Preparation of micelles with azo dye and UV absorbent at their cores or coronas using non-amphiphilic block copolymers

Micelles with azo dye and UV absorbent at their cores or coronas were prepared from non-amphiphilic random diblock copolymers by α,ω-diamine. Poly[4-(phenylazophenoxymethyl)styrene-ran-4-(2-hydroxybenzophenoxymethyl)styrene-ran-vinylphenol]-block-polystyrene (P(AS-r-HBS-r-VPh)-b-PSt) and poly(vinylphenol)-block-poly[4-(phenylazophenoxymethyl)styrene-ran-4-(2-hydroxybenzophenoxymethyl)styrene-ran-styrene] (PVPh-b-P(AS-r-HBS-r-St)) diblock copolymers were prepared by living radical polymerization mediated by 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl. The former copolymer had a molecular weight of Mn[P(AS-r-HBS-r-VPh)-b-PSt] = 10,000-b-250,000 by ¹H NMR and a molar ratio of AS:HBS:VPh = 0.01:0.01:0.98, while the latter had a molecular weight of Mn[PVPh-b-P(AS-r-HBS-r-St)] = 10,000-b-111,000 and a molar ratio of AS:HBS:St = 0.02:0.03:0.95. The copolymers showed no self-assembly in 1,4-dioxane because this solvent was non-selective to the copolymers. Dynamic light scattering demonstrated that the copolymers formed micelles in the solvent in the presence of α,ω-diamine. The hydrodynamic radii of the micelles slightly increased with the copolymer concentration decrease, while the aggregation numbers were almost independent of the copolymer concentration. It was found that P(AS-r-HBS-r-VPh)-b-PSt formed smaller micelles with a lower aggregation number than PVPh-b-P(AS-r-HBS-r-St) because of the steric hindrance of the AS and HBS units present at the micellar coronas.     

Separation and quantitative determination of 6α-hydroxycortisol and 6β-hydroxycortisol in human urine by high-performance liquid chromatography with ultraviolet absorption detection

The present study developed an high-performance liquid chromatography (HPLC) method for the simultaneous determination of urinary metabolites of endogenous cortisol, 6α-hydroxycortisol (6α-OHF) and 6β-hydroxycortisol (6β-OHF), in human urine, using 6α-hydroxycorticosterone as internal standard. 6α-OHF and 6β-OHF were extracted from urine with ethyl acetate by using a Sep-Pak C₁₈ plus cartridge. Separation of the stereoisomers was achieved on a reversed-phase hybrid column by a gradient elution of (A) 0.05 M KH₂PO₄–0.01 M CH₃COOH (pH 3.77) and (B) 0.05 M KH₂PO₄–0.01 M CH₃COOH/acetonitrile (2:3, v/v). 6α-OHF and 6β-OHF were well separated on an XTerra MS C₁₈ 5 μm column using two types of stepwise gradient elution program (programs 2 and 3). Resolutions of 6α-OHF and 6β-OHF were Rs = 4.41 for program 2 and Rs = 4.60 for program 3. The analysis was performed within 23~26 min, monitored by UV absorbance at 239 nm. The lower limits of detection of 6α-OHF and 6β-OHF were 0.80 ng per injection (s/n = ca. 8), and the lower limits of quantification were 5.02 ng/ml for 6α-OHF and 41.08 ng/ml for 6β-OHF, respectively. The within-day reproducibilities in the amounts of 6α-OHF and 6β-OHF determined were in good agreement with the actual amounts added, the relative errors being −5.37% and −3.73% (gradient 2) and −5.69% and −3.96% (gradient 3) for both 6α-OHF and 6β-OHF, respectively. The inter-assay precisions (RSDs) for 6α-OHF and 6β-OHF were less than 1.99% (gradient 2) and 2.61% (gradient 3), respectively. The present HPLC method was applied to the measurement of 6α-OHF and 6β-OHF in urine to evaluate the time courses of 6α-hydroxylation and 6β-hydroxylation clearances of cortisol during 40 days for phenotyping CYP3A in a healthy subject.     

