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  • 1
    Electronic Resource
    Electronic Resource
    Intermolecular vibrations of jet-cooled (2-pyridone)2: A model for the uracil dimer (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 3717-3725 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The 2-pyridone dimer, (2PY)2, which is linked by two antiparallel N–H⋅⋅⋅O hydrogen bonds, is a model for hydrogen bonded nucleotide base pairs, e.g., the uracil dimer. Mass- and isomer-selected S2←S0 vibronic spectra of supersonically cooled (2PY)2 were measured by laser two-color resonant two-photon ionization and UV/UV-holeburning techniques. The latter allows the identification of the spectrum of the 2-pyridone⋅2-hydroxypyridine mixed dimer, present at (approximate)5% relative concentration. S2→S0 fluorescence emission spectra show dominantly the hydrogen bond shearing vibration ν4″ at 98.5 cm−1 and the stretching vibration ν6″ at 163.5 cm−1. The hydrogen bond stretching vibration force constant was determined to be 75.4 N/m, or 37.7 N/m per hydrogen bond, a very high value. The ν2″ (au) torsional and the ν3″ (bu) slanting vibrations were also identified. Ground state structures, rotational constants, harmonic intermolecular and intramolecular vibrational frequencies, interaction, and dissociation energies were calculated using Hartree–Fock and density functional (B3LYP) methods. The B3LYP/6-311++(2d,2p) results are in excellent agreement with all experimental observations. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480524
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  • 2
    Electronic Resource
    Electronic Resource
    Water-chain clusters: Vibronic spectra of 7-hydroxyquinoline⋅(H2O)2 (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 1192-1203 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Mass- and isomer-selected S1←S0 resonant two-photon ionization and S1→S0 fluorescence spectra were obtained for the supersonically cooled 7-hydroxyquinoline⋅(H2O)2 cluster. UV/UV-holeburning measurements show that 〉98% of the spectrum is due to a single "water-chain" cluster isomer, although two different tautomers (7-keto- and 7-hydroxyquinoline), two different rotamers (cis- and trans-hydroxy), and two torsional conformers of the chain are possible. Ab initio calculations of structures and vibrations of five different tautomers/ rotamers/ conformers of this cluster are reported. These predict that the cis-7-hydroxyquinoline⋅(H2O)2 "up/down" water-chain form is the most stable cluster. The experimentally observed S0 and S1 state vibrational frequencies agree well with those calculated for this isomer. We find no evidence for either the trans-rotamer or the keto tautomer clusters. S1←S0 excitation leads to contraction of all three hydrogen-bonds along the hydrogen-bonded water chain, inducing intermolecular stretching vibrations, but no proton transfer. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480672
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  • 3
    Electronic Resource
    Electronic Resource
    Brownian Motion: A Tool To Determine the Pair Potential between Colloid Particles (1994)
    s.l. : American Chemical Society
    Langmuir 10 (1994), S. 1351-1353 
    Details
    ISSN: 1520-5827
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/la00017a007
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  • 4
    Electronic Resource
    Electronic Resource
    S1/S2 exciton splitting in the (2-pyridone)2 dimer (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 2836-2847 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The S1↔S0 and S2↔S0 vibronic spectra of the supersonically cooled 2-pyridone dimer (2PY)2 and its 13C-, d1-, and d2-isotopomers were investigated by two-color resonant two-photon ionization and fluorescence spectroscopies. For the C2h symmetric (2PY)2–h2 and (2PY)2–d2 complexes, the 2PY moieties are equivalent and the S1↔S0 (1Ag↔1Ag) transition is forbidden. A single H/D or 12C/13C isotopic substitution reduces the symmetry to Cs, so that (2PY)2–13C and (2PY)2–d1 both exhibit S1↔S0 and S2↔S0 transitions. The S1/S2 state exciton splittings are 43.6 cm−1 and 52.4 cm−1, respectively. These are analyzed in terms of a Frenkel model and compared to calculated splittings based on ab initio monomer transition dipole moments. For (2PY)2–d1, whose 2PY subunits are different, an excitation transfer time of 318 fs is calculated from the exciton splitting. The S1↔S0 and S2↔S0 spectra are analyzed and assigned. Several bu intermolecular vibrations of S1 appear via vibronic coupling to the S2(Bu) state. Combination of the fluorescence data from excitation of the S1 and S2 origins and vibrational excitations of (2PY)2–h2, (2PY)2–d1, and (2PY)2–d2 allows the determination of the six S0 state intermolecular vibrational frequencies.© 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1434987
