The Experts below are selected from a list of 333 Experts worldwide ranked by ideXlab platform
Henry F Schaefer - One of the best experts on this subject based on the ideXlab platform.
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electron attachment to solvated dgpdg effects of stacking on base centered and Phosphate centered valence bound radical anions
Chemistry: A European Journal, 2012Co-Authors: Jiande Gu, Guoming Liang, Henry F SchaeferAbstract:: To explore the nature of electron attachment to guanine-centered DNA single strands in the presence of a polarizable medium, a theoretical investigation of the DNA oligomer Dinucleoside Phosphate deoxyguanylyl-3',5'-deoxyguanosine (dGpdG) was performed by using density functional theory. Four different electron-distribution patterns for the radical anions of dGpdG in aqueous solution have been located as local minima on the potential energy surface. The excess electron is found to reside on the proton of the Phosphate group (dGp(H-)dG), or on the Phosphate group (dGp(.-)dG), or on the nucleobase at the 5' position (dG(.-)pdG), or on the nucleobase at the 3' position (dGpdG(.-)), respectively. These four radical anions are all expected to be electronically viable species under the influence of the polarizable medium. The predicted energetics of the radical anions follows the order dGp(.-)dG>dG(.-)pdG>dGpdG(.-)>dGp(H-)dG. The base-base stacking pattern in DNA single strands seems unaffected by electron attachment. On the contrary, intrastrand H-bonding is greatly influenced by electron attachment, especially in the formation of base-centered radical anions. The intrastrand H-bonding patterns revealed in this study also suggest that intrastrand proton transfer might be possible between successive guanines due to electron attachment to DNA single strands.
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electron attachment to a hydrated dna duplex the Dinucleoside Phosphate deoxyguanylyl 3 5 deoxycytidine
Chemistry: A European Journal, 2010Co-Authors: Ningbew Wong, Yaoming Xie, Henry F SchaeferAbstract:The minimal essential section of DNA helices, the Dinucleoside Phosphate deoxyguanylyl-3′,5′-deoxycytidine dimer octahydrate, [dGpdC]2, has been constructed, fully optimized, and analyzed by using quantum chemical methods at the B3LYP/6-31+G(d,p) level of theory. Study of the electrons attached to [dGpdC]2 reveals that DNA double strands are capable of capturing low-energy electrons and forming electronically stable radical anions. The relatively large vertical electron affinity (VEA) predicted for [dGpdC]2 (0.38 eV) indicates that the cytosine bases are good electron captors in DNA double strands. The structure, charge distribution, and molecular orbital analysis for the fully optimized radical anion [dGpdC]2.− suggest that the extra electron tends to be redistributed to one of the cytosine base moieties, in an electronically stable structure (with adiabatic electron affinity (AEA) 1.14 eV and vertical detachment energy (VDE) 2.20 eV). The structural features of the optimized radical anion [dGpdC]2.− also suggest the probability of interstrand proton transfer. The interstrand proton transfer leads to a distonic radical anion [d(G−H)pdC: d(C+H)pdG].−, which contains one deprotonated guanine anion and one protonated cytosine radical. This distonic radical anion is predicted to be more stable than [dGpdC]2.−. Therefore, experimental evidence for electron attachment to the DNA double helices should be related to [d(G−H)pdC:d(C+H)pdG].− complexes, for which the VDE might be as high as 2.7 eV (in dry conditions) to 3.3 eV (in fully hydrated conditions). Effects of the polarizable medium have been found to be important for increasing the electron capture ability of the dGpdC dimer. The ultimate AEA value for cytosine in DNA duplexes is predicted to be 2.03 eV in aqueous solution.
Jerzy Leszczynski - One of the best experts on this subject based on the ideXlab platform.
