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Nagle A, Biggart A, Be C, Srinivas H, Hein A, Caridha D, Sciotti RJ, Pybus B, Kreishman-Deitrick M, Bursulaya B, Lai YH, Gao MY, Liang F, Mathison CJN, Liu X, Yeh V, Smith J, Lerario I, Xie Y, Chianelli D, Gibney M, Berman A, Chen YL, Jiricek J, Davis LC, Liu X, Ballard J, Khare S, Eggimann FK, Luneau A, Groessl T, Shapiro M, Richmond W, Johnson K, Rudewicz PJ, Rao SPS, Thompson C, Tuntland T, Spraggon G, Glynne RJ, Supek F, Wiesmann C, Molteni V. Discovery and Characterization of Clinical Candidate LXE408 as a Kinetoplastid-Selective Proteasome Inhibitor for the Treatment of Leishmaniases. J Med Chem 2020; 63:10773-10781. [PMID: 32667203 PMCID: PMC7549094 DOI: 10.1021/acs.jmedchem.0c00499] [Citation(s) in RCA: 54] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
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Visceral
leishmaniasis is responsible for up to 30,000 deaths every
year. Current treatments have shortcomings that include toxicity and
variable efficacy across endemic regions. Previously, we reported
the discovery of GNF6702, a selective inhibitor of the kinetoplastid
proteasome, which cleared parasites in murine models of leishmaniasis,
Chagas disease, and human African trypanosomiasis. Here, we describe
the discovery and characterization of LXE408, a structurally related
kinetoplastid-selective proteasome inhibitor currently in Phase 1
human clinical trials. Furthermore, we present high-resolution cryo-EM
structures of the Leishmania tarentolae proteasome
in complex with LXE408, which provides a compelling explanation for
the noncompetitive mode of binding of this novel class of inhibitors
of the kinetoplastid proteasome.
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Affiliation(s)
- Advait Nagle
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California 92121, United States
| | - Agnes Biggart
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California 92121, United States
| | - Celine Be
- Novartis Institutes for Biomedical Research, CH-4056 Basel, Switzerland
| | - Honnappa Srinivas
- Novartis Institutes for Biomedical Research, CH-4056 Basel, Switzerland
| | - Andreas Hein
- Novartis Institutes for Biomedical Research, CH-4056 Basel, Switzerland
| | - Diana Caridha
- Experimental Therapeutics, Walter Reed Army Institute of Research, Silver Spring, Maryland 20910, United States
| | - Richard J Sciotti
- Experimental Therapeutics, Walter Reed Army Institute of Research, Silver Spring, Maryland 20910, United States
| | - Brandon Pybus
- Experimental Therapeutics, Walter Reed Army Institute of Research, Silver Spring, Maryland 20910, United States
| | - Mara Kreishman-Deitrick
- Experimental Therapeutics, Walter Reed Army Institute of Research, Silver Spring, Maryland 20910, United States
| | - Badry Bursulaya
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California 92121, United States
| | - Yin H Lai
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California 92121, United States
| | - Mu-Yun Gao
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California 92121, United States
| | - Fang Liang
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California 92121, United States
| | - Casey J N Mathison
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California 92121, United States
| | - Xiaodong Liu
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California 92121, United States
| | - Vince Yeh
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California 92121, United States
| | - Jeffrey Smith
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California 92121, United States
| | - Isabelle Lerario
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California 92121, United States
| | - Yongping Xie
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California 92121, United States
| | - Donatella Chianelli
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California 92121, United States
| | - Michael Gibney
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California 92121, United States
| | - Ashley Berman
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California 92121, United States
| | - Yen-Liang Chen
- Novartis Institute of Tropical Diseases, Emeryville, California 94608, United States
| | - Jan Jiricek
- Novartis Institute of Tropical Diseases, Emeryville, California 94608, United States
