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Mostrando recursos 1 - 20 de 51

  1. v-abl causes hematopoietic disease distinct from that caused by bcr-abl

    Scott, Martin L.; Van Etten, Richard A.; Daley, George Q.; Baltimore, David
    v-abl, the oncogene transduced by Abelson murine leukemia virus, was first characterized by its ability to transform lymphoid cells. bcr-abl, the oncogene formed by a t(9;22) translocation thought to occur in human hematopoietic stem cells, is detectable in almost all cases of chronic myelogenous leukemia (CML), a malignancy of granulocytic cells. bcr-abl also causes a CML-like syndrome in mice whose bone-marrow cells are infected with a retrovirus transducing the gene. More recent reports have suggested that v-abl can, however, cause a disease similar to CML. We demonstrate here that v-abl, when transduced in a helper virus-containing system, causes disease similar...

  2. Tunable far infrared laser spectroscopy of van der Waals bonds: Extended measurements on the lowest Sigma bend of ArHCl

    Busarow, Kerry L.; Blake, Geoffrey A.; Laughlin, K. B.; Cohen, R. C.; Lee, Y. T.; Saykally, R. J.
    A tunable far infrared laser system has been used to measure the vibration–rotation spectrum of the lowest Sigma bending state of ArHCl near 24 cm^−1 in a cw planar jet operating with a terminal jet temperature near 3 K. Over 60 transitions have been observed for both 35Cl and 37Cl isotopes with resolution of the quadrupole hyperfine structure. An improved set of molecular parameters was determined, including B, D, H, and eqQ for both upper and lower states. Very narrow linewidths (approximately 300 kHz) resulting in high resolution and sensitivity make this technique a powerful new method for the detailed...

  3. Substrate-binding sites of UBR1, the ubiquitin ligase of the N-end rule pathway

    Xia, Zanxian; Webster, Ailsa; Du, Fangyong; Piatkov, Konstantin; Ghislain, Michel; Varshavsky, Alexander
    Substrates of a ubiquitin-dependent proteolytic system called the N-end rule pathway include proteins with destabilizing N-terminal residues. N-recognins, the pathway’s ubiquitin ligases, contain three substrate-binding sites. The type-1 site is specific for basic N-terminal residues (Arg, Lys, His). The type-2 site is specific for bulky hydrophobic N-terminal residues (Trp, Phe, Tyr, Leu, Ile). We show here that the type-1/2 sites of UBR1, the sole N-recognin of the yeast Saccharomyces cerevisiae, are located in the first ~700 residues of the 1,950-residue UBR1. These sites are distinct in that they can be selectively inactivated by mutations, identified through a genetic screen. Mutations...

  4. Electronic spectroscopy of trans-azomethane by electron impact

    Mosher, Oren A.; Foster, Michael S.; Flicker, Wayne M.; Beauchamp, J. L.; Kuppermann, Aron
    The electron impact excitation of trans-azomethane (i.e., trans-dimethyl diazine CH3–N–N–CH3) has been studied by both trapped electron (TE) and differential electron scattering (DES) techniques. The nature of the excited state in each of several transitions has been identified by the energy and angular dependences of the excitation cross section. Two previously unreported singlet-->triplet transitions are observed with maxima at 2.75 and 4.84 eV. Theoretical calculations on the parent compound, trans-diimide (H–N=N–H), suggest that these are the χ 1Ag-->1 3Bg (produced by excitation of an electron from an n + molecular orbital to a pi* molecular orbital) and the χ 1Ag-->1...

  5. Determination and optimization of mode matching into optical cavities by heterodyne detection

    Mueller, Guido; Shu, Qi-ze; Adhikari, Rana X.; Tanner, D. B.; Reitze, David; Sigg, Daniel; Mavalvala, Nergis; Camp, Jordan
    We report on a novel high-sensitivity method to characterize and improve mode matching into optical cavities. This method is based on heterodyne detection of cylindrical transverse cavity modes. A specially designed annular-segmented photodiode is used to measure the amplitude of nonresonant modes reflected by the cavity. Our measurements allow us to optimize cavity mode matching to nearly 99.98% and will play an important diagnostic role in gravitational-wave detectors.