The generalized Hulthén potential

A generalization of the Hulthén potential is presented on the basis of an approach that uses the factorization of a general Hamiltonian by means of a specific model of operational equations with the structure ∼β(r)∓(d/dr). To achieve this goal, the treatment of the V _Hs(r) standard Hulthén potential for bound s states is carried out by proposing a particular β_p(r) ansatz to identify V _Hs(r) by means of a particular Riccati-type relationship. Once the identification has been achieved, the generalized Hulthén potential is obtained straightforwardly with the aid of a general Riccati formula. As expected, the Hamiltonian of the generalized Hulthén potential is isospectral when compared with the corresponding standard Hamiltonian. Moreover, according to the Darboux transform there exists a modified Hulthén potential which is also isospectral. We show that the latter is just a particular case of the generalized Hulthén interaction model. Received: 14 September 1999 / Accepted: 3 February 2000 / Published online: 19 April 2000     

Aqueous solution behavior of alkali-soluble polyethylene periodic polyelectrolyte, poly(ethylene- per-ethylene-per-acrylic acid)

A sequence-ordered, periodic copolymer of ethylene, ethylene, and acrylic acid, poly (ethylene-per-ethylene-per-acrylic acid) (PEEA), with M _w=1.44×10⁵ has been synthesized by alternating copolymerization of 1,3-butadiene and methyl acrylate, followed by hydrogenation and hydrolysis. Aqueous solution and dissociation properties of the alkali-soluble PEEA were explored by potentiometric titration and intrinsic viscosity at 25 °C. The pH values of PEEA were almost constant (pH = 6.48 ∼ 6.55) with an increasing degree of dissociation (α) from 0.3 to 0.8 at C _s=50 mN NaCl. Correspondingly, the plots of negative logarithm of apparent dissociation constant (pK _a) against α showed a reversed S-shape curve over the whole α, indicating an extensive precipitation and subsequent tran-sition from compact to coiled conformation. The intrinsic viscosity steeply increased with α above 0.4 up to 9.97 dl/g at α = 1.0. Good agreement between the observed electrostatic potential and that calculated from the rod model with a smeared charge density was observed in the region of α higher than 0.9. The dissociation and dissolution processes of PEEA with neutralization in water were described. Received: 14 April 1998 Accepted: 3 June 1998     

Positional selectivity in electrophilic substitution reactions of π-excessive heterocycles (review)

Existing experimental data on positional selectivity in electrophilic substitution reactions of π-excessive heterocycles are classified. These data are discussed basing on the results of the authors' quantum-chemical calculations [RHF/6-31G(d), MP2/6-31G(d), and B3LYP/6-31G(d)] of the σ-complexes formed during attack of electrophiles such as H⁺, Me⁺, Me₃Si⁺, Br⁺, NO₂ ⁺, MeCO⁺, and SO₃ at the α- and β-positions of furan, thiophene, selenophene, pyrrole and its N-substituted derivatives, N-R-pyrroles (R = Me, t-Bu, SiMe₃, Si(i-Pr)₃, C₆H₄(p-NO₂), SO₂Ph, CHO, CO₂Me), and the corresponding α- and β-substituted electrophilic substitution products. The differences in energies of the α-and β-isomers of the σ-complexes characterize the preferred direction of electrophilic attack, while the differences in the energies of the isomeric products make it possible to assess the energy preference of one of them. Analysis of the obtained data demonstrates the effects of the studied heterocycles' structure, the nature of the electrophile, and the thermal and steric factors on the positional selectivity (α/β ratio) in electrophilic substitution reactions of π-excessive five-membered heteroaromatic compounds.     

Steroidal glycosides of gitogenin from Allium rotundum

Two new steroidal glycosides were isolated by fractionation of total extracted substances from inflorescences and flower stalks of Allium rotundum (Alliaceae). The structures were determined on the basis of chemical transformations, physical constants, and spectral data as 26-O-β-D-glucopyranosyl-(25R)-5α-furostan2α,3β,22α,26-tetraol 3-O-β-D-glucopyranosyl-(1 → 2)[β-D-xylopyranosyl-(1 → 3)]-β-D-glucopyranosyl(1 → 4)-β-D-galactopyranoside (2) and (25R)-5α-spirostan-2α,3β-diol 3-O-β-D-glucopyranosyl-(1 → 3)-βD-glucopyranosyl-(1 → 2)-[β-D-xylopyranosyl-(1 → 3)]-β-D-glucopyranosyl-(1 → 4)-β-D-galactopyranoside (3).     