| | - Lauren C Davis
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California 92121, United States
| | - Xianzhong Liu
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California 92121, United States
| | - Jaime Ballard
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California 92121, United States
| | - Shilpi Khare
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California 92121, United States
| | | | - Alexandre Luneau
- Novartis Institutes for Biomedical Research, CH-4056 Basel, Switzerland
| | - Todd Groessl
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California 92121, United States
| | - Michael Shapiro
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California 92121, United States
| | - Wendy Richmond
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California 92121, United States
| | - Kevin Johnson
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California 92121, United States
| | - Patrick J Rudewicz
- Novartis Institute of Tropical Diseases, Emeryville, California 94608, United States
| | - Srinivasa P S Rao
- Novartis Institute of Tropical Diseases, Emeryville, California 94608, United States
| | - Christopher Thompson
- Novartis Institutes for Biomedical Research, Cambridge, Massachusetts 02139, United States
| | - Tove Tuntland
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California 92121, United States
| | - Glen Spraggon
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California 92121, United States
| | - Richard J Glynne
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California 92121, United States
| | - Frantisek Supek
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California 92121, United States
| | | | - Valentina Molteni
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California 92121, United States
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2
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Sharma T, Yeh V, Debanne S, Bordeaux J. 196 Perceived magnitude of skin cancer risk reduction predicts sunscreen use. J Invest Dermatol 2017. [DOI: 10.1016/j.jid.2017.02.211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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3
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Shaw DE, Baig F, Bruce I, Chamoin S, Collingwood SP, Cross S, Dayal S, Drückes P, Furet P, Furminger V, Haggart D, Hussey M, Konstantinova I, Loren JC, Molteni V, Roberts S, Reilly J, Saunders AM, Stringer R, Sviridenko L, Thomas M, Thomson CG, Tomlins C, Wen B, Yeh V, Pearce AC. Optimization of Platelet-Derived Growth Factor Receptor (PDGFR) Inhibitors for Duration of Action, as an Inhaled Therapy for Lung Remodeling in Pulmonary Arterial Hypertension. J Med Chem 2016; 59:7901-14. [PMID: 27502700 DOI: 10.1021/acs.jmedchem.6b00703] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
A series of potent PDGFR inhibitors has been identified. The series was optimized for duration of action in the lung. A novel kinase occupancy assay was used to directly measure target occupancy after i.t. dosing. Compound 25 shows 24 h occupancy of the PDGFR kinase domain, after a single i.t. dose and has efficacy at 0.03 mg/kg, in the rat moncrotaline model of pulmonary arterial hypertension. Examination of PK/PD data from the optimization effort has revealed in vitro:in vivo correlations which link duration of action in vivo with low permeability and high basicity and demonstrate that nonspecific binding to lung tissue increases with lipophilicity.
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Affiliation(s)
- Duncan E Shaw
- Novartis Institutes of Biomedical Research (NIBR) , 100 Technology Square, Cambridge, Massachusetts 02139, United States
| | | | | | | | | | - Sarah Cross
- Novartis Institutes of Biomedical Research (NIBR) , 100 Technology Square, Cambridge, Massachusetts 02139, United States
| | | | - Peter Drückes
- NIBR , Basel Fabrikstrasse 2, 4056 Basel, Switzerland
| | - Pascal Furet
- NIBR , Basel Fabrikstrasse 2, 4056 Basel, Switzerland
| | | | - Deborah Haggart
- Genomics Institute of the Novartis Research Foundation , 10675 John Jay Hopkins Drive, San Diego, California 92121, United States
| | | | | | - Jon C Loren
- Genomics Institute of the Novartis Research Foundation , 10675 John Jay Hopkins Drive, San Diego, California 92121, United States
| | - Valentina Molteni
