Potentiometric and Multinuclear Magnetic Resonance Study of the Solution Equilibria Between Aluminium(III) Ion and L-Aspartic Acid

Solution equilibria between aluminium(III) ion and L-aspartic acid were studied by potentiometric, ²⁷Al, ¹³C, and ¹H NMR measurements. Glass electrode equilibrium potentiometric studies were performed on solutions with ligand to metal concentration ratios 1:1, 3:1, and 5:1 with the total metal concentration ranging from 0.5 to 5.0 mmol/dm³ in 0.1 mol/dm³ LiCl ionic medium, at 298 K. The pH of the solutions was varied from ca. 2.0 to 5.0. The non-linear least squares treatment of the data performed with the aid of the Hyperquad program, indicated the formation of the following complexes with the respective stability constants log β_p,q,r given in parenthesis (p, q, r are stoichiometric indices for metal, ligand, and proton, respectively): Al(HAsp)²⁺ (log β_1,1,1 = 11.90 ± 0.02); Al(Asp)⁺ (log β_1,1,0 = 7.90 ± 0.03); Al(OH)Asp⁰ (log β_1,1,−1 = 3.32 ± 0.04); Al(OH)₂Asp⁻ (log β_1,1−2 = −1.74 ± 0.08), and Al₂(OH) Asp³⁺ (log β_2,1,−1 = 6.30 ± 0.04). ²⁷Al NMR spectra of Al³⁺ + aspartic acid solutions (pH 3.85) indicate that sharp symmetric resonance at δ∼10 ppm can be assigned to (1, 1, 0) complex. This resonance increases in intensity and slightly broadens upon further increasing the pH. In Al(Asp)⁺ complex the aspartate is bound tridentately to aluminum. The ¹H and ¹³C NMR spectra of aluminium + aspartic acid solutions at pH 2.5 and 3.0 indicate that β-methylene group undergoes the most pronounced changes upon coordination of aluminum as well as α-carboxylate group in ¹³C NMR spectrum. Thus, in Al(HAsp)²⁺ which is the main complex in this pH interval the aspartic acid acts as a bidentate ligand with –COO⁻ and –NH₂ donors closing a five-membered ring.     

Structure of Diels-Alder adduct of phenylated germole and 1,4-epoxy-1,4-dihydronaphthalene revisited

High pressure synthesis of Diels-Alder adduct of 1,1-dimetyl-2,3,4,5-tetraphenylgermole and 6,7-dibromo-1,4-epoxy-1,4-dihydronaphthalene is described. The X-ray crystallography analysis of the so obtained adduct indicated that the adduct has exo,endo-structure in agreement with our earlier proposal for the stereochemistry of the structurally related germa analogue, 11,11-dimethyl-9,10-epoxy-1,4-germa-1,2,3,4-tetraphenyl-1,4,4a,9,9a,10-hexahydroanthracene based on NMR analysis.     

Screening of laccase, manganese peroxidase, and versatile peroxidase activities of the genus Pleurotus in media with some raw plant materials as carbon sources

Species of the genus Pleurotus are among the most efficient natural species in lignin degradation belonging to the subclass of ligninolytic organisms that produce laccase (Lac), Mn-dependent peroxidase (MnP), versatile peroxidase (VP), and the H₂O₂-generating enzyme aryl-alcohol oxidase, but not lignin peroxidases. Production of Lac and oxidation of 2,6-dimethoxyphenol (DMP) in the presence and absence of Mn²⁺ were detected both in submerged fermentation (SF) of dry ground mandarine peels and in solid-state fermentation (SSF) of grapevine sawdust in all investigated Pleurotus species and strains. Evidence of cultivation methods having a distinct influence on the level of enzyme activities has been demonstrated. Most of the species and strains had higher Lac activity under SSF conditions than under SF conditions. DMP oxidation in the presence and absence of Mn²⁺ was detected in all investigated species and strains, but was lower under SF conditions than under SSF conditions for most of them. However, relative activities of DMP oxidation in the absence of Mn²⁺, as percentages of activity agasint DMP in the presence of Mn²⁺, were higher under conditions of SF than in SSF cultures in most of the investigated species and strains. The obtained results showed that strains of different origins have different efficiently ligninolytic systems and that conditions of SSF are more favorable for ligninolytic activity than those in SF owing to their similarity to natural conditions on wood substrates.     

The Synthesis of Novel Iodinated Iminodiacetic Acid Analogues as Hepatobiliary Imaging Agents

The synthesis and characterization of N-[2-[[4-iodo-2,6-bis(1-methylethyl)phenyl]amino]-2-oxoethyl]-N-(carboxymethyl)glycine and N-[2-[(4-iodo-2,6-diethylphenyl)amino]-2-oxoethyl]-N-(carboxymethyl)glycine is presented, as well as a modified and improved synthesis of N-[2-[(2,4-diiodo-6-methylphenyl)amino]-2-oxoethyl]-N-(carboxymethyl)glycine. These compounds are new agents for hepatobiliary imaging.     

Solvent,ligand, pressure,and temperature effects on charge-transfer spectra of tetracarbonylmolybdenum(0) diimine complexes

Summary The solvent, pressure, and temperature-dependence of the lowest energy metal-to-ligand charge-transfer absorption bands are reported for a series of [Mo(CO)₄(LL)], compounds where LL is a bidentate diimine ligand containing the chelating fragment –N=CRCR=N–, and one terdentate ligand analogue [Mo(CO)₃(LLL)]. The effects of ligand nature on these dependences are discussed, as are their interrelations and their connection with solvent properties such as polarity.     

