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Knispel T, Berges J, Schobert A, van Loon EGCP, Jolie W, Wehling T, Michely T, Fischer J. Unconventional Charge-Density-Wave Gap in Monolayer NbS 2. Nano Lett 2024; 24:1045-1051. [PMID: 38232959 PMCID: PMC10835735 DOI: 10.1021/acs.nanolett.3c02787] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2024]
Abstract
Using scanning tunneling microscopy and spectroscopy, for a monolayer of transition metal dichalcogenide H-NbS2 grown by molecular beam epitaxy on graphene, we provide unambiguous evidence for a charge density wave (CDW) with a 3 × 3 superstructure, which is not present in bulk NbS2. Local spectroscopy displays a pronounced gap on the order of 20 meV at the Fermi level. Within the gap, low-energy features are present. The gap structure with its low-energy features is at variance with the expectation for a gap opening in the electronic band structure due to a CDW. Instead, comparison with ab initio calculations indicates that the observed gap structure must be attributed to combined electron-phonon quasiparticles. The phonons in question are the elusive amplitude and phase collective modes of the CDW transition. Our findings advance the understanding of CDW mechanisms in 2D materials and their spectroscopic signatures.
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Affiliation(s)
- Timo Knispel
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, D-50937 Köln, Germany
| | - Jan Berges
- U Bremen Excellence Chair, Bremen Center for Computational Materials Science, and MAPEX Center for Materials and Processes, University of Bremen, D-28359 Bremen, Germany
| | - Arne Schobert
- I. Institute of Theoretical Physics, Universität Hamburg, D-22607 Hamburg, Germany
| | - Erik G C P van Loon
- NanoLund and Division of Mathematical Physics, Department of Physics, Lund University, SE-22100 Lund, Sweden
| | - Wouter Jolie
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, D-50937 Köln, Germany
| | - Tim Wehling
- I. Institute of Theoretical Physics, Universität Hamburg, D-22607 Hamburg, Germany
- The Hamburg Centre for Ultrafast Imaging, Luruper Chaussee 149, D-22761 Hamburg, Germany
| | - Thomas Michely
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, D-50937 Köln, Germany
| | - Jeison Fischer
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, D-50937 Köln, Germany
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2
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Jolie W, Lux J, Pörtner M, Dombrowski D, Herbig C, Knispel T, Simon S, Michely T, Rosch A, Busse C. Suppression of Quasiparticle Scattering Signals in Bilayer Graphene Due to Layer Polarization and Destructive Interference. Phys Rev Lett 2018; 120:106801. [PMID: 29570315 DOI: 10.1103/physrevlett.120.106801] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Revised: 01/29/2018] [Indexed: 06/08/2023]
Abstract
We study chemically gated bilayer graphene using scanning tunneling microscopy and spectroscopy complemented by tight-binding calculations. Gating is achieved by intercalating Cs between bilayer graphene and Ir(111), thereby shifting the conduction band minima below the chemical potential. Scattering between electronic states (both intraband and interband) is detected via quasiparticle interference. However, not all expected processes are visible in our experiment. We uncover two general effects causing this suppression: first, intercalation leads to an asymmetrical distribution of the states within the two layers, which significantly reduces the scanning tunneling spectroscopy signal of standing waves mainly present in the lower layer; second, forward scattering processes, connecting points on the constant energy contours with parallel velocities, do not produce pronounced standing waves due to destructive interference. We present a theory to describe the interference signal for a general n-band material.
