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  • 1
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    Potent monofunctional platinum anticancer agent [Chemistry] (2012)
    National Academy of Sciences
    Details
    Publication Date: 2012-07-25
    Description: Monofunctional platinum(II) complexes of general formula cis-[Pt(NH3)2(N-heterocycle)Cl]Cl bind DNA at a single site, inducing little distortion in the double helix. Despite this behavior, these compounds display significant antitumor properties, with a different spectrum of activity than that of classic bifunctional cross-linking agents like cisplatin. To discover the most potent monofunctional platinum(II) compounds, the N-heterocycle was systematically varied to generate a small library of new compounds, with guidance from the X-ray structure of RNA polymerase II (Pol II) stalled at a monofunctional pyriplatin-DNA adduct. In pyriplatin, the N-heterocycle is pyridine. The most effective complex evaluated was phenanthriplatin, cis-[Pt(NH3)2(phenanthridine)Cl]NO3, which exhibits significantly greater activity than the Food and Drug Administration-approved drugs cisplatin and oxaliplatin. Studies of phenanthriplatin in the National Cancer Institute 60-cell tumor panel screen revealed a spectrum of activity distinct from that of these clinically validated anticancer agents. The cellular uptake of phenanthriplatin is substantially greater than that of cisplatin and pyriplatin because of the hydrophobicity of the phenanthridine ligand. Phenanthriplatin binds more effectively to 5′-deoxyguanosine monophosphate than to N-acetyl methionine, whereas pyriplatin reacts equally well with both reagents. This chemistry supports DNA as a viable cellular target for phenanthriplatin and suggests that it may avoid cytoplasmic platinum scavengers with sulfur-donor ligands that convey drug resistance. With the use of globally platinated Gaussia luciferase vectors, we determined that phenanthriplatin inhibits transcription in live mammalian cells as effectively as cisplatin, despite its inability to form DNA cross-links.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 2
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    Estimation of the Non‐Darcy Coefficient Using Supercritical CO2 and Various Sandstones (2019)
    Wiley
    Details
    Publication Date: 2019
    Description: Abstract Non‐Darcy flow (also known as high‐velocity flow, inertial flow, etc.) often occurs in the near‐well region of a reservoir during injection or production. This flow needs to be characterized and its origins fully understood, as it is a critical factor in reducing well productivity. The Forchheimer equation, which describes fluid flow considering an inertial effect, can be adopted to analyze non‐Darcy flow. In particular, the non‐Darcy coefficient in the equation represents inertial resistance in a porous medium and is an empirical value that depends on the pore geometry and fluid properties. This study, as part of research on geological CO2 storage, reports non‐Darcy flow tests with a high flow rate and examines the non‐Darcy coefficient by using supercritical CO2 and various sandstones. The dependence of the coefficient on the properties of the supercritical CO2 was also assessed in a series of non‐Darcy tests under different pore pressures. The coefficient varied with the properties of the supercritical CO2 and sandstone. As the permeability of sandstone increased, the non‐Darcy coefficient decreased nonlinearly and converged to a value. The results also indicate that the coefficient is reduced with a decreasing ratio of density to viscosity for the supercritical CO2. An equation predicting the coefficient was derived, having the advantage that both the hydraulic properties of rock and the fluid properties can be considered simultaneously in a dimensionally correct analysis.
    Print ISSN: 2169-9313
    Electronic ISSN: 2169-9356
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
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    Polycomb proteins targeted by a short repeat RNA to the mouse X chromosome (2008)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2008-11-01
    Description: To equalize X-chromosome dosages between the sexes, the female mammal inactivates one of her two X chromosomes. X-chromosome inactivation (XCI) is initiated by expression of Xist, a 17-kb noncoding RNA (ncRNA) that accumulates on the X in cis. Because interacting factors have not been isolated, the mechanism by which Xist induces silencing remains unknown. We discovered a 1.6-kilobase ncRNA (RepA) within Xist and identified the Polycomb complex, PRC2, as its direct target. PRC2 is initially recruited to the X by RepA RNA, with Ezh2 serving as the RNA binding subunit. The antisense Tsix RNA inhibits this interaction. RepA depletion abolishes full-length Xist induction and trimethylation on lysine 27 of histone H3 of the X. Likewise, PRC2 deficiency compromises Xist up-regulation. Therefore, RepA, together with PRC2, is required for the initiation and spread of XCI. We conclude that a ncRNA cofactor recruits Polycomb complexes to their target locus.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2748911/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2748911/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zhao, Jing -- Sun, Bryan K -- Erwin, Jennifer A -- Song, Ji-Joon -- Lee, Jeannie T -- R01 GM058839/GM/NIGMS NIH HHS/ -- R01 GM058839-10/GM/NIGMS NIH HHS/ -- R01 GM110090/GM/NIGMS NIH HHS/ -- R01GM58839/GM/NIGMS NIH HHS/ -- Howard Hughes Medical Institute/ -- New York, N.Y. -- Science. 2008 Oct 31;322(5902):750-6. doi: 10.1126/science.1163045.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Howard Hughes Medical Institute, Boston, MA 02115, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18974356" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Cell Differentiation ; Cell Line ; Chromatin Immunoprecipitation ; Electrophoretic Mobility Shift Assay ; Embryonic Stem Cells ; Female ; Fibroblasts ; Male ; Mice ; Mice, Transgenic ; Molecular Sequence Data ; Polycomb-Group Proteins ; Polymerase Chain Reaction ; RNA, Long Noncoding ; RNA, Untranslated/genetics/*metabolism ; Repetitive Sequences, Nucleic Acid ; Repressor Proteins/*metabolism ; Up-Regulation ; X Chromosome/*metabolism ; X Chromosome Inactivation