- Genomics Institute of the Novartis Research Foundation , 10675 John Jay Hopkins Drive, San Diego, California 92121, United States
| | | | | | | | | | | | | | - Christopher G Thomson
- Novartis Institutes of Biomedical Research (NIBR) , 100 Technology Square, Cambridge, Massachusetts 02139, United States
| | | | - Ben Wen
- Genomics Institute of the Novartis Research Foundation , 10675 John Jay Hopkins Drive, San Diego, California 92121, United States
| | - Vince Yeh
- Genomics Institute of the Novartis Research Foundation , 10675 John Jay Hopkins Drive, San Diego, California 92121, United States
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4
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Khare S, Roach SL, Barnes SW, Hoepfner D, Walker JR, Chatterjee AK, Neitz RJ, Arkin MR, McNamara CW, Ballard J, Lai Y, Fu Y, Molteni V, Yeh V, McKerrow JH, Glynne RJ, Supek F. Utilizing Chemical Genomics to Identify Cytochrome b as a Novel Drug Target for Chagas Disease. PLoS Pathog 2015; 11:e1005058. [PMID: 26186534 PMCID: PMC4506092 DOI: 10.1371/journal.ppat.1005058] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Accepted: 06/30/2015] [Indexed: 11/19/2022] Open
Abstract
Unbiased phenotypic screens enable identification of small molecules that inhibit pathogen growth by unanticipated mechanisms. These small molecules can be used as starting points for drug discovery programs that target such mechanisms. A major challenge of the approach is the identification of the cellular targets. Here we report GNF7686, a small molecule inhibitor of Trypanosoma cruzi, the causative agent of Chagas disease, and identification of cytochrome b as its target. Following discovery of GNF7686 in a parasite growth inhibition high throughput screen, we were able to evolve a GNF7686-resistant culture of T. cruzi epimastigotes. Clones from this culture bore a mutation coding for a substitution of leucine by phenylalanine at amino acid position 197 in cytochrome b. Cytochrome b is a component of complex III (cytochrome bc1) in the mitochondrial electron transport chain and catalyzes the transfer of electrons from ubiquinol to cytochrome c by a mechanism that utilizes two distinct catalytic sites, QN and QP. The L197F mutation is located in the QN site and confers resistance to GNF7686 in both parasite cell growth and biochemical cytochrome b assays. Additionally, the mutant cytochrome b confers resistance to antimycin A, another QN site inhibitor, but not to strobilurin or myxothiazol, which target the QP site. GNF7686 represents a promising starting point for Chagas disease drug discovery as it potently inhibits growth of intracellular T. cruzi amastigotes with a half maximal effective concentration (EC50) of 0.15 µM, and is highly specific for T. cruzi cytochrome b. No effect on the mammalian respiratory chain or mammalian cell proliferation was observed with up to 25 µM of GNF7686. Our approach, which combines T. cruzi chemical genetics with biochemical target validation, can be broadly applied to the discovery of additional novel drug targets and drug leads for Chagas disease. Chagas Disease, or American trypanosomiasis, is caused by the kinetoplastid protozoan Trypanosoma cruzi and is primarily transmitted to a mammalian host via a triatomine insect vector (the “kissing bug”) infected with T. cruzi parasites. Although discovered in 1909 by the physician Dr. Carlos Chagas, the disease gained recognition by the public health community only following a major outbreak in Brazil during the 1960s. Approximately eight million people (primarily in Central and South America) are infected with T. cruzi and cases are becoming more widespread due to migration out of the endemic regions. Current treatment options have severe problems with toxicity, limited efficacy, and long administration. Hence, discovery of new drugs for treatment of Chagas disease has become of prime interest to the biomedical research community. In this study, we report identification of a potent inhibitor of T. cruzi growth and use a chemical genetics-based approach to elucidate the associated mechanism of action. We found that this compound, GNF7686, targets cytochrome b, a component of the mitochondrial electron transport chain crucial for ATP generation. Our study provides new insights into the use of phenotypic screening to identify novel targets for kinetoplastid drug discovery.