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Affiliation(s)
- Wouter Jolie
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany
- Institut für Materialphysik, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Straße 10, 48149 Münster, Germany
| | - Jonathan Lux
- Institut für Theoretische Physik, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany
| | - Mathias Pörtner
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany
| | - Daniela Dombrowski
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany
- Institut für Materialphysik, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Straße 10, 48149 Münster, Germany
| | - Charlotte Herbig
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany
| | - Timo Knispel
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany
| | - Sabina Simon
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany
| | - Thomas Michely
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany
| | - Achim Rosch
- Institut für Theoretische Physik, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany
| | - Carsten Busse
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany
- Institut für Materialphysik, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Straße 10, 48149 Münster, Germany
- Department Physik, Universität Siegen, 57068 Siegen, Germany
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Simon S, Voloshina E, Tesch J, Förschner F, Enenkel V, Herbig C, Knispel T, Tries A, Kröger J, Dedkov Y, Fonin M. Layer-by-Layer Decoupling of Twisted Graphene Sheets Epitaxially Grown on a Metal Substrate. Small 2018; 14:e1703701. [PMID: 29450969 DOI: 10.1002/smll.201703701] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Revised: 12/23/2017] [Indexed: 06/08/2023]
Abstract
The electronic properties of graphene can be efficiently altered upon interaction with the underlying substrate resulting in a dramatic change of charge carrier behavior. Here, the evolution of the local electronic properties of epitaxial graphene on a metal upon the controlled formation of multilayers, which are produced by intercalation of atomic carbon in graphene/Ir(111), is investigated. Using scanning tunneling microscopy and Landau-level spectroscopy, it is shown that for a monolayer and bilayers with small-angle rotations, Landau levels are fully suppressed, indicating that the metal-graphene interaction is largely confined to the first graphene layer. Bilayers with large twist angles as well as twisted trilayers demonstrate a sequence of pronounced Landau levels characteristic for a free-standing graphene monolayer pointing toward an effective decoupling of the top layer from the metal substrate. These findings give evidence for the controlled preparation of epitaxial graphene multilayers with a different degree of decoupling, which represent an ideal platform for future electronic and spintronic applications.
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Affiliation(s)
- Sabina Simon
- Department of Physics, University of Konstanz, 78457, Konstanz, Germany
| | - Elena Voloshina
- Physics Department, Shanghai University, Shanghai, 200444, China
| | - Julia Tesch
- Department of Physics, University of Konstanz, 78457, Konstanz, Germany
| | - Felix Förschner
- Department of Physics, University of Konstanz, 78457, Konstanz, Germany
| | - Vivien Enenkel
- Department of Physics, University of Konstanz, 78457, Konstanz, Germany
| | - Charlotte Herbig
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937, Köln, Germany
- Department of Physics, University of California at Berkeley, Berkeley, CA, 94720, USA
| | - Timo Knispel
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937, Köln, Germany
| | - Alexander Tries
- Institut für Physik, Technische Universität Ilmenau, 98693, Ilmenau, Germany
| | - Jörg Kröger
- Institut für Physik, Technische Universität Ilmenau, 98693, Ilmenau, Germany
| | - Yuriy Dedkov
- Physics Department, Shanghai University, Shanghai, 200444, China
| | - Mikhail Fonin
- Department of Physics, University of Konstanz, 78457, Konstanz, Germany
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Herbig C, Knispel T, Simon S, Schröder UA, Martínez-Galera AJ, Arman MA, Teichert C, Knudsen J, Krasheninnikov AV, Michely T. From Permeation to Cluster Arrays: Graphene on Ir(111) Exposed to Carbon Vapor. Nano Lett 2017; 17:3105-3112. [PMID: 28426934 DOI: 10.1021/acs.nanolett.7b00550] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Our scanning tunneling microscopy and X-ray photoelectron spectroscopy experiments along with first-principles calculations uncover the rich phenomenology and enable a coherent understanding of carbon vapor interaction with graphene on Ir(111). At high temperatures, carbon vapor not only permeates to the metal surface but also densifies the graphene cover. Thereby, in addition to underlayer graphene growth, upon cool down also severe wrinkling of the densified graphene cover is observed. In contrast, at low temperatures the adsorbed carbon largely remains on top and self-organizes into a regular array of fullerene-like, thermally highly stable clusters that are covalently bonded to the underlying graphene sheet. Thus, a new type of predominantly sp2-hybridized nanostructured and ultrathin carbon material emerges, which may be useful to encage or stably bind metal in finely dispersed form.
