Abstract Titanium dioxide (TiO2) and zinc oxide (ZnO) are among the most used catalysts in photodegradation. Paracetamol and salicylic acid are widely used as pharmaceutical drugs. We found that paracetamol is less susceptible to photodegradation compared to salicylic acid. From a chemical perspective, this was not expected since paracetamol is more vulnerable to chemical oxidation. Aiming the comprehension of this phenomenon, studies were performed comparing the efficiency of photodegradation of paracetamol versus salicylic acid and acetophenone versus 4-aminoacetophenone. The presence of amino/amide group decreased the efficiency of degradation significantly. It was also found that salicylic acid improved the degradation of paracetamol when both compounds were present in the reaction medium. The lower efficiency of photodegradation of the amino-based compounds seems to be related to the deactivation of the excited states of the TiO2 and ZnO. Theoretical calculations at the TD-PBE0/6-311++G(3df,2p) high level were performed and corroborated our proposal.
In this manuscript we have evaluated the computational methods performance in the calculation of thermochemical properties using graphical analysis. The analysis was carried out in a set of 74 organic molecules considering the following thermochemical properties: standard enthalpy of formation, ionization energy and electron and proton affinities. The evaluated methodologies were: G3, G3MP2, G3B3, G3MP2B3, G4 and G4MP2, and the exchange-correlation func- tionals: SOGGA11, RevTPSS, B3LYP, PBE0, B98, M06-2X, BMK and HSE06. Larger basis function sets (G3LargeXP) were employed with these functionals. It was observed that Gaussian-4 theory using reduced order perturbation theory (G4MP2) offered the best relationships between accuracy and computational cost.
Human serum albumin (HSA) plays an important role in the transport of a wide variety of substances, including compounds with pharmacological properties. The dansylglycine (DanG) is a fluorescent amino acid derivative specific for the site II of HSA. This work aimed to elucidate the induction of chirality in the DanG due to its bonding to the HSA. Theoretical electronic circular dichroism spectra (ECDs) were simulated using the Density Functional Theory (DFT) and the implicit Solvation Model based on Density (SMD). The DanG-HSA complexation resulted in the appearance of a positive ECD spectrum centered at 346 nm. Focusing on the dihedral angles between the -N(CH3)2 group bounded to the naphthalene ring, the potential energy surface (PES) of the DanG was obtained. Analysis of the various conformations obtained revealed that the calculated dihedral angle (150º) is in agreed with the experimental ECD spectrum. In addition, we observed that the nitrogen atom of the -N(CH3)2 group presented the greatest contribution to the HOMO-LUMO transition that gives rise to the n→π* electronic transition involved in the generation of the ECD signal. Molecular docking analysis of the complexation between DanG and HSA revealed a conformation with a dihedral angle similar to that obtained by DFT.
The purpose of this work is to demonstrate the usefulness of low cost high performance computers. It is presented technics and software packages used by computational chemists. Access to high-performance computing power remains crucial for many computational quantum chemistry. So, this work introduces the concept of PC cluster, an economical computing plataform.
This article introduces a simplified model for the theoretical study of the physical adsorption process of gaseous He on the planes (100) and (111) of the solid Xe matrix, whose crystalline structure is face centered cubic (fcc). The Ab initio calculations were carried out at the MP2 level of theory employing basis sets obtained through the Generator Coordinate Method, where the core electrons were represented by a pseudopotential. The calculated adsorption energies for the (100) and (111) faces are 5,39 and 4,18 kJ/mol, respectively. This simplified model is expected to be suitable for treating complex systems of applied interest.