Conceptual Density Functional Theory

Abstract

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Combined Docking and Quantum Chemical Study on CYP-Mediated Metabolism of Estrogens in Man

“…In the case of compound I the reactions may happen both in the quartet or the doublet states, but earlier calculations clearly show that aromatic carbon oxidation has a lower barrier on the doublet surface. 64,65 The doublet state calculations were preceded by calculations in the quartet state and the molecular orbitals were checked to ensure that the correct doublet state was obtained, where the spin of the electron found on the molecular orbital composed of a combination of a porphyrin π orbital with idealized a2u symmetry and a p orbital on sulfur was opposite to the spins of the electrons found in the Reactivity indices 66 have been calculated based on eq (1), eq (2) and eq (3) at the B3LYP/6-311+G* level of theory from the NPA charges 67 of the neutral, positively and negatively charged species, all calculated at the optimized geometry of the neutral species: Fukui function for a nucleophilic attack ( + ) provoking an electron increase in the system, Fukui function for electrophilic attack ( − ) provoking an electron decrease in the system, and ( 0 ) for a radical attack on the system. 68…”

The conserved active site tryptophan of thioredoxin has no effect on its redox properties

“…It is not possible to exclude one of the possibilities experimentally, because upon the introduction of the Trp28Ala mutation, Trx shows the tendency to partially unfold. 5 Therefore, theoretical pKa calculations and density functional theory (DFT) [7][8][9] reactivity analysis on model systems with Trp28 replaced by alanine within the structural environment of wild type Trx are used to give insight in the intrinsic role of Trp28 on the redox behavior of Trx.…”

“…To compare the reactivity of Cys29 and Cys32 in the presence and absence of the indole side chain of Trp28, we used the local version of the soft acids and bases principle (HSAB). [17][18][19] This principle has been formulated in a conceptual DFT 9 context and states that hard acids prefer to react with hard bases whereas soft acids prefer to interact with soft bases. Disulfide exchange reactions are soft-soft interactions; as such the softness is used as a reactivity descriptor.…”

“…9 f is the Fukui function 8,9 and indicates the orientation effect of a chemical reaction: which nucleophilic sulfur atom (f À ) will attack and which sulfur (f þ ) of the disulfide will receive electrons. The À and þ sign indicate the reactivity towards nucleophilic and electrophlic attacks respectively.…”

“…f À is related to the electron density of the highest occupied molecular orbital and f þ to the density of the lowest unoccupied molecular orbital when electrons are received. 20 The global and local softness and the Fukui function are well established and extensively used to study generalized acid/base reactions including most of the organic reactions (additions, substitutions, eliminations) 9 of which disulfide exchange reactions are an example.…”