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Affiliation(s)
- Shilpi Khare
- Department of Genetics and Neglected Diseases, Genomics Institute of the Novartis Research Foundation, San Diego, California, United States of America
| | - Steven L. Roach
- Department of Medicinal Chemistry, Genomics Institute of the Novartis Research Foundation, San Diego, California, United States of America
| | - S. Whitney Barnes
- Department of Genetics and Neglected Diseases, Genomics Institute of the Novartis Research Foundation, San Diego, California, United States of America
| | - Dominic Hoepfner
- Novartis Institutes for BioMedical Research, Novartis Campus, Basel, Switzerland
| | - John R. Walker
- Department of Genetics and Neglected Diseases, Genomics Institute of the Novartis Research Foundation, San Diego, California, United States of America
| | - Arnab K. Chatterjee
- Department of Medicinal Chemistry, Genomics Institute of the Novartis Research Foundation, San Diego, California, United States of America
| | - R. Jeffrey Neitz
- Small Molecule Discovery Center and Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, California, United States of America
| | - Michelle R. Arkin
- Small Molecule Discovery Center and Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, California, United States of America
| | - Case W. McNamara
- Department of Genetics and Neglected Diseases, Genomics Institute of the Novartis Research Foundation, San Diego, California, United States of America
| | - Jaime Ballard
- Department of Genetics and Neglected Diseases, Genomics Institute of the Novartis Research Foundation, San Diego, California, United States of America
| | - Yin Lai
- Department of Genetics and Neglected Diseases, Genomics Institute of the Novartis Research Foundation, San Diego, California, United States of America
| | - Yue Fu
- Department of Genetics and Neglected Diseases, Genomics Institute of the Novartis Research Foundation, San Diego, California, United States of America
| | - Valentina Molteni
- Department of Medicinal Chemistry, Genomics Institute of the Novartis Research Foundation, San Diego, California, United States of America
| | - Vince Yeh
- Department of Medicinal Chemistry, Genomics Institute of the Novartis Research Foundation, San Diego, California, United States of America
| | - James H. McKerrow
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, California, United States of America
| | - Richard J. Glynne
- Department of Genetics and Neglected Diseases, Genomics Institute of the Novartis Research Foundation, San Diego, California, United States of America
| | - Frantisek Supek
- Department of Genetics and Neglected Diseases, Genomics Institute of the Novartis Research Foundation, San Diego, California, United States of America
- * E-mail:
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Neitz RJ, Chen S, Supek F, Yeh V, Kellar D, Gut J, Bryant C, Gallardo-Godoy A, Molteni V, Roach SL, Chatterjee AK, Robertson S, Renslo AR, Arkin M, Glynne R, McKerrow J, Siqueira-Neto JL. Lead Identification to Clinical Candidate Selection. ACTA ACUST UNITED AC 2014; 20:101-11. [DOI: 10.1177/1087057114553103] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Chagas disease affects 8 million people worldwide and remains a main cause of death due to heart failure in Latin America. The number of cases in the United States is now estimated to be 300,000, but there are currently no Food and Drug Administration (FDA)–approved drugs available for patients with Chagas disease. To fill this gap, we have established a public-private partnership between the University of California, San Francisco and the Genomics Institute of the Novartis Research Foundation (GNF) with the goal of delivering clinical candidates to treat Chagas disease. The discovery phase, based on the screening of more than 160,000 compounds from the GNF Academic Collaboration Library, led to the identification of new anti-Chagas scaffolds. Part of the screening campaign used and compared two screening methods, including a colorimetric-based assay using Trypanosoma cruzi expressing β-galactosidase and an image-based, high-content screening (HCS) assay using the CA-I/72 strain of T. cruzi. Comparing molecules tested in both assays, we found that ergosterol biosynthesis inhibitors had greater potency in the colorimetric assay than in the HCS assay. Both assays were used to inform structure-activity relationships for antiparasitic efficacy and pharmacokinetics. A new anti– T. cruzi scaffold derived from xanthine was identified, and we describe its development as lead series.
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Affiliation(s)
- R. Jeffrey Neitz
- Small Molecule Discovery Center and Department of Pharmaceutical Chemistry, University of California, San Francisco, CA, USA
| | - Steven Chen
- Small Molecule Discovery Center and Department of Pharmaceutical Chemistry, University of California, San Francisco, CA, USA
| | - Frantisek Supek
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, CA, USA
| | - Vince Yeh
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, CA, USA
| | - Danielle Kellar
- Center for Discovery and Innovation in Parasitic Diseases, University of California, San Francisco, CA, USA
- Department of Pathology, University of California, San Francisco, CA, USA
- Five Prime Therapeutics, San Francisco, CA, USA
| | - Jiri Gut
- Center for Discovery and Innovation in Parasitic Diseases, University of California, San Francisco, CA, USA
- Department of Pathology, University of California, San Francisco, CA, USA
| | - Clifford Bryant
- Small Molecule Discovery Center and Department of Pharmaceutical Chemistry, University of California, San Francisco, CA, USA
| | - Alejandra Gallardo-Godoy
- Small Molecule Discovery Center and Department of Pharmaceutical Chemistry, University of California, San Francisco, CA, USA
