9-Methylpurine

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Robert J. Stanley - One of the best experts on this subject based on the ideXlab platform.

  • 2-Aminopurine excited state electronic structure measured by stark spectroscopy.
    Journal of Physical Chemistry B, 2008
    Co-Authors: Goutham Kodali, Kurt A Kistler, Spiridoula Matsika, Robert J. Stanley
    Abstract:

    2-Aminopurine (2AP) is an adenine analogue that has a high fluorescence quantum yield. Its fluorescence yield decreases significantly when the base is incorporated into DNA, making it a very useful real-time probe of DNA structure. However, the basic mechanism underlying 2AP fluorescence quenching by base stacking is not well understood. A critical element in approaching this problem is obtaining an understanding of the electronic structure of the excited state. We have explored the excited state properties of 2AP and 2-amino,9-Methylpurine (2A9MP) in frozen solutions using Stark spectroscopy. The experimental data were correlated with high level ab initio (MRCI) calculations of the dipole moments, μ0 and μ1, of the ground and excited states. The magnitude and direction of the dipole moment change, Δμ01 = μ1 − μ0, of the lowest energy optically allowed transition was determined. While other studies have reported on the magnitude of the dipole moment change, we believe that this is the first report of the ...

  • 2-Aminopurine Excited State Electronic Structure Measured by Stark Spectroscopy
    The journal of physical chemistry. B, 2008
    Co-Authors: Goutham Kodali, Kurt A Kistler, Spiridoula Matsika, Robert J. Stanley
    Abstract:

    2-Aminopurine (2AP) is an adenine analogue that has a high fluorescence quantum yield. Its fluorescence yield decreases significantly when the base is incorporated into DNA, making it a very useful real-time probe of DNA structure. However, the basic mechanism underlying 2AP fluorescence quenching by base stacking is not well understood. A critical element in approaching this problem is obtaining an understanding of the electronic structure of the excited state. We have explored the excited state properties of 2AP and 2-amino,9-Methylpurine (2A9MP) in frozen solutions using Stark spectroscopy. The experimental data were correlated with high level ab initio (MRCI) calculations of the dipole moments, mu0 and mu1, of the ground and excited states. The magnitude and direction of the dipole moment change, Deltamu01 = mu1 - mu0, of the lowest energy optically allowed transition was determined. While other studies have reported on the magnitude of the dipole moment change, we believe that this is the first report of the direction of Deltamu, a quantity that will be of great value in interpreting absorption spectral changes of the 2AP chromophore. Polarizability changes due to the transition were also obtained.

Spiridoula Matsika - One of the best experts on this subject based on the ideXlab platform.

  • A benchmark of excitonic couplings derived from atomic transition charges.
    The journal of physical chemistry. B, 2013
    Co-Authors: Kurt A Kistler, Francis C. Spano, Spiridoula Matsika
    Abstract:

    In this report we benchmark Coulombic excitonic couplings between various pairs of chromophores calculated using transition charges localized on the atoms of each monomer chromophore, as derived from a Mulliken population analysis of the monomeric transition densities. The systems studied are dimers of 1-methylthymine, 1-methylcytosine, 2-amino-9-Methylpurine, all-trans-1,3,5-hexatriene, all-trans-1,3,5,7-octatetraene, trans-stilbene, naphthalene, perylenediimide, and dithia-anthracenophane. Transition densities are taken from different single-reference electronic structure excited state methods: time-dependent density functional theory (TDDFT), configuration-interaction singles (CIS), and semiempirical methods based on intermediate neglect of differential overlap. Comparisons of these results with full ab initio calculations of the electronic couplings using a supersystem are made, as are comparisons with experimental data. Results show that the transition charges do a good job of reproducing the supersy...

