recent laboratory studies have demonstrated that isoprene oxidation products can partition to atmospheric aerosols by reacting with condensed phase sulfuric acid, forming low-volatility organosulfate compounds. We have identified organosulfate compounds in free tropospheric aerosols by single particle mass spectrometr...
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.1012561107
更新日期:2010-12-14 00:00:00
abstract::The 24 nucleotides comprising the carbohydrate-recognition domain of Maackia amurensis hemagglutinin (MAH) cDNA were randomly mutated. The mutant lectins were expressed as glutathione-S-transferase fusion proteins in Escherichia coli and 16 clones were randomly chosen. Although all of 16 recombinant lectins reacted st...
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.041621998
更新日期:2001-02-27 00:00:00
abstract::After treatment with nitrite, Japanese soy sauce was strongly mutagenic to Salmonella typhimurium TA100 without S9 mixture. Two precursors of the mutagen were isolated from Japanese soy sauce, and these were identified as (-)-(1S,3S)-1-methyl-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid [(-)-(1S,3S)-MTCA] and i...
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.80.10.2912
更新日期:1983-05-01 00:00:00
abstract::Mutations affecting mismatch repair result in elevated frequencies of microsatellite length alteration in prokaryotes and eukaryotes. However, the finding that microsatellite instability is found often in cells with a functional mismatch repair system prompted a search for other factors of tract alteration. In the pre...
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.95.17.10003
更新日期:1998-08-18 00:00:00
abstract::We assess the significance of high-frequency variability of environmental parameters (sunlight, precipitation, temperature) for the structure and function of terrestrial ecosystems under current and future climate. We examine the influence of hourly, daily, and monthly variance using the Ecosystem Demography model ver...
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.0912032107
更新日期:2010-05-04 00:00:00
abstract::Human P-glycoprotein (Pgp) confers multidrug resistance to cancer cells by ATP-dependent extrusion of a great many structurally dissimilar hydrophobic compounds. The manner in which Pgp recognizes these different substrates is unknown. The protein shows internal homology between its N- and C-terminal halves, each comp...
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.94.20.10594
更新日期:1997-09-30 00:00:00
abstract::Mounting effective T cell responses is critical for eliciting long-lasting immunity following viral infection and vaccination. A multitude of inhibitory and stimulatory factors are induced following infection, and it is the compilation of these signals that quantitatively and qualitatively program the ensuing effector...
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.0914500107
更新日期:2010-02-16 00:00:00
abstract::Nonhomologous integration vectors have been used to demonstrate the feasibility of insertional mutagenesis in haploid tachyzoites of the protozoan parasite Toxoplasma gondii. Mutant clones resistant to 5-fluorouracil were identified at a frequency of approximately 10(-6) (approximately 2 x 10(-5) of the stable transfo...
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.92.12.5749
更新日期:1995-06-06 00:00:00
abstract::Ski8p is implicated in degradation of non-poly(A) and double-stranded RNA, and in meiotic DNA recombination. We have identified the Sordaria macrospora SKI8 gene. Ski8p is cytoplasmically localized in all vegetative and sexual cycle cells, and is nuclear localized, specifically in early-mid-meiotic prophase, in tempor...
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.2034282100
更新日期:2003-10-28 00:00:00
abstract::In the penis, nitric oxide (NO) can be formed by both neuronal NO synthase and endothelial NOS (eNOS). eNOS is activated by viscous drag/shear stress in blood vessels to produce NO continuously, a process mediated by the phosphatidylinositol 3-kinase (PI3kinase)/Akt pathway. Here we show that PI3-kinase/Akt physiologi...
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.052712499
更新日期:2002-03-19 00:00:00
abstract::The activation of plant defensive genes in leaves of tomato plants in response to herbivore damage or mechanical wounding is mediated by a mobile 18-amino acid polypeptide signal called systemin. Systemin is derived from a larger, 200-amino acid precursor called prosystemin, similar to polypeptide hormones and soluble...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章,评审
doi:10.1073/pnas.93.22.12053
更新日期:1996-10-29 00:00:00
abstract::The cellular response to ionizing radiation (IR) includes induction of the c-jun and EGR1 early response genes. The present work has examined potential cytoplasmic signaling cascades that transduce IR-induced signals to the nucleus. The results demonstrate activation of the 40S ribosomal protein S6 kinase, pp90rsk, 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.91.12.5416
更新日期:1994-06-07 00:00:00
abstract::Genetic analysis of Parkinson disease (PD) has identified several genes whose mutation causes inherited parkinsonism, as well as risk loci for sporadic PD. PTEN-induced kinase 1 (PINK1) and parkin, linked to autosomal recessive PD, act in a common genetic pathway regulating the autophagic degradation of mitochondria, ...
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.1321207111
更新日期:2014-06-10 00:00:00
abstract::Humans choose actions based on both habit and planning. Habitual control is computationally frugal but adapts slowly to novel circumstances, whereas planning is computationally expensive but can adapt swiftly. Current research emphasizes the competition between habits and plans for behavioral control, yet many complex...
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.1506367112
更新日期:2015-11-10 00:00:00
abstract::RNA was synthesized in vitro from a T3 DNA template by T3 RNA polymerase and subsequently separated into seven discrete size classes (molecular weights ranging between 0.21 x 10(6) and 6.2 x 10(6)) by electrophoresis in polyacrylamide slab gels. RNase T1-generated 3'-terminal oligonucleotide fragments were then select...
