Computational prediction of retention times of veterinary antibiotics obtained by liquid chromatography-mass spectrometry.

Background: Veterinary antibiotics are chemical compounds used to kill or inhibit the growth of pathogenic bacteria associated with animal diseases. These molecules can be defined by their retention times (t) in liquid chromatography-mass spectrometry (LC-MS). One strategy to predict the t of new veterinary antibiotics is the development of predictive quantitative structure-property relationships (QSPRs), which were used in this study.

Chemoinformatic modelling of the antioxidant activity of phenolic compounds.

Background: Antioxidants are chemicals used to protect foods from deterioration by neutralizing free radicals and inhibiting the oxidative process. One approach to investigate the antioxidant activity is to develop quantitative structure-activity relationships (QSARs).

Results: A curated database of 165 structurally heterogeneous phenolic compounds with the Trolox equivalent antioxidant capacity (TEAC) was developed.

Quantitative structure-property relationship analysis for the retention index of fragrance-like compounds on a polar stationary phase.

A quantitative structure-property relationship (QSPR) was developed for modeling the retention index of 1184 flavor and fragrance compounds measured using a Carbowax 20M glass capillary gas chromatography column. The 4885 molecular descriptors were calculated using Dragon software, and then were simultaneously analyzed through multivariable linear regression analysis using the replacement method (RM) variable subset selection technique. We proceeded in three steps, the first one by considering all descriptor blocks, the second one by excluding conformational descriptor blocks, and the last one by analyzing only 3D-descriptor families.

Structural, spectroscopic and DFT study of 4-methoxybenzohydrazide Schiff bases. A new series of polyfunctional ligands.

Five Schiff bases obtained from condensation of 4-methoxybenzohydrazide with related aldehydes, namely o-vanillin, vanillin, 5-bromovanillin, 5-chlorosalicylaldehyde and 5-bromosalicylaldehyde were prepared. A detailed structural and spectroscopic study is reported. The crystal structures of four members of the family were determined and compared with one another.

Determining the molecular basis for the pH-dependent interaction between 2'-deoxynucleotides and 9H-pyrido[3,4-b]indole in its ground and electronic excited states.

Interaction between norharmane and three different 2'-deoxynucleotides (dNMP) (2'-deoxyguanosine 5'-monophosphate (dGMP), 2'-deoxyadenosine 5'-monophosphate (dAMP) and 2'-deoxycytidine 5'-monophosphate (dCMP)), in aqueous solution, was studied in the ground state by means of UV-vis and (1)H-NMR spectroscopy and in the first electronic excited state using steady-state and time-resolved fluorescence spectroscopy. In all cases, the norharmane-dNMP interaction dependence on the pH was examined. Possible mechanisms for the interaction of both ground and electronic excited states of norharmane with nucleotides are discussed.

An experimental and DFT study of a disulfide-linked Schiff base: synthesis, characterization and crystal structure of bis (3-methoxy-salicylidene-2-aminophenyl) disulfide in its anhydrous and monohydrate forms.

A detailed structural and spectroscopic study of the disulfide Schiff base obtained from condensation of 2-aminothiophenol and o-vanillin is reported. It includes the analyses of the anhydrous and monohydrate forms of the title compound. Structures of both solids were resolved by X-ray diffraction methods.

Comment on "The diatomic dication CuZn2+ in the gas phase" [J. Chem. Phys. 135, 034306 (2011)].

In this Comment, the density functional theory (DFT) calculations carried out by Diez et al. [J. Chem.

Computational chemical analysis of unconjugated bilirubin anions and insights into pKa values clarification.

The pKa, the negative logarithm of the acid dissociation equilibrium constant, of the carboxylic acid groups of unconjugated bilirubin in water is a discussed issue because there are quite different experimental values reported. Using quantum mechanical calculations we have studied the conformational behavior of unconjugated bilirubin species (in gas phase and in solution modeled implicitly and explicitly) to provide evidence that may clarify pKa values because of its pathophysiological relevance. Our results show that rotation of carboxylate group, which is not restricted, settles it in a suitable place to establish stronger interactions that stabilizes the monoanion and the dianion to be properly solvated, demonstrating that the rationalization used to justify the high pKa values of unconjugated bilirubin is inappropriate.

Sertraline and its iodine product: experimental and theoretical vibrational studies: potential in vitro anti-thyroid activity of sertraline and iodine product toxicity with respect to male Wistar rats.

Mayor depression, obsessive-compulsive panic, social anxiety disorders are common diseases that are usually treated with sertraline hydrochloride which is the active ingredient of the well known drugs as Zoloft and Lustral. In this work, we presented a more complete vibrational characterization of the solid phase FT-IR spectra of Sertraline hydrochloride and its sertraline-iodine product in which the conformational space of the molecules was investigated performing molecular dynamic simulations within an NVT ensemble. Geometrical, electronic and vibrational properties were calculated with the density functional theory.

Photosensitized electron transfer within a self-assembled norharmane-2'-deoxyadenosine 5'-monophosphate (dAMP) complex.

Norharmane is a compound that belongs to a family of alkaloids called β-carbolines (βCs). These alkaloids are present in a wide range of biological systems, playing a variety of significant photo-dependent roles. Upon UV-A irradiation, βCs are able to act as efficient photosensitizers.