  • 2-Aminopurine excited state electronic structure measured by stark spectroscopy.
    Journal of Physical Chemistry B, 2008
    Co-Authors: Goutham Kodali, Kurt A Kistler, Spiridoula Matsika, Robert J. Stanley
    Abstract:

    2-Aminopurine (2AP) is an adenine analogue that has a high fluorescence quantum yield. Its fluorescence yield decreases significantly when the base is incorporated into DNA, making it a very useful real-time probe of DNA structure. However, the basic mechanism underlying 2AP fluorescence quenching by base stacking is not well understood. A critical element in approaching this problem is obtaining an understanding of the electronic structure of the excited state. We have explored the excited state properties of 2AP and 2-amino,9-Methylpurine (2A9MP) in frozen solutions using Stark spectroscopy. The experimental data were correlated with high level ab initio (MRCI) calculations of the dipole moments, μ0 and μ1, of the ground and excited states. The magnitude and direction of the dipole moment change, Δμ01 = μ1 − μ0, of the lowest energy optically allowed transition was determined. While other studies have reported on the magnitude of the dipole moment change, we believe that this is the first report of the ...

  • 2-Aminopurine Excited State Electronic Structure Measured by Stark Spectroscopy
    The journal of physical chemistry. B, 2008
    Co-Authors: Goutham Kodali, Kurt A Kistler, Spiridoula Matsika, Robert J. Stanley
    Abstract:

    2-Aminopurine (2AP) is an adenine analogue that has a high fluorescence quantum yield. Its fluorescence yield decreases significantly when the base is incorporated into DNA, making it a very useful real-time probe of DNA structure. However, the basic mechanism underlying 2AP fluorescence quenching by base stacking is not well understood. A critical element in approaching this problem is obtaining an understanding of the electronic structure of the excited state. We have explored the excited state properties of 2AP and 2-amino,9-Methylpurine (2A9MP) in frozen solutions using Stark spectroscopy. The experimental data were correlated with high level ab initio (MRCI) calculations of the dipole moments, mu0 and mu1, of the ground and excited states. The magnitude and direction of the dipole moment change, Deltamu01 = mu1 - mu0, of the lowest energy optically allowed transition was determined. While other studies have reported on the magnitude of the dipole moment change, we believe that this is the first report of the direction of Deltamu, a quantity that will be of great value in interpreting absorption spectral changes of the 2AP chromophore. Polarizability changes due to the transition were also obtained.

Kurt A Kistler - One of the best experts on this subject based on the ideXlab platform.

  • A benchmark of excitonic couplings derived from atomic transition charges.
    The journal of physical chemistry. B, 2013
    Co-Authors: Kurt A Kistler, Francis C. Spano, Spiridoula Matsika
    Abstract:

    In this report we benchmark Coulombic excitonic couplings between various pairs of chromophores calculated using transition charges localized on the atoms of each monomer chromophore, as derived from a Mulliken population analysis of the monomeric transition densities. The systems studied are dimers of 1-methylthymine, 1-methylcytosine, 2-amino-9-Methylpurine, all-trans-1,3,5-hexatriene, all-trans-1,3,5,7-octatetraene, trans-stilbene, naphthalene, perylenediimide, and dithia-anthracenophane. Transition densities are taken from different single-reference electronic structure excited state methods: time-dependent density functional theory (TDDFT), configuration-interaction singles (CIS), and semiempirical methods based on intermediate neglect of differential overlap. Comparisons of these results with full ab initio calculations of the electronic couplings using a supersystem are made, as are comparisons with experimental data. Results show that the transition charges do a good job of reproducing the supersy...

  • 2-Aminopurine excited state electronic structure measured by stark spectroscopy.
    Journal of Physical Chemistry B, 2008
    Co-Authors: Goutham Kodali, Kurt A Kistler, Spiridoula Matsika, Robert J. Stanley
    Abstract:

    2-Aminopurine (2AP) is an adenine analogue that has a high fluorescence quantum yield. Its fluorescence yield decreases significantly when the base is incorporated into DNA, making it a very useful real-time probe of DNA structure. However, the basic mechanism underlying 2AP fluorescence quenching by base stacking is not well understood. A critical element in approaching this problem is obtaining an understanding of the electronic structure of the excited state. We have explored the excited state properties of 2AP and 2-amino,9-Methylpurine (2A9MP) in frozen solutions using Stark spectroscopy. The experimental data were correlated with high level ab initio (MRCI) calculations of the dipole moments, μ0 and μ1, of the ground and excited states. The magnitude and direction of the dipole moment change, Δμ01 = μ1 − μ0, of the lowest energy optically allowed transition was determined. While other studies have reported on the magnitude of the dipole moment change, we believe that this is the first report of the ...