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.76.10.5110
更新日期:1979-10-01 00:00:00
abstract::Circadian timekeeping by intracellular molecular clocks is evident widely in prokaryotes and eukaryotes. The clockworks are driven by autoregulatory feedback loops that lead to oscillating levels of components whose maxima are in fixed phase relationships with one another. These phase relationships are the key metric ...
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.0904837106
更新日期:2009-07-07 00:00:00
abstract::This paper provides transcendental and algebraic framework for the classification of identities expressing pi and other logarithms of algebraic numbers as rapidly convergent generalized hypergeometric series in rational parameters. Algebraic and arithmetic relations between values of p+1Fp hypergeometric functions and...
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.95.6.2744
更新日期:1998-03-17 00:00:00
abstract::Recent studies have implicated local inflammation and activation of complement amongst the processes involved in the pathogenesis of age-related macular degeneration (AMD). Several lines of investigation also indicate that bis-retinoid pigments, such as A2E, that accumulate as lipofuscin in retinal pigment epithelial ...
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.0604255103
更新日期:2006-10-31 00:00:00
abstract::Bacterial mutants have been isolated, called groN, that block phage development by interference with the action of the product of the phage N gene. lambdatrp phages, which depend on the N product for the synthesis of tryptophan enzymes, do not make these enzymes in groN bacteria. Two type of phage mutants have been is...
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.68.12.2977
更新日期:1971-12-01 00:00:00
abstract::Fibronectins isolated from the conditioned medium produced by cultures of undifferentiated (monolayer) and differentiated (nodular) swine vascular smooth muscle cells are similar but not identical. In general, the nodular-cell fibronectin has a smaller molecular mass than monolayer-cell fibronectin and appears to lack...
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.82.9.2746
更新日期:1985-05-01 00:00:00
abstract::Cortical networks that have been found to operate close to a critical point exhibit joint activations of large numbers of neurons. However, in motor cortex of the awake macaque monkey, we observe very different dynamics: massively parallel recordings of 155 single-neuron spiking activities show weak fluctuations on th...
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.1818972116
更新日期:2019-06-25 00:00:00
abstract::Proteins fold through a variety of mechanisms. For a given protein, folding routes largely depend on the protein's stability and its native-state geometry, because the landscape is funneled. These ideas are corroborated for cytochrome c by using a coarse-grained topology-based model with a perfect funnel landscape tha...
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.0505274102
更新日期:2005-08-30 00:00:00
abstract::RNA-directed DNA polymerase (reverse transcriptase) from leukocytes of individual leukemic patients can be grouped by velocity gradient analyses into two distinct classes, a low-molecular-weight (LMW) class of approximately 70,000 and a high-molecular-weight (HMW) class of 130,000 to 140,000. The reverse transcriptase...
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.72.3.1194
更新日期:1975-03-01 00:00:00
abstract::Clinical data showing correlations between low thyroid-stimulating hormone (TSH) levels and high bone turnover markers, low bone mineral density, and an increased risk of osteoporosis-related fractures are buttressed by mouse genetic and pharmacological studies identifying a direct action of TSH on the skeleton. Here ...
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.1308336110
更新日期:2013-06-11 00:00:00
abstract::By selective attachment of a DNA cleavage agent to specific residues in the yeast TATA box binding protein (yTBP), we demonstrate that, in solution, yTBP binds to the TATA boxes of both the adenovirus major late promoter and the yeast CYC1 promoter with only a modest preference in orientation and binds well to several...
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.94.25.13475
更新日期:1997-12-09 00:00:00
abstract::The glycogen content of yeast rises dramatically just before the onset of the stationary phase of growth. Concomitantly, a rapid increase was found in the glucose 6-phosphate-independent (I) activity of glycogen synthetase, as well as in the total amount of enzyme. A mutant (GS 1-36) was obtained, which did not accumu...
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.66.3.967
更新日期:1970-07-01 00:00:00
abstract::A system for studying Z-DNA formation in the Escherichia coli chromosome was developed. Prior investigations in recombinant plasmids showed that alternating (Pur-Pyr) sequences can adopt a left-handed Z-DNA conformation both in vitro and in vivo. We constructed mobile, transposon-based cassettes carrying cloned (Pur-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.91.21.9980
更新日期:1994-10-11 00:00:00
abstract::Aging and disease processes may be due to deleterious and irreversible changes produced by free radical reactions. The enzyme copper-zinc superoxide dismutase (Cu-Zn SOD; superoxide:superoxide oxidoreductase, EC 1.15.1.1) performs a protective function by scavenging superoxide radicals. The Cu-Zn SOD gene (Sod) cloned...
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.87.11.4270
更新日期:1990-06-01 00:00:00
abstract::The large class of adhesion G protein-coupled receptors (aGPCRs) bind extracellular matrix or neighboring cell-surface ligands to regulate organ and tissue development through an unknown activation mechanism. We examined aGPCR activation using two prototypical aGPCRs, GPR56 and GPR110. Active dissociation of the nonco...
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.1421785112
更新日期:2015-05-12 00:00:00
abstract::Organ graft rejection is a T-cell-dependent process. The activation of alloreactive T cells requires stimulation of the T-cell receptor/CD3 complex by foreign major histocompatibility complex (MHC)-encoded gene products. However, accumulating evidence suggests that, in addition to T-cell receptor occupancy, other cost...
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.89.22.11102
更新日期:1992-11-15 00:00:00