Steroidal glycosides from Allium cyrillii bulbs

Two spirostanol saponins, one of which was a new compound, were isolated among the steroidal glycosides of Allium cyrillii Ten. Bulbs. The structures of these glycosides were established using chemical and spectral analytical methods as β-D-glycopyranosyl-(1 → 2)-[β-D-xylopyranosyl-(1 → 3)]-β-D-glucopyranosyl-(1 → 4)β-D-galactopyranosyl-(1 → 3)-(25R)-5α-spirostan-2α,3β-diol and β-D-glucopyranosyl-(1 → 2)-[4-O-(3hydroxy-3-methylglutaryl)-β-D-xylopyranosyl-(1 → 3)]-β-D-glucopyranosyl-(1 → 4)-β-D-galactopyranosyl(1 → 3)-(25R)-5α-spirostan-2α,3β-diol.     

Stannum film electrode for square wave voltammetric determination of trace copper(II)

An anodic stripping voltammetric procedure for the determination of Cu(II) at an in situ-plated stannum film electrode (SnFE) was described. The results indicated that the SnFE had an attractive electroanalytical performance, with two distinct voltammetric stripping signals for copper and stannum, and showed the superior advantage for the determination of copper compared with the bismuth film electrode. Several experimental parameters were optimized. The SnFE exhibited highly linear behavior in the concentration range from 1.0 to 100.0 μg L⁻¹ of Cu(II) (r = 0.994) with the detection limit of 0.61 μg L⁻¹ (S/N = 3), and the relative standard deviation for a solution containing 40.0 μg L⁻¹ Cu(II) was 2.2% (n = 8). The procedure has been successfully applied for the determination of Cu(II) in lake water sample.     

Fast dynamic wetting of polymer surfaces by miscible and immiscible liquids

The initial stages of spontaneous spreading of a solvent drop (toluene) on the surface of a soluble polymer (polystyrene) have been studied with a high-speed camera. For drops of 1–4 μL volume, the increase in contact radius r can be described by a power law r μ t^a r \propto {t^{\alpha }} , with the spreading exponent α = 0.50 and for the first ≈8 ms. Thereafter, the three-phase contact line was pinned leading to a macroscopic static contact angle of Θ₀ = 12–15°. The insoluble liquids ethanol (α = 0.47, Θ₀ = 0) and water (α = 0.35, Θ₀ = 90°) showed a slower spreading. We attribute the fast spreading of toluene to the strong interaction with the polymer, like in reactive wetting. The finite macroscopic contact angle indicates the formation of a ridge by softening of polystyrene due to permeated toluene and the subsequent plastic deformation by the surface tension of the liquid. This interpretation is supported by experiments on polymers grafted from a silicon wafer. Toluene completely wets polymer brush surfaces. Transport of toluene through the vapor phase plays a significant role.     

Chromatographic investigation of the hydrophobic properties of isomeric naphthalene derivatives

Summary Selected isomeric α and β derivatives of naphthalene were semi-quantitatively compared in respect of their hydrophobic properties. Investigations were carried out by both adsorption and partition TLC chromatography; the solubilities of the individual substances in water were also determined. The results were explained of electronic and steric effects. Permanent dipole moments in terms (literature data) are also utilized to explain the comparatively weak hydrophobic properties of the β isomers as compared to the α isomers.     

