Investigation of Proton Transport Tautomerism in Clusters of Protonated Nucleic Acid Bases (Cytosine, Uracil, Thymine, and Adenine) and Ammonia by High-Pressure Mass Spectrometry and Ab Initio Calculations

2007 ◽  
Vol 129 (3) ◽  
pp. 569-580 ◽  
Author(s):  
Ronghu Wu ◽  
Terry B. McMahon
Keyword(s):  
Mass Spectrometry ◽  
High Pressure ◽  
Nucleic Acid ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Proton Transport ◽  
Nucleic Acid Bases

Ab initio calculations with electronic correlation (MP2) on the nucleic acid bases and their methyl derivatives

1994 ◽  
Vol 116 (16) ◽  
pp. 7282-7286 ◽  
Author(s):  
Eugene L. Stewart ◽  
Charles K. Foley ◽  
Norman L. Allinger ◽  
J. Phillip Bowen
Keyword(s):  
Nucleic Acid ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Electronic Correlation ◽  
Nucleic Acid Bases ◽  
Methyl Derivatives

An investigation of the ion–molecule interactions of protonated glycine with ammonia by high pressure mass spectrometry and ab initio calculations

2005 ◽  
Vol 83 (11) ◽  
pp. 1978-1993 ◽  
Author(s):  
Ronghu Wu ◽  
Terry B McMahon
Keyword(s):  
Mass Spectrometry ◽  
High Pressure ◽  
Potential Energy ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Gas Phase ◽  
Energy Surface ◽  
Stable Isomer ◽  
Molecule Interactions ◽  
Gas Phase Ion

The thermochemistry of gas-phase ion molecule interactions and the structures of various clusters between protonated glycine (GlyH+), glycine, and ammonia have been studied by high pressure mass spectrometry (HP-MS) and ab initio calculations. For the association reactions of GlyH+ with NH3, Gly(NH3)H+ with NH3, and (Gly)2H+ with NH3, the enthalpy changes experimentally determined are –23.2, –18.3, and –19.1 kcal mol–1 (1 cal = 4.184 J), respectively. For all clusters investigated, the measured binding enthalpies are in excellent agreement with those obtained from ab initio calculations at the B3LYP/6-311+G(d,p) level of theory. Different isomers of each of these clusters have been obtained and the corresponding binding energies have been computed. The potential energy surface for isomerization of the clusters of protonated glycine with ammonia has also been computed at the same level. For this cluster, the three most stable isomers all involve a proton transfer from protonated glycine to ammonia. According to the calculated potential energy surface, the barrier between GN4, the least stable isomer, and the most stable isomer (GN1) is 11.5 kcal mol–1 at 298 K. Thus, this isomerization will be facile given the exothermicity of the association reaction. Therefore, a statistical distribution of isomers will be present under thermal equilibrium conditions. Single point energy calculations at the MP2(full)/6-311++G(2d,2p)//B3LYP/6-311+G(d,p) level of theory reveal that the isomer GN2 in which glycine has a zwitterionic structure has the same energy as the most stable non-zwitterionic isomer GN1. NH4+ evidently may stabilize the zwitterionic structure of glycine. In contrast, N2H7+ and GlyH+ are not as effective in stabilizing the zwitterionic structure of glycine. This likely results from the more localized charge in NH4+ giving rise to stronger hydrogen bonds with the carboxylate moiety of zwitterionic glycine. This conjecture is supported by the computational results.Key words: high pressure mass spectrometry, glycine, gas-phase ion thermochemistry, ab initio calculations, cluster structure.

Ab-initio Calculations of Properties for NbB 2 Under High-Pressure Using Quantum ESPRESSO

2019 ◽  
Author(s):  
Tara Prasad ◽  
MC Shah ◽  
Pankaja Singh ◽  
Tanveer Ahmad Wani
Keyword(s):  
High Pressure ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Quantum Espresso

Photoionization and dissociation of BF3·((CH3)2O)n mixed aggregates (n=1, 2) studied by mass spectrometry and ab initio calculations

1997 ◽  
Vol 280 (3-4) ◽  
pp. 251-259 ◽  
Author(s):  
S. Ring ◽  
C.G. Eisenhardt ◽  
H. Baumgärtel
Keyword(s):  
Mass Spectrometry ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Mixed Aggregates

Structural nonrigidity of nucleic acid bases. Post-Hartree-Fock ab initio study

2000 ◽  
Vol 80 (4-5) ◽  
pp. 1116-1124 ◽  
Author(s):  
Oleg V. Shishkin ◽  
Leonid Gorb ◽  
Pavel Hobza ◽  
Jerzy Leszczynski
Keyword(s):  
Nucleic Acid ◽  
Ab Initio ◽  
Ab Initio Study ◽  
Nucleic Acid Bases ◽  
Hartree Fock ◽  
Structural Nonrigidity

High-pressure study of a nanostructured SnSe1−xSx (x = 0.5) solid solution by in-situ X-ray diffraction and ab-initio calculations

2019 ◽  
Vol 792 ◽  
pp. 536-542
Author(s):  
Larissa da Silva Marques ◽  
Joelma Maria de Oliveira Ferreira ◽  
Querem Hapuque Félix Rebelo ◽  
Angsula Ghosh ◽  
Daniela Menegon Trichês ◽  
...  
Keyword(s):  
Solid Solution ◽  
High Pressure ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
X Ray Diffraction ◽  
X Ray ◽  
High Pressure Study

High-pressure melting line of helium from ab initio calculations

2019 ◽  
Vol 100 (18) ◽  
Author(s):  
Martin Preising ◽  
Ronald Redmer
Keyword(s):  
High Pressure ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Melting Line ◽  
Pressure Melting
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