  6. B-cell- and myocyte-specific E2-box-binding factors contain E12/E47-like subunits

    Murre, Cornelis; Voronova, Anna; Baltimore, David
    Recent studies have identified a family of DNA-binding proteins that share a common DNA-binding and dimerization domain with the potential to form a helix-loop-helix (HLH) structure. Various HLH proteins can form heterodimers that bind to a common DNA sequence, termed the E2-box. We demonstrate here that E2-box-binding B-cell- and myocyte-specific nuclear factors contain subunits which are identical or closely related to ubiquitously expressed (E12/E47) HLH proteins. These biochemical function for E12/E47-like molecules in mammalian differentiation, similar to the genetically defined function of daughterless in Drosophila development.

  7. Quantitative analysis of semiconductor alloy composition during growth by reflection-electron energy loss spectroscopy

    Nikzad, Shouleh; Ahn, Channing C.; Atwater, Harry A.
    Determination of alloy composition during epitaxial growth of GexSi1–x alloys has been demonstrated using reflection-electron energy loss spectroscopy (REELS) at reflection high-energy electron diffraction (RHEED) energies. Measurements of inelastic scattering intensities from Si K (1840 eV) and Ge L2,3 (1217 eV) core losses were performed using a conventional RHEED gun together with an electron energy loss spectrometer in a molecular beam epitaxy system. Comparison of ex situ composition measurements by Rutherford backscattering and energy dispersive x-ray spectroscopy in a transmission electron microscope indicate excellent agreement with composition determination by REELS, demonstrating the capability of REELS as a quantitative in situ...

  8. The synthesis of D-erythro- and D-threo-α-amino-β,γ-dihydroxy-n-butyric acids

    Niemann, Carl; Nichols, Peter L., Jr.
    We repeated the synthesis of Fischer and Feldmann [2] and obtained, as they did, the amino acid with [α]D24 = -13.7° in good yield. However, in addition another α-amino-β,γ-dihydroxy-n-butyric acid, with [α]D24 = 16.0°, was isolated from the reaction mixture. It is the purpose of this communication to show that the amino acid with [α]D24 = -13.7° is not a mixture of disastereoisomers, but is D-threo-α-amino-β,γ-dihydroxy-n-butyric acid, and that the amino acid with [α]D24 = 16.0° is D-erythro-α-amino-β,γ-dihydroxy-n-butyric acid.

  9. Study on the precision of the multiaperture scintillation sensor turbulence profiler (MASS) employed in the site testing campaign for the Thirty Meter Telescope

    Els, S. G.; Schöck, M.; Seguel, J.; Tokovinin, A.; Komilov, V.; Riddle, R.; Skidmore, W.; Travouillon, T.; Vogiatzis, K.; Blum, R.; Bustos, E.; Gregory, B.; Vasquez, J.; Walker, D.; Gillett, P.
    The multiaperture scintillation sensor (MASS) has become a device widely employed to measure the altitude distribution of atmospheric turbulence. An empirical study is reported that investigates the dependence of the MASS results on the knowledge of the instrumental parameters. Also, the results of a side-by-side comparison of two MASS instruments are presented, indicating that MASS instruments permit measurements of the integrated seeing to a precision better than 0.05 arc sec and of the individual turbulence layer strength Cn2(h)dh to better than 10^−14 m^(1/3).

  10. Localization of the Abelson murine leukemia virus protein in a detergent-insoluble subcellular matrix: architecture of the protein

    Boss, Michael A.; Dreyfuss, Gideon; Baltimore, David
    We examined the interaction of Abelson murine leukemia virus protein P120 with other cellular components after extraction with the nonionic detergent Triton X-100. Most of the Abelson murine leukemia virus P120-associated kinase activity was found in the detergent-insoluble matrix in both lymphoid and fibroblast cell lines. The P120 labeled during a short exposure of cells to [35S]-methionine was mainly in the detergent-insoluble matrix (lymphoid cells) or equally distributed in the detergent-insoluble matrix and the soluble fraction (fibroblasts). Steady-state-labeled P120 was distributed equally in the two fractions (lymphoid cells) or mostly in the soluble portion (fibroblasts). Thus, there was an apparent...

