Theoretical Calculations for the Acidity of Cyanopolyynes HC2n+1N (n = 0–5) in Gas and Aqueous Phases Using Ab initio Methods

Cyanopolyynes have been found in the interstellar medium, cold dust cloud Taurus Molecular Cloud-1, and the Titan’s atmosphere. Theoretical calculations are carried out to predict gas and aqueous phase acidities of a series of cyanopolyynes acids. Two levels of theory were used in this study, with the combination of density functional theory, and Møller–Plesset perturbation (MP2) theory, MP2 methods with two types of basis set, namely, Pople’s 6–311++g (d, p) basis set and Dunning’s aug-cc-pVTZ basis set. The calculations of these molecules reveal that pKa values varying from 12.25 to 17.25 and indicate that the acidity of these molecules in aqueous phase increases whereas the acidity in gas phase decreases with an increasing chain length of these acids

Theoretical Study of the [4+2] Cycloaddition Reaction of Trifluoroethylene with Five-membered Chalcogens Heterocyclic Compounds

[4+2] cycloaddition reaction has enormous significant in organic chemistry synthesis reactions and yet remains unexplored for the synthesis of fluorine-containing compounds. A density functional theory study of the stereo- and regioselectivity of the [4+2] cycloaddition reaction of trifluoroethylene with furan, thiophene, and selenophene was carried out in the gas phase. The B3LYP functional is used throughout in combination with 6-31G(d) basis set. The analysis of stationary points and the energetic parameters indicates that the reaction mechanism is concerted and confirms that the exo-adducts are thermodynamically and kinetically more favored than endo-adducts. The calculated branching ratio indicates that the exo-adducts have the higher percent yield than endoadducts and the yield of endo-adducts is increased only slightly on proceeding from furan, through thiophene, and onto selenophene. The analysis of the frontier molecular highest occupied molecular orbital (MO) and lowest unoccupied MO orbitals indicates that the exo-adducts are more stable due to their higher energy gab. The reaction energies were compared to the MP2/6-31G(d) and CCSD(T)/6-31G(d) calculations

Studying of the complexes product of the nerve agent Soman with the Butyrylcholinesterase and Acetylcholinesterase Enzymes

Cholinesterases are among the most efficient enzymes known. They are divided into two groups: acetylcholinesterase (AChE) involved in the hydrolysis of the neurotransimitter acetylcholine, and butyrylcholinesterase (BChE) of unknown function. Several crystal structures of the former have shown that the active site is located at the bottom of a deep and narrow gorge. Human BChE has attracted attention because it can hydrolyze toxic esters and nerve agents. Here we analyze the complexes of cholinesterase with soman by describing the 3D geometry of the complex, the active site, the changes happened through the inhibition and provide a description for the mechanism of inhibition. Soman undergoes degradation in the active site of the AChE and BChE. We calculate the energy of the products of the degradation reaction and suggest the reaction path. The product of the former reaction bind to serine residue in the active site and forming a stable bond and ends the catalytic function of the enzyme. This study has a useful role in the search of inhibitors to help in the treatment of Alzahimer's disease

Length-weight relationships for 13 fish species from the Gulf of Gabes (Southern Tunisia, Central Mediterranean)

Length-weight relationships (LWR) were estimated for 13 fish species which are of economic relevance in the commercial fisheries of the Gulf of Gabes (southern Tunisia). A total of 2403 fish specimens were sampled with several fishing gears from October 2008 to September 2009. The sample size ranged from 65 individuals for Coryphaena hippurus to 346 for Euthynnus alletteratus. The b values in the LWR, W = aLb ranged from 2.807 to 3.284, with a mean of 3.015 ± 0.102 and intercepts between 0.0011 and 0.0432 with a mean of 0.0139. The condition factor (c.f.) values significantly (p < 0.05) ranged from 0.64 to 1.55.Key words: Gulf of Gabes, length-weight, fish species, condition factor

Predictive model of 2-cyclohexylthiophene for corrosion inhibition in mild steel using computational method