| | - Valentina Molteni
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, CA, USA
| | - Steven L. Roach
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, CA, USA
- Dart Neuroscience, San Diego, CA, USA
| | - Arnab K. Chatterjee
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, CA, USA
- California Institute for Biomedical Research (Calibr), San Diego, CA, USA
| | - Stephanie Robertson
- Innovation, Technology, and Alliances, University of California, San Francisco, CA, USA
| | - Adam R. Renslo
- Small Molecule Discovery Center and Department of Pharmaceutical Chemistry, University of California, San Francisco, CA, USA
| | - Michelle Arkin
- Small Molecule Discovery Center and Department of Pharmaceutical Chemistry, University of California, San Francisco, CA, USA
| | - Richard Glynne
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, CA, USA
| | - James McKerrow
- Center for Discovery and Innovation in Parasitic Diseases, University of California, San Francisco, CA, USA
- Department of Pathology, University of California, San Francisco, CA, USA
- Skaggs School of Pharmacy and Pharmaceutical Science, University of California, San Diego, CA, USA
| | - Jair L. Siqueira-Neto
- Center for Discovery and Innovation in Parasitic Diseases, University of California, San Francisco, CA, USA
- Department of Pathology, University of California, San Francisco, CA, USA
- Skaggs School of Pharmacy and Pharmaceutical Science, University of California, San Diego, CA, USA
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Park P, Cote D, Yeh V, Schulak J, Sanchez E, Sarabu N, Augustine J, Ammori J, Woodside K. Screening Colonoscopy Should Be Required Prior to Kidney Transplant. Transplantation 2014. [DOI: 10.1097/00007890-201407151-00727] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Tang SJ, Lee CY, Huang CC, Chang TR, Cheng CM, Tsuei KD, Jeng HT, Yeh V, Chiang TC. Electronic versus lattice match for metal-semiconductor epitaxial growth: Pb on Ge(111). Phys Rev Lett 2011; 107:066802. [PMID: 21902356 DOI: 10.1103/physrevlett.107.066802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2011] [Indexed: 05/31/2023]
Abstract
Lattice match is important for epitaxial growth. We show that a competing mechanism, electronic match, can dominate at small film thicknesses for metal-semiconductor systems, where quantum confinement and symmetry requirements may favor a different growth pattern. For Pb(111) on Ge(111), an accidental lattice match leads to a √3 × √3 configuration involving a 30° in-plane rotation at large film thicknesses, but it gives way to an incommensurate (1 × 1) configuration at small film thickness. The transformation follows an approximately inverse-film-thickness dependence with superimposed bilayer oscillations.
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Affiliation(s)
- S-J Tang
- Department of Physics, National Tsing Hua University, Hsinchu, Taiwan.
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8
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Lin CI, Tseng CM, Lee YD, Yeh V, Huang YL. Raman scattering and growth disorders in single as-grown TiO2 nanowires. Nanotechnology 2011; 22:285707. [PMID: 21646697 DOI: 10.1088/0957-4484/22/28/285707] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
An oxidation procedure has been developed to grow single-crystalline TiO(2) nanowires of the pure rutile phase, allowing subsequent characterizations of SEM, XRD, Raman, and TEM without any post-growth preparations. TEM observations support that the 1D anisotropic growth is dominated by oriented attachment processes, leading to typical growth-induced defects in the nanowires. Spatial variations of the rutile E(g) and A(1g) Raman modes were unambiguously revealed on single nanowires while scanned along the growth direction parallel to the rutile [110]. Symmetry-sensitive deviations were identified by comparing the Raman data with the spatial correlation model calculations based on realistic dispersion relations of the rutile, reflecting morphology-correlated defect distributions along single nanowires. This work provides an efficient, non-destructive in situ characterization approach for guiding growth design in future nanotechnology.
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Affiliation(s)
- C I Lin
- Department of Physics, National Dong Hwa University, Hualien 97401, Taiwan
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9
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Chuang FC, Lin WH, Huang ZQ, Hsu CH, Kuo CC, Ozolins V, Yeh V. Electronic structures of an epitaxial graphene monolayer on SiC(0001) after gold intercalation: a first-principles study. Nanotechnology 2011; 22:275704. [PMID: 21597151 DOI: 10.1088/0957-4484/22/27/275704] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The atomic and electronic structures of an Au-intercalated graphene monolayer on the SiC(0001) surface were investigated using first-principles calculations. The unique Dirac cone of graphene near the K point reappeared as the monolayer was intercalated by Au atoms. Coherent interfaces were used to study the mismatch and the strain at the boundaries. Our calculations showed that the strain at the graphene/Au and Au/SiC(0001) interfaces also played a key role in the electronic structures. Furthermore, we found that at an Au coverage of 3/8 ML, Au intercalation leads to a strong n-type doping of graphene. At 9/8 ML, it exhibited a weak p-type doping, indicative that graphene was not fully decoupled from the substrate. The shift in the Dirac point resulting from the electronic doping was not only due to the different electronegativities but also due to the strain at the interfaces. Our calculated positions of the Dirac points are consistent with those observed in the ARPES experiment (Gierz et al 2010 Phys. Rev. B 81 235408).
