Immunochemical method for sulfasalazine determination in human plasma

Sulfasalazine is an antibiotic used in the treatment of inflammatory bowel diseases. For the assessment of sulfasalazine in several biological matrices, an Enzyme-Linked Immunosorbent Assay (ELISA) method based on polyclonal antibodies was developed and characterized.The immunoassay showed a high sensitivity (IC₅₀ = 0.51 ng mL⁻¹) and specificity, a detection limit of 0.02 ng mL⁻¹ and a dynamic range of 0.06-3.75 ng mL⁻¹ (80-20% inhibition). The immunoassay performed well when it was applied to spiked plasma samples (from 0.5 to 2.0 ng mL⁻¹) previously cleaned up by protein precipitation with methanol. Recoveries ranged from 83 to 119%, with a mean value of 99% (CV = 13%).Since sulfasalazine remaining of a treatment reaches the systemic circulation in unchanged form, the immunoassay can be applied to the determination of this pharmaceutical in human plasma in order to facilitate the control of the patients through the application of personal doses.     

Differences between ab initio and density functional electron densities

We analyzed the energy contributions and the spatial distribution differences of several electron densities of atoms and small molecules. The results show the insensitivity of local spin density correlation functionals in respect to differences in the electron densities. On the other hand, significant changes in one-electron and two-electron energy contributions are observed, although both compensate each other. The projection of the differences between these electron densities, referred to as the Hartree-Fock density, shows a qualitative resemblance between multideterminantal and Kohn-Sham wavefunctions. Finally, a comparative analysis of the optimized conformational parameters obtained using several methods shows that the inclusion of the correlation energy in SCF or in post-SCF procedures gives similar results and that the exchange potential is more important than is the correlation potential to improve these conformational parameters. © 1997 John Wiley & Sons, Inc.     

A Polycationic Metallodendrimer with 24 [Fe(η5-C5Me5)(η6-N-Alkylaniline)]+ Termini That Recognizes Chloride and Bromide Anions

Pronounced dendritic effects are shown by the title compound 1 in the recognition of Cl⁻ and Br⁻—this is shown by the comparison with a mononuclear compound with one dendrimer arm and a trinuclear compound with a tripodal dendrimer branch. Thus, 1 differs distinctly from 24-ferrocene dendrimers of comparable topology.     

Can the disproportion of oxidation state III be favored in RuII-OH2/RuIV=O systems?

Three new Ru-aqua complexes containing a mixed carbene and pyridylic ligands with general formulas [Ru(CNC)(bpy)(H2O)](PF6)2 (1) (CNC is 2,6-bis(butylimidazol-2-ylidene)pyridine; bpy is 2,2'-bipyridine) and cis-/trans-[Ru(CNC)(nBu-CN)(H2O)](PF6)2 (cis-2 and trans-2) (nBu-CN is 2-(butylimidazol-2-ylidene)pyridine) have been prepared and structurally characterized both in the solid state (monocrystal X-ray diffraction analysis for 1 and for the related complex trans-[Ru(Br)(CNC)(nBu-CN)](PF6)) and in solution (for all of them) through NMR. The electrochemical properties of these three Ru-aqua complexes have been investigated by cyclic voltammetry, differential pulse voltammetry and Coulombimetric techniques. It is found that, for complex 1 at pH 7, the difference between the IV/III and the III/II redox couples (DeltaE1/2) is 50 mV, which is the smallest ever reported for this type of complex. On the other hand, for complexes cis-2 and trans-2, the oxidation state III is unstable with respect to disproportionation to II and IV. The reactivity of their Ru=O species has been tested toward cis-beta-methylstyrene oxidation, and it has been compared to [Ru(O)(trpy)(bpy)]2+. An inverse correlation between the degree of cis/trans-epoxide isomerization and DeltaE1/2 is found. In particular, for complexes cis-2 and trans-2, which have a DeltaE1/2 < 0, the epoxidation is highly stereoselective, yielding only cis-epoxide.     

Liquid-crystalline bisadducts of [60]fullerene

A second-generation cyanobiphenyl-based dendrimer was used as a liquid-crystalline promoter to synthesize mesomorphic bisadducts of [60]fullerene. Liquid-crystalline trans-2, trans-3, and equatorial bisadducts were obtained by condensation of the liquid-crystalline promoter, which carries a carboxylic acid function, with the corresponding bisaminofullerene derivatives. A monoadduct of fullerene was also prepared for comparative purposes. All the compounds gave rise to smectic A phases. An additional mesophase, which could not be identified, was observed for the trans-2 derivative. The supramolecular organization of the monoadduct derivative is governed by steric constraints. Indeed, for efficient space filling, adequacy between the cross-sectional areas of fullerene (approximately 100 A(2)) and of the mesogenic groups (approximately 22-25 A(2) per mesogenic group) is required. As a consequence, the monoadduct forms a bilayered smectic A phase. The supramolecular organization of the bisadducts is essentially governed by the nature and structure of the mesogenic groups and dendritic core. Therefore, the bisadducts form monolayered smectic A phases. The title compounds are promising supramolecular materials as they combine the self-organizing behavior of liquid crystals with the properties of fullerene.     