  11. Analytical carbon-oxygen reactive potential

    Kutana, A.; Giapis, K. P.
    We present a reactive empirical potential with environment-dependent bond strengths for the carbon-oxygen (CO) system. The distinct feature of the potential is the use of three adjustable parameters characterizing the bond: the strength, length, and force constant, rather than a single bond order parameter, as often employed in these types of potentials. The values of the parameters are calculated by fitting results obtained from density functional theory. The potential is tested in a simulation of oxidative unzipping of graphene sheets and carbon nanotubes. Previous higher-level theoretical predictions of graphene unzipping by adsorbed oxygen atoms are confirmed. Moreover, nanotubes with externally...

  12. Optical cavity modes in gold shell colloids

    Penninkhof, J. J.; Sweatlock, L. A.; Moroz, A.; Atwater, H. A.; van Blaaderen, A.; Polman, A.
    Core-shell colloids composed of a dielectric core surrounded by a metal shell show geometric cavity resonances with optical properties that are distinctly different than those of the collective plasmon modes of the metal shell. We use finite-difference time domain calculations on silica colloids with a core diameter of 456 nm, surrounded by a 38 nm thick Au shell, to study the temporal evolution of the mode field intensity inside the cavity upon pulsed excitation. Calculations using Mie theory and the T-matrix method are used to analytically determine the dipolar cavity resonance spectrum, which is found superimposed on the broad collective...

  13. The Particulate Methane Monooxygenase from Methylococcus capsulatus (Bath) Is a Novel Copper-containing Three-subunit Enzyme: isolation and charactization

    Nguyen, Hiep-Hoa T.; Elliott, Sean J.; Yip, John Hon-Kay; Chan, Sunney I.
    The particulate methane monooxygenase (pMMO) is known to be very difficult to study mainly due to its unusual activity instability in vitro. By cultivating Methylococcus capsulatus (Bath) under methane stress conditions and high copper levels in the growth medium, membranes highly enriched in the pMMO with exceptionally stable activity can be isolated from these cells. Purified and active pMMO can be subsequently obtained from these membrane preparations using protocols in which an excess of reductants and anaerobic conditions were maintained during membrane solubilization by dodecyl beta-D-maltoside and purification by chromatography. The pMMO was found to be the major constituent in...

  14. Constitutive expression of the neuron-restrictive silencer factor (NRSF)/REST in differentiating neurons disrupts neuronal gene expression and causes axon pathfinding errors in vivo

    Paquette, Alice J.; Perez, Sharon E.; Anderson, David J.
    The neuron-restrictive silencer factor (NRSF; also known as REST for repressor element-1 silencing transcription factor) is a transcriptional repressor of multiple neuronal genes, but little is known about its function in vivo. NRSF is normally down-regulated upon neuronal differentiation. Constitutive expression of NRSF in the developing spinal cord of chicken embryos caused repression of two endogenous target genes, N-tubulin and Ng-CAM, but did not prevent overt neurogenesis. Nevertheless, commissural neurons that differentiated while constitutively expressing NRSF showed a significantly increased frequency of axon guidance errors. These data suggest that down-regulation of NRSF is necessary for the proper development of at...

  15. RAG-1 Interacts with the Repeated Amino Acid Motif of the Human Homologue of the Yeast Protein SRP1

    Cortes, Patricia; Ye, Zheng-Sheng; Baltimore, David
    Genes for immunoglobulins and T-cell receptor are generated by a process known as V(D)J recombination. This process is highly regulated and mediated by the recombination activating proteins RAG-1 and RAG-2. By the use of the two-hybrid protein interaction system, we isolated a human protein that specifically interacts with RAG-1. This protein is the human homologue of the yeast SRP1 (suppressor of a temperature-sensitive RNA polymerase I mutation). The SRP1-1 mutation is an allele-specific dominant suppressor of a temperature-sensitive mutation in the zinc binding domain of the 190-kDa subunit of Saccharomyces cerevisiae RNA polymerase I. The human SRP cDNA clone was...