Sequestering Ability of Dicarboxylic Ligands Towards Dioxouranium(VI) in NaCl and KNO<Subscript>3</Subscript> Aqueous Solutions at <Emphasis Type="Italic">T</Emphasis>=298.15 K

The formation constants of dioxouranium(VI)-2,2′-oxydiacetic acid (diglycolic acid, ODA) and 3,6,9-trioxaundecanedioic acid (diethylenetrioxydiacetic acid, TODA) complexes were determined in NaCl (0.1≤I≤1.0 mol⋅L⁻¹) and KNO₃ (I=0.1 mol⋅L⁻¹) aqueous solutions at T=298.15 K by ISE-[H⁺] glass electrode potentiometry and visible spectrophotometry. Quite different speciation models were obtained for the systems investigated, namely: ML⁰, MLOH⁻, ML₂²⁻, M₂L₂(OH)⁻, and M₂L₂(OH)₂²⁻, for the dioxouranium(VI)–ODA system, and ML⁰, MLH⁺, and MLOH⁻ for the dioxouranium(VI)–TODA system (M=UO₂²⁺ and L = ODA or TODA), respectively. The dependence on ionic strength of the protonation constants of ODA and TODA and of both metal-ligand complexes was investigated using the SIT (Specific Ion Interaction Theory) approach. Formation constants at infinite dilution are [for the generic equilibrium pUO₂²⁺+q(L²⁻)+rH⁺ ⇌(UO₂²⁺) _p (L) _q H _r ^(2p−2q+r);β _pqr ]: log ₁₀ β ₁₁₀=6.146, log ₁₀ β ₁₁₋₁=0.196, log ₁₀ β ₁₂₀=8.360, log ₁₀ β ₂₂₋₁=8.966, log ₁₀ β ₂₂₋₂=3.529, for the dioxouranium(VI)–ODA system and log β ₁₁₀=3.636, log ₁₀ β ₁₁₁=6.650, log ₁₀ β ₁₁₋₁=−1.242 for dioxouranium(VI)–TODA system. The influence of etheric oxygen(s) on the interaction towards the metal ion was discussed, and this effect was quantified by means of a sigmoid Boltzman type equation that allows definition of a quantitative parameter (pL ₅₀) that expresses the sequestering capacity of ODA and TODA towards UO₂²⁺; a comparison with other dicarboxylates was made. A visible absorption spectrum for each complex reaching a significant percentage of formation in solution (KNO₃ medium) has been calculated to better characterize the compounds found by pH-metric refinement.     

Characterising latex particles and fractal aggregates using image analysis

The fractal nature of latex particles and their aggregates was characterised by image analysis in terms of fractal dimensions. The one- and two-dimensional fractal dimensions, D ₁ and D ₂, were estimated for polystyrene latex aggregates formed by flocculation in citric acid/phosphate buffer solutions. The dimensional analysis method was used, which is based on power law correlations between aggregate perimeter, projected area and maximum length. These aggregate characteristics were measured by image analysis. A two-slopes method using cumulative size distributions of aggregate length and solid volume has been developed to determine the three-dimensional fractal dimension (D ₃) for the latex aggregates. The fractal dimensions D ₁, D ₂ and D ₃ measured for single latex particles in distilled water agreed well with D ₁ = 1, D ₂ = 2 and D ₃ = 3 expected for Euclidean spherical objects. For the aggregates, the fractal dimension D ₂ of about 1.67 ± 0.04 (±standard deviation) was comparable to the fractal dimension D ₃ of approximately 1.72 ± 0.13 (±standard deviation), taking the standard deviations into account. The measured three-dimensional fractal dimension for latex aggregates is within the fractal dimension range 1.6–2.2 expected for aggregates formed through a cluster-cluster mechanism, and is close to the D ₃ value of about 1.8 indicated for cluster formation via diffusion-limited colloidal aggregation. Received: 28 September 1998 Accepted: 29 October 1998     

Evidences for temperature-dependent mechanism of host-guest complexation

Summary High-performance liquid chromatography and ultraviolet spectroscopy methods were applied to the studies on the influence of temperature on the complexation of β-cyclodextrin with naphthalene and its derivatives. The strong nonlinearity of Van't Hoff plots suggests, that the retention mechanism of hydrocarbons investigated might be different in high and low temperature region. The total lack of correlation (r=−0.230) between chromatographic data (capacity factors ratio:k _PAH/k _PAH×CD) and spectrophotometric data (ΔA) at high temperature (60°) as well as a significant correlation (r=0.922) at subambient temperature (15°C) suggest, that the inclusion mechanism starts to be important at low temperature region and the predominant mechanism for chromatographic retention is the formation of an inclusion complexes in the mobile phase.     

