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Timothy M. Korter - One of the best experts on this subject based on the ideXlab platform.
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examination of phencyclidine hydrochloride via cryogenic terahertz spectroscopy solid state density functional theory and x ray diffraction
Journal of Physical Chemistry A, 2009Co-Authors: Patrick M Hakey, Damian G Allis, Wayne Ouellette, Matthew R Hudson, Timothy M. KorterAbstract:The terahertz (THz) spectrum of phencyclidine hydrochloride from 7.0 to 100.0 cm -1 has been measured at cryogenic (78.4 K) temperature. The complete structural analysis and vibrational assignment of the compound have been performed employing solid-state density functional theory utilizing eight generalized gradient approximation density functionals and both solid-state and Isolated-Molecule methods. The structural results and the simulated spectra display the substantial improvement obtained by using solid-state simulations to accurately assign and interpret solid-state THz spectra. A complete assignment of the spectral features in the measured THz spectrum has been completed at a VWN-BP/DNP level of theory, with the VWN-BP density functional providing the best-fit solid-state simulation of the experimentally observed spectrum. The cryogenic THz spectrum contains eight spectral features that, at the VWN-BP/DNP level, consist of 15 infrared-active vibrational modes. Of the calculated modes, external crystal vibrations are predicted to account for 42% of the total spectral intensity.
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cryogenic terahertz spectrum of methamphetamine hydrochloride and assignment using solid state density functional theory
Journal of Physical Chemistry A, 2009Co-Authors: Patrick M Hakey, Damian G Allis, Wayne Ouellette, Timothy M. KorterAbstract:The cryogenic terahertz spectrum of (+)-methamphetamine hydrochloride from 10.0 to 100.0 cm(-1) is presented, as is the complete structural analysis and vibrational assignment of the compound using solid-state density functional theory. This cryogenic investigation reveals multiple spectral features that were not previously reported in room-temperature terahertz studies of the title compound. Modeling of the compound employed eight density functionals utilizing both solid-state and Isolated-Molecule methods. The results clearly indicate the necessity of solid-state simulations for the accurate assignment of solid-state THz spectra. Assignment of the observed spectral features to specific atomic motions is based on the BP density functional, which provided the best-fit solid-state simulation of the experimental spectrum. The seven experimental spectral features are the result of thirteen infrared-active vibrational modes predicted at a BP/DNP level of theory with more than 90% of the total spectral intensity associated with external crystal vibrations.
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theoretical analysis of the solid state terahertz spectrum of the high explosive rdx
Chemical Physics Letters, 2008Co-Authors: Damian G Allis, Axel J Zeitler, P F Taday, Timothy M. KorterAbstract:Abstract The solid-state terahertz (THz) spectrum (2–120 cm −1 ) of α-form cyclotrimethylenetrinitramine (RDX) has been simulated using solid-state density functional calculations at a BP/DNP level of theory. BP/DNP features are in good agreement with both 298 K and a new 7 K polycrystalline RDX THz spectrum. The 7 K RDX spectrum is noteworthy for several mode shifts and spectral detail that greatly aids mode assignments. Previous RDX Isolated-Molecule calculations (with six calculated modes below 125 cm −1 ) are incapable of accurately predicting the numerous features in this region, highlighting the importance of solid-state theoretical methods for solid-state terahertz feature assignments.
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assignment of the lowest lying thz absorption signatures in biotin and lactose monohydrate by solid state density functional theory
Chemical Physics Letters, 2007Co-Authors: Damian G Allis, Timothy M. Korter, Anna M Fedor, J E Bjarnason, E R BrownAbstract:The narrow terahertz (THz) features in crystalline biotin and lactose monohydrate observed in recent experimental studies are considered by solid-state density functional theory (DFT) calculations. The lowest-frequency THz features in both solid-state biotin and lactose monohydrate are assigned to external hindered rotational modes and not to the lowest-frequency internal modes predicted from Isolated-Molecule calculations. The motions of the Molecules associated with these narrow THz features and the interactions between Molecules in the hydrogen-bonded networks of these molecular crystals are discussed, and comparisons are made to similar studies on molecular crystals not exhibiting strong intermolecular interactions.
