Λεπτομέρειες βιβλιογραφικής εγγραφής
| Τίτλος: |
Model Simulations of the Thermal Dissociation of the TIK(H+)2 Tripeptide: Mechanisms and Kinetic Parameters. |
| Συγγραφείς: |
Homayoon Z; Department of Chemistry and Biochemistry, Texas Tech University , Lubbock, Texas 79409-1061, United States., Pratihar S; Department of Chemistry and Biochemistry, Texas Tech University , Lubbock, Texas 79409-1061, United States., Dratz E, Snider R, Spezia R; Laboratoire Analyse et Modélisation pour la Biologie et l'Environnement, Université d'Evry Val d'Essonne UMR 8587 CNRS-CEA-UEVE , Bd. F. Mitterrand, 91025 Evry Cedex, France., Barnes GL; Department of Chemistry and Biochemistry, Siena College , Loudonville, New York 12211, United States., Macaluso V; Laboratoire Analyse et Modélisation pour la Biologie et l'Environnement, Université d'Evry Val d'Essonne UMR 8587 CNRS-CEA-UEVE , Bd. F. Mitterrand, 91025 Evry Cedex, France., Martin Somer A; Laboratoire Analyse et Modélisation pour la Biologie et l'Environnement, Université d'Evry Val d'Essonne UMR 8587 CNRS-CEA-UEVE , Bd. F. Mitterrand, 91025 Evry Cedex, France., Hase WL; Department of Chemistry and Biochemistry, Texas Tech University , Lubbock, Texas 79409-1061, United States. |
| Πηγή: |
The journal of physical chemistry. A [J Phys Chem A] 2016 Oct 27; Vol. 120 (42), pp. 8211-8227. Date of Electronic Publication: 2016 Oct 13. |
| Τύπος έκδοσης: |
Journal Article |
| Γλώσσα: |
English |
| Στοιχεία περιοδικού: |
Publisher: American Chemical Society Country of Publication: United States NLM ID: 9890903 Publication Model: Print-Electronic Cited Medium: Internet ISSN: 1520-5215 (Electronic) Linking ISSN: 10895639 NLM ISO Abbreviation: J Phys Chem A Subsets: PubMed not MEDLINE |
| Imprint Name(s): |
Original Publication: Washington, D.C. : American Chemical Society, c1997- |
| Περίληψη: |
Direct dynamics simulations, utilizing the RM1 semiempirical electronic structure theory, were performed to study the thermal dissociation of the doubly protonated tripeptide threonine-isoleucine-lysine ion, TIK(H+)2, for temperatures of 1250-2500 K, corresponding to classical energies of 1778-3556 kJ/mol. The number of different fragmentation pathways increases with increase in temperature. At 1250 K there are only three fragmentation pathways, with one contributing 85% of the fragmentation. In contrast, at 2500 K, there are 61 pathways, and not one dominates. The same ion is often formed via different pathways, and at 2500 K there are only 14 m/z values for the product ions. The backbone and side-chain fragmentations occur by concerted reactions, with simultaneous proton transfer and bond rupture, and also by homolytic bond ruptures without proton transfer. For each temperature the TIK(H+)2 fragmentation probability versus time is exponential, in accord with the Rice-Ramsperger-Kassel-Marcus and transition state theories. Rate constants versus temperature were determined for two proton transfer and two bond rupture pathways. From Arrhenius plots activation energies Ea and A-factors were determined for these pathways. They are 62-78 kJ/mol and (2-3) × 1012 s-1 for the proton transfer pathways and 153-168 kJ/mol and (2-4) × 1014 s-1 for the bond rupture pathways. For the bond rupture pathways, the product cation radicals undergo significant structural changes during the bond rupture as a result of hydrogen bonding, which lowers their entropies and also their Ea and A parameters relative to those for C-C bond rupture pathways in hydrocarbon molecules. The Ea values determined from the simulation Arrhenius plots are in very good agreement with the reaction barriers for the RM1 method used in the simulations. A preliminary simulation of TIK(H+)2 collision-induced dissociation (CID), at a collision energy of 13 eV (1255 kJ/mol), was also performed to compare with the thermal dissociation simulations. Though the energy transferred to TIK(H+)2 in the collisions is substantially less than the energy for the thermal excitations, there is substantial fragmentation as a result of the localized, nonrandom excitation by the collisions. CID results in different fragmentation pathways with a significant amount of short time nonstatistical fragmentation. Backbone fragmentation is less important, and side-chain fragmentation is more important for the CID simulations as compared to the thermal simulations. The thermal simulations provide information regarding the long-time statistical fragmentation. |
| Entry Date(s): |
Date Created: 20160928 Latest Revision: 20191120 |
| Update Code: |
20260130 |
| DOI: |
10.1021/acs.jpca.6b05884 |
| PMID: |
27673376 |
| Βάση Δεδομένων: |
MEDLINE |