The saddle point of the nucleophilic substitution reaction Cl− + CH3Cl: results of large-scale coupled cluster calculations

On the basis of large-scale coupled cluster calculations including connectedz triple substitutions in a perturbative way, the geometrical parameters of the D _{3 h} saddle point of the Walden inversion reaction Cl⁻ + CH₃Cl′→ ClCH₃ + Cl′⁻ are predicted to be R _s (C—Cl) = 2.301 ? and r _s (C—H) = 1.069 ?. The barrier height with respect to the reactants is recommended to be 11.5 ± 1.0 kJ mol⁻¹. Connected triple substitutions lower the barrier height by almost a factor of 2, but have very little influence on the geometric structure of the saddle point. Received: 26 June 1998 / Accepted: 15 July 1998 / Published online: 28 September 1998     

Flavonoid oligosides from georgian <Emphasis Type="Italic">Astragalus falcatus</Emphasis>

New flavonoid oligosides were isolated from leaves and flowers of Astragalus falcatus Lam. It was found on the basis of chemical transformations, UV, IR, PMR, ¹³ C NMR, HMBC, HSQC, 1D-TOCSY, and mass spectral properties that falcoside C had the structure quercetin 3-O-[β-D-glucopyranosyl(1 → 3)-α-Lrhamnopyranosyl(1 → 6)]-β-D-galactopyranoside 7-O-β-D-glucopyranoside; falcoside D, isorhamnetin 3-O-[β-D-xylopyranosyl(1 → 3)-α-L-rhamnopyranosyl(1 → 6)]-β-D-galactopyranoside 7-O-α-Lrhamnopyranoside.     

Accelerated sample treatment for screening of banned doping substances by GC–MS: ultrasonication versus microwave energy

A comparison between ultrasonication and microwave irradiation as tools to achieve a rapid sample treatment for the analysis of banned doping substances in human urine by means of gas chromatography–mass spectrometry (GC–MS) was performed. The following variables were studied and optimised: (i) time of treatment, (ii) temperature, (iii) microwave power and (iv) ultrasonic amplitude. The results were evaluated and compared with those achieved by the routine method used in the World Anti-Doping Agency (WADA) accredited Antidoping Laboratory of Rome. Only under the effect of the ultrasonic field was it possible to enhance the enzymatic hydrolysis reaction rate of conjugated compounds. Similar reaction yield to the routine method was achieved after 10 min for most compounds. Under microwave irradiation, denaturation of the enzyme occurs for high microwave power. The use of both ultrasonic or microwave energy to improve the reaction rate of the derivatisation of the target compounds with trimethyliodosilane/methyl-N-trimethylsilyltrifluoroacetamide (TMSI/MSTFA/NH₄I/2-mercaptoethanol) was also evaluated. To test the use of the two systems in the acceleration of the reaction with TMSI, a pool of 55 banned substances and/or their metabolites were used. After 3 min of ultrasonication, 34 of the 55 compounds had recoveries similar to those obtained with the classic procedure that lasts for 30 min (Student’s t test, n = 5), 18 increased to higher silylation yields, and for the compounds 13β,17α-diethyl-3α,17β-dihydroxy-5α-gonane (norboletone metabolite 1), metoprolol and metipranolol the same results were obtained increasing the ultrasonication time to 5 min. Similar results were obtained after 3 min of microwave irradiation at 1,200 W. In this case, 30 of the 55 compounds had recoveries similar to the classic procedure (Student’s t test, n = 5) whilst 18 had higher silylation yields. For the compounds 3α-hydroxy-1α-methyl-5α-androstan-17-one (mesterolone metabolite 1), 17α-ethyl-5β-estrane-3α,17β,21-triol (norethandrolone metabolite 1), epioxandrolone, 4-chloro-6β,17β-dihydroxy-17α-methyl-1,4-androstadien-3-one (chlormetandienone metabolite 1), carphedon, esmolol and bambuterol the same results were obtained after 5 min under microwave irradiation.     