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terahertz spectroscopy of solid serine and cysteine
Chemical Physics Letters, 2006Co-Authors: Timothy M. Korter, R Balu, M B Campbell, Matthew C Beard, S K Gregurick, Edwin J HeilweilAbstract:Abstract Terahertz (THz) absorption spectra of the similarly structured amino acids l -serine and l -cysteine in the solid phase at 77 and 298 K are reported and compared to Isolated Molecule and solid-state infrared vibrational spectral calculations using empirical force field and density functional theory. These comparisons suggest that many higher frequency internal modes can readily be assigned but lowest frequency intermolecular and phonon modes can adequately be understood with more advanced solid-state theory using currently available potential functions.
Damian G Allis - One of the best experts on this subject based on the ideXlab platform.
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examination of phencyclidine hydrochloride via cryogenic terahertz spectroscopy solid state density functional theory and x ray diffraction
Journal of Physical Chemistry A, 2009Co-Authors: Patrick M Hakey, Damian G Allis, Wayne Ouellette, Matthew R Hudson, Timothy M. KorterAbstract:The terahertz (THz) spectrum of phencyclidine hydrochloride from 7.0 to 100.0 cm -1 has been measured at cryogenic (78.4 K) temperature. The complete structural analysis and vibrational assignment of the compound have been performed employing solid-state density functional theory utilizing eight generalized gradient approximation density functionals and both solid-state and Isolated-Molecule methods. The structural results and the simulated spectra display the substantial improvement obtained by using solid-state simulations to accurately assign and interpret solid-state THz spectra. A complete assignment of the spectral features in the measured THz spectrum has been completed at a VWN-BP/DNP level of theory, with the VWN-BP density functional providing the best-fit solid-state simulation of the experimentally observed spectrum. The cryogenic THz spectrum contains eight spectral features that, at the VWN-BP/DNP level, consist of 15 infrared-active vibrational modes. Of the calculated modes, external crystal vibrations are predicted to account for 42% of the total spectral intensity.
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cryogenic terahertz spectrum of methamphetamine hydrochloride and assignment using solid state density functional theory
Journal of Physical Chemistry A, 2009Co-Authors: Patrick M Hakey, Damian G Allis, Wayne Ouellette, Timothy M. KorterAbstract:The cryogenic terahertz spectrum of (+)-methamphetamine hydrochloride from 10.0 to 100.0 cm(-1) is presented, as is the complete structural analysis and vibrational assignment of the compound using solid-state density functional theory. This cryogenic investigation reveals multiple spectral features that were not previously reported in room-temperature terahertz studies of the title compound. Modeling of the compound employed eight density functionals utilizing both solid-state and Isolated-Molecule methods. The results clearly indicate the necessity of solid-state simulations for the accurate assignment of solid-state THz spectra. Assignment of the observed spectral features to specific atomic motions is based on the BP density functional, which provided the best-fit solid-state simulation of the experimental spectrum. The seven experimental spectral features are the result of thirteen infrared-active vibrational modes predicted at a BP/DNP level of theory with more than 90% of the total spectral intensity associated with external crystal vibrations.
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theoretical analysis of the solid state terahertz spectrum of the high explosive rdx
Chemical Physics Letters, 2008Co-Authors: Damian G Allis, Axel J Zeitler, P F Taday, Timothy M. KorterAbstract:Abstract The solid-state terahertz (THz) spectrum (2–120 cm −1 ) of α-form cyclotrimethylenetrinitramine (RDX) has been simulated using solid-state density functional calculations at a BP/DNP level of theory. BP/DNP features are in good agreement with both 298 K and a new 7 K polycrystalline RDX THz spectrum. The 7 K RDX spectrum is noteworthy for several mode shifts and spectral detail that greatly aids mode assignments. Previous RDX Isolated-Molecule calculations (with six calculated modes below 125 cm −1 ) are incapable of accurately predicting the numerous features in this region, highlighting the importance of solid-state theoretical methods for solid-state terahertz feature assignments.
