X-ray absorption fine structure study of the atomic and electronic structure of molybdenum disulfide intercalation compounds with transition metals

The local structures of ‘host’ and ‘guest’ layers of MoS₂ intercalated with M(OH)₂ (M=Mn, Co and Ni) prepared via interaction of single-layer MoS₂ dispersions and solutions of M²⁺ salts were studied by X-ray absorption spectroscopy. According to M K-edge extended X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge structure (XANES) results, the electronic structure and atomic environment of the M atoms in the intercalates are similar to that of the crystalline hydroxides M(OH)₂. In the Ni intercalate, Mo K-edge EXAFS revealed a structural change of the ‘host’ MoS₂ layers similar to that reported for water dispersions of MoS₂ single layers. S K-edge XANES data indicate that the change is associated with increased electron density on the S atoms in the matrix. SO₄²⁻ and Mo″⁻ (4 < n < 6) were detected in the intercalated materials exposed to air, suggesting that transition metal intercalation may increase the susceptibility of the MoS₂ layers to oxidation.     

Benzotriazole stabilized lithium intermediates as a route to the elaboration of N-substituents in amides

Lithiation of N-(benzotriazol-1-ylmethyl)benzamide or N-(benzotriazol-1-ylmethyl)-2,2-dimethylbutyramide, readily prepared from the corresponding amides, formaldehyde and benzotriazole, followed by quenching with various electrophiles, such as alkyl halides, ketones or ester, gives the corresponding N-substituted derivatives. Subsequent displacement of the benzotriazole group with Grignard reagents, thiols or alcohols provides access to a wide variety of N-substituted amides in good yields. Treatment of the N-(benzotriazol-1-ylalkyl)benzamides with n- BuLi afforded the 1,1-dibenzamidoalkanes.     

Triphosphorus pentaiodide (P3I5), a new phosphorus(III) halide

The novel phosphorus(III) halide I₂PP(I)PI₂ (P₃I₅) has been obtained in solution as one component of a complex reaction mixture by two different routes, and characterised by ³¹P NMR spectroscopy.     

Rhizobium strain effects on yield and bleeding sap amino compounds in Pisum sativum

Bleeding sap composition, dry matter production and nitrogen distribution in pea ( Pisum sativum L. cv. 'Bodil') grown with and without nitrate and nodulated with either Rhizobium leguminosarum strain 128c53 or strain 1044 were compared. Nitrate increased the total dry matter production of both symbioses, but decreased both the proportions of below-ground dry matter to total dry matter production and nodule dry matter to total below-ground dry matter production. The total dry matter yield and N-accumulation was greater in the symbiosis with strain 1044, whereas the accumulation of N in the roots plus nodules relative to the total N-accumulation was greater with strain 128c53 due to a higher production of nodule tissue. The root bleeding sap of the symbiosis with the greater yield (strain 1044) contained high levels of asparagine and aspartic acid. In the 128c53 symbiosis, glutamine plus bomoserine accounted for a higher percentage of the organic solutes transporting newly assimilated nitrogen from the root system than in the association with 1044. The Rhizobium strain effect on amino compound composition of the bleeding sap may indicate an influence of the bacteroids on either the N-assimilatory enzyme system in the plant cytosol, or on the pools of the Krebs cycle intermediates or related compounds in the nodules.     

Novel inhibitors of the methicillin-resistant Staphylococcus aureus (MRSA)-pyruvate kinase

Novel bisindolyl-cycloalkane indoles resulted from the reaction of aliphatic dialdehydes and indole. As bisindolyl-natural alkaloid compounds have recently been reported as inhibitors of the methicillin-resistant Staphylococcus aureus (MRSA)-pyruvate kinase (PK), we tested our novel compounds as MRSA PK inhibitors and now report first inhibiting activities. We discuss structure–activity relationships of structurally varied compounds. Activity influencing substituents have been characterized and relations to antibacterial activities of the most active compounds have been proved.     

