The effect of La, Ce, Pr and Nd ions on four Ln(ligand)3 complexes and at three DFT levels of calculation was analyzed. Four ligands were chosen, three of which were based on the 1,2,3-triazole ring. The DFT methods used were B3LYP, CAM-B3LYP and M06-2X. The relationships established were between the geometric parameters, atomic charges, HOMO-LUMO energies and other molecular properties. These comparisons and trends will facilitate the synthesis of new complexes by selecting the ligand and lanthanide ion best suited to the desired property of the complex. The experimental IR and Raman spectra of Ln(2b\')3 complexes where Ln = La, Ce, Pr, Nd, Sm, Gd, Dy, Ho and Er ions have been recorded and compared to know the effect of the lanthanide ion on the complex. The hydration in these complexes was also analyzed. Additionally, the effect of the type of coordination center on the ability of an Ln(ligand)3 complex to participate in electron exchange and hydrogen transfer was investigated using two in vitro model systems-DPPH and ABTS.

BACKGROUND: Bismuth complexes with dithiocarbamate ligands have attracted attention because of their biological applications, such as antimicrobial, antileishmanial, and anticancer properties. These complexes have high cytotoxic activity against cancer cells, being more active than the standard drugs cisplatin, doxorubicin, and tamoxifen. In the present study, we investigated the ability of some DFT methods to reproduce the geometries and NMR spectra of the Bi(III) dithiocarbamate complexes, selected based on their proven antitumor activity. Our investigation revealed that the M06-L/def2-TZVP/ECP/CPCM method presented good accuracy in predicting geometries, while the TPSSh/def2-SVP/ECP/CPCM method proved effective in analyzing the 13C NMR spectra of these molecules. In general, all examined methods exhibited comparable performance in predicting 1H NMR signals.
METHODS: Calculations were performed with the Gaussian 09 program using the def2-SVP and def2-TZVP basis sets, employing relativistic effective core potential (ECP) for Bi and using the CPCM solvent model. The exchange-correlation functionals BP86, PBE, OLYP, M06-L, B3LYP, B3LYP-D3, M06-2X, TPSSh, CAM-B3LYP, and ωB97XD were used in the study. Geometry optimizations were started from crystallographic structures available at the Cambridge Structural Database. The theoretical results were compared with experimental data using the mean root-mean-square deviation (RMSD), mean absolute deviations (MAD), and linear correlation coefficient (R2).

BACKGROUND: The influence of hybrid solvation models on the molecular structures and vibrational characteristics of g-aminobutyric acid (GABA) and a-aminoisobutyric acid (AIB) zwitterions was assessed by employing a variety of Density Functional Theory (DFT). The quantum chemical methods included the B3LYP and B3PW91 hybrid functionals and the 6‑311++G(d,p) basis set.
METHODS: The most stable conformation derived from the potential energy surface (PES) scans using the B3LYP/6-311++G(d,p) model chemistry for each studied molecule was predicted within a continuum environment represented by the COSMO and SMD solvation models. The stable structures were subsequently immersed in explicit/COSMO and explicit/SMD hybrid solvation models, where 10 and 8 water molecules were explicitly positioned around the functional groups of the GABA and AIB zwitterions, respectively. The number of water molecules chosen was sufficient to prevent proton transfer among the carboxylate group (COO-) and the ammonium group (NH3+) within each molecule under investigation. After optimizing the geometry of each hydrated complex, the normal vibrational modes were determined. The scaled theoretical frequencies obtained from the various model chemistries were then compared to available experimental data from infrared (IR) and Raman spectroscopy.
RESULTS: In the case of GABA and AIB molecules, the comparisons revealed that the B3LYP/6-311++G(d,p) model chemistry yielded wavenumber values that closely matched the experimental IR and Raman data, particularly when the explicit/SMD solvent was employed. The computed results indicate deviations of less than 4% when compared to the experimental data for the two molecules under investigation.

A structural and spectroscopic study of 5-chloroorotic acid (5-ClOA) biomolecule was carried out by IR and FT-Raman and the results obtained were compared to those achieved in 5-fluoroorotic acid and 5-aminoorotic acid compounds. The structures of all possible tautomeric forms were determined using DFT and MP2 methods. To know the tautomer form present in the solid state, the crystal unit cell was optimized through dimer and tetramer forms in several tautomeric forms. The keto form was confirmed through an accurate assignment of all the bands. For this purpose, an additional improvement in the theoretical spectra was carried out using linear scaling equations (LSE) and polynomic equations (PSE) deduced from uracil molecule. Base pairs with uracil, thymine and cytosine nucleobases were optimized and compared to the natural Watson-Crick (WC) pairs. The counterpoise (CP) corrected interaction energies of the base pairs were also calculated. Three nucleosides were optimized based on 5-ClOA as nucleobase, and their corresponding WC pairs with adenosine. These modified nucleosides were inserted in DNA:DNA and RNA:RNA microhelices, which were optimized. The position of the -COOH group in the uracil ring of these microhelices interrupts the DNA/RNA helix formation. Because of the special characteristic of these molecules they can be used as antiviral drugs.Communicated by Ramaswamy H. Sarma.

The catecholase activities were routinely modeled using transition metal complexes as catalyst and in some case basic pH were used as a reaction condition. In this article, the catalytic aerobic oxidation of proxy substrate 3,5-di-tert-butylcatechol (DTBC) in methanol using triethylamine/diethylamine as catalyst was demonstrated as a functional mimic of catecholase activity. The kinetic manifestation of DTBC oxidation was explained as enzymatic substrate inhibition pattern in Michaelis-Menten kinetic model. The mechanistic insight of the aerobic oxidation of DTBC was further validated using various spectroscopic techniques and DFT methods.