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assignment of the lowest lying thz absorption signatures in biotin and lactose monohydrate by solid state density functional theory
Chemical Physics Letters, 2007Co-Authors: Damian G Allis, Timothy M. Korter, Anna M Fedor, J E Bjarnason, E R BrownAbstract:The narrow terahertz (THz) features in crystalline biotin and lactose monohydrate observed in recent experimental studies are considered by solid-state density functional theory (DFT) calculations. The lowest-frequency THz features in both solid-state biotin and lactose monohydrate are assigned to external hindered rotational modes and not to the lowest-frequency internal modes predicted from Isolated-Molecule calculations. The motions of the Molecules associated with these narrow THz features and the interactions between Molecules in the hydrogen-bonded networks of these molecular crystals are discussed, and comparisons are made to similar studies on molecular crystals not exhibiting strong intermolecular interactions.
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inelastic neutron scattering spectrum of cs2 b12h12 reproduction of its solid state vibrational spectrum by periodic dft
Journal of Physical Chemistry A, 2006Co-Authors: Damian G Allis, Bruce S HudsonAbstract:The inelastic neutron scattering (INS) spectrum of polycrystalline Cs 2 [B 12 H 12 ] is assigned through 1200 cm -1 on the basis of aqueous and solid-state Raman/IR measurements and normal mode analyses from solid-state density functional theory. The Cs + cations are responsible for frequency shifts of the internal cage vibrational modes and I h cage mode splittings due to the crystal T h site symmetry. These changes to the [B 12 H 12 ] 2- molecular modes make Isolated-Molecule calculations inadequate for use in complete assignments. Solid-state calculations reveal that 30/40 cm -1 shifts of Tg/Hg molecular modes are responsible for structure in the INS spectrum unobserved by optical methods or in aqueous solutions.
David W. Pratt - One of the best experts on this subject based on the ideXlab platform.
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intramolecular structure and dynamics of mequinol and guaiacol in the gas phase rotationally resolved electronic spectra of their s1 states
Journal of Chemical Physics, 2015Co-Authors: Jose Arturo Ruizsantoyo, Marcela Rodriguezmatus, Jose Luis Cabellos, John T Yi, David W. Pratt, Gabriel Merino, Leonardo AlvarezvaltierraAbstract:The molecular structures of guaiacol (2-methoxyphenol) and mequinol (4-methoxyphenol) have been studied using high resolution electronic spectroscopy in a molecular beam and contrasted with ab initio computations. Mequinol exhibits two low frequency bands that have been assigned to electronic origins of two possible conformers of the Molecule, trans and cis. Guaiacol also shows low frequency bands, but in this case, the bands have been assigned to the electronic origin and vibrational modes of a single conformer of the Isolated Molecule. A detailed study of these bands indicates that guaiacol has a vibrationally averaged planar structure in the ground state, but it is distorted along both in-plane and out-of-plane coordinates in the first electronically excited state. An intramolecular hydrogen bond involving the adjacent –OH and –OCH3 groups plays a major role in these dynamics.
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high resolution electronic spectroscopy of 4 methylanisole in the gas phase barrier height determinations for the methyl group torsional motion
Physical Chemistry Chemical Physics, 2010Co-Authors: Philip J Morgan, Leonardo Alvarezvaltierra, David W. PrattAbstract:Rotationally resolved fluorescence excitation spectra of the S1 ← S0 origin band transition of 4-methylanisole have been recorded in the gas phase. The origin band spectrum is split into two subbands owing to tunneling motions along the methyl group torsional coordinate. An analysis of this data provides information about the preferred configuration of the methyl group and the barrier opposing its motion in both the ground and excited electronic states. The results show that electronic excitation has a significant impact on the torsional dynamics of the Isolated Molecule.