Database on pharmacophore analysis of active principles, from medicinal plants

Plants continue to be a major source of medicines, as they have been throughout human history. In the present days, drug discovery from plants involves a multidisciplinary approach combining ethnobotanical, phytochemical and biological techniques to provide us new chemical compounds (lead molecules) for the development of drugs against various pharmacological targets, including cancer, diabetes and its secondary complications. In view of this need in current drug discovery from medicinal plants, here we describe another web database containing the information of pharmacophore analysis of active principles possessing antidiabetic, antimicrobial, anticancerous and antioxidant properties from medicinal plants. The database provides the botanical, taxonomic classification, biochemical as well as pharmacological properties of medicinal plants. Data on antidiabetic, antimicrobial, anti oxidative, anti tumor and anti inflammatory compounds, and their physicochemical properties, SMILES Notation, Lipinski's properties are included in our database. One of the proposed features in the database is the predicted ADMET values and the interaction of bioactive compounds to the target protein. The database alphabetically lists the compound name and also provides tabs separating for anti microbial, antitumor, antidiabetic, and antioxidative compounds. AVAILABILITY: http://www.hccbif.info /     

Headspace solid-phase microextraction profiling of volatile compounds in urine: application to metabolic investigations

Volatile compounds contribute substantially to the metabolic pool in man. Their analysis in body fluids is problematic. We investigated headspace solid-phase microextraction (HS-SPME) with Carboxen–polydimethylsiloxane fibres and gas chromatography–mass spectrometry for profiling urinary volatile components. These fibres were more sensitive for very volatile and sulfur compounds than three other phases tested. We detected a wide range of compounds in normal urine at acid and alkaline pH. Profiles presented for five individuals with metabolic disturbances demonstrate abnormal accumulation of sulfur compounds, fatty acids and plasticisers. HS-SPME can complement profiling of non-volatile compounds in metabolic investigations and could be a useful extension of the diagnostic repertoire.     

Determination of dopaminergic prodrugs by high-performance liquid chromatography followed by post-column ion-pair extraction

One possibility to optimize the therapeutic application of dopaminergic compounds with a catechol function is the reversible protection of this moiety using a prodrug approach. Important features in this respect are a proper chemical stability in the gastrointestinal tract, an adequate release rate after arrival in the blood stream or the possibility to cross the blood–brain barrier. A HPLC method was developed to measure the hydrolysis of prodrugs of dopamine and epinine directly. The method is based on reversed-phase separation followed by post-column ion-pair extraction with a fluorescent counter-ion. The separation of di-isobutyryl esters of dopamine and epinine is obtained within 10 min while the more hydrophobic dopaminergic esters, di-benzoyl and di-pivaloyl dopamine, are retained for 30 min. The precision of the assay measuring 160 ng dibudop and 100 ng ibopamine was 1.2 and 1.0%, respectively. The detection limit of all prodrugs tested was approximately 10 ng.     

Comparative Study of Guanidino Compounds in Serum and Brain of Mouse, Rat, Rabbit, and Man

Abstract: The levels of 12 guanidino compounds were determined in the serum and brain of mouse, rat, rabbit, and man using cation-exchange column chromatography with the fluorescence ninhydrin detection method. A comparative study of these compounds was made in the four groups studied, for serum and brain. In rabbit and man the different guanidino compounds were also determined in various brain regions. This study provides basic analytical data that could facilitate the interpretation of further biochemical and neurochemical studies dealing with guanidino compounds that are identified as being toxins in hyperargininemia and uremia.     

Relative hydrophobicity of organic compounds measured by partitioning in aqueous two-phase systems

Partitioning of a variety of organic compounds, the majority of which represent therapeutic drugs, was examined in an aqueous dextran–polyethylene glycol (Dex–PEG) two-phase system containing 0.15 M NaCl in 0.01 M sodium phosphate buffer at pH 7.3 and in an octanol–buffer (0.15 M NaCl in 0.01 M sodium phosphate buffer, pH 7.3) system. The possibility of introducing compounds to be partitioned in an aqueous two-phase system with dimethyl sulfoxide, and the effect of this solvent on the solute partitioning was explored. Relative hydrophobicity of the compounds was estimated and expressed in equivalent numbers of methylene units. Comparison of the results obtained for several subsets of compounds in the octanol–buffer and in aqueous Dex–PEG two-phase systems clearly demonstrates the advantage of aqueous two-phase partitioning for the hydrophobicity measurements over partitioning in octanol–buffer system.     

