Structural characterization of gas-phase ions of cysteine (Cys) and cysteine methyl ester (CysOMe) complexed to zinc and cadmium is investigated by infrared multiple photon dissociation (IRMPD) action spectroscopy using a free electron laser in combination with density functional theory calculations. IRMPD spectra are measured for [Zn(Cys-H)](+), [Cd(Cys-H)](+), [Zn(CysOMe-H)](+), [Cd(CysOMe-H)...

A practical method for calculating the pKa's of selenols in aqueous solution has been developed by using density functional theory with the SMD solvation model and up to three explicit water molecules. The pKa's of 30 different organoselenols, 16 with known experimental pKa's, have been calculated by using three different functionals (ωB97XD, B3LYP, and M06-2X) and two basis sets (6-31+G(d,p) a...

The IR low-temperature Ar and Kr matrix spectra of l-isoserine were registered for the first time and interpreted by means of the anharmonic DFT frequencies calculated at the B3LYP/aug-cc-pVTZ and B3LYP/aug-cc-pVDZ levels. 54 l-isoserine conformers were predicted to be stable at the B3LYP/aug-cc-pVDZ level. Population of the 8 most stable conformers was based on the QCISD/aug-cc-pVDZ energies, ...

Relative populations of the three energy-lowest IPR (isolated-pentagon-rule) isomers Ho@C 82 under high-temperature synthetic conditions are computed using Gibbs energy based on characteristics from density functional theory calculations (B3LYP/3-21G ∼ SDD entropy term, B3LYP/6-31G* energetics). Two major species predicted, Ho@ C 2 v ; 9-C and s ( c ); 6-C , with rather comparable supposed temp...

We investigate the performance of CC2 and TDDFT/CAM-B3LYP for the calculation of two-photon absorption (TPA) strengths and cross sections and contrast our results to a recent coupled cluster equation-of-motion (EOM-EE-CCSD) benchmark study [K. D. Nanda and A. I. Krylov, J. Chem. Phys., 2015, 142, 064118]. In particular, we investigate whether CC2 TPA strengths are significantly overestimated co...

Получено распределение электронной плотности трех транс- и цис- изомеров метилового красного с помощью квантово-химических расчётов (DFT) функционалом B3LYP. Изучены внутримолекулярные слабые взаимодействия в рамках «квантовой теории атомов молекулах» (QTAIM). The electron density distribution of three trans- and cis -forms methyl red is obtained by the B3LYP approximation. comparison intramole...

Phenylalanine (Phe) is one of the amino acids that cannot be produced in body and must ingested through diet. Tyrosine (Tyr) also a non-essential acid can by Phe hydroxylation liver when dietary intake Tyr low. Structure analysis very important to know correct synthesis reactivity molecule. In this study, characterization molecules were investigated using quantum chemical calculations. The mole...

Depending on the selected DFT functional, two different mechanisms are found for two organic reactions (an intramolecular nucleophilic aromatic substitution and a nucleophilic addition on a carbonyl moiety). Indeed, B3LYP predicts a concerted mechanism whereas M06-2X foresees a multistep one. Calculations at the MP4(SDQ) level proved the mechanisms to be stepwise. We studied these reactions wit...