Corrosion inhibition activity of 2-cyclohexylthiophene (2CHT) for mild steel in acidic media was predicted using QSAR tool. The model used two descriptors namely; Moran autocorrelation of lag4 weighted by mass (MATS4M) which explained the linearity and branching of the compounds and largest eigen values n3 of burden matrix weighted by mass (SPMAX3-Bh(m)) describes the nature and size of the neighboring atom. The modeling results revealed the potential of the compounds as a good corrosion inhibitor with percentage inhibition efficiency (%IE) of 76.5%. Quantum chemical calculation using DFT with 6-311G++(d,p) basis was used to evaluate the performance of the predicted compound as corrosion inhibitor by quantum chemical parameters such as EHUMO, ELUMO, Energy gap (Egap), hardness (?), softness (S), dipole moment (µ), electronegativity (X), electron affinity (A), ionization energy (I) and total energy (TE). The results obtained from quantum chemical parameters were found to be consistent with predicted result

Chimeric design, synthesis, and biological assays of a new nonpeptide insulin-mimetic vanadium compound to inhibit protein tyrosine phosphatase 1B

Prior to its total synthesis, a new vanadium coordination compound, called TSAG0101, was computationally designed to inhibit the enzyme protein tyrosine phosphatase 1B (PTP1B). The PTP1B acts as a negative regulator of insulin signaling by blocking the active site where phosphate hydrolysis of the insulin receptor takes place. TSAG001, [VVO2(OH)(picolinamide)], was characterized by infrared (IR) and nuclear magnetic resonance (NMR) spectroscopy; IR: ν/cm−1 3,570 (NH), 1,627 (C=O, coordinated), 1,417 (C−N), 970/842 (O=V=O), 727 δ. (pyridine ring); 13C NMR: 5 bands between 122 and 151 ppm and carbonyl C shifted to 180 ppm; and 1H NMR: 4 broad bands from 7.6 to 8.2 ppm and NH2 shifted to 8.8 ppm. In aqueous solution, in presence or absence of sodium citrate as a biologically relevant and ubiquitous chelator, TSAG0101 undergoes neither ligand exchange nor reduction of its central vanadium atom during 24 hours. TSAG0101 shows blood glucose lowering effects in rats but it produced no alteration of basal- or glucose-induced insulin secretion on β cells during in vitro tests, all of which excludes a direct mechanism evidencing the extrapancreatic nature of its activity. The lethal dose (LD50) of TSAG0101 was determined in Wistar mice yielding a value of 412 mg/kg. This value is one of the highest among vanadium compounds and classifies it as a mild toxicity agent when compared with literature data. Due to its nonsubstituted, small-sized scaffold design, its remarkable complex stability, and low toxicity; TSAG0101 should be considered as an innovative insulin-mimetic principle with promising properties and, therefore, could become a new lead compound for potential nonpeptide PTP1B inhibitors in antidiabetic drug research. In view of the present work, the inhibitory concentration (IC50) and extended solution stability will be tested

Bis(2,6-diamino­pyridinium) tartrate monohydrate

In the title compound, 2C5H8N3 +·C4H4O6 2−·H2O, the two cations are essentially planar [maximum deviations = 0.023 (1) and 0.026 (1) Å]. In one of the cations, the protonated N atom and one of the amino group H atoms are hydrogen bonded to one of the carboxyl groups of the dianion through a pair of N—H⋯O hydrogen bonds, forming an R 2 2(8) ring motif. In the crystal structure, the tartrate anions and water mol­ecules are linked into chains along the c axis by inter­molecular O—H⋯O and C—H⋯O hydrogen bonds. The cations further link the anions and water mol­ecules into a three-dimensional extended structure by a network of N—H⋯O hydrogen bonds. The crystal structure is also stabilized by weak inter­molecular π–π inter­actions [centroid–centroid distance = 3.6950 (6) Å]

HR Award II. na UK - KA7

Příspěvek představí aktivity open access univerzitní knihovny chystané v projektech výzvy Rozvoj kapacit pro VaV (MŠMT)

Tetra­guanidinium bis­[citrato(3−)]cuprate(II) dihydrate

The asymmetric unit of the title compound, (CH6N3)4[Cu(C6H5O7)2]·2H2O, contains one-half of a centrosymmetric CuII complex anion, two guanidinium cations and a water mol­ecule. The CuII ion, lying on a crystallographic inversion center, is hexa­coordinated with two citrate anions in a distorted octahedral geometry. An intra­molecular O—H⋯O hydrogen bond generates an S(6) ring motif. In the crystal structure, mol­ecules are linked into a three-dimensional framework by inter­molecular N—H⋯O and O—H⋯O hydrogen bonds