An alternative Gentzenisation of

In this paper, we give a sequent calculus for the positive contraction‐less relevant logic and we give a proof that it is cut‐free without the use of the truth constant t. Based on , we re‐prove the decidability of the logic .     

The Antiferromagnetic Spin Coupling in Non‐Kekulé Acenes—Impressive Polyradical Character Revealed by High‐Level Multireference Methods

Complete active space (CASSCF) and multireference (MR‐CISD(Q) and MR‐AQCC) calculations were performed for non‐Kekulé analogues of acenes, dimethylenepolycyclobutadienes, with lengths of up to eight cyclobutadiene (CBD) units. Multireference calculations predict that the most stable energy state of the system is either triplet (if there is an odd number of CBD units) or singlet (if there is an even number of CBD units) due to antiferromagnetic spin coupling, which thus violates Hund's rule in larger molecules. We also show an impressive polyradical character in the system that increases with the size of the molecule, as witnessed by more than eleven unpaired electrons in the singlet state of the molecule with eight CBD units. Together with the small energy gap between singlet and higher multiplicity energy states even above the triplet state, this demonstrates the exceptional polyradical properties of these π‐conjugated oligomeric chains.     

Chemical composition, antioxidant and antibacterial properties of Achillea collina Becker ex Heimerl s.l. and A. pannonica Scheele essential oils

The in vitro antioxidant and antimicrobial activities of two Achillea millefolium (Adanson) Koch s.l species essential oils (A. collina Becker ex Heimerl s.l. and A. pannonica Scheele, Asteraceae) originating from the Golija and Radan mountains (Serbia) were investigated. The chemical profiles of the essential oils were evaluated by GC-MS. Antioxidant activity was assessed as free radical scavenging capacity (RSC) towards 2,2-diphenyl-1-picrylhydrazil (DPPH) radicals, together with effects on lipid peroxidation (LP). Antibacterial activity was examined on 21 bacterial strains. Based on the chemical composition of the essential oil, A. collina s.l. from Mount Golija was classified as a chamazulene chemotype (tetraploid). The high percentage of oxygenated monoterpenes and absence of azulene in the essential oil obtained from A. pannonica from Radan pointing that this population is octaploid. Essential oil of A. pannonica expressed stronger antimicrobial activity on almost all tested bacteria. Furthermore, this essential oil expressed higher scavenging effects on DPPH radical (IC(50) = 0.52 comparing to 0.62 mug/mL). Only in the LP evaluation, essential oil of A. collina s.l. from Golija exhibited stronger antioxidant activity (IC(50) = 0.75 comparing to 2.12 mug/mL).     

Prediction of excess molar volumes of binary mixtures of organic compounds from refractive indices

The excess molar volumes of 51 binary mixtures containing diverse groups of organic compounds: alcohols (methanol, ethanol, propan-1-ol, butan-1-ol, pentan-1-ol, hexan-1-ol, and heptan-1-ol), (cyclo-) alkanes (hexane, heptane, octane, nonane, decane, undecane, dodecane, and cyclohexane), esters (diethyl carbonate and ethyl chloroacetate), aromatics (o-xylene, m-xylene, p-xylene, and ethylbenzene), ketones (acetone), and ethers (anisole), were predicted from the refractive index data, using three types of equations coupled with several different mixing rules for refractive index calculations: the Lorentz-Lorenz, Dale-Gladstone, Eykman, Arago-Biot, Newton, and the Oster. These systems were chosen since they belong to different classes of organic species forming molecular interactions and intermolecular forces during mixing resulting in positive or negative, smaller or larger deviations from ideal behaviour. The obtained results were analysed in terms of the applied equation and mixing rule, the nature of compounds of the mixtures and the influence of alkyl chain length of the alkane or alcohol molecule. Presented at the 34th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 21–25 May 2007.     

Computer-assisted optimization and validation of LC analysis of trimetazidine dihydrochloride and its impurities

Trimetazidine dihydrochloride is an anti-anginal drug, which possesses protective properties against ischemia inducing heart damage. In this paper, a new procedure for liquid chromatographic analysis was successfully developed, optimized, and applied in assessment of trimetazidine dihydrochloride content and its impurities, Y-145, Y-235, and Y-234 at most 1.0%, 0.2%, and 0.2%, respectively, in commercially available pharmaceutical preparation containing 35 mg of trimetazidine dihydrochloride. The retention behavior of trimetazidine dihydrochloride and its impurities is investigated by using several stationary and mobile phases to settle a simple, sensitive, and precise RP-HPLC method. The separation conditions are optimized by DryLab 2000 Plus Chromatography Optimization Software version 3.5.00. Separations are performed on PurospherSTAR RP18 endcapped (150 x 4.6 mm, 5 microm particle size) column at 20 degrees C with UV detection at 210 nm. The mobile phase composition is acetonitrile-aqueous phase (10 mmol/L disodium hydrogenphosphate and 2 mmol/L sodium dihydrogen phosphate, pH 7.6) (30:70 v/v). Afterwards, the method is validated; the important statistical parameters for selectivity/specificity, linearity, precision, limit of detection, and quantitation are defined. The recovery value of the trimetazidine dihydrochloride is 98.06%, and the content of impurities is 0.23% for Y-145, less than 0.02% for Y-235, and less than 0.01% for Y-234. In addition, this method is used for analyzing trimetazidine dihydrochloride and its impurities in pharmaceuticals and bulk drug.