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Affiliation(s)
- Feng-Chuan Chuang
- Department of Physics, National Sun Yat-Sen University, Kaohsiung 804, Taiwan.
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Abstract
IMPORTANCE OF THE FIELD Liver X receptors (LXRs) are ligand activated transcription factors involved in cholesterol metabolism, glucose homeostasis, inflammation and lipogenesis. With the important physiological role of LXRs in reverse cholesterol transport (RCT), atherosclerosis is the best investigated therapeutic indication. While atherosclerosis is not yet clinically validated, Wyeth's LXRalpha/beta agonist LXR-623 indicated the key LXR target genes involved in RCT (ABCA1 and ABCG1) are upregulated in peripheral blood cells in a dose-dependent manner. While discontinued for CNS safety concerns, investigation of LXR-623 supports atherosclerosis as a clinical indication, and the possibility of identifying LXR agonists with profiles that avoid the strong lipogenic effects of full LXRalpha/beta agonists. AREAS COVERED IN THIS REVIEW Patents for LXR agonists from late 2006 up to August 2009 with emphasis on chemical matters and relationship to earlier disclosures, the biological data associated with selected analogues and therapeutic indications. WHAT THE READER WILL GAIN An overview of the majority of LXR scaffolds with representative structure activity relationships as well as the companies that are the chief players in the field. TAKE HOME MESSAGE The future application of LXR agonists depends upon the discovery of LXR agents without lipogenic effects. Limiting activation of LXRalpha is a popular strategy.
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Affiliation(s)
- Xiaolin Li
- Genomics Institute of the Novartis Research Foundation, Department of Medicinal Chemistry, San Diego, CA 92121, USA
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Vazquez-Figueroa E, Yeh V, Broering JM, Chaparro-Riggers JF, Bommarius AS. Thermostable variants constructed via the structure-guided consensus method also show increased stability in salts solutions and homogeneous aqueous-organic media. Protein Eng Des Sel 2008; 21:673-80. [PMID: 18799474 DOI: 10.1093/protein/gzn048] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Enzyme instability is a major factor preventing widespread adoption of enzymes for catalysis. Stability at high temperatures and in the presence of high salt concentrations and organic solvents would allow enzymes to be employed for transformations of compounds not readily soluble in low temperature or in purely aqueous systems. Furthermore, many redox enzymes require costly cofactors for function and consequently a robust cofactor regeneration system. In this work, we demonstrate how thermostable variants developed via an amino acid sequence-based consensus method also showed improved stability in solutions with high concentrations of kosmotropic and chaotropic salts and water-miscible organic solvents. This is invaluable to protein engineers since deactivation in salt solutions and organic solvents is not well understood, rendering a priori design of enzyme stability in these media difficult. Variants of glucose 1-dehydrogenase (GDH) were studied in solutions of different salts along the Hofmeister series and in the presence of varying amounts of miscible organic solvent. Only the most stable variants showed little deactivation dependence on salt-type and salt concentration. Kinetic stability, expressed by the deactivation rate constant k(d,obs), did not always correlate with thermodynamic stability of variants, as measured by melting temperature T(m). However, a strong correlation (R(2) > 0.95) between temperature stability and organic solvent stability was found when plotting T(50)(60) versus C(50)(60) values. All GDH variants retained stability in homogeneous aqueous-organic solvents with >80% v/v of organic solvent.