Evaluation of the Hg2+ binding potential of fulvic acids from fluorescence excitation-emission matrices.

The effect of Hg(2+) on the fluorescence intensity of three fulvic acids (Pahokee Peat, Pony Lake and Suwannee River) was studied. The fluorescence intensity decreased in the presence of added Hg(2+), while the fluorescence lifetimes were independent of the concentration of Hg(2+) in solution. These results are indicative of ground-states association between the fulvic acids and Hg(2+) with formation of stable non-fluorescent complexes (static quenching process).

Conformational behavior of peracetylated β-D-mannopyranosyl methanesulfonamide: implications for the mechanism of sulfonamidoglycosylation of carbohydrate derivatives.

The conformational behavior of 2,3,4,6-tetra-O-acetyl-β-D-mannopyranosyl methanesulfonamide has been investigated from a combined theoretical and experimental point of view. The study of the conformational space of the glycosyl sulfonamide revealed that the β anomer is thermodynamically more stable than the α one. This fact suggests that the synthesis reaction could take place mainly under thermodynamic control as the main experimental product is the β-anomeric form of the sulfonamide.

Photoinduced reduction of divalent mercury by quinones in the presence of formic acid under anaerobic conditions.

The laser flash photolysis technique (λ(exc)=355 nm) was used to investigate the mechanism of the HgCl(2) reduction mediated by CO(2)(-) radicals generated from quenching of the triplet states of 1,4-naphthoquinone (NQ) by formic acid. Kinetic simulations of the experimental signals support the proposed reaction mechanism. This system is of potential interest in the development of UV-A photoinduced photolytic procedures for the treatment of Hg(II) contaminated waters.

The diatomic dication CuZn2+ in the gas phase.

In the present combined experimental and theoretical study we report the observation of the novel gas-phase dication CuZn(2+) and provide some theoretical insight into the electronic binding of this exotic metastable molecule and its formation mechanism. Using mass spectrometry we have detected four isotopomer signals of CuZn(2+) at half-integer m/z values for ion flight times of about 14 μs. CuZn(2+) was unambiguously identified by its isotopic abundance.

A combined theoretical and spectroscopic study of 4,6-di-O-acetyl-2,3-dideoxy-D-erythro-hex-2-enopyranosyl sulfamide: a novel glycosyl carbonic anhydrase IX inhibitor.

The novel 4,6-di-O-acetyl-2,3-dideoxy-D-erythro-hex-2-enopyranosyl sulfamide, which exhibits selectivity for inhibiting isoform IX of carbonic anhydrase as overexpressed in many tumors, has been investigated from a combined theoretical and spectroscopic point of view. The conformational study of the compound shows that the α-anomeric form is more stable than the β-anomeric form from a thermodynamic point of view after including solvent effects. This fact suggests that the synthesis reaction could take place mainly under thermodynamic control as the main experimental product is the α-anomeric form of the sulfamide.

Reduction of mercury(II) by the carbon dioxide radical anion: a theoretical and experimental investigation.

The laser flash photolysis technique (λ(exc) = 266 nm) was used to investigate the mechanism of the HgCl(2) reduction mediated by CO(2)(·-) radicals in the temperature range 291.7-308.0 K.

A combined theoretical and experimental study on the oxidation of fulvic acid by the sulfate radical anion.

The kinetics of the reaction of sulfate radicals with the IHSS Waskish peat fulvic acid in water was investigated in the temperature range from 289.2 to 305.2 K.

Observation of Zr2(2+), Cd2(2+), Hf2(2+), W2(2+), and Pt2(2+) in the gas phase.

Five homonuclear diatomic dications Zr(2)(2+), Cd(2)(2+), Hf(2)(2+), W(2)(2+), and Pt(2)(2+) have been observed in the gas phase by mass spectrometry. These exotic doubly positively charged molecules were produced indirectly in the ion extraction region of a secondary ion mass spectrometer during sputtering of zirconium, cadmium, hafnium, tungsten, and platinum metal foils, respectively, by energetic high-current Ar(+) ion surface bombardment. They were detected in positive ion mass spectra at half-integer mz values for ion flight times of the order of approximately 10(-5) s.

Vibrational spectra, NMR and theoretical studies of the enantiomers and rotamers of alpha-cypermethrin.

NMR, infrared and Raman vibrational spectra of alpha-cypermethrin have been measured at room temperature. Infrared spectra were also recorded to low temperature. The spectra were analyzed by means of ab initio calculations.

A theoretical study of a family of new quinoxaline derivatives.

Hybrid density functional calculations are performed on a series of 21 new quinoxaline derivatives, which would likely exhibit important biological activities. Optimized geometries, harmonic vibrational frequencies, and (1)H chemical shifts are reported and compared with experimental data when available. In addition, melting points of 75 derivatives are predicted resorting to the Quantitative Structure-Property Relationship (QSPR) Theory, doing the variable selection by means of the Replacement Method and using 875 theoretical descriptors obtained from Dragon 5 software.

A density-functional study on the formation of Mo(2)2+.

The presence of metastable states in the doubly ionized molybdenum dimer is studied using gradient-corrected scalar-relativistic density-functional theory. Seventeen metastable states are found within an energy range of less than 6.5 eV.