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  • 5
    Electronic Resource
    Electronic Resource
    Intermolecular vibrations of the jet-cooled 2-pyridone⋅2-hydroxypyridine mixed dimer, a model for tautomeric nucleic acid base pairs (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 5192-5202 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The 2-pyridone⋅2-hydroxypyridine mixed dimer, 2PY⋅2HP, is linked by antiparallel N–H(centered ellipsis)N and O–H(centered ellipsis)O hydrogen bonds, closely analogous to tautomeric hydrogen-bonded DNA base pairs such as isoguanine⋅uracil. Mass-selected S1←S0 vibronic spectra of supersonic jet-cooled 2PY⋅2HP and three N–D or O–D deuterated isotopomers were measured by two-color resonant two-photon ionization and UV/UV-holeburning techniques. S1→S0 fluorescence spectra show intense hydrogen bond stretching vibrations ν6″=158 cm−1, observed for all four isotopomers and the weak ν5″ "shear" vibration at 116 cm−1. The "slanting" intermolecular vibration ν4″=89 cm−1 was tentatively identified via the 2ν4″ overtone. The observation of 2-pyridone intramolecular overtone and combination transitions for two out-of-plane modes indicate slight nonplanarity of the 2-pyridone moiety in the S1 state. Ab initio calculations using Hartree–Fock, configuration interaction among single excitations (CIS), and B3LYP density functional methods were employed to calculate ground- and excited-state structures, rotational constants, harmonic intermolecular and intramolecular vibrational frequencies, binding energies De, and dissociation energies D0. The B3LYP/6-311++(d,p) ν4″ and ν6″ frequencies are in very good agreement with the experimental ground-state intermolecular frequencies. Electronic excitation of the 2-pyridone moiety in 2PY⋅2HP leads to a decrease of dissociation energy by 2.36 kcal/mol and a concurrent increase of H bond lengths by (approximate)0.08 Å, in qualitative agreement with the self-consistent field (SCF) and CIS ab initio calculations. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1394942
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  • 6
    Electronic Resource
    Electronic Resource
    Computer simulation study of the Rayleigh and Raman spectra of fluid N2 (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 4993-5001 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Computer simulations of the Rayleigh and Raman spectral time-correlation functions (TCFs) are reported for N2 at 323 K and densities ranging from 0.48 to 2.5 times the critical value. The results are compared with experiment. Particular attention is paid to the density dependence of the spectral intensity due to the correlated permanent polarizability and to the interaction-induced contributions to the polarizability. The partial cancellations that occur between various two-, three-, and four-body terms in the cross and collision induced (CI) parts of the spectral TCFs are evaluated. It is shown that these terms are significant in both the Raman and the Rayleigh spectra, but cancellation greatly reduces their net contribution at all densities studied. The weak but uncancelled TCFs that are associated with orientational correlations of the molecular polarizability anisotropies are shown to be a significant part of the high density Rayleigh TCFs. It is argued that the long-range nature of this TCF means that its simulated values are poorly known.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466001
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  • 7
    Electronic Resource
    Electronic Resource
    Effect of molecular elongation on the dipolar free energy (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 3946-3949 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The dipolar contribution to the Helmholtz energy FD has been determined for dipolar two-center Lennard-Jones molecules of increasing elongation at one corresponding state point in the liquid. The calculation is based on the dipole–dipole energy obtained from simulations and subsequent integration according to the λ-coupling technique. It results, that at fixed values of the reduced dipole moment μ*2=μ2/(εσ3) with ε and σ being the Lennard-Jones site–site interaction parameters, the dipolar free energy FD is nearly constant as function of the molecular elongation. Keeping the effective dipole moment μ˜2=μ2(ρp/Tp) constant with Tp and ρp being the critical temperature and density obtained from WCA-type perturbation theory, FD increases somewhat with the elongation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466141