Laser Control of Zeolite Nucleation

Precursor solutions for the synthesis of zeolites are irradiated by means of a Nd‐YAG laser. These solutions are subsequently submitted to a hydrothermal treatment and the results analyzed by X‐ray diffraction and electron microscopy. Laser irradiation promotes the formation of silica nanoparticles that nucleate into zeolite (silicalite‐1), following a hydrothermal treatment. The average crystal size (in the 0.6–3.6 μm range) of the zeolite exponentially decreases as a function of laser irradiation time. In addition, a longer irradiation time results in a narrower crystal size distribution.     

The Use of the Electron-Reservoir Complexes [Fe(I)Cp(arene)] for the Electrocatalytic Synthesis of Redox-Reversible Metal-Carbonyl Clusters Containing Ferrocenyldiphenylphosphine

Starting from [M₃(CO)₁₂] (M = Fe or Ru) and [CH₃CCo₃(CO)₉], the electron-tranfer-chain catalyzed synthesis of new Fe, Ru, and Co carbonyl clusters in which one or several carbonyl ligands have been selectively substituted by one or several ferrocenyldiphenylphosphine (FDPP) ligands has been achieved using the electron-reservoir complexes [Fe(I)Cp(arene)] as electrocatalysts. The number of FDPP ligands selectively introduced can be chosen from one per cluster for the three clusters up to one per metal for the Ru and Co clusters. The advantage of this family of electrocatalysts is that the driving force for the initiation step can be varied by changing the number of methyl groups on the rings. The FDPP substituted clusters show one reversible wave by cyclic voltammetry.     

Asymptotic Expansions for Two Singularly Perturbed Convection–Diffusion Problems with Discontinuous Data: The Quarter Plane and the Infinite Strip

We consider a singularly perturbed convection–diffusion equation,     , defined on two domains: a quarter plane,  ( x , y ) ∈ (0, ∞) × (0, ∞)  , and an infinite strip,  ( x , y ) ∈ (−∞, ∞) × (0, 1)  . We consider for both problems discontinuous Dirichlet boundary conditions:   u ( x , 0) = 0  and   u (0, y ) = 1  for the first one and   u ( x , 0) =χ_{[ a , b ]}( x )  and   u ( x , 1) = 0  for the second. For each problem, asymptotic expansions of the solution are obtained from an integral representation in two limits: (a) when the singular parameter  ε→ 0⁺  (with fixed distance r to the discontinuity points of the boundary condition) and (b) when that distance   r → 0⁺  (with fixed ε). It is shown that in both problems, the first term of the expansion at  ε= 0  is an error function or a combination of error functions. This term characterizes the effect of the discontinuities on the ε-behavior of the solution and its derivatives in the boundary or internal layers. On the other hand, near the discontinuities of the boundary condition, the solution u ( x , y ) of both problems is approximated by a linear function of the polar angle at the discontinuity points.     

Facile synthesis of azocino[4,3-b]indoles by ring-closing metathesis

The azocino[4,3-b]indole system, tricyclic substructure of the indole alkaloids apparicine and ervaticine, is efficiently assembled by ring-closing metathesis of 2-allyl-3-(allylaminomethyl)indoles. The metathesis sites are introduced into the indole nucleus by reductive amination of a 3-formyl derivative with allylamine, followed by α-lithiation with subsequent electrophilic trapping with acrolein.     

Screening of Dowex® anion-exchange resins for invertase immobilization

Commercial yeast invertase (Bioinvert^®) was immobilized by adsorption on anion-exchange resins, collectively named Dowex^® (1×8:50–400, 1×4:50–400, and 1×2:100–400). Optimal binding was obtained at pH 5.5 and 32°C. Among different polystyrene beads, the complex Dowex-1×4–200/invertase showed a yield coupling and an immobilization coefficient equal to 100%. The thermodynamic and kinetic parameters for sucrose hydrolysis for both soluble and insoluble enzyme were evaluated. The complex Dowex/invertase was stable without any desorption of enzyme from the support during the reaction, and it had thermodynamic parameters equal to the soluble form. The stability against pH presented by the soluble invertase was between 4.0 and 5.0, whereas for insoluble enzyme it was between 5.0 and 6.0. In both cases, the optimal pH values were found in the range of the stability interval. The K _m and V _max for the immobilized invertase were 38.2 mM and 0.0489 U/mL, and for the soluble enzyme were 40.3 mM and 0.0320 U/mL.