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Affiliation(s)
- E Vazquez-Figueroa
- School of Chemical and Biomolecular Engineering, Parker H. Petit Institute for Bioengineering and Bioscience, Atlanta, GA 30332-0363, USA
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Yeh V, Berbil-Bautista L, Wang CZ, Ho KM, Tringides MC. Role of the Metal/Semiconductor interface in quantum size effects: Pb /Si(111). Phys Rev Lett 2000; 85:5158-5161. [PMID: 11102210 DOI: 10.1103/physrevlett.85.5158] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2000] [Indexed: 05/23/2023]
Abstract
Self-organized islands of uniform heights can form at low temperatures on metal/semiconductor systems as a result of quantum size effects, i.e., the occupation of discrete electron energy levels in the film. We compare the growth mode on two different substrates [Si(111)- (7x7) vs Si(111)- Pb(sqrt[3]xsqrt[3] )] with spot profile analysis low-energy electron diffraction. For the same growth conditions (of coverage and temperature) 7-step islands are the most stable islands on the (7x7) phase, while 5-step (but larger islands) are the most stable islands on the (sqrt[3]xsqrt[3] ). A theoretical calculation suggests that the height selection on the two interfaces can be attributed to the amount of charge transfer at the interface.
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Affiliation(s)
- V Yeh
- Department of Physics, Iowa State University, Ames, Iowa and and Ames Laboratory, U.S.-DOE, Ames, Iowa 50011, USA
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Yeh V, Hopp ML, Goldstein NS, Meyer RD. Herpes simplex chronic laryngitis and vocal cord lesions in a patient with acquired immunodeficiency syndrome. Ann Otol Rhinol Laryngol 1994; 103:726-31. [PMID: 8085735 DOI: 10.1177/000348949410300912] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Chronic laryngitis in patients with acquired immunodeficiency syndrome may be due to infections or tumors, such as Kaposi's sarcoma and non-Hodgkin's lymphoma. We present what we believe to be the first proven case of herpes simplex virus chronic laryngitis in a man positive for human immunodeficiency virus. Direct laryngoscopy showed leukoplakic lesions on both vocal cords. Biopsy of the lesions showed squamous epithelial cells with the characteristic features of herpes simplex virus, which was confirmed by immunohistochemical stains. We discuss the differential diagnosis of chronic laryngitis in a human immunodeficiency virus infection. Herpes simplex viral infection of the vocal cords should be considered in patients with acquired immunodeficiency syndrome presenting with chronic hoarseness and leukoplakic lesions on direct laryngoscopy, especially with no evidence of Kaposi's sarcoma, tumor, or cytomegaloviral or fungal infection elsewhere. Treatment should be acyclovir, except in the face of acyclovir resistance.
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Affiliation(s)
- V Yeh
- Department of Medicine, Cedars-Sinai Medical Center, Cedars-Sinai Research Institute, Los Angeles, California
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Abstract
Atovaquone is a new hydroxynapthoquinone antiprotozoal agent active against Pneumocystis carinii in vitro and in animal models. The authors report an experience using atovaquone to treat 25 patients with mild to moderate P. carinii pneumonia. Eligible patients were treated for 21 days with 750 mg of atovaquone orally three times daily. Prednisone was added when the P(A-a)O2 gradient was between 35-45 mm Hg. Patients were treated under three treatment protocols. Patients in Group 1 participated in one of two randomized comparative drug trials, designed for patients with and without sulfonamide intolerance. Six of seven patients successfully completed treatment, and one patient discontinued treatment because of an adverse reaction (> 5 times baseline increase in transaminase level). Patients in Group 2 were treated with atovaquone for mild to moderate P. carinii pneumonia under a treatment Investigational New Drug protocol because of prior sulfonamide reactions. Fifteen of these 18 patients successfully completed treatment; one died from other complications during treatment and two discontinued treatment for adverse reactions (> 5 times baseline increase in transaminase levels, and a diffuse rash). Serum transaminase levels returned to normal at the end of treatment in all patients with elevated levels. All patients demonstrated clinical resolution of their pneumonia and improvement of pretreatment hypoxemia (Group 1: pretreatment PaO2 = 82 +/- 14 mm Hg, posttreatment PaO2 = 92 +/- 9 mm Hg). Overall, 21 (84%) of 25 patients successfully finished therapy without significant adverse reactions. Atovaquone appears to be an effective and well-tolerated oral treatment for mild to moderate P. carinii pneumonia.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- L J Epstein
- Division of Pulmonary and Critical Care Medicine, Wilford Hall Medical Center, Lackland Air Force Base, San Antonio, Texas
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