Orbital phase control of the conformations of α- and β-substituted enamines and vinyl ethers

The conformational stabilities of the α- and β-substituted enamines and vinyl ethers were predicted by orbital phase theory and confirmed by ab initio molecular orbital calculations. Cyclic interaction significantly occurs among the nonbonding orbital n _Y for the lone pair on the hetero atom Y (N in the enamines or O in the ethers), the π and π* orbitals of the CC bond, and the σ_C-H or σ*_C-X orbitals on the substituent CH₂X. The cyclic -n _Y-π-σ_C-H-π*- interaction is favored by the orbital phase continuity in the α-substituted molecules, while the cyclic -n _Y-π-σ*_C-X-π*- interaction is favored in the β-substituted molecules. The most stable conformation was then predicted to be synperiplanar or (pseudo)equatorial in the α-substituted molecules and anticlinical or (pseudo)axial in the β-substituted molecules. Received: 8 May 1998 / Accepted: 30 July 1998 / Published online: 16 November 1998     

Predicting the cross-reactivities of polycyclic aromatic hydrocarbons in ELISA by regression analysis and CoMFA methods

Immunoassays have been regarded as a possible alternative or supplement for measuring polycyclic aromatic hydrocarbons (PAHs) in the environment. Since there are too many potential cross-reactants for PAH immunoassays, it is difficult to determine all the cross-reactivities (CRs) by experimental tests. The relationship between CR and the physical-chemical properties of PAHs and related compounds was investigated using the CR data from a commercial enzyme-linked immunosorbent assay (ELISA) kit test. Two quantitative structure-activity relationship (QSAR) techniques, regression analysis and comparative molecular field analysis (CoMFA), were applied for predicting the CR of PAHs in this ELISA kit. Parabolic regression indicates that the CRs are significantly correlated with the logarithm of the partition coefficient for the octanol-water system (log K _ow) (r ² = 0.643, n = 23, P < 0.0001), suggesting that hydrophobic interactions play an important role in the antigen-antibody binding and the cross-reactions in this ELISA test. The CoMFA model obtained shows that the CRs of the PAHs are correlated with the 3D structure of the molecules (r _cv ² = 0.663, r  ² = 0.873, F _4,32 = 55.086). The contributions of the steric and electrostatic fields to CR were 40.4 and 59.6%, respectively. Both of the QSAR models satisfactorily predict the CR in this PAH immunoassay kit, and help in understanding the mechanisms of antigen-antibody interaction.     

A new furostanol glycoside with fatty acid synthase inhibitory activity from <Emphasis Type="Italic">Ophiopogon japonicusa</Emphasis>

A new furostanol glycoside, named ophiopogonin J (1), was isolated from the fibrous root of Ophiopogon japonicas. The structure of the compound was established as (25R)-26-[(O-β-D-glucopyranosyl-(1 → 2)-β-D-glucopyranosyl)]-20α -hydroxyfurost-5, 22-diene-3-O-α-L-rhamnopyranosyl-(1 → 2)-[β-D-xylopyranosyl(1 → 4)]-β-D-glucopyranoside on the basis of spectroscopic methods, including HR-ESI-MS and 1D and 2D NMR experiments.     

Self-assembled sulfonated β-Cyclodextrin layer on gold electrode for the selective electroanalysis of dopamine

Gold electrode with self-assembled D,L-cysteine grafted β-cyclodextrin sulfonic acid (Cys-β-CD∼SO₃) layer was fabricated and used to investigate the electrochemical behavior of dopamine. The experimental results indicated that the self-assembled Cys-β-CD∼SO₃ layer modified gold electrode has selective electrochemical response to dopamine with high sensitivity and excellent tolerance of ascorbic acid, which is the most common accompanying component in biological samples. Dopamine could be accurately determined in the concentration range of 1–200 μM in the presence of ascorbic acid of 5 mM. The relative standard deviation of 1.9% (n = 5) was achieved at a dopamine concentration of 5 × 10⁻⁵ M. The proposed sensor was successfully applied to the determination of dopamine in human blood serum samples.