  • 2-Aminopurine Excited State Electronic Structure Measured by Stark Spectroscopy
    The journal of physical chemistry. B, 2008
    Co-Authors: Goutham Kodali, Kurt A Kistler, Spiridoula Matsika, Robert J. Stanley
    Abstract:

    2-Aminopurine (2AP) is an adenine analogue that has a high fluorescence quantum yield. Its fluorescence yield decreases significantly when the base is incorporated into DNA, making it a very useful real-time probe of DNA structure. However, the basic mechanism underlying 2AP fluorescence quenching by base stacking is not well understood. A critical element in approaching this problem is obtaining an understanding of the electronic structure of the excited state. We have explored the excited state properties of 2AP and 2-amino,9-Methylpurine (2A9MP) in frozen solutions using Stark spectroscopy. The experimental data were correlated with high level ab initio (MRCI) calculations of the dipole moments, mu0 and mu1, of the ground and excited states. The magnitude and direction of the dipole moment change, Deltamu01 = mu1 - mu0, of the lowest energy optically allowed transition was determined. While other studies have reported on the magnitude of the dipole moment change, we believe that this is the first report of the direction of Deltamu, a quantity that will be of great value in interpreting absorption spectral changes of the 2AP chromophore. Polarizability changes due to the transition were also obtained.

Helmut Sigel - One of the best experts on this subject based on the ideXlab platform.

  • Steric Guiding of Metal Ion Binding to a Purine Residue by a Non-Coordinating Amino Group: Examplified by 9-[(2-Phosphonomethoxy)ethyl]-2-aminopurine (PME2AP), an Isomer of the Antiviral Nucleotide Analogue 9-[(2-Phosphonomethoxy)ethyl]adenine (PMEA)
    Coordination Chemistry Reviews, 2011
    Co-Authors: Astrid Sigel, Bert P. Operschall, Helmut Sigel
    Abstract:

    Abstract The role that the amino group plays in the metal ion (M2+) binding properties of the adenine residue is of great relevance because this residue occurs widely in nature. It is the aim of this review to evaluate this role. We consider first several 9-Methylpurine derivatives with amino and methyl substituents at various positions: the data indicate that substituents at C6 inhibit M2+ binding at both, the N1 and N7 sites. To separate these effects we use (i) o-amino(methyl)pyridines as models for the pyrimidine part of the adenine residue, i.e., for N1, and (ii) benzimidazole derivatives regarding the properties of N7. The inhibiting effects of ortho-amino and ortho-methyl groups on N1 of pyridines are identical, which agrees with the fact that such an amino group has no basic properties at all. This is different with 1-methyl-4-aminobenzimidazole (MABI) ( 9-methyl-1,3-dideazaadenine) and 1,4-dimethylbenzimidazole (DMBI) ( 6,9-dimethyl-1,3-dideazapurine) because the amino group in MABI still has some basic properties and thus, its steric inhibition is somewhat smaller than that of the methyl group in DMBI. It is suggested that the methyl group in DMBI mimics the steric effects of (C6)NH2 upon (N7)-M2+ coordination in the adenine residue. The evaluation of the N1 versus N7 dichotomy for 2,9-dimethylpurine, 2-amino-9-Methylpurine, and 6-amino-9-Methylpurine ( 9-methyladenine) reveals that the (N7)-M2+ isomer dominates. It is further suggested that the (C6)NH2 adenine group may act as a proton donor and the O atom of a coordinated water molecule as acceptor. The metal ion-binding properties of the two acyclic nucleotide analogues 9-[(2-phosphonomethoxy)ethyl]adenine (PMEA) and 9-[(2-phosphonomethoxy)ethyl]-2-aminopurine (PME2AP), which are structural isomers due to the shift of the (C6)NH2 group in PMEA to the C2 site in PME2AP, fit into the indicated coordination patterns. In the monoprotonated species M(H;PMEA)+ and M(H;PME2AP)+ the proton is located at the phosphonate group and M2+ at N7. However, the M(H;PME2AP)+ complexes are considerably more stable than the M(H;PMEA)+ ones: indeed, the steric effect on N1 is the same in both types of complexes, but the one on N7 has disappeared in M(H;PME2AP)+. Furthermore, there is evidence that the (N7)-coordinated M2+ interacts with the P(O)2(OH)− group in an outersphere manner leading to practically identical formation degrees of the macrochelates formed with Mn2+, Co2+, Ni2+, Cu2+ or Zn2+ [on average 65 ± 15% (3σ)]. The coordination chemistry of PMEA2− and PME2AP2− differs for the 3d ions as well, whereas for the alkaline earth ions, which are primarily coordinated (like all other M2+) to the phosphonate group, 5-membered chelates form involving the ether O of the – CH 2 CH 2 – O – CH 2 – P O 3 2 − residue. In contrast, Co2+, Ni2+, and Cu2+ form with PMEA2− a further isomer, which involves next to the ether O also N3; macrochelates involving N7 and the phosphonate-coordinated M2+ are minority species, but for Ni2+ and Cu2+ they occur and formation degrees of all four isomers could be determined. In the M(PME2AP) complexes a N3 interaction practically does not occur; macrochelate formation of the phosphonate-coordinated M2+ with N7, which is the dominating species for Co2+, Ni2+, Cu2+ or Zn2+ is important here. The possible interrelations between M2+ coordination and the antiviral activity of the two acyclic nucleotide analogues, PMEA being especially active, are discussed shortly.