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Affiliation(s)
- Charlotte Herbig
- II. Physikalisches Institut, Universität zu Köln , Zülpicher Straße 77, 50937 Köln, Germany
| | - Timo Knispel
- II. Physikalisches Institut, Universität zu Köln , Zülpicher Straße 77, 50937 Köln, Germany
| | - Sabina Simon
- II. Physikalisches Institut, Universität zu Köln , Zülpicher Straße 77, 50937 Köln, Germany
| | - Ulrike A Schröder
- II. Physikalisches Institut, Universität zu Köln , Zülpicher Straße 77, 50937 Köln, Germany
| | | | | | - Christian Teichert
- II. Physikalisches Institut, Universität zu Köln , Zülpicher Straße 77, 50937 Köln, Germany
| | | | - Arkady V Krasheninnikov
- Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf , 01328 Dresden, Germany
- Department of Applied Physics, Aalto University School of Science , P.O. Box 11100, 00076 Aalto, Finland
| | - Thomas Michely
- II. Physikalisches Institut, Universität zu Köln , Zülpicher Straße 77, 50937 Köln, Germany
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Balzarini J, Aquaro S, Knispel T, Rampazzo C, Bianchi V, Perno CF, De Clercq E, Meier C. Cyclosaligenyl-2',3'-didehydro-2',3'-dideoxythymidine monophosphate: efficient intracellular delivery of d4TMP. Mol Pharmacol 2000; 58:928-35. [PMID: 11040039 DOI: 10.1124/mol.58.5.928] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [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: 11/22/2022] Open
Abstract
Cyclosaligenyl-2',3'-didehydro-2', 3'-dideoxythymidine-5'-monophosphate (cycloSal-d4TMP) is a potent and selective inhibitor of human immunodeficiency virus replication in cell culture and differs from other nucleotide prodrug approaches in that it is designed to selectively deliver the nucleotide 5'-monophosphate by a controlled, chemically induced hydrolysis. Its antiviral efficacy in cell culture is at least as good as, if not superior to, that of d4T. CycloSal-d4TMP was found to lead to the efficient intracellular release of d4TMP in a variety of cell lines, including both wild-type CEM and thymidine kinase-deficient CEM/TK(-) cells. Under similar experimental conditions, exposure of CEM/TK(-) cells to d4T failed to result in significant d4TTP levels. The intracellular conversion of cycloSal-d4TMP proved to be both time and dose dependent. The half-life of d4TTP generated intracellularly from d4T- or cycloSal-d4TMP-treated CEM cells was approximately 3.5 h, and the intracellular ratios of d4TTP/d4TMP in cells exposed to cycloSal-d4TMP gradually increased from 1 to 3.4 upon prolonged incubation. Radiolabeled cycloSal-d4TMP could be separated as its two R(p) and S(p) diastereomers on high-performance liquid chromatography. The R(p) diastereomer of cycloSal-d4TMP was 3- to 7-fold more efficient in releasing d4TMP and generating d4TTP than the S(p) cycloSal-d4TMP diastereomer. This correlated well with the 5-fold more pronounced antiviral activity of the R(p) diastereomer versus the S(p) diastereomer. d4TMP is a poor substrate for the cytosolic 5'(3')-deoxyribonucleotidase (V(max)/K(m) for d4TMP: 0.08 of V(max)/K(m) for dTMP) and is only slowly hydrolyzed to d4T. This contributes to the efficient conversion of the prodrug of d4TTP.
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Affiliation(s)
- J Balzarini
- Rega Institute for Medical Research, Katholieke Universiteit Leuven, Leuven, Belgium.
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Mu L, Sarafianos SG, Nicklaus MC, Russ P, Siddiqui MA, Ford H, Mitsuya H, Le R, Kodama E, Meier C, Knispel T, Anderson L, Barchi JJ, Marquez VE. Interactions of conformationally biased north and south 2'-fluoro-2', 3'-dideoxynucleoside 5'-triphosphates with the active site of HIV-1 reverse transcriptase. Biochemistry 2000; 39:11205-15. [PMID: 10985766 DOI: 10.1021/bi001090n] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [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: 11/28/2022]
Abstract
Molecular dynamics simulations of a ternary complex of HIV-1 reverse transcriptase (RT), double-stranded DNA, and bound dideoxynucleoside-5'-triphosphate (RT-DNA-ddNTP), utilizing the ddNTPs ddATP, betaFddATP, and alphaFddATP, explain the experimentally observed order of potency of these 5'-triphosphates as inhibitors of RT: ddATP > betaFddATP > alphaFddATP. On the basis of RT's known preference to bind the incoming dNTP (or ddNTP) with a north conformation at the polymerase site, alphaFddATP, which in solution prefers almost exclusively a north conformation, was predicted to be the most potent inhibitor. However, Tyr115, which appears to function as a steric gate to preclude the binding of ribonucleoside 5'-triphosphates, prevents the effective binding of alphaFddATP in its preferred north conformation. The south-biased betaFddATP, while able to bind to RT without hindrance by Tyr115, has to pay a high energy penalty to be flipped to the active north conformation at the polymerase site. Finally, the more flexible and less conformationally biased ddATP is able to switch to a north conformation at the RT site with a smaller energy penalty than betaFddATP. These results highlight the opposite conformational preferences of HIV-1 RT for alphaFddATP and betaFddATP and help establish conformational guidelines for optimal binding at the polymerase site of this enzyme.