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  • 8
    Electronic Resource
    Electronic Resource
    Water–wire clusters: Vibronic spectra of 7-hydroxyquinoline⋅(H2O)3 (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 9032-9043 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The supersonically cooled 7-hydroxyquinoline⋅(H2O)3 cluster was investigated by mass- and isomer-selected S1←S0 resonant two-photon ionization and S1→S0 fluorescence spectroscopy. UV(ultraviolet)/UV-holeburning measurements prove that a single cluster isomer is formed, although different tautomers (7-keto- and 7-hydroxyquinoline), rotamers (cis and trans) and isomers (cyclic and water–wire) are possible. Ab initio calculations of structures and vibrations of different tautomers and isomers of this cluster predict that the cis-enol-7-hydroxyquinoline⋅(H2O)3 "water–wire" cluster is the most stable species. The experimental S0 and S1 inter- and intramolecular vibrational frequencies are in good agreement with the calculated harmonic frequencies. S1←S0 excitation leads to contraction of all four hydrogen bonds along the hydrogen bonded water wire, inducing intense intermolecular stretching vibrations of the O–H(centered ellipsis)O and HO–H(centered ellipsis)N(quinoline) hydrogen bonds which terminate the water–wire. There are no spectroscopic signs of proton transfer. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1319352
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  • 9
    Electronic Resource
    Electronic Resource
    Detection of HHV-8 sequences and antigens in a MALT lymphoma associated with Sjögren's syndrome (2003)
    Oxford, UK : Munksgaard International Publishers
    Journal of oral pathology & medicine 32 (2003), S. 0 
    Details
    ISSN: 1600-0714
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: We describe the case of a bilateral parotid mucosa-associated lymphoid tissue (MALT) lymphoma associated with 2 years history of Sjögren's syndrome (SS), which was linked to human herpes virus 8 (HHV-8) infection. Using polymerase chain reaction (PCR) assay HHV-8 sequences were detectable in the lymphoma tissue of both sides. Serologic testing of the patient revealed HHV-8 antibodies in enzyme-linked immunosorbent assay (ELISA) and immunofluorescence assay (IFA). Immunohistologic staining with two antibodies against open reading frame (ORF) 26 and v-cyclin homologues of HHV-8 revealed positive staining of the salivary acinic cells whereas the lymphoma cells were negative. The potential influence of HHV-8 infection for MALT lymphoma development in this case and possible parallels to gastric MALT lymphoma are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1600-0714.2003.00092.x
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  • 10
    Electronic Resource
    Electronic Resource
    Somatic Hybridization of Nitrate Reductase Deficient Mutants of Nicotiana tabacum by Protoplast Fusion (1978)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 44 (1978), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Protoplasts were isolated from two mutant cell lines of Nicotiana tabacum L. cv. Gatersleben and fused with the aid of polyethylene glycol. Both mutants lacked nitrate reductase and were thus auxotrophic for reduced nitrogen. The fusion resulted in a high frequency of hybrid cells which were detected by their regained ability to grow in media containing nitrate as sole nitrogen source. Thus, the two mutants were found to complement each other in the hybrids. In control experiments, back mutation and cross-feeding were excluded as possible explanations for the occurrence of cell lines utilizing nitrate. A total of 1061 hybrid lines capable of sustained proliferation were isolated. Some of them were further characterized with respect to nitrate reductase activity, chlorate sensitivity, chromosome number, and shoot formation.The results demonstrate that protoplast fusion can be used for the genetic analysis of cell variants of higher plants and that nitrate reductase-deficient mutants provide efficient selective systems for hybrid cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1978.tb08631.x
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