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experimental measurement of the induced dipole moment of an Isolated Molecule in its ground and electronically excited states indole and indole h2o
Journal of Chemical Physics, 2005Co-Authors: Cheolhwa Kang, Timothy M. Korter, David W. PrattAbstract:Reported here are measurements of the magnitude and orientation of the induced dipole moment that is produced when an indole Molecule in its ground S0 and electronically excited S1 states is polarized by the attachment of a hydrogen bonded water Molecule in the gas phase complex indole–H2O. For the complex, we find the permanent dipole moment values μIW(S0)=4.4D and μIW(S1)=4.0D, values that are substantially different from calculated values based on vector sums of the dipole moments of the component parts. From this result, we derive the induced dipole moment values μI*(S0)=0.7D and μI*(S1)=0.5D. The orientation of the induced moment also is significantly different in the two electronic states. These results are quantitatively reproduced by a purely electrostatic calculation based on ab initio values of multipole moments.
Arnold L Rheingold - One of the best experts on this subject based on the ideXlab platform.
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concomitant polymorphism in an organic solid molecular and crystal structure and intra and intermolecular potential contributions to tert butyl and methyl group rotation
ChemPhysChem, 2019Co-Authors: Peter A Beckmann, Paul R Rablen, Jason R Schmink, Steven T Szewczyk, Arnold L RheingoldAbstract:We investigate the relationship between structure (crystal and molecular) and tert-butyl and methyl group dynamics in 2-(tert-butyl)-9-(4-(tert-butyl)phenyl)anthracene. Powder and single-crystal X-ray diffraction, taken together, show that different polycrystalline samples recrystallized from different solvents have different amounts of at least four polymorphs (crystallites having different crystal structures), of which we have identified three by single crystal X-ray diffraction. The Molecules in the asymmetric units of the different crystal structures differ by the dihedral angle the tert-butylphenyl group makes with the anthracene moiety. Ab initio electronic structure calculations on the Isolated Molecule show that very little intramolecular energy is required to change this angle over a range of about 60° which is probably the origin of the concomitant polymorphism (crystals of more than one polymorph in a polycrystalline sample). Solid state 1 H nuclear magnetic resonance (NMR) spin-lattice relaxation experiments support the powder and single-crystal X-ray results and provide average NMR activation energies (closely related to rotational barriers) for the rotation of the tert-butyl groups and their constituent methyl groups. These barriers have both an intramolecular and an intermolecular component. The latter is sensitive to the crystal structure. The intramolecular components of the rotational barriers of the two tert-butyl groups in the Isolated Molecule are investigated with ab initio electronic structure calculations.
Fatima Laraba-djebari - One of the best experts on this subject based on the ideXlab platform.
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Isolation and characterization of an anti-leishmanial disintegrin from Cerastes cerastes venom
Journal of Biochemical and Molecular Toxicology, 2018Co-Authors: Dihia Allane, Habiba Oussedik-oumehdi, Zoubir Harrat, Michel Seve, Fatima Laraba-djebariAbstract:Investigating new antimicrobial and antiparasitic components from Viperidae venoms represents an alternative therapeutic strategy. In this study, we report the characterization of a disintegrin Isolated from Cerastes cerastes venom, exhibiting antiparasitic activity on Leishmania infantum promastigotes. Indeed, Isolated disintegrin, referred to Disintegrin_Cc, induced 84.75% of parasiticidal activity and deep morphological alterations on the parasites. SDS-PAGE analysis indicated that this disintegrin was homogenous. This dimeric disintegrin of 14,193.97 Da contains an RGD domain and four intramolecular disulfide bridges. It presents a high percentage of identity with other related snake disintegrins. Predicted 3D structure indicated that this peptide shares partial homology with well-known active antimicrobial peptides. Disintegrin_Cc inhibited 80% of arachidonic acid-induced platelet aggregation. The obtained results suggest that the Isolated Molecule plays a dual role as a disintegrin and as an anti-leishmanial compound. This component could be useful as a drug in the treatment of leishmaniasis.
