A DFT Study of the Reaction of Acrylamide with L-Cysteine and L-Glutathione.

Thermal processing of certain foods implies the formation of acrylamide, which has been proven to provoke adverse effects on human health. Thus, several strategies to mitigate it have been developed. One of them could be the application of organosulfur compounds obtained from natural sources to react with the acrylamide, forming non-toxic adducts. A DFT study of the acrylamide reaction with the organosulfur model compounds L-cysteine and L-glutathione by Michael addition and a free radical pathway complemented by a kinetic study of these model molecules has been applied. The kinetic evaluation results demonstrate that the L-glutathione reaction exhibited a higher rate constant than the other studied compound.

Assessment of Simultaneous Global Optimization of Geometry and Total Spin of Small Iron Clusters.

In this work, simultaneous global optimization of geometry and total spin of small iron clusters Fen (3 ≤ n ≤ 40) is assessed using Simulated Annealing (SA) simulations with forces calculated at the DFT-based Tight-Binding (DFTB) level of theory. In order to optimize the total spin, the occupancies of α and ß densities were allowed to relax at each SA step, resulting in a continuous variation of the total spin along the trajectory. The behavior and performance of the procedure were investigated running two series of 10 independent "long" molecular dynamics simulations and one series of 100 independent "short" simulations. Cluster structures optimized with the assessed methodology reproduced geometries and magnetic moments reported in a previous work very well where multiple fixed total spin and geometries of iron clusters were individually probed, and for some clusters, more stable global minima were found. Other properties such as binding energies and second energy differences were also calculated in order to compare with previously reported theoretical and experimental values. The few mismatches were found to be driven by quasi degenerated ground states with different magnetic moments or by states with crossing free energies at high temperatures.

Electrochemical and theoretical studies of the interactions of a pyridyl-based corrosion inhibitor with iron clusters (Fe15, Fe30, Fe45, and Fe60).

The capacity of 2,6-bis[((2-pyridylmethyl)oxy)methyl)]pyridine (BPMMP) to inhibit the corrosion of mild carbon steel in HCl was analyzed. In a polarization study, both the cathodic and anodic currents were appreciably decreased in the presence of BPMMP, suggesting that this ligand is effective at inhibiting corrosion at the metal surface. This conclusion is consistent with the results of impedance analysis, where only one time constant corresponding to one depressed capacitive loop was detected, and the diameter of the impedance plot was directly related to the concentration of BPMMP. Furthermore, when recurrence analysis was performed, a decrease in regular noise was observed due to the change of Shannon entropy when the inhibitor was present in the corrosive medium, showing that a high degree of recurrence increases the entropy of the system. Electrochemical data on some pyridyl-based inhibitors were collected from the literature and used to plot (i) I corr (A/cm2) vs. inhibition efficiency (η%) and (ii) ΔG°ads vs. inhibition efficiency (ƞ%) in order to examine the general relationships between these parameters. Furthermore, the interactions of the ligand BPMMP with different iron clusters (Fe15, Fe30, Fe45, and Fe60) were analyzed theoretically using density functional theory (DFT). The structural and electronic properties of BPMMP and its protonated form BPMMPH+ were studied before and after the interactions of BPMMP with the iron clusters. The first protonation was found to occur at pyridine nitrogen atom N1, resulting in a Gibbs free energy ΔG of -10.2 kcal/mol, with an energy difference of 5.3 kcal/mol between the two possible protonated conformers. Graphical abstract Recurrence and Noise signal performance of BPMMP as corrosion inhibitor.

Reduced density gradient as a novel approach for estimating QSAR descriptors, and its application to 1, 4-dihydropyridine derivatives with potential antihypertensive effects.

The relationship between the chemical structure and biological activity (log IC50) of 40 derivatives of 1,4-dihydropyridines (DHPs) was studied using density functional theory (DFT) and multiple linear regression analysis methods. With the aim of improving the quantitative structure-activity relationship (QSAR) model, the reduced density gradient s( r) of the optimized equilibrium geometries was used as a descriptor to include weak non-covalent interactions. The QSAR model highlights the correlation between the log IC50 with highest molecular orbital energy (E HOMO), molecular volume (V), partition coefficient (log P), non-covalent interactions NCI(H4-G) and the dual descriptor [Δf(r)]. The model yielded values of R 2=79.57 and Q 2=69.67 that were validated with the next four internal analytical validations DK=0.076, DQ=-0.006, R P =0.056, and R N=0.000, and the external validation Q 2boot=64.26. The QSAR model found can be used to estimate biological activity with high reliability in new compounds based on a DHP series. Graphical abstract The good correlation between the log IC50 with the NCI (H4-G) estimated by the reduced density gradient approach of the DHP derivatives.