Abstract:
:Colloidal and sol-gel procedures have been used to prepare heterogeneous catalysts consisting of platinum metal particles with narrow size distributions and well defined shapes dispersed on high-surface-area silica supports. The overall procedure was developed in three stages. First, tetrahedral and cubic colloidal metal particles were prepared in solution by using a procedure derived from that reported by El-Sayed and coworkers [Ahmadi TS, Wang ZL, Green TC, Henglein A, El-Sayed MA (1996) Science 272:1924-1926]. This method allowed size and shape to be controlled independently. Next, the colloidal particles were dispersed onto high-surface-area solids. Three approaches were attempted: (i) in situ reduction of the colloidal mixture in the presence of the support, (ii) in situ sol-gel synthesis of the support in the presence of the colloidal particles, and (iii) direct impregnation of the particles onto the support. Finally, the resulting catalysts were activated and tested for the promotion of carbon-carbon double-bond cis-trans isomerization reactions in olefins. Our results indicate that the selectivity of the reaction may be controlled by using supported catalysts with appropriate metal particle shapes.
journal_name
Proc Natl Acad Sci U S Aauthors
Lee I,Morales R,Albiter MA,Zaera Fdoi
10.1073/pnas.0805691105subject
Has Abstractpub_date
2008-10-07 00:00:00pages
15241-6issue
40eissn
0027-8424issn
1091-6490pii
0805691105journal_volume
105pub_type
杂志文章abstract::The action of cyclin-dependent kinases (CDKs) is regulated by phosphorylation, cyclin levels, the abundance of CDK inhibitors, and, as recently has been shown for cyclin B/cdc2, their localization. It is unclear how localization regulates the action of cyclin E/Cdk2 and its inhibitors. Here, we show that the closest k...
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.97.14.7796
更新日期:2000-07-05 00:00:00
abstract::Cdc10-dependent transcript 1 (Cdt1) is an essential DNA replication protein whose accumulation at the end of the cell cycle promotes the formation of pre-replicative complexes and replication in the next cell cycle. Geminin is thought to be involved in licensing replication by promoting the accumulation of Cdt1 in mit...
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.1310677110
更新日期:2013-07-23 00:00:00
abstract::R. A. Fisher's 1930 "reproductive value" is defined as the contribution made by a population's initial age elements to its asymptotically dominating exponential growth mode. For the Leslie discrete-time model, it is the characteristic row vector of the Leslie matrix, and for the integral-equation model of Lotka the si...
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.74.11.5189
更新日期:1977-11-01 00:00:00
abstract::During differentiation of 3T3-L1 preadipocytes into adipocytes, transcription of the C/EBP alpha (CCA-AT/enhancer binding protein alpha) gene is activated. The promoter of the C/EBP alpha gene contains a bipartite cis element with binding sites for C/EBP alpha undifferentiated protein (CUP) and an Sp1-like GT box bind...
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.90.15.7312
更新日期:1993-08-01 00:00:00
abstract::Higher plants process two distinct, nuclear gene-encoded glyceraldehyde-3-phosphate dehydrogenase (GAPDH) proteins, a Calvin-cycle enzyme active within chloroplasts and a glycolytic enzyme active within the cytosol. The gene for the chloroplast enzyme was previously suggested to be of endosymbiotic origin. Since 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.90.18.8692
更新日期:1993-09-15 00:00:00
abstract::We demonstrate the application of molecular rotational spectroscopy to measure the conformation isomerization rate of vibrationally excited pent-1-en-4-yne (pentenyne). The rotational spectra of single quantum states of pentenyne are acquired by using a combination of IR-Fourier transform microwave double-resonance sp...
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.0800520105
更新日期:2008-09-02 00:00:00
abstract::Experimental intramolecular vibrational dephasing transients for several large organic molecules are reanalyzed. Fits to the experimental data, as well as full numerical quantum calculations with a factorized potential surface for all active degrees of freedom of fluorene indicate that power law decays, not exponentia...