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Affiliation(s)
- L Mu
- Laboratory of Medicinal Chemistry, Division of Basic Sciences, and Experimental Retrovirology Section, Medicine Branch, Division of Clinical Sciences, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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Balzarini J, Naesens L, Aquaro S, Knispel T, Perno C, De Clercq E, Meier C. Intracellular metabolism of CycloSaligenyl 3'-azido-2', 3'-dideoxythymidine monophosphate, a prodrug of 3'-azido-2', 3'-dideoxythymidine (zidovudine). Mol Pharmacol 1999; 56:1354-61. [PMID: 10570065 DOI: 10.1124/mol.56.6.1354] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [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: 11/22/2022] Open
Abstract
The administration of CycloSaligenyl 3'-azido-2',3'-dideoxythymidine monophosphate (CycloSal-AZTMP) to CEM cells resulted in a concentration- and time-dependent conversion to the 5'-monophosphate (AZTMP), 5'-diphosphate (AZTDP), and 5'-triphosphate (AZTTP) derivatives. High ratios of AZTMP/AZTTP were found in the CEM cell cultures treated with CycloSal-AZTMP. The intracellular T(1/2) of AZTTP in CEM cell cultures treated with either AZT and CycloSal-AZTMP was approximately 3 h. A variety of human T- and B-lymphocyte cell lines efficiently converted the prodrug to the AZT metabolites, whereas peripheral blood lymphocytes and primary monocyte/macrophages showed at least 10-fold lower metabolic conversion of the prodrug. CycloSal-AZTMP failed to generate marked levels of AZT metabolites in thymidine kinase-deficient CEM/TK(-) cells, an observation that is in agreement with the substantial loss of antiviral activity of CycloSal-AZTMP in CEM/TK(-) cells. The inability of CycloSal-AZTMP to generate AZTMP in CEM/TK(-) cells is presumably due to a relatively high hydrolysis rate of AZTMP to the parent nucleoside AZT, combined with the inability of CEM/TK(-) cells to phosphorylate AZT to AZTMP through the cytosolic salvage enzyme thymidine kinase.
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Affiliation(s)
- J Balzarini
- Rega Institute for Medical Research, Katholieke Universiteit Leuven, Leuven, Belgium.
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Meier C, Knispel T, Marquez VE, Siddiqui MA, De Clercq E, Balzarini J. cycloSal-Pronucleotides of 2'-fluoro-ara- and 2'-fluoro-ribo-2',3'- dideoxyadenosine as a strategy to bypass a metabolic blockade. J Med Chem 1999; 42:1615-24. [PMID: 10229630 DOI: 10.1021/jm981097r] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.1] [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: 11/29/2022]
Abstract
Novel, lipophilic cycloSal triesters 4a-c and 5a-c were synthesized, respectively, from the ara- and ribo-configurated 2'-fluorinated-2', 3'-dideoxyadenosines 2 and 3. The cycloSal phosphotriesters were used as tools to study the effects of the two different sugar pucker conformations induced by two opposite configurations of the fluorine substituent at C2' of the dideoxyribose moiety. F-ara-ddA (2) is known to be an active anti-HIV agent, whereas the ribo-analogue 3 is inactive. Hydrolysis studies with the triester precursors 4a-c and 5a-c showed selective formation of the monophosphates of 2 and 3. The lipophilicity of the triester prodrugs was considerably increased by the cycloSal mask with respect to ddA (1), F-ara-ddA (2), and F-ribo-ddA (3). Phosphotriesters 4 and 5 proved to be completely resistant to ADA and AMPDA deamination. In parallel experiments, ribo-nucleoside 3 showed a 50-fold faster deamination rate relative to the ara-analogue 2. Against HIV in CEM cells, the phosphotriesters 4 proved to be 10-fold more potent than the parent nucleoside 2. Furthermore, the prodrugs 4 were active against MSV-induced transformation of C3H/3T3 fibroblasts, while 2 was inactive. More interestingly, the ribo-configurated phosphotriesters 5, prepared from the inactive F-ribo-ddA (3), showed a level of anti-HIV activity that was even higher than that of F-ara-ddA (2). Our findings clearly prove that the application of the cycloSal-pronucleotide concept to F-ribo-ddA (3) overcomes a metabolic blockade in the formation of the corresponding monophosphate.
