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  • 1
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Nuclear Physics B (Proceedings Supplements) 26 (1992), S. 337-340 
    ISSN: 0920-5632
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2012-03-07
    Description: Activation of p53 target genes for tumor suppression depends on the stress-specific regulation of transcriptional coactivator complexes. Strap (stress-responsive activator of p300) is activated upon DNA damage by ataxia telangiectasia mutated (ATM) and Chk2 kinases and is a key regulator of the p53 response. In addition to antagonizing Mdm2, Strap facilitates the recruitment of p53 coactivators, including JMY and p300. Strap is a predicted TPR-repeat protein, but shows only limited sequence identity with any protein of known structure. To address this and to elucidate the molecular mechanism of Strap activity we determined the crystal structure of the full-length protein at 2.05 Å resolution. The structure of Strap reveals an atypical six tetratricopeptide repeat (TPR) protein that also contains an unexpected oligonucleotide/oligosaccharide-binding (OB)-fold domain. This previously unseen domain organization provides an extended superhelical scaffold allowing for protein-protein as well as protein-DNA interaction. We show that both of the TPR and OB-fold domains localize to the chromatin of p53 target genes and exhibit intrinsic regulatory activity necessary for the Strap-dependent p53 response.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 3
    Publication Date: 2012-04-21
    Description: Protein-folding intermediates have been implicated in amyloid fibril formation involved in neurodegenerative disorders. However, the structural mechanisms by which intermediates initiate fibrillar aggregation have remained largely elusive. To gain insight, we used relaxation dispersion nuclear magnetic resonance spectroscopy to determine the structure of a low-populated, on-pathway folding intermediate of the A39V/N53P/V55L (A, Ala; V, Val; N, Asn; P, Pro; L, Leu) Fyn SH3 domain. The carboxyl terminus remains disordered in this intermediate, thereby exposing the aggregation-prone amino-terminal beta strand. Accordingly, mutants lacking the carboxyl terminus and thus mimicking the intermediate fail to safeguard the folding route and spontaneously form fibrillar aggregates. The structure provides a detailed characterization of the non-native interactions stabilizing an aggregation-prone intermediate under native conditions and insight into how such an intermediate can derail folding and initiate fibrillation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Neudecker, Philipp -- Robustelli, Paul -- Cavalli, Andrea -- Walsh, Patrick -- Lundstrom, Patrik -- Zarrine-Afsar, Arash -- Sharpe, Simon -- Vendruscolo, Michele -- Kay, Lewis E -- 089703/Wellcome Trust/United Kingdom -- Canadian Institutes of Health Research/Canada -- New York, N.Y. -- Science. 2012 Apr 20;336(6079):362-6. doi: 10.1126/science.1214203.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22517863" target="_blank"〉PubMed〈/a〉
    Keywords: Amyloid/*chemistry ; Animals ; Chickens ; Hydrogen Bonding ; Models, Molecular ; Molecular Dynamics Simulation ; Mutant Proteins/chemistry ; Nuclear Magnetic Resonance, Biomolecular ; Protein Conformation ; *Protein Folding ; Protein Structure, Secondary ; Proto-Oncogene Proteins c-fyn/*chemistry/genetics ; Thermodynamics ; *src Homology Domains
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 4
    Publication Date: 2016-12-24
    Description: We report that the anticancer activity of the widely used diabetic drug metformin is strongly potentiated by syrosingopine. Synthetic lethality elicited by combining the two drugs is synergistic and specific to transformed cells. This effect is unrelated to syrosingopine’s known role as an inhibitor of the vesicular monoamine transporters. Syrosingopine binds to the glycolytic enzyme α-enolase in vitro, and the expression of the -enolase isoform correlates with nonresponsiveness to the drug combination. Syrosingopine sensitized cancer cells to metformin and its more potent derivative phenformin far below the individual toxic threshold of each compound. Thus, combining syrosingopine and codrugs is a promising therapeutic strategy for clinical application for the treatment of cancer.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 183-196 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Rovibrational absorption spectra of weakly bonded complexes of N2O with HF, DF, HCl, and HBr were recorded in the ν3 region of N2O by using pulsed, slotted nozzle expansions and tunable diode lasers. A fast-scan technique was used that takes advantage of the rapid tuning capabilities of diode lasers; i.e., 4000 resolution elements were recorded with a single opening of the nozzle. Of the two known NH- and OH-bonded isomers of N2O–HF, we detected only linear ONN–HF; the ground-state rotational constants are in excellent agreement with previous microwave and IR results. Deuteration resulted in ONN–DF linewidths that are much narrower than those of ONN–HF, as observed previously in studies of the analogous CO2–H(D)F system. Vibrational band origins for ONN–HF and ONN–DF are blue shifted 21.8 and 23.4 cm−1, respectively, relative to uncomplexed N2O. The additional blue shift upon deuteration is attributed to enhanced hydrogen bonding