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.95.11.5965
更新日期:1998-05-26 00:00:00
abstract::Coimmunoprecipitation of members of the phytochrome red/farred photoreceptor family from plant extracts has been used to analyze their heteromeric binding interactions. Phytochrome (phy)B or phyD apoproteins with six myc epitopes fused to their N termini are biologically active when expressed in Arabidopsis. Immunopre...
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.0404286101
更新日期:2004-08-03 00:00:00
abstract::We present a synthesis theorem for a family of locally equivalent measures defined on a ring of sets. This theorem is then used to exhibit a control measure for weakly compact sets of unbounded measures. In addition, the existence of a local control measure for locally strongly bounded vector measures is proved by mea...
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.69.5.1083
更新日期:1972-05-01 00:00:00
abstract::The phosphoinositide 3-kinase (PI3K) pathway is central to the metabolic actions of insulin on liver. Here, we show that mice with a liver-specific deletion of the p85alpha regulatory subunit of PI3K (L-Pik3r1KO) exhibit a paradoxical improvement of hepatic and peripheral insulin sensitivity. Although PI3K enzymatic 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.0604628103
更新日期:2006-08-08 00:00:00
abstract::Immune responses to several soluble antigens were compared between B6.C-H-2bm12 mutant and wild-type B6 mice by using a lymph node T-cell proliferation assay. B6.C-H-2bm12 mice failed to respond to beef insulin whereas other IA gene-controlled responses, such as response to poly(L-Tyr, L-Glu)--poly(DL-Ala, L-Lys) 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.78.10.6406
更新日期:1981-10-01 00:00:00
abstract::Marine viruses constitute a major ecological and evolutionary driving force in the marine ecosystems. However, their dispersal mechanisms remain underexplored. Here we follow the dynamics of Emiliania huxleyi viruses (EhV) that infect the ubiquitous, bloom-forming phytoplankton E. huxleyi and show that EhV are emitted...
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.1423667112
更新日期:2015-05-26 00:00:00
abstract::We and other groups have recently reported the potentiation by ribonucleotide reductase inhibitors such as hydroxyurea of the anti-human immunodeficiency virus type 1 (HIV-1) activity of purine and pyrimidine 2',3'-dideoxynucleosides in both resting and phytohemagglutinin-stimulated peripheral blood mononuclear cells....
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.92.18.8333
更新日期:1995-08-29 00:00:00
abstract::Adult-born granule cells in the dentate gyrus of the rodent hippocampus are important for memory formation and mood regulation, but the cellular mechanism underlying their polarized development, a process critical for their incorporation into functional circuits, remains unknown. We found that deletion of the serine-t...
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.1321454111
更新日期:2014-01-07 00:00:00
abstract::Using short-term cultures of hamster embryo cells, we have examined the effects of the free-radical scavenger superoxide dismutase (superoxide:superoxide oxidoreductase, EC 1.15.1.1) and the enzyme catalase (hydrogen-peroxide:hydrogenperoxide oxidoreductase, EC 1.11.1.6) on x-ray- and bleomycin-induced transformation ...
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.80.5.1304
更新日期:1983-03-01 00:00:00
abstract::Assessing temporal variability in extreme rainfall events before the historical era is complicated by the sparsity of long-term "direct" storm proxies. Here we present a 2,200-y-long, accurate, and precisely dated record of cave flooding events from the northwest Australian tropics that we interpret, based on an integ...
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.1422270112
更新日期:2015-04-14 00:00:00
abstract::Ocular dominance (OD) plasticity in mouse primary visual cortex (V1) declines during postnatal development and is absent beyond postnatal day 110 if mice are raised in standard cages (SCs). An enriched environment (EE) promotes OD plasticity in adult rats. Here, we explored cellular mechanisms of EE in mouse V1 and 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.1313385111
更新日期:2014-01-21 00:00:00
abstract::A readily accessible new class of near infrared (NIR) molecular probes has been synthesized and evaluated. Specific fluorophores in this unique xanthene based regioisomeric seminaphthofluorone dye series exhibit a combination of desirable characteristics including (i) low molecular weight (339 amu), (ii) aqueous solub...
