| 1. |
- Andres, J, et al.
(författare)
-
Transition-state structures for describing the enzyme-catalyzed mechanisms of rubisco
- 1999
-
Ingår i: THEORETICAL CHEMISTRY ACCOUNTS. - : SPRINGER VERLAG. - 1432-881X. ; 101:1-3, s. 234-240
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The carboxylation and oxygenation processes of a model substrate, 3,4-dihydroxy-2-pentanone, have been theoreticaly characterized as a set of steps? mimicking the corresponding reactions of D-ribulose-1,5-bisphosphate catalyzed by rubisco. A theoretical c
|
|
| 2. |
- Andres, J, et al.
(författare)
-
Transition structures for hydride transfer reactions in vacuo and their role in enzyme catalysis
- 1996
-
Ingår i: Journal of Molecular Structure: THEOCHEM. - : Elsevier. - 0166-1280. ; 371, s. 299-312
-
Forskningsöversikt (refereegranskat)abstract
- A general discussion as to the role of in vacuo transition structure in enzyme catalysis is presented. Quantum mechanical aspects are emphasized. The transition structures defined as saddle points of index one (SPi-1) for the hydride transfer step on different model enzyme systems from flavoproteins to dehydrogenases have been characterized with analytical gradients at different levels of theory: semi-empirical; ab initio with different basis sets within the Hartree-Fock scheme; density functional theory using different approaches. Quantum chemical characteristics of the SPi-1 are used to discuss hydride transfer step in enzyme catalyzed reactions and mechanistic implications. With the exception of dihydrofolate reductase, the results for all other systems studied suggest that the endo relative orientation imposed by the active site on the reactants is essential for polarizing the CdHt bond and situating the system in the quadratic region of the endo SPi-1. The geometry and transition vector components are both model independent and weakly dependent on the level of theory used in their determination. Comparisons of the SPi-1 geometries with available X-ray coordinates show that the SPi-1 can be fitted without any stress at the active site. The geometrical arrangement of the SPi-1 results in optimal frontier LUMO orbital interactions, and the transition vector amplitudes show primary and secondary isotope effects to be strongly coupled. A comparison between simple and sophisticated molecular models shows that there is a minimal molecular model associated with geometrical parameters describing the essentials of the chemical interconversion step. For hydride transfer, the corresponding transition vector is an invariant feature.
|
|
| 3. |
|
|
| 4. |
- Contreras, R, et al.
(författare)
-
Hydrogen bonding and dissociation effects on the gas phase proton transfer reactions of ozone
- 1998
-
Ingår i: THEORETICAL CHEMISTRY ACCOUNTS. - : SPRINGER VERLAG. ; 99:1
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Recently, the proton affinity (PA) of ozone was experimentally determined by Cacace and Speranza [Science (1994) 265: 208] using a bracketing technique that involved the proton transfer (PT) reactions: O3H+ + B double right arrow O-3 + BH+; for different
|
|
| 5. |
|
|
| 6. |
- Oliva, M, et al.
(författare)
-
A theoretical study of the molecular mechanism for the carboxylation chemistry in Rubisco
- 1999
-
Ingår i: JOURNAL OF PHYSICAL CHEMISTRY A. - : AMER CHEMICAL SOC. - 1089-5639. ; 103:43, s. 8725-8732
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Stereochemical and structural aspects for the carbon dioxide fixation followed by hydration of D-ribulose 1,5-bisphosphate catalyzed by Rubisco are analyzed by using two model substrates, hydroxypropanone and 3,4-dihydroxy-2-pentanone. The molecular mecha
|
|
| 7. |
- Oliva, M, et al.
(författare)
-
Electronic mechanistic pattern for C-C bond-breaking from transition structures in Rubisco's chemistry
- 2001
-
Ingår i: CHEMICAL PHYSICS LETTERS. - : ELSEVIER SCIENCE BV. - 0009-2614. ; 340:5-6, s. 391-399 Language: English
-
Tidskriftsartikel (refereegranskat)abstract
- The transition structures (TSs) for the carbon-carbon bond-breaking step in the carboxylation and oxygenation reactions catalyzed by Rubisco are studied at HF/6-31G** and full MP2/6-31G** levels. The active atoms of the substrate (ribulose 1,5-bisphosphat
|
|
| 8. |
|
|
| 9. |
- Oliva, M, et al.
(författare)
-
Theoretical study of the molecular mechanism for the oxygenation chemistry in rubisco
- 1999
-
Ingår i: JOURNAL OF PHYSICAL CHEMISTRY A. - : AMER CHEMICAL SOC. - 1089-5639. ; 103:30, s. 6009-6016
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- A set of transition structures (TSs) related to the oxygenation reaction catalyzed by Rubisco is characterized theoretically. The TSs correspond to dioxygen fixation at the C2 center, hydrolysis, and C2-C3 bond breaking; reaction intermediates were found
|
|
| 10. |
|
|