Synthesis and antiproliferative activity of new cytotoxic tri- and tetraazabenzo[3,2-a]fluorene-5,6-dione derivatives

A new series of substituted tri-/tetraazabenzo[3,2-a]fluorene-5,6-diones and their corresponding oxime derivatives have been synthesized and spectroscopically characterized. The antiproliferative activities of all compounds were evaluated on at least three different cell lines.     

Six-coordinate phosphorus compounds. Crystal structures and dynamic NMR studies of phosphoranes containing chelating ligands

Hexacoordination of the neutral phosphorus compounds 4–6 is evidenced by their high field ³¹P NMR chemical shifts and is further substantiated by the crystal structure of 5 and 6.5 contains the potentially bis-chelating ligand Ar = (C₆H₃(CH₂NMe₂)₂-2,6) and 6 the same ligand with a protonated amino group. In both cases the compounds exhibit slightly distorted octahedral geometry. In compound 5, only one NMe₂ group is coordinated to the phosphorus atom with an N → P bond of 2.063 Å. In compound 6, the NMe₂ group is coordinated to the phosphorus atom with an N → P bond of 2.007 Å while the dimethylammonium substituent is pointing away from the phosphorus atom forming a hydrogen bridge with two oxygen atoms. The fluxional behavior of these three novel six-coordinate phosphorus compounds was studied by dynamic ¹H NMR spectroscopy.     

Derivation of class II force fields. VI. Carbohydrate compounds and anomeric effects

The methodology for deriving class II force fields has been applied to acetal, hemiacetal, and carbohydrate compounds. A set of eighteen model compounds containing one or more anomeric centers was selected for generating the quantum mechanical energy surface, from which the force field was derived and the functional form assessed. The quality of the fit was tested by comparing the energy surface predicted by the force field with ab initio results. Structural, energetic, and dynamic properties (vibrational frequencies) were analyzed. In addition, α and β anomeric equilibrium structures and energies of 2-methoxytetrahydropyran, 2-deoxyribose, and glucose were computed at the HF/6-31G* and higher ab initio levels. These calculations provide test data from molecules outside the training set used to derive the force field. The quantum calculations were used to assess the ability of the class II force field and two quadratic diagonal (class I) force fields, CVFF, and Homans' extension of the AMBER force field, to account for the anomeric effects on the structural and energetic properties of carbohydrate systems. These class I force fields are unable to account for observed structural and energetic trends, exhibiting deviations as large as 5 kcal/mol in relative energies. The class II force field, on the other hand, is shown to reproduce anomeric structural as well as energetic differences. An energy component analysis of this force field shows that the anomeric differences are dominated by torsional energies, although coupling terms, especially angle/torsion, also make significant contributions (roughly 1 kcal/mol in glucose). In addition, the force field accurately accounts for both anomeric and exo-anomeric energy differences in 2-methoxytetrahydropyran, and anomeric energy differences in 2-deoxyribose and glucose. © 1998 John Wiley & Sons, Inc. Biopoly 45: 435–468, 1998     

Liquid chromatography method for the analysis of adenosine compounds

A newly available chromatography column packing material that employs hybrid particle technology was used to improve the analysis of adenosine compounds. Using a TBAS buffer/acetonitrile gradient this material permits separation of etheno-adenosine compounds in less than 4 min with excellent resolution and sensitivity (50 fmol). Variability of compound quantification is small (coefficients of variation 0.23+/-0.14% for 50 pmol and 1.70+/-0.53% for 0.5 pmol). The new method is well suited for the analysis of adenosine compounds in small biological samples and permits a high sample throughput in autosampler setups with high precision and reproducibility.     

Synthesis and antiproliferative activity of new cytotoxic azanaphthoquinone pyrrolo-annelated derivatives: Part II

A series of 6-azanaphthoquinone pyrrolo-annelated derivatives carrying different basic side chains have been synthesized. The antiproliferative activities of all compounds were evaluated on at least four different cell lines with Mitoxantrone as reference compound. Cytotoxic effects and DNA intercalation behavior were investigated.     