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Affiliation(s)
- C Meier
- Institute of Organic Chemistry, Julius-Maximilians-University Würzburg, Am Hubland, D-97074 Würzburg, Germany
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Meier C, Knispel T, De Clercq E, Balzarini J. cycloSal-Pronucleotides of 2',3'-dideoxyadenosine and 2', 3'-dideoxy-2',3'-didehydroadenosine: synthesis and antiviral evaluation of a highly efficient nucleotide delivery system. J Med Chem 1999; 42:1604-14. [PMID: 10229629 DOI: 10.1021/jm981096z] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.6] [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: 11/28/2022]
Abstract
The synthesis, hydrolysis, and antiviral evaluation of novel, lipophilic cycloSal-ddAMP (9a-d) and cycloSal-d4AMP (10a-d) derivatives of the antiviral purine dideoxynucleoside analogues 2', 3'-dideoxyadenosine (ddA) (2) and 2',3'-dideoxy-2', 3'-didehydroadenosine (d4A) (3) are reported. These potential pronucleotides release ddAMP (7) or d4AMP (8) selectively by a controlled, chemically induced tandem reaction. All new compounds 9 and 10a-d were synthesized in good yields using our previously reported phosphorus(III) method starting from substituted salicyl alcohols 14a-h. The phosphotriesters 9 and 10 were obtained with a stereochemical preference of 2:1 with respect to the configuration at the phosphorus center. In an 1-octanol/water mixture phosphotriesters 9 and 10 exhibited 7-43-fold higher lipophilicity than the parent nucleosides ddA (2) and d4A (3) as judged by their log P values. In hydrolysis studies, 9 and 10 decomposed under mild aqueous basic conditions releasing solely ddAMP (7) and d4AMP (8), as well as the diols 14. Further hydrolysis studies under acidic conditions showed a marked increase in stability with respect to the acid-catalyzed cleavage of the glycosyl bond. Phosphotriesters 9 and 10 exhibited antiviral potencies against wild-type HIV-1 and HIV-2 strains in human T-lymphocyte (CEM/O) cells that were, respectively, 100- and 600-fold higher than those of ddA (2) and d4A (3). Furthermore, all triesters 9 and 10 were markedly more active than the corresponding ddI compounds 11 and 12, which supports the concept of the delivery of the adenine nucleotides. Studies with adenosine deaminase (ADA) and adenosine monophosphate deaminase (AMPDA) showed that the triesters were not substrates for enzymatic deamination. The studies reported herein demonstrate conclusively that the cycloSal triesters deliver exclusively the nucleotides ddAMP and d4AMP, not only under chemical-simulated hydrolysis but also under intracellular conditions fulfilling the adenosine deaminase bypass premise.
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Affiliation(s)
- C Meier
- Institute of Organic Chemistry, Julius-Maximilians-University Würzburg, Am Hubland, D-97074 Würzburg, Germany
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Meier C, Knispel T, Marquez VE, De Clercq E, Balzarini J. CycloSal-2'-ara(ribo)-fluoro-2',3'-dideoxyadenosine monophosphates--an effort to solve the structure-activity relationship of 2'-fluoro-ddA. Nucleosides Nucleotides 1999; 18:907-12. [PMID: 10432708 DOI: 10.1080/15257779908041598] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Novel lipophilic cycloSal-triesters 3 and 4 from the ara- and ribo-configurated 2'-fluorinated ddAs 1 and 2, respectively, were prepared. The title compounds 3 and 4 delivered the corresponding monophosphates and thus, increasing the bioactivity or convert a formerly inactive compound into a RT inhibitor.
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Affiliation(s)
- C Meier
- Institut für Organische Chemie, Universität Hamburg, Germany
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