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 4
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    Argonaute2 is the catalytic engine of mammalian RNAi (2004)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2004-07-31
    Description: Gene silencing through RNA interference (RNAi) is carried out by RISC, the RNA-induced silencing complex. RISC contains two signature components, small interfering RNAs (siRNAs) and Argonaute family proteins. Here, we show that the multiple Argonaute proteins present in mammals are both biologically and biochemically distinct, with a single mammalian family member, Argonaute2, being responsible for messenger RNA cleavage activity. This protein is essential for mouse development, and cells lacking Argonaute2 are unable to mount an experimental response to siRNAs. Mutations within a cryptic ribonuclease H domain within Argonaute2, as identified by comparison with the structure of an archeal Argonaute protein, inactivate RISC. Thus, our evidence supports a model in which Argonaute contributes "Slicer" activity to RISC, providing the catalytic engine for RNAi.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Liu, Jidong -- Carmell, Michelle A -- Rivas, Fabiola V -- Marsden, Carolyn G -- Thomson, J Michael -- Song, Ji-Joon -- Hammond, Scott M -- Joshua-Tor, Leemor -- Hannon, Gregory J -- New York, N.Y. -- Science. 2004 Sep 3;305(5689):1437-41. Epub 2004 Jul 29.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Cold Spring Harbor Laboratory, Watson School of Biological Sciences, 1 Bungtown Road, Cold Spring Harbor, NY 11724, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/15284456" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Animals ; Argonaute Proteins ; Catalysis ; Cell Line ; Cells, Cultured ; Central Nervous System/embryology ; Embryonic and Fetal Development ; Eukaryotic Initiation Factor-2 ; Gene Expression Profiling ; Gene Expression Regulation, Developmental ; Humans ; In Situ Hybridization ; Mice ; MicroRNAs/metabolism ; Molecular Sequence Data ; Mutagenesis, Insertional ; Oligonucleotide Array Sequence Analysis ; Peptide Initiation Factors/chemistry/*metabolism ; Point Mutation ; *RNA Interference ; RNA, Double-Stranded ; RNA, Messenger/*metabolism ; RNA, Small Interfering/metabolism ; RNA-Induced Silencing Complex/chemistry/*metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 5
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    Crystal structure of Argonaute and its implications for RISC slicer activity (2004)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2004-07-31
    Description: Argonaute proteins and small interfering RNAs (siRNAs) are the known signature components of the RNA interference effector complex RNA-induced silencing complex (RISC). However, the identity of "Slicer," the enzyme that cleaves the messenger RNA (mRNA) as directed by the siRNA, has not been resolved. Here, we report the crystal structure of the Argonaute protein from Pyrococcus furiosus at 2.25 angstrom resolution. The structure reveals a crescent-shaped base made up of the amino-terminal, middle, and PIWI domains. The Piwi Argonaute Zwille (PAZ) domain is held above the base by a "stalk"-like region. The PIWI domain (named for the protein piwi) is similar to ribonuclease H, with a conserved active site aspartate-aspartate-glutamate motif, strongly implicating Argonaute as "Slicer." The architecture of the molecule and the placement of the PAZ and PIWI domains define a groove for substrate binding and suggest a mechanism for siRNA-guided mRNA cleavage.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Song, Ji-Joon -- Smith, Stephanie K -- Hannon, Gregory J -- Joshua-Tor, Leemor -- New York, N.Y. -- Science. 2004 Sep 3;305(5689):1434-7. Epub 2004 Jul 29.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Watson School of Biological Sciences, 1 Bungtown Road, Cold Spring Harbor, NY 11724, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/15284453" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Archaeal Proteins/*chemistry/metabolism ; Binding Sites ; Catalytic Domain ; Crystallography, X-Ray ; Models, Molecular ; Molecular Sequence Data ; Protein Conformation ; Protein Folding ; Protein Structure, Secondary ; Protein Structure, Tertiary ; Pyrococcus furiosus/*chemistry ; *RNA Interference ; RNA, Messenger/*metabolism ; RNA, Small Interfering/*metabolism ; RNA-Induced Silencing Complex/*metabolism ; Ribonuclease H/chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 6
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    Effect of pore and confining pressure on the supercritical CO2 permeability of sandstone: Implications for the effective pressure law (2017)
    Wiley
    Details
    Publication Date: 2017-08-01
    Description: The liquid permeability of rock with distilled water or brine is different from that obtained using gas by variation in the confining pressure P c and pore pressure P p . In this study, as part of the research on CO 2 geological storage, the permeability of sandstone was measured using supercritical CO 2 , and the effect of P c and P p on this permeability was analyzed. For applying the effective pressure law to the analysis, an effective pressure coefficient for permeability was derived experimentally. In order to utilize supercritical CO 2 , a non-Darcy flow test with a high flow rate was conducted, and the permeability was estimated through the Forchheimer equation. We contoured iso-permeability lines with confining and pore pressure conditions that have identical permeability and the effective pressure coefficient, χ , was derived from the gradient of the lines following the definition of the effective pressure law. It was identified that the coefficient could be different depending on the pressure conditions. To clarify the variation of the coefficient, we derived the coefficient of χ (P c , P p ) as a function of pore and confining pressure. The coefficient increased non-linearly as the difference between P c and P p decreased, with a maximum of 1.36 being observed. The correlation between the effective pressure and the permeability were examined by applying empirical models. It was determined that the power law model was appropriate to estimate the change in supercritical CO 2 permeability. Especially, it was deduced that the effective pressure with the derived coefficient would be more valid than the Terzaghi effective pressure.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 7