Comparison of different liquid chromatography conditions for the separation and analysis of organotin compounds in mussel and oyster tissue by liquid chromatography-inductively coupled plasma mass spectrometry

In this paper, a new high-performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS) methodology for the analysis of organotin compounds in complex matrices is described. Earlier studies had failed to show baseline resolution between dibutyltin (DBT) and triphenyltin (TPhT). The data presented in this paper show that, by using a different C-18 stationary phase material (Ace C-18) with decreased particle size, baseline resolution of DBT and TPhT can be achieved, with the resultant separation of a third interfering component. In addition, the Ace C-18 stationary phase yields a significant increase in the number of theoretical plates, and, combined with changes in the mobile phase composition, a reduction in run-time by approximately 25%. It is shown that the minor compounds detected are present in the sample and not artefacts of the analytical procedure. The accuracy and precision of the proposed HPLC-ICP-MS method was demonstrated for the determination of TBT in oyster tissue during the BCR "MULSPOT" international interlaboratory certification project.     

源于大型真菌的小分子抗肿瘤化合物研究进展

大型真菌是一类药用资源极为丰富的真菌,许多大型真菌具有显著的抗肿瘤活性。本文综述了源于大型真菌的具有抗肿瘤活性的小分子物质,如萜类、酚类、苯并吡喃酮类和甾类等。以期对大型真菌的活性筛选、化学分析和开发利用提供帮助。     

Synthesis, structures and luminescent behaviour of tridentate salicylaldiminato-type borate complexes

Treatment of the ligands 3,5-tBu₂-2-(OH)C₆H₂CHNR [R = 2-(CO₂H)C₆H₄ (1a) and 2-(CO₂H)C₁₀H₆ (1b)] with trimethylborate, B(OMe)₃, in toluene yields, after work-up, the yellow crystalline complexes {[3,5-tBu₂-2-(O)C₆H₂CHNR]B(OMe)} [R = 2-(CO₂)C₆H₄ (2a) and 2-(CO₂)C₁₀H₆ (2b)], respectively. Further treatment of these complexes with trifluoromethanesulfonic (triflic) acid, CF₃SO₃H, followed by recrystallisation from tetrahydrofuran (thf) afforded the triflate salts [{3,5-tBu₂-2-(O)C₆H₂CHNR}B(thf)][CF₃SO₃] [R = 2-(CO₂)C₆H₄ (3a) and 2-(CO₂)C₁₀H₆ (3b)]. An electroluminescent device was constructed using 2a, which produced orange-green light with broad emission spectra (maximum brightness of 5 cd/m² being observed at 13 V). Compounds 1a and 2b·2MeCN have been characterised by single crystal X-ray structure determinations.     

Primary roles for secondary compounds

Although the proposed roles for secondary compounds in plants are varied, recent investigators have emphasized their defensive properties. However, because these compounds exist in dynamic equilibrium and may be recycled to primary metabolities, natural selection may be for their role in primary metabolic processes as well as in defence.     

Synthesis, structures and DNA binding of ternary transition metal complexes M(II)L with the 2,2′-bipyridylamine (L = p-aminobenzenecarboxylic acid, M = Ni, Cu and Zn)

New ternary transition metal complexes of formulations [Ni(bpa)(p-AB)Cl]_n · 3nH₂O (bpa = 2,2′-bipyridylamine, p-AB = aminobenzenecarboxylic acid) (1), [Cu(bpa)(p-AB)Cl] · H₂O (2), [Zn(bpa)(p-AB)₂] · H₂O (3) are prepared, their structural features are characterized by crystal structural studies, and their DNA binding propensity has been evaluated by fluorescence and viscosity method. In complex 2 and 3, both bpa and p-AB act as the bidentate N and O-donor ligand, respectively. While in complex 1, p-AB acts as a rare tridentate ligand. In the packing pattern of each complex, π-π interaction in their solid state is also described. The complexes show the competitive inhibition of ethidium binding to DNA, and the DNA binding propensity can be reflected as the relative order: 1 > 2 > 3.