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.0710341105
更新日期:2008-07-01 00:00:00
abstract::When encountering unexpected event changes, memories of relevant past experiences must be updated to form new representations. Current models of memory updating propose that people must first generate memory-based predictions to detect and register that features of the environment have changed, then encode the new eve...
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.1918063117
更新日期:2020-11-24 00:00:00
abstract::The circadian clock in eukaryotes controls transcriptional and posttranscriptional events, including regulation of the levels and phosphorylation state of translation factors. However, the mechanisms underlying clock control of translation initiation, and the impact of this potential regulation on rhythmic protein syn...
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.1918459117
更新日期:2020-05-19 00:00:00
abstract::Ca2+-induced inhibition of alpha1C voltage-gated Ca2+ channels is a physiologically important regulatory mechanism that shortens the mean open time of these otherwise long-lasting high-voltage-activated channels. The mechanism of action of Ca2+ has been a matter of some controversy, as previous studies have proposed t...
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.96.5.2435
更新日期:1999-03-02 00:00:00
abstract::We study inverse statistical mechanics: how can one design a potential function so as to produce a specified ground state? In this article, we show that unexpectedly simple potential functions suffice for certain symmetrical configurations, and we apply techniques from coding and information theory to provide mathemat...
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.0901636106
更新日期:2009-06-16 00:00:00
abstract::The 3' flanking region of the apolipoprotein B (apoB) gene contains a hypervariable region consisting of a variable number of tandemly repeated short A + T-rich DNA sequences (VNTRs). We present a general method that utilizes the polymerase chain reaction to rapidly and accurately type this and other VNTR loci. We use...
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.86.1.212
更新日期:1989-01-01 00:00:00
abstract::For isolated rat hepatocytes, glucagon, 3':5'-cyclic AMP, 3':5'-cyclic GMP, and epinephrine stimulate the rate of gluconeogenesis from substrates not involving pathways of mitochondrial metabolism. From estimation of the rates of glucose formation, fructose 6-phosphate phosphorylation, and lactate and pyruvate formati...
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.71.11.4523
更新日期:1974-11-01 00:00:00
abstract::During the last several decades corals have been in decline and at least one-third of all coral species are now threatened with extinction. Coral disease has been a major contributor to this threat, but little is known about the responsible pathogens. To date most research has focused on bacterial and fungal diseases;...
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.0808985105
更新日期:2008-11-25 00:00:00
abstract::Coordinated changes in gene expression underlie the early patterning and cell-type specification of the central nervous system. However, much less is known about how such changes contribute to later stages of circuit assembly and refinement. In this study, we employ single-cell RNA sequencing to develop a detailed, wh...
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.1717871115
更新日期:2018-01-30 00:00:00
abstract::Protein kinase C (PKC) and Syk protein tyrosine kinase play critical roles in immune cell activation including that through the high-affinity IgE receptor, FcepsilonRI. Mechanisms by which PKC activation leads to the activation of Ras, a family of GTPases essential for immune cell activation, have been elusive. We 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.1633695100
更新日期:2003-08-05 00:00:00
abstract::A line of nonobese diabetic (NOD) mice expressing the human diabetes-associated HLA-DQ8 transgene in the absence of mouse IAbeta failed to show spontaneous insulitis or diabetes, but rather developed dilated cardiomyopathy, leading to early death from heart failure. Pathology in these animals results from an organ- an...
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.2235552100
更新日期:2003-11-11 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::Infection is a major complication of implantable medical devices, which provide a scaffold for biofilm formation, thereby reducing susceptibility to antibiotics and complicating treatment. Hematogenous implant-related infections following bacteremia are particularly problematic because they can occur at any time in 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.1703427114
更新日期:2017-06-27 00:00:00