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electron interaction with Phosphate cytidine oligomer dcpdc base centered radical anions and their electronic spectra
Journal of Physical Chemistry B, 2014Co-Authors: Jing Wang, Jerzy LeszczynskiAbstract:Computational chemistry approach was applied to explore the nature of electron attachment to cytosine-rich DNA single strands. An oligomer Dinucleoside Phosphate deoxycytidylyl-3′,5′-deoxycytidine (dCpdC) was selected as a model system for investigations by density functional theory. Electron distribution patterns for the radical anions of dCpdC in aqueous solution were explored. The excess electron may reside on the nucleobase at the 5′ position (dC•–pdC) or at the 3′ position (dCpdC•–). From comparison with electron attachment to the cytosine related DNA fragments, the electron affinity for the formation of the cytosine-centered radical anion in DNA is estimated to be around 2.2 eV. Electron attachment to cytosine sites in DNA single strands might cause perturbations of local structural characteristics. Visible absorption spectroscopy may be applied to validate computational results and determine experimentally the existence of the base-centered radical anion. The time-dependent DFT study shows the abso...
Reto A Schwendener - One of the best experts on this subject based on the ideXlab platform.
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synthesis and in vitro antitumor activity of 2 deoxy 5 fluorouridylyl 3 5 2 deoxy 5 fluoro n4 octadecylcytidine a new amphiphilic Dinucleoside Phosphate
Liebigs Annalen, 1997Co-Authors: Herbert Schott, Peter Stephan Ludwig, Frank Gansauge, Susanne Gansauge, Reto A SchwendenerAbstract:The new amphiphilic Dinucleoside Phosphate, 2′-deoxy-5-fluorouridylyl-(3′5′)-2′-deoxy-5-fluoro-N4-octadecylcytidine (4) was synthesized on a gram scale, using the phosphotriester method, starting from the cytostatic drug 2′-deoxy-5-fluorouridine (5FdU) and 2′-deoxy-5-fluoro-N4-octadecylcytidine (1d). In in vitro clonogenic growth assays using the human pancreatic adenocarcinoma cell line MIA PaCa 2, the amphiphilic dimer was significantly more effective than the parent monomeric 5FdU. The IC50 of the dimer was 10 μg/ml when applied as an aqueous solution and 12 μg/ml when given as a liposome dispersion, whereas with 5FdU the IC50 concentration was not reached within the concentration range used.
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synthesis and in vitro antiviral properties of amphiphilic Dinucleoside Phosphate derivatives of 2 3 dideoxycytidine ddc
Antiviral Chemistry & Chemotherapy, 1995Co-Authors: Herbert Schott, Markus P Haussler, P Gowland, A Bender, H Von Briesen, Reto A SchwendenerAbstract:N 4 -hexadecyl-5'-O-(4-monomethoxytrityl)-2'-deoxycytidine-3'-hydrogenphosphonate and 5'-O-(4-monomethoxytrityl)-2'-deoxythymidine-3'-O-hydrogenphos phonate were condensed with 2',3'-dideoxycytidine (ddC) according to the hydrogenphosphonate method to yield N 4 -hexadecyl-2'-deoxycytidylyl-(3'-5')-2',3'-dideoxycytidine (N 4 -hexadecyldC-ddC) and 2'-deoxythymidylyl-(3'-5')-N 4 -palmitoyl-2',3'-dideoxycytidine (dT-N 4 -palmddC). N 4 -palmitoyl-2',3'-dideoxycytidine (N 4 -palmddC) was synthesized by reacting palmitic anhydride with ddC. Both Dinucleoside Phosphates have amphiphilic properties and represent a new class of ddC derivatives in which in the case of the Dinucleosides, the ddC-5'-monoPhosphate is masked with lipophilic residues of variable stability. The ddC derivatives can be solubilized in water by micelle formation and, because they have lipophilic residues, they can be incorporated into the lipid membranes of liposomes. The ddC derivatives were shown to have antiviral activities comparable to those of AZT and ddC when tested in vitro against HIV-1-infected HeLa and H9 cells as well as infected human monocytes/macrophages.
