TY  - JOUR
A1  - Baranac-Stojanovic, Marija
A1  - Koch, Andreas
A1  - Kleinpeter, Erich
T1  - Is the conventional interpretation of the anisotropic effects of C=C double bonds and aromatic rings in NMR spectra in terms of the p-electron shielding/deshielding contributions correct?
JF  - Chemistry - a European journal
N2  - Based on the nucleus-independent chemical shift (NICS) concept, isotropic magnetic shielding values have been computed along the three Cartesian axes for ethene, cyclobutadiene, benzene, naphthalene, and benzocyclobutadiene, starting from the molecular/ring center up to 10 angstrom away. These through-space NMR spectroscopic shielding (TSNMRS) values, which reflect the anisotropic effects, have been broken down into contributions from localized- and canonical molecular orbitals (LMOs and CMOs); these contributions revealed that the proton NMR spectroscopic chemical shifts of nuclei that are spatially close to the C?C double bond or the aromatic ring should not be explained in terms of the conventionally accepted p-electron shielding/deshielding effects. In fact, these effects followed the predictions only for the antiaromatic cyclobutadiene ring.
KW  - ab initio calculations
KW  - anisotropic effects
KW  - NMR spectroscopy
KW  - nucleus-independent chemical shift
KW  - pi interactions
Y1  - 2012
U6  - https://doi.org/10.1002/chem.201101882
SN  - 0947-6539
VL  - 18
IS  - 1
SP  - 370
EP  - 376
PB  - Wiley-Blackwell
CY  - Malden
ER  - 
TY  - JOUR
A1  - Boese, Adrian Daniel
T1  - Density Functional Theory and Hydrogen Bonds: Are We There Yet?
JF  - ChemPhysChem : a European journal of chemical physics and physical chemistry
N2  - Density functional theory (DFT) has become more successful at introducing dispersion interactions, and can be thus applied to a wide range of systems. Amongst these are systems that contain hydrogen bonds, which are extremely important for the biological regime. Here, the description of hydrogen-bonded interactions by DFT with and without dispersion corrections is investigated. For small complexes, for which electrostatics are the determining factor in the intermolecular interactions, the inclusion of dispersion with most functionals yields large errors. Only for larger systems, in which van der Waals interactions are more important, do dispersion corrections improve the performance of DFT for hydrogen-bonded systems. None of the studied functionals, including double hybrid functionals (with the exception of DSD-PBEP86 without dispersion corrections), are more accurate than MP2 for the investigated species.
KW  - ab initio calculations
KW  - basis sets
KW  - density functional calculations
KW  - hydrogen bonds
KW  - intermolecular interactions
Y1  - 2015
U6  - https://doi.org/10.1002/cphc.201402786
SN  - 1439-4235
SN  - 1439-7641
VL  - 16
IS  - 5
SP  - 978
EP  - 985
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Rackwitz, Jenny
A1  - Kopyra, Janina
A1  - Dabkowska, Iwona
A1  - Ebel, Kenny
A1  - Rankovic, MiloS Lj.
A1  - Milosavljevic, Aleksandar R.
A1  - Bald, Ilko
T1  - Sensitizing DNA Towards Low-Energy Electrons with 2-Fluoroadenine
JF  - Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition
N2  - 2-Fluoroadenine ((2F)A) is a therapeutic agent, which is suggested for application in cancer radiotherapy. The molecular mechanism of DNA radiation damage can be ascribed to a significant extent to the action of low-energy (<20 eV) electrons (LEEs), which damage DNA by dissociative electron attachment. LEE induced reactions in (2F)A are characterized both isolated in the gas phase and in the condensed phase when it is incorporated into DNA. Information about negative ion resonances and anion-mediated fragmentation reactions is combined with an absolute quantification of DNA strand breaks in (2F)A-containing oligonucleotides upon irradiation with LEEs. The incorporation of (2F)A into DNA results in an enhanced strand breakage. The strand-break cross sections are clearly energy dependent, whereas the strand-break enhancements by (2F)A at 5.5, 10, and 15 eV are very similar. Thus, (2F)A can be considered an effective radiosensitizer operative at a wide range of electron energies.
KW  - ab initio calculations
KW  - dissociative electron attachment
KW  - DNA origami
KW  - DNA radiation damage
KW  - fludarabine
Y1  - 2016
U6  - https://doi.org/10.1002/anie.201603464
SN  - 1433-7851
SN  - 1521-3773
VL  - 55
SP  - 10248
EP  - 10252
PB  - Wiley-VCH
CY  - Weinheim
ER  -