Abstract:
:The reliability of (13)C NMR chemical shift correlations in the application of the "tool of increasing electron demand" to stable long-lived carbocationic systems is demonstrated by a comprehensive analysis of 22 stable aryl-substituted carbocationic systems. The observation of slopes of less than unity in such chemical shift correlations for several cationic systems has been attributed to additional charge delocalizing mechanisms present in the system (such as homoallylic, cyclopropyl, and pi conjugations). The onset of nonclassical sigma-delocalization in 2-aryl-2-norbornyl cations with electron withdrawing-substituents previously observed was further verified by using sigma(C+) substituent constants. Difficulties in relating the C(alpha)NMR shifts in different carbocationic systems are also discussed.
journal_name
Proc Natl Acad Sci U S Aauthors
Olah GA,Berrier AL,Prakash GKdoi
10.1073/pnas.78.4.1998subject
Has Abstractpub_date
1981-04-01 00:00:00pages
1998-2002issue
4eissn
0027-8424issn
1091-6490journal_volume
78pub_type
杂志文章abstract::Heme oxygenase (HO) catalyzes the opening of the heme ring with the release of iron in both plants and animals. In cyanobacteria, red algae, and cryptophyceae, HO is a key enzyme in the synthesis of the chromophoric part of the photosynthetic antennae. In an attempt to study the regulation of this key metabolic step, ...
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.94.21.11736
更新日期:1997-10-14 00:00:00
abstract::The "protein only" hypothesis states that the infectious agent causing transmissible spongiform encephalopathies is a conformational isomer of PrP, a host protein predominantly expressed in brain, and is strongly supported by many lines of evidence. Prion diseases are so far unique among conformational diseases in 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.172403799
更新日期:2002-12-10 00:00:00
abstract::Dimers of bacteriochlorophyll a (Bchla) with optical absorption maximum at 853 nm and a nonconservative circular dichroism spectrum are formed in a solution of formamide/water that contains micelles of Triton X-100. The apparent equilibrium constant and the corresponding Gibbs energy change for the Bchl self-organizat...
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.86.5.1505
更新日期:1989-03-01 00:00:00
abstract::Zinc is an essential micronutrient for all living organisms. When facing a shortage in zinc supply, plants adapt by enhancing the zinc uptake capacity. The molecular regulators controlling this adaptation are not known. We present the identification of two closely related members of the Arabidopsis thaliana basic-regi...
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.1004788107
更新日期:2010-06-01 00:00:00
abstract::TIM-4, a member of the TIM family expressed on antigen-presenting cells, binds to phosphatidylserine exposed on the surface of apoptotic bodies. However, the significance of this interaction in vivo remains unknown because other receptors have been implicated in the clearance of apoptotic bodies and could compensate f...
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.0910359107
更新日期:2010-05-11 00:00:00
abstract::Genes that are up- and down-regulated by thyroid hormone in the tail resorption program of Xenopus laevis have been isolated by a gene expression screen, sequenced, and identified in the GenBank data base. The entire program is estimated to consist of fewer than 35 up-regulated and fewer than 10 down-regulated genes; ...
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.93.5.1924
更新日期:1996-03-05 00:00:00
abstract::To study the permanency of response to selection for a quantitative character in finite populations and the nature of the genetic effects that contribute to this response, we have used the covariance between ancestors and descendents within populations. Effects and variances are defined for an initial equilibrium rand...
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.85.5.1563
更新日期:1988-03-01 00:00:00
abstract::The perceptual quality of odors usually is robust to variability in concentration. However, maps of neural activation across the olfactory bulb glomerular layer are not stable in this respect; rather, glomerular odor representations both broaden and intensify as odorant concentrations are increased. The relative level...
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.0608564104
更新日期:2007-02-06 00:00:00
abstract::The x-ray crystal structure of an oligomeric miniprotein has been determined to a 1.2-A resolution by means of multiwavelength anomalous diffraction phasing with selenomethionine analogs that retain the biophysical characteristics of the native peptide. Peptide 1, comprising alpha and beta secondary structure elements...
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.0401245101
更新日期:2004-08-17 00:00:00
abstract::Stimulation of cells with various peptide growth factors induces the production of phosphatidylinositol 3,4,5-trisphosphate (PIP3) through activation of phosphatidylinositol 3-kinase. The action of this enzyme is reversed by that of the tumor suppressor PTEN. With the use of cells overexpressing NADPH oxidase 1 or per...
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.0407396101
更新日期:2004-11-23 00:00:00
abstract::Chloroplast DNA (cpDNA) is under great photooxidative stress, yet its evolution is very conservative compared with nuclear or mitochondrial genomes. It can be expected that DNA repair mechanisms play important roles in cpDNA survival and evolution, but they are poorly understood. To gain insight into how the most seve...
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.1004326107
更新日期:2010-08-03 00:00:00
abstract::Treatment of cultured human tumor cells with the chloroethylnitrosourea antitumor drug 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) selectively induces transcription and protein synthesis of a subset of the human heat shock or stress-induced genes (HSP90 and HSP70) with little effect on other stress genes or on express...
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.88.11.4825
更新日期:1991-06-01 00:00:00
abstract::The three-dimensional structure of the N-acyl-l-homoserine lactone hydrolase (AHL lactonase) from Bacillus thuringiensis has been determined, by using single-wavelength anomalous dispersion (SAD) phasing, to 1.6-angstroms resolution. AHLs are produced by many Gram-negative bacteria as signaling molecules used in quoru...