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synthesis and some properties of amphiphilic Dinucleoside Phosphate derivatives of 3 azido 2 3 dideoxythymidine azt
Antiviral Chemistry & Chemotherapy, 1994Co-Authors: Herbert Schott, Markus P Haussler, P Gowland, D H Horber, Reto A SchwendenerAbstract:N 4 -hexadecyl-5'-O-(4-monomethoxytrityl)-2'-deoxycytidine-3'-hydrogenPhosphate was reacted with 3'-azido-2',3'-dideoxythymidine (AZT) according to the hydrogenPhosphate method to yield N 4 -hexadecyl-2'-deoxycytidylyl-(3'-5')-3'-azido-2',3'-dideoxythymidine. N 4 -palmitoyl-5'-O-(4-monomethoxytrityl)-2'-deoxycytidine-3'-(2-chlorophenyl)-Phosphate was condensed to AZT using the triester method to give N 4 -palmitoyl-2'-deoxycytidylyl-(3'-5')-3'-azido-2',3'-dideoxythymidine. Both DinucleosidePhosphates have amphiphilic properties and represent a new class of AZT derivatives in which the polar AZT-5'-monoPhosphate is masked with lipophilic deoxycytidine residues of variable stability
Ningbew Wong - One of the best experts on this subject based on the ideXlab platform.
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electron attachment to a hydrated dna duplex the Dinucleoside Phosphate deoxyguanylyl 3 5 deoxycytidine
Chemistry: A European Journal, 2010Co-Authors: Ningbew Wong, Yaoming Xie, Henry F SchaeferAbstract:The minimal essential section of DNA helices, the Dinucleoside Phosphate deoxyguanylyl-3′,5′-deoxycytidine dimer octahydrate, [dGpdC]2, has been constructed, fully optimized, and analyzed by using quantum chemical methods at the B3LYP/6-31+G(d,p) level of theory. Study of the electrons attached to [dGpdC]2 reveals that DNA double strands are capable of capturing low-energy electrons and forming electronically stable radical anions. The relatively large vertical electron affinity (VEA) predicted for [dGpdC]2 (0.38 eV) indicates that the cytosine bases are good electron captors in DNA double strands. The structure, charge distribution, and molecular orbital analysis for the fully optimized radical anion [dGpdC]2.− suggest that the extra electron tends to be redistributed to one of the cytosine base moieties, in an electronically stable structure (with adiabatic electron affinity (AEA) 1.14 eV and vertical detachment energy (VDE) 2.20 eV). The structural features of the optimized radical anion [dGpdC]2.− also suggest the probability of interstrand proton transfer. The interstrand proton transfer leads to a distonic radical anion [d(G−H)pdC: d(C+H)pdG].−, which contains one deprotonated guanine anion and one protonated cytosine radical. This distonic radical anion is predicted to be more stable than [dGpdC]2.−. Therefore, experimental evidence for electron attachment to the DNA double helices should be related to [d(G−H)pdC:d(C+H)pdG].− complexes, for which the VDE might be as high as 2.7 eV (in dry conditions) to 3.3 eV (in fully hydrated conditions). Effects of the polarizable medium have been found to be important for increasing the electron capture ability of the dGpdC dimer. The ultimate AEA value for cytosine in DNA duplexes is predicted to be 2.03 eV in aqueous solution.
Konrad Kowalski - One of the best experts on this subject based on the ideXlab platform.
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redox active glycol nucleic acid gna components synthesis and properties of the ferrocenyl gna nucleoside phosphoramidite and semicanonical Dinucleoside Phosphate
Organometallics, 2020Co-Authors: Michal Piotrowicz, Aleksandra Kowalczyk, Damian Trzybinski, Krzysztof Woźniak, Konrad KowalskiAbstract:Ferrocenylated glycol nucleic acid (Fc-GNA) components are rarely studied in the field of xeno nucleic acid (XNA) chemistry. As an attempt to contribute to XNA chemistry, in the present article we report a seven-step synthesis of the first semicanonical Dinucleoside containing the Fc-GNA nucleoside linked to the adenosine nucleoside with a phosphodiester bond. First, the nucleoside-bearing ethynylferrocenyl moiety in the C5 position of the uracil nucleobase was obtained. In the following steps, the nucleoside was transformed into the phosphoramidite intermediate that in turn was reacted with N6-benzoyl-2′,3′-O-isopropylideneadenosine to afford the target Dinucleoside Phosphate with 47% yield. The newly obtained Fc-GNA nucleoside is redox-active, and on the basis of this property (function), it belongs to a new class of functional GNA (fun-GNA) nucleosides. The electrochemistry of the Fc-GNA nucleoside, Dinucleoside Phosphate, and ferrocenyl furanopyrimidone nucleoside that was obtained as an undesired byp...