  16. Super-replication in stochastic volatility models under portfolio constraints

    Cvitanić, Jakša; Pham, Huyên; Touzi, Nizar
    We study a financial market with incompleteness arising from two sources: stochastic volatility and portfolio constraints. The latter are given in terms of bounds imposed on the borrowing and short-selling of a `hedger' in this market, and can be described by a closed convex set K. We find explicit characterizations of the minimal price needed to super-replicate European-type contingent claims in this framework. The results depend on whether the volatility is bounded away from zero and/or infinity, and also, on if we have linear dynamics for the stock price process, and whether volatility process depends on the stock price. We...

  17. Growth of Pseudotypes of Vesicular Stomatitis Virus with N-Tropic Murine Leukemia Virus Coats in Cells Resistant to N-Tropic Viruses

    Huang, Alice S.; Besmer, Peter; Chu, Louise; Baltimore, David
    Formation of pseudotypes between murine RNA tumor viruses and vesicular stomatitis virus (VSV) has been confirmed. Pseudotypes of VSV genomes coated by the surface envelope from an N-tropic tumor virus grew equally well in cells homozygous for either the Fv-1n or Fv-1b alleles. Therefore, the product of the Fv-1 locus, which restricts growth of murine RNA tumor viruses, must act on an intracellular aspect of tumor virus replication, a step after attachment and penetration.

  18. Ribonucleic Acud Polymerase in Virions of Newcastle Disease Virus: Comparison with the Vesicular Stomatitis Virus Polymerase

    Huang, Alice S.; Baltimore, David; Bratt, Michael A.
    The virions of Newcastle disease virus (NDV) contained an enzyme that catalyzed the incorporation of ribonucleotides into ribonucleic acid (RNA). Optimal conditions for this polymerase activity were identical to the conditions for the vesicular stomatitis virus (VSV) polymerase, and both enzymes were active for longer times at 32 C than at 37 C. However, the specific activity of the NDV polymerase was less than 3% that of the VSV polymerase. Product RNA species from the NDV and VSV polymerase reactions annealed specifically to the homologous virion RNA species. Transcriptive intermediates containing product RNA attached to the respective virion RNA could...

  19. Six distinct nuclear factors interact with the 75-base-pair repeat of the Moloney murine leukemia virus enhancer

    Speck, Nancy A.; Baltimore, David
    Binding sites for six distinct nuclear factors on the 75-base-pair repeat of the Moloney murine leukemia virus enhancer have been identified by an electrophoretic mobility shift assay combined with methylation interference. Three of these factors, found in WEHI 231 nuclear extracts, which we have named LVa, LVb, and LVc (for leukemia virus factors a, b, and c) have not been previously identified. Nuclear factors that bind to the conserved simian virus 40 corelike motif, the NF-1 motif, and the glucocorticoid response element were also detected. Testing of multiple cell lines showed that most factors appeared ubiquitous, except that the NF-1...

  20. Polyadenylic acid on poliovirus RNA. III. In vitro addition of polyadenylic acid to poliovirus RNAs

    Spector, Deborah H.; Baltimore, David
    A crude RNA polymerase preparation was made from HeLa cells infected for 3 h with poliovirus. All virus-specific RNA species labeled in vitro (35S RNA, replicative intermediate RNA [RI], and double-stranded RNA [dsRNA]) would bind to poly(U) filters and contained RNase-resistant stretches of poly(A) which could be analyzed by electrophoresis in polyacrylamide gels. After incubation for 45 min with [3-H]ATP in the presence of the other three nucleoside triphosphates, the labeled poly(A) on the RI and dsRNA migrated on gels as relatively homogenous peaks approximately 200 nucleotides in length. In contrast, the poly(A) from the 35S RNA had a heterogeneous...

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