    Electronic Resource
    Electronic Resource
    Interband transitions in InAsxP1−x/InP strained multiple quantum wells (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 1645-1647 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the optical study of the interband transitions in InAsxP1−x/InP strained-layer multiple quantum wells grown by gas-source molecular beam epitaxy. Low-temperature photoluminescence, photoluminescence excitation, and room temperature photomodulated transmission measurements were performed to investigate optical interband transitions. In addition to transitions associated with the heavy-hole and the light-hole bands, a transition involved with the spin-orbit split-off band was observed. We also observed spectral linewidth broadening due to compositional inhomogeneity and layer-thickness fluctuations from the sample using short-period superlattices as the well materials. Calculations based on the envelope-function approximation and phenomenological deformation potential theory, including both band nonparabolicity and strain-induced valence-band mixing, were compared with experimental data to identify the optical transitions between quantized states in the wells. We found good agreement between theory and experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351683
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  • 8
    Electronic Resource
    Electronic Resource
    Stimulated emission and gain measurements in molecular-beam epitaxially grown CdTe (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6612-6616 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Stimulated emission has been observed in molecular-beam epitaxially (MBE) grown films of cadmium telluride (CdTe), using a nanosecond pulsed dye laser as an excitation source. The films were 2.0–2.4 μm thick. Stimulated emission (SE) is seen to arise at several energy positions of the spectra. The different SE peaks exhibited different gain values. The gain was measured using the single beam method, by varying the length of excitation. The bulk CdTe sample studied exhibited stronger saturation effects than those seen in the MBE films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348874
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  • 9
    Electronic Resource
    Electronic Resource
    Optical properties of wurtzite GaN grown by low-pressure metalorganic chemical-vapor deposition (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 3691-3696 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present the results of optical studies on the properties of GaN grown by low-pressure metalorganic chemical-vapor deposition, with emphasis on the issues vital to device applications such as stimulated emission and laser action as well as carrier relaxation dynamics. By optical pumping, stimulated emission and lasing were investigated over a wide temperature range up to 420 K. Using a picosecond streak camera, the free and bound exciton emission decay times were examined. In addition, the effects of temperature and pressure on the optical interband transitions and the transitions associated with impurity/defect states were studied using a variety of spectroscopic methods, including photoluminescence and photoreflectance. The fundamental band gap of GaN was mapped out as a function of temperature using the empirical Varshni relation. The pressure coefficient of the gap was determined using diamond-anvil pressure-cell technique. The hydrostatic deformation potential for the direct Γ band gap was also derived from the experimental results. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361200
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  • 10
    Electronic Resource
    Electronic Resource
    Excitation energy-dependent optical characteristics of InGaN/GaN multiple quantum wells (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 3181-3183 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have systematically studied the optical properties of InGaN/GaN multiple quantum wells (MQWs) at 10 K under different excitation conditions using photoluminescence (PL), PL excitation, and time-resolved PL spectroscopy. We found that the PL emission consists of a strong main peak at 2.80 eV and a much weaker and broader secondary peak at ∼2.25 eV. We observed that the peak position blueshifts and the spectral width narrows for the main peak when the excitation energies are varied from 3.81 eV (above the band gap of the AlGaN capping layer) to 2.99 eV (below the band gap of the GaN barrier layers). The intensity ratio of the main peak to the secondary peak also varied with excitation energy. The two observed emission peaks originate from different layers of the MQWs. Time-integrated and time-resolved PL revealed that the InGaN-related spontaneous emission processes are strongly affected by inhomogeneity and carrier localization in the MQWs. From these studies under varying excitation energies, we conclude that interface-related defects and roughness may play an important role in the InGaN-related emission mechanism during the carrier transfer between different layers of the MQWs. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122711
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