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.0505255102
更新日期:2005-08-16 00:00:00
abstract::Protein-binding DNA sequence elements encode a variety of regulated functions of genomes. Information about such elements is currently in a state of rapid growth, but improved methods are required to characterize the sequence specificity of DNA-binding proteins. We have established an in vitro method for specific 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.0611229104
更新日期:2007-02-27 00:00:00
abstract::Estradiol-17beta administration to young (10- to 12-week-old) rabbits to produce the "estrogen-dominated" uterus increased the uterine contractile response to both oxytocin and methacholine in vitro. In "progesterone-dominated" uteri, obtained from rabbits that received progesterone for 4 days after estrogen pretreatm...
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.75.4.2044
更新日期:1978-04-01 00:00:00
abstract::Members of the tumor necrosis factor receptor (TNFR) superfamily are important for cell growth and survival. In addition to providing costimulatory signals for cell proliferation, ligation of both TNFR1 and Fas can result in programmed cell death or apoptosis. The underlying mechanism requires an intact 80-aa stretch ...
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.94.12.6346
更新日期:1997-06-10 00:00:00
abstract::The necroptosis cell death pathway has been implicated in host defense and in the pathology of inflammatory diseases. While phosphorylation of the necroptotic effector pseudokinase Mixed Lineage Kinase Domain-Like (MLKL) by the upstream protein kinase RIPK3 is a hallmark of pathway activation, the precise checkpoints ...
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.1919960117
更新日期:2020-04-14 00:00:00
abstract::Blood viscosity decreases with shear stress, a property essential for an efficient perfusion of the vascular tree. Shear thinning is intimately related to the dynamics and mutual interactions of RBCs, the major component of blood. Because of the lack of knowledge about the behavior of RBCs under physiological conditio...
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.1608074113
更新日期:2016-11-22 00:00:00
abstract::Measles virus (MeV) is the poster child for acute infection followed by lifelong immunity. However, recent work shows the presence of MeV RNA in multiple sites for up to 3 mo after infection in a proportion of infected children. Here, we use experimental infection of rhesus macaques to show that prolonged RNA presence...
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.1211138109
更新日期:2012-09-11 00:00:00
abstract::The binding of bovine TSH (thyroid stimulating hormone), LH (luteinizing hormone), and their subunits to the TSH receptor of beef thyroid membranes was compared to stimulation by these agents of adenylate cyclase [ATP pyrophosphate-lyase(cyelizing), EC 4.6.1.1] in the same membranes, glucose oxidation in dog thyroid 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.71.9.3460
更新日期:1974-09-01 00:00:00
abstract::To repurpose compounds for diffuse large B cell lymphoma (DLBCL), we screened a library of drugs and other targeted compounds approved by the US Food and Drug Administration on 9 cell lines and validated the results on a panel of 32 genetically characterized DLBCL cell lines. Dasatinib, a multikinase inhibitor, was ef...
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.1905239116
更新日期:2019-08-20 00:00:00
abstract::The structural analysis of the Fab' fragment of human myeloma immunoglobulin IgGl(lambda) New has been extended to a nominal resolution of 2.0 A. Each of the structural subunits corresponding to the variable and to the constant homology regions of the light and heavy chains contains two irregular beta-sheets which are...
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.71.9.3440
更新日期:1974-09-01 00:00:00
abstract::We established a pancreatic adenocarcinoma cell line (CFPAC-1) from a patient with cystic fibrosis (CF) and assessed some of its properties. The cells show epithelial morphology and express cytokeratin and oncofetal antigens characteristic of pancreatic duct cells. Basal and stimulated levels of cAMP and cAMP-dependen...
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.87.10.4012
更新日期:1990-05-01 00:00:00
abstract::As a first step in assessing the efficacy of a gene transfer approach to the induction of transplantation tolerance in our miniature swine model, double-copy retroviral vectors engineered to express a drug-resistance marker (neomycin) and a swine class II DRB cDNA were constructed. Infectious particles containing thes...
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.88.21.9760
更新日期:1991-11-01 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::The major Hsp70 of the mitochondrial matrix (Ssc1 in yeast) is critically important for the translocation of proteins from the cytosol, across the mitochondrial inner membrane, and into the matrix. Tim44, a peripheral inner membrane protein with limited sequence similarity to the J domain of J-type cochaperones, tethe...
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.1936150100
更新日期:2003-11-25 00:00:00
abstract::The brain disturbances that place a person at risk for developing depression are unknown. We imaged the brains of 131 individuals, ages 6 to 54 years, who were biological descendants (children or grandchildren) of individuals identified as having either moderate to severe, recurrent, and functionally debilitating depr...
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.0805311106
更新日期:2009-04-14 00:00:00
abstract::This paper describes a variety of statistical methods for obtaining precise quantitative estimates of the similarities and differences in the structures of semantic domains in different languages. The methods include comparing mean correlations within and between groups, principal components analysis of interspeaker c...
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.97.1.518
更新日期:2000-01-04 00:00:00
abstract::Addition of a 0.5 M KCl wash fraction from rabbit reticulocyte ribosomes causes a 3- to 10-fold increase in the extent of translation of natural mRNAs by Krebs-cell lysates. In the presence of the wash fraction, 1 pmol of rabbit or mouse 10S RNA directs the incorporation of 80 pmol of leucine into rabbit globin. The 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.69.5.1299
更新日期:1972-05-01 00:00:00
abstract::Listeriolysin O (LLO) is a cholesterol-dependent cytolysin that is an essential virulence factor of Listeria monocytogenes. LLO pore-forming activity is pH-dependent; it is active at acidic pH (<6), but not at neutral pH. In contrast to other pH-dependent toxins, we have determined that LLO pore-forming activity is co...
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.0500558102
更新日期:2005-08-30 00:00:00