Kinetics and thermodynamics of enzymatic decarboxylation of α,β-unsaturated acid: a theoretical study.

Enzymatic decarboxylation of α,β-unsaturated acid through ferulic acid decarboxylase (FDC1) has been of interest because this reaction has been anticipated to be a promising, environmentally friendly industrial process for producing styrene and its derivatives from natural resources. Because the local dielectric constant at the active site is not exactly known, enzymatic decarboxylation to generate β-methylstyrene (β-MeSt) was studied under two extreme conditions ( = 1 and 78 in the gas phase and aqueous solution, respectively) using the B3LYP/DZP method and transition state theory (TST). The model molecular clusters consisted of an α-methylcinnamate (Cin) substrate, a prenylated flavin mononucleotide (PrFMN) cofactor and all relevant residues of FDC1.

The mechanism of excited state proton dissociation in microhydrated hydroxylamine clusters.

The dynamics and mechanism of excited-state proton dissociation and transfer in microhydrated hydroxylamine clusters are studied using NH2OH(H2O)n (n = 1-4) as model systems and the DFT/B3LYP/aug-cc-pVDZ and TD-DFT/B3LYP/aug-cc-pVDZ methods as model calculations. This investigation is based on the Förster acidity scheme and emphasizes the photoacid dissociation in the ground (S0) and lowest singlet-excited states (S1) and the interplay between the photo and thermal excitations. The quantum chemical results suggest that the intermediate complexes are formed only in the S1 state in a low local-dielectric environment (e.

Proton transfer reactions and dynamics of sulfonic acid group in Nafion®.

Proton transfer reactions and dynamics of the hydrophilic group (-SO(3)H) in Nafion® were studied at low hydration levels using the complexes formed from CF(3)SO(3)H, H(3)O(+) and nH(2)O, 1 ≤n≤ 3, as model systems. The equilibrium structures obtained from DFT calculations suggested at least two structural diffusion pathways at the -SO(3)H group namely, the "pass-through" and "pass-by" mechanisms. The former involves the protonation and deprotonation at the -SO(3)H group, whereas the latter the proton transfer in the adjacent Zundel complex.

Proton transfer reactions and dynamics in protonated water clusters.

Proton transfer reactions and dynamics were theoretically studied using the hydrogen-bond (H-bond) complexes formed from H(3)O(+) and nH(2)O, n = 1-4, as model systems. The investigations began with searching for characteristics of transferring protons in the gas phase and continuum aqueous solution using DFT method at the B3LYP/TZVP level, followed by Born-Oppenheimer molecular dynamics (BOMD) simulations at 350 K. B3LYP/TZVP calculations revealed the threshold asymmetric O-H stretching frequencies (ν(OH)*) for the proton transfers in the Zundel complex (H(5)O) in the gas phase and continuum aqueous solution at 1984 and 1881 cm(-1), respectively.

Mechanisms of proton transfer in Nafion: elementary reactions at the sulfonic acid groups.

Proton transfer reactions at the sulfonic acid groups in Nafion were theoretically studied, using complexes formed from triflic acid (CF3SO3H), H3O+ and H2O, as model systems. The investigations began with searching for potential precursors and transition states at low hydration levels, using the test-particle model (T-model), density functional theory (DFT) and ab initio calculations. They were employed as starting configurations in Born-Oppenheimer molecular dynamics (BOMD) simulations at 298 K, from which elementary reactions were analyzed and categorized.