Goutham Kodali - One of the best experts on this subject based on the ideXlab platform.

  • 2-Aminopurine excited state electronic structure measured by stark spectroscopy.
    Journal of Physical Chemistry B, 2008
    Co-Authors: Goutham Kodali, Kurt A Kistler, Spiridoula Matsika, Robert J. Stanley
    Abstract:

    2-Aminopurine (2AP) is an adenine analogue that has a high fluorescence quantum yield. Its fluorescence yield decreases significantly when the base is incorporated into DNA, making it a very useful real-time probe of DNA structure. However, the basic mechanism underlying 2AP fluorescence quenching by base stacking is not well understood. A critical element in approaching this problem is obtaining an understanding of the electronic structure of the excited state. We have explored the excited state properties of 2AP and 2-amino,9-Methylpurine (2A9MP) in frozen solutions using Stark spectroscopy. The experimental data were correlated with high level ab initio (MRCI) calculations of the dipole moments, μ0 and μ1, of the ground and excited states. The magnitude and direction of the dipole moment change, Δμ01 = μ1 − μ0, of the lowest energy optically allowed transition was determined. While other studies have reported on the magnitude of the dipole moment change, we believe that this is the first report of the ...

  • 2-Aminopurine Excited State Electronic Structure Measured by Stark Spectroscopy
    The journal of physical chemistry. B, 2008
    Co-Authors: Goutham Kodali, Kurt A Kistler, Spiridoula Matsika, Robert J. Stanley
    Abstract:

    2-Aminopurine (2AP) is an adenine analogue that has a high fluorescence quantum yield. Its fluorescence yield decreases significantly when the base is incorporated into DNA, making it a very useful real-time probe of DNA structure. However, the basic mechanism underlying 2AP fluorescence quenching by base stacking is not well understood. A critical element in approaching this problem is obtaining an understanding of the electronic structure of the excited state. We have explored the excited state properties of 2AP and 2-amino,9-Methylpurine (2A9MP) in frozen solutions using Stark spectroscopy. The experimental data were correlated with high level ab initio (MRCI) calculations of the dipole moments, mu0 and mu1, of the ground and excited states. The magnitude and direction of the dipole moment change, Deltamu01 = mu1 - mu0, of the lowest energy optically allowed transition was determined. While other studies have reported on the magnitude of the dipole moment change, we believe that this is the first report of the direction of Deltamu, a quantity that will be of great value in interpreting absorption spectral changes of the 2AP chromophore. Polarizability changes due to the transition were also obtained.