The antioxidant activity of nine lichen substances, including methylatrarate (1), methyl haematommate (2), lobaric acid (3), fumarprotocetraric acid (4), sphaerophorin (5), subsphaeric acid (6), diffractaic acid (7), barbatolic acid (8) and salazinic acid (9) has been determined through cyclic voltammetry. The compounds 1-4 presented slopes close to the Nernst constant of 0.059 V, indicating a 2H+/2e- relation between protons and electrons, as long as the compounds 5, 6, 7, 8, and 9 present slopes between 0.037 V and 0.032 V, indicating a 1H+/2e- relation between protons and electrons. These results show a high free radical scavenging activity by means of the release of H+, suggesting an important antioxidant capacity of these molecules. Theoretical calculations of hydrogen bond dissociation enthalpies (BDE), proton affinities (PA), and Proton Transfer (PT) mechanisms, at M06-2x/6-311+G(d,p) level complement the experimental results. Computations support that the best antioxidant activity is obtained for the molecules (3, 4, 5, 6, 7 and 8), that have a carboxylic acid group close to a phenolic hydroxyl group, through hydrogen atomic transfer (HAT) and sequential proton loss electron transfer (SPLET) mechanisms. Additional computations were performed for modelling binding affinity of the lichen substances with CYPs enzymes, mainly CYP1A2, CYP51, and CYP2C9*2 isoforms, showing strong affinity for all the compounds described in this study.

This work is focused on evaluating the performance of exchange-correlation functionals from density functional theory in providing descriptor values derived from the electron density of saddle point structures (transition states) in chemical reactions. The properties investigated were obtained from the quantum theory of atoms in molecules, including atomic charges and electron density topological data at the bond critical points. In addition, parameters from the Interacting quantum atom energy partition were used as well in this comparative study. The reference values are attained in coupled cluster calculations with iterative single and double excitations (CCSD). Six elementary reactions are considered here: CO + H2  ↔ H2 CO, CO + H2 O ↔ HCOOH, HCN ↔ HNC, H + F2  ↔ HF + F, H + N2  ↔ HN2 , and H + CO ↔ HCO. In general, the BB1K functional (hybrid-meta-generalized gradient approximation) provides the best description of these properties. Our study indicates that an intermediate percentage of nonlocal exact exchange, around 40%-55% (perhaps even larger), is probably required for attaining more accurate values with actual functionals, although this condition is not able of explaining all the trends observed.

Biologically active compounds containing sulfhydryl groups (RSHs: N-acetyl-l-cysteine, d-penicillamine, glutathione and acetylthiocholine chloride) were used to develop a luminometric method for their quantification. The title substrate capable of chemiluminescence (CL) was isolated in a highly pure state as a chloride salt (99.9% using RP-HPLC) and identified using mass spectrometry (ESI Q-TOF) and 1 H NMR spectroscopy. The cation included in the salt, 9-CMA+ , underwent oxidation in an alkaline environment containing RSHs by molecular oxygen, generating CL of various intensities, with no need for the use of hydrogen peroxide. The amount of produced light was linearly proportional to the content of investigated analytes in the system over the concentration range ~0.2-2 μM, with the detection limits in the range 0.19-1.73 μM. The mechanism of chemiluminogenic oxidation of 9-CMA+ in the presence of RSHs and molecular oxygen is proposed, using computational methods at the density-functional theory level. The presence of RSHs in an alkaline medium seems to be crucial to produce hydroperoxide anions (- OOH), which initiate the \'light path\' of 9-CMA+ transformations, ending with the excretion of electronically excited molecules of 10 methyl-acridan-9-one.

Taxanes (paclitaxel, docetaxel, cabazitaxel) are anticancer drugs as microtubule inhibitors. Following our previous studies on paclitaxel and docetaxel, in this work, we examine cabazitaxel and compare these three taxenes. The binding interaction of three taxanes with various β-tubulin isotypes is studied by homology modeling, molecular docking, and molecular dynamics simulations. The results show that the effects of docetaxel on βI-tubulin (- 29.5 kcal/mol) and of paclitaxel on βIIa-tubulin (- 25.5 kcal/mol) are much stronger than their effects on βIII-tubulin (- 17.8 kcal/mol and - 8.6 kcal/mol, respectively). However, the effect of cabazitaxel on βIII-tubulin (- 23.0 kcal/mol) is comparable with that on βI-tubulin (- 24.0 kcal/mol) and βIIa-tubulin (- 25.9 kcal/mol), consistent with the fact that overexpression of βIII-tubulin increases the drug resistance to paclitaxel and docetaxel, but has little influence for cabazitaxel. This theoretical research supports the use of cabazitaxel for patients who are resistant to the action of paclitaxel and docetaxel.

5-Fluorouracil (5FU), a common anti-cancer drug, occurs in four tautomeric forms and possesses two potential sites of both protonation and deprotonation. Tautomeric and resonance structures of the ionized forms of 5FU create the systems of connected equilibriums. Since there are contradictory reports on the ionized forms of 5FU in the literature, complex theoretical studies on neutral, protonated and deprotonated forms of 5FU, based on the broad spectrum of DFT methods, are presented. These indicate that the O4 oxygen is more willingly protonated than the O2 oxygen and the N1 nitrogen is more willingly deprotonated than the N3 nitrogen in a gas phase. Such preferences are due to advantageous charge delocalization of the respective ions, which is demonstrated by the NBO and ESP analyses. In an aqueous phase, stability differences between respective protonated and deprotonated forms of 5FU are significantly diminished due to the competition between the mesomeric effect and solvation. The calculated pKa values of the protonated, neutral and singly deprotonated 5FU indicate that 5FU does not exist in the protonated and double-deprotonated forms in the pH range of 0-14. The neutral form dominates below pH 8 and the N1 deprotonated form dominates above pH 8.