Functional Binding Surface of a β‐Hairpin VEGF Receptor Targeting Peptide Determined by NMR Spectroscopy in Living Cells

In this study, the functional interaction of HPLW peptide with VEGFR2 (Vascular Endothelial Growth Factor Receptor 2) was determined by using fast ¹⁵N‐edited NMR spectroscopic experiments. To this aim, ¹⁵N uniformly labelled HPLW has been added to Porcine Aortic Endothelial Cells. The acquisition of isotope‐edited NMR spectroscopic experiments, including ¹⁵N relaxation measurements, allowed a precise characterization of the in‐cell HPLW epitope recognized by VEGFR2.     

Reaction between quinone and thiazolidine. A study on the formation mechanism of new antiproliferative quinolindiones

Reaction between quinolinquinone and thiazolidine in basic medium was investigated. 2-Arylthiazolidine-4-carboxylic acid ethyl esters undergo two different cleavages in basic medium, yielding the 1-aryl-2-azadiene and a thiolic species. In the presence of quinolinquinone, the isomeric 1-aryl-3-ethoxycarbonyl-pyridoisoquinolin-5,10-diones and 3-amino-3-ethoxycarbonyl-dihydrothienoquinolin-4,9-diones are formed by a hetero-Diels-Alder reaction and 1,4-Michael addition reaction, respectively. A mechanism for the formation of the reaction products is presented.     

UV photoelectron spectra of 5- and 6-azauracil

The He(I) photoelectron spectra of 5-azauracil (1,3,5-triazine-2,4(1H,3H)-dione) and 6-azauracil (1,2,4-triazine-3, 5(2H,4H)-dione) are presented. The spectra are assigned by using INDO/S calculations and comparison arguments with uracil. The first ionization energy in the title compounds is higher than in the usual nucleic acid bases.     

1H-NMR,Ultraviolet and infrared spectra of some (Z)-α-(phenyl)-β-(2-furyl), -(2-pyrrolyl) and -(N-methyl-2-pyrrolyl)acrylonitriles

The ¹H-nmr data of some (Z)-α-(p-substituted-phenyl)-β-(2-furyl), -(2-pyrrolyl), and -(N-methyl-2-pyrrolyl)-acrylonitriles have been investigated to indicate the preferred conformation and to establish the conformational preferences of the β-heterocyclic ring. The ultraviolet spectra have been discussed in order to obtain information about the chromophores responsible for the absorption. The infrared spectra have been analyzed for the identification of the main absorption frequencies of cyano and ethylenic groups and to assign the characteristic absorption bands to specific normal vibrations of the heteroaromatic nuclei.     

Effects of temperature on the triplet behavior of the styrylphenanthrene isomers

The properties of the triplet state of five styrylphenanthrene (StPh) trans isomers were studied in 2-methyltetrahydrofuran (MTHF) as a function of temperature. At room temperature the T-T absorption was observed only for 4- and 9-StPh, while under these conditions 1-, 2-, and 3-StPh have too low a quantum yield of triplet formation (Φ_T <0.02); their T-T absorption spectra were obtained at low temperature. Φ_T of 1- and 2-StPh increases more than tenfold on going from 293 to 77 K, and the triplet lifetime (τ_T) increases by four orders of magnitude and approaches values of 5–40 ms at 77 K. The change in τ_T is explained in terms of an equilibrium between trans and perpendicular (perp) conformations of the lowest triplet state in fluid solution and temperature and viscosity effects on the trans → perp rotation. Evidence is presented for the existence of two conformeric trans triplet states of 3-StPh at 77 K. Semi-empirical calculations were performed to obtain the energy of the triplet state, the wavelengths of several T-T absorption maxima (λ_T), and the oscillator strength. The calculated λ_T values coincide with those measured in n-hexane.     

Reaction of N,N'-dialkyldithiodianilines with β-ketoesters. A new synthesis of N-alkyl-2-acyl-3-oxo-3,4-dihydro-1,4-benzothiazines

The title compounds 3a-j together with the N-alkylacylketene S,N-acetals 12a-j were obtained by reaction of N,N'-dialkyldithiodianilines with β-ketoesters compounds. A possible reaction pathway is suggested.     

Multivariate calibration techniques applied to the spectrophotometric analysis of one-to-four component systems

The UV spectrophotometric analysis of a multicomponent mixture containing paracetamol, caffeine, tripelenamine and salicylamide by using multivariate calibration methods, such as principal component regression (PCR) and partial least-squares regression (PLS), was described. The calibration set was based on 47 reference samples, consisting of quaternary, ternary, binary and single-component mixtures, with the aim to develop models able to predict the concentrations of unknown samples containing as many as one-to-four components. The calibration models were optimized by an appropriate selection of the number of factors as well as wavelength ranges to be used for building up the data matrix and excluding any information about the interfering excipients included in pharmaceutics. The PCR and PLS models were compared and their predictive performance was inferred by a successful application to the assays of synthetic mixtures and pharmaceutical formulations.     

Copper(II) halide reactions with the - NH · CS - group in heterocyclic pentaatomic rings

Summary White crystalline complexes of general formula Cu₂L₄X₂ (where X = Cl, Br and L = 1, 3-oxazolidine-2-thione, pyrrolidine-2-thione,N-methyl-1,3-imidazolidine-2-thione andN-ethyl-1,3-imidazolidine-2-thione) and CuLX (where L = 1,3-imidazolidine-2-thione) were prepared by reduction of copper(II) halides and studied by i.r. spectroscopy in the 4000–200 cm^– range. Evidence for ligand coordination to the metal through sulphur was found in each case. The(CuCI) vibration in all the chloro derivatives falls atca. 240 cm^–.     

The acidic constants of 2-hydroxybenzohydroxamic acid in NaClO4 solutions at 25 degrees C

The protolysis equilibria of 2-hydroxybenzohydroxamic acid, H2SAX, have been studied at 25 degrees C in different ionic media by potentiometric titration with a glass electrode. The media were 0.513, 1.05, 2.21 and 3.5 mol/kg NaClO4. The constants beta(-p)(H2SAX<==>H(2-p)SAX(-p)+pH+), combined with salting effects of NaClO4 on H2SAX deduced from solubility determinations, were processed by the specific interaction theory, SIT, to give equilibrium constants at infinite dilution, log beta(-1)(o) = -7.655 +/- 0.013 and log beta(-2)(o) = -17.94 +/- 0.04, as well as specific interaction coefficients b(HSAX-,Na+) = 0.12 +/- 0.01 and b(SAX2-,Na+) = 0.17 +/- 0.02, molal(-1).     

Structural and Transport Properties of Mg1−xMnxMn2O4±δ Spinels

The synthesis and structural properties of Mg_1−xMn_2+xO₄, for 0≤x≤1 are described. Complete miscibility in the solid state exists for this system. For the material with the correct stoichiometry, i.e. MgMn₂O₄, the effect of temperature on the cation distribution was investigated= above 600°C the inversion degree (m) starts increasing. The electrical conductivity shows a small dependence on P(O₂) which is consistent with the small oxygen non-stoichiometry determined by means of thermogravimetry. The main contribution to the transport properties arises from the inversion equilibrium. Two distinct conductivity regimes, below and above the inversion threshold, can be assumed to explain the electrical conductivity and thermoelectric power results.