in a highly anharmonic potential. High-resolution spectra of NNO–HCl and NNO–HBr are presented for the first time. The average NNO–HCl geometry is asymmetric, with the separation between the N2O and HCl centers-of-mass Rcm equal to 3.51 A(ring). The angle between Rcm and the NNO principal axis θ1 is 72°–76°. NNO–HBr complexes are also asymmetric (θ1=75°–82°) with Rcm =3.62 A(ring). Linear ONN–HCl(Br) isomers were not observed. Blue shifts in the NNO–HCl and NNO–HBr band origins are 2.44 and 1.86 cm−1, relative to uncomplexed N2O. The qualitative changes observed in the NNO–HX geometries and force fields are attributed to competing effects arising from hydrogen–bonding and dispersion forces, as were observed with CO2–HF(Cl) and CO2–HBr. The experimental geometries and vibrational frequencies are compared to ab initio calculations; agreement with N2O–HF is good, CO2–HCl less so. Although the H atom position cannot be determined experimentally with NNO–HCl(Br), ab initio estimates suggest it is localized near the O atom. Implications for photoinitiated reactions in weakly bonded complexes are discussed.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 5392-5402 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A high resolution rovibrational absorption spectrum of the weakly bonded CO2–DBr complex has been recorded in the 2350 cm−1 region by exciting the CO2 asymmetric stretch vibration with a tunable diode laser. The CO2–DBr band origin associated with this mode is 2348.2710 cm−1, red-shifted by 0.87 cm−1 from uncomplexed CO2. The position of the hydrogen atom is determined from differences in moments-of-inertia between CO2–DBr and CO2–HBr, i.e., by using the Kraitchman method. From this, we conclude that ground state CO2–H(D)Br has an average geometry that is planar and inertially T-shaped, with essentially parallel HBr and CO2 axes. Average values of intermolecular parameters are: Rcm=3.58 A(ring), θBrCO=79.8°, and θHBrC=93.1°. The validity of using the Kraitchman method, which was designed for use with rigid molecules, with a floppy complex like CO2–HBr is discussed. The experimental structure is corroborated qualitatively by results from Møller–Plesset second-order perturbation calculations, corrected for basis set superposition errors. The theoretical equilibrium geometry for the inertially T-shaped complex is planar with structural parameters: RCBr=3.62 A(ring), θBrCO=89°, and θHBrC=86°. A number of cuts on the four dimensional intermolecular potential surface confirm large zero-point amplitudes, which are known to be characteristic of such systems, and these cuts are used to estimate tunneling splittings. Tunneling is shown to occur by out-of-plane rotation of the H atom, in accord with the experimental observations of Rice et al. There is no significant in-plane tunneling. A quasilinear hingelike isomer (OCO–HBr) with ROH=2.35 A(ring) at equilibrium is calculated to be as stable as the T-shaped complex; however, this species has yet to be observed experimentally. Photoinitiated reactions in CO2–HX complexes are discussed.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 943-958 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Infrared absorption spectra associated with the CO2 asymmetric stretch vibration have been recorded for weakly bonded gas-phase complexes of CO2 with HF, DF, HCl, DCl, and HBr, using tunable diode laser spectroscopy and a pulsed slit expansion (0.15×38 mm2) that provides 〉20 MHz overall resolution. Results obtained with CO2–HF are in agreement with earlier studies, in which the HF-stretch region near 3900 cm−1 was examined. In both cases, broad linewidths suggest subnanosecond predissociation. With CO2–DF, the natural linewidths are markedly narrower than with CO2–HF (e.g., 28 vs 182 MHz), and this difference is attributed to slower predissociation, possibly implicating resonances in the case of CO2–HF. Both CO2–HF and CO2–DF exhibited overlapping features: simple P and R branches associated with a linear rotor, and P and R branches containing doublets. As in earlier studies, the second feature can be assigned to either a slightly asymmetric rotor with Ka=1, or a hot band involving a low-frequency intermolecular bend mode.Results obtained with CO2–HCl are in excellent agreement with earlier microwave measurements on the ground vibrational state, and the vibrationally excited state is almost identical to the lower state. Like CO2–DF, linewidths of CO2–HCl and CO2–DCl are much sharper than those of CO2–HF, and in addition, CO2–HCl and CO2–DCl exhibited weak hot bands, as were also evident with CO2–HF and CO2–DF. Upon forming complexes with either HF or HCl, the asymmetric stretch mode of CO2 underwent a blue shift relative to uncomplexed CO2. This can be understood in terms of the nature of the hydrogen bonds, and ab initio calculations are surprisingly good at predicting these shifts. Deuteration of both HF and HCl resulted in further blue shifts of the band origins. These additional shifts are attributed to stronger intermolecular interactions, i.e., deuteration lowers the zero-point energy, and in a highly anharmonic field this results in a more compact average structure. While both HF and HCl complexes exhibit nearly linear geometries,CO2–HBr is asymmetric, with the Br–C symmetry line essentially perpendicular to the CO2 axis, and the H atom probably localized near one of the oxygens. Although the moments of inertia are insensitive to the location of the H atom in CO2–HBr, Bose–Einstein statistics require that odd K‘a states are missing for C2v symmetry, as is observed with T-shaped CO2–(rare gas) complexes. However, we observe a full complement of odd and even Ka states, indicating that the H atom is not located symmetrically about the C2v axis on the time scale of the measurement. With CO2–HBr, the low gas-phase acidity of HBr and the high Br-atom polarizability encourage a qualitative change in the geometry relative to CO2–HCl and CO2–HF. This has valuable implications for photoinitiated reactions in such complexes.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 233-238 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The rovibrational absorption spectrum of CO2–Ar has been recorded in the 2376 cm−1 region by using a pulsed, slit nozzle expansion and tunable IR diode laser. The spectrum is ascribed to the 410510 combination band, where ν4 corresponds to the asymmetric stretch of the CO2 moiety and ν5 is the intermolecular bend. This combination band is ∼102 times less intense and 27.82 cm−1 higher in energy than the 410 fundamental. Effective upper-state rotational constants were determined for this nearly prolate rotor, and the ν4+ν5 moments of inertia show a large inertial defect, Δ=9.48 amu A(ring)2. In planar molecules, this indicates large vibrational amplitude, and reflects inadequacy of the rotational Hamiltonian. From the moments of inertia derived using a Watson Hamiltonian, geometric properties of ν4+ν5 can be calculated. The average O–C–Ar angle is 76.9°, while the center-of-mass separation between CO2 and Ar is 3.60 A(ring). These values differ from those of the ground state (83.1° and 3.51 A(ring)) and ν4=1 (83.0° and 3.50 A(ring)). Results are compared with previous work, which used different models and approximations to obtain intermolecular frequencies. In addition, inertial defects were calculated for the ground and vibrationally excited states using a simple normal mode model developed by Herschbach and Laurie, and Oka and Morino. With harmonic force fields, it accounts for most of the inertial defect in the ground and excited states, and yields reasonable R and θ values. However, we conclude that the good agreement between experimental and calculated inertial defects may be fortuitous, since several positive and negative contributions cancel.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 6162-6169 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Rotationally resolved vibrational spectra consisting of a-type transitions have been observed for the low-frequency, intermolecular bending mode in combination with the highest frequency, intramolecular stretching mode of Ar–N2O. Analysis of the spectral data places the origin of the combination band at 2256.1 cm −1 while the origin of the intramolecular stretching fundamental is at 2223.9 cm−1. The difference between these two origins is approximately 32.2 cm−1 and agrees well with our calculated frequency of 31.5 cm−1 for the intermolecular bending mode, which was obtained by analysis of the centrifugal distortion constants. In addition, argon–nitrous oxide exhibits an anomalously large inertial defect of 10.96 amu A(ring)2 in the combination state. This indicates a breakdown in the assumption of separation between vibration and rotation. While much of the inertial defect in the ground state can be accounted for by including Coriolis interactions, that occurring in the combination state is only partially accounted for by a similar analysis. Small, but significant changes, are observed in both the radial and angular parameters for Ar–N2O when going from the ground to the combination state, indicating large amplitude motion. The combination band is approximately 200 times less intense than the high-frequency, stretching fundamental of Ar–N2O. In addition, over 400 new rovibrational transitions are assigned to the previously observed 101 intramolecular stretching fundamental of the complex, and the subsequent rotational analysis is found to be in close agreement with earlier studies. Data were taken on a newly built, rapid-scan, diode laser spectrometer that incorporates a 12 cm×200 μm pulsed slit-expansion nozzle.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 3380-3383 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Feedback between optical elements can be a major source of noise when trying to attain high sensitivity in infrared absorption experiments. We find that a conventional White-cell optical arrangement introduces étaloning fringes that modulate the peak-to-peak amplitude of our signals by 1 part in 16 666, a fractional change of 6×10−5. Although relatively small, this "noise'' is systematic and adds coherently with averaging, obscuring interesting absorption features. An easily constructed multipass optical system suited for performing high-resolution infrared spectroscopy in molecular beams is described. The design is based on a variation of the White cell and has been optimized for use with lead salt diode lasers. One of the key components in the improved design is the addition of an oscillating mirror for spoiling optical feedback generated by laser scatter and/or poor mode coupling of the laser to the multipass optics.
    Type of Medium: Electronic Resource
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