Kompressionsverhalten und Gleichgewichtsspreitungsdrücke binÄrer monomolekularer Dimyristoylkephalin/Dilauroylkephalin-Mischungen

1. The concentration dependence of theF/A-isotherms (premixed spreading, separate spreading) and the equilibrium spreading pressuresF ^e of the system dimyristoyl-cephaline/dilauroyl-cephaline were studied atT=295 K. The results were analysed and compared with respect to the miscibility using thermodynamical criteria.
2. It was shown that various spreading techniques lead to different experimental results. In the case of the premixed spreading it is formed initially an equilibrium monolayer. The analysis of the concentration dependence of the phase transition point (liquid expanded → condensed) shows that the components are completely miscible.
3. From theF/A-isotherms of premixed spreading the A(area)-x ^τ (surface concentrations-diagrams were calculated. The deviation from the ideal behaviour of the A-x ^τ-curves is caused by a phase separation.
4. From the concentration dependence of the equilibrium spreading pressures by means of the surface phase rule follows that the components are approximately ideally miscible.
5. By the analysis of the collapse and equilibrium spreading pressures follows that the mixed films during the compression are in a metastabile state.

     

A New Method for Identifying and Estimating the Parameters of the Instrumental Spreading Function in Size Exclusion Chromatography-Application to Particle Size Analysis

Abstract

Herein is reported a new method for identifying and estimating the instrumental spreading function in size exclusion chromatography. The method is based on the solution of the integral equation when the size distribution of the injected standards are known. A numerical method after Ishige et al. (1) to solve the integral equation for the corrected distribution is suitably modified to estimate instead the spreading function when the true and measured chromatograms are both known. The method is evaluated for synthesized chromatograms using the particle size distribution of Dow polystyrene latices. It is then applied to experimental chromatograms of the latices obtained by size exclusion chromatography. The resulting spreading functions were then analysed for variance, skewness and kurtosis.     

A Critique of Literature on Thickeners in Textile Printing

Abstract

“Thickeners” [1,2] used in textile printing are high molecular weight compounds, giving viscous pastes in water. These impart stickiness and plasticity to the printing paste so that it can be applied to a fabric surface without spreading and be capable of maintaining the design outlines even under high pressure. Their main function is to hold or adhere the dye particles in the desired place on the fabric until the transfer of dye into the fabric and its fixation are complete.     

Iridoid glycosides and polyphenolic compounds from Teucrium chamaedrys L.

In this work, the phytochemical analysis of Teucrium chamaedrys L. collected in Italy was reported. Eight compounds were isolated and identified by means of classical column chromatography and spectroscopic techniques, such as NMR and MS. In detail, these compounds were: verbascoside (1), forsythoside b (2), samioside (3), alyssonoside (4), harpagide (5), 8-O-acetyl-harpagide (6), cirsiliol (7) and β-arbutin (8). The presence of these compounds, in particular iridoids and phenyl-ethanoid glycosides, has a chemotaxonomic relevance and results to be in perfect accordance with the current botanical classification of the species. In addition, it provides a phytochemical rationale for the use of this particular plant in the ethno-pharmacological field. Conversely, it is worth of mention the absence of potentially toxic components, unlike to what observed in other species of the genus which can no longer be used for ethno-medicinal purposes.     

Recycling Technique in Preparative Liquid Chromatography

Abstract

A theoretical and practical study of recycling technique is developped for preparative liquid chromatography. The optimal cycle number, n_opt, is determined for the separation of two solutes in such a way that the resolution between the second peak of cycle (n-1) and the first one of cycle n is equal to the resolution between the peaks of cycle n. A simple relationship is propounded to determine n_opt which only depends on retention volumes and external volume, but it does not depend on band spreading. With this recycling technique it is shown that the maximum injection volume under optimal recycling conditions is greater than n_opt times the maximum injection volume for one cycle. So the use of recycling can be opportune and beneficial to increase the throughput in preparative liquid chromatography.     

Calibration of Separation and Instrumental Peak Broadening in Sec Coupled with Light Scattering of Simple Polymers

Abstract

A recently developed procedure for calibration of separation and instrumental peak broadening in SEC was used for a comparative study of separation and axial dispersion of polystyrene, poly(methyl methacrylate) and poly(vinylchloride). The influence of the uncertainty in the volume lag between the concentration and LALLS detectors upon peak broadening was investigated and a new procedure for the determination of the lag was proposed. The applicability of the universal calibration concept was tested; all the polymers have been found to match a single universal calibration function. Polystyrene and poly(methyl methacrylate) also coincided very well with respect to the instrumental spreading, but for poly(vinylchloride) spreading was found to be a function of polymer concentration.     

Optimization of GPC Experiments as an Effective Means of Significantly Enhancing the Resolution of Multicolumn Sets to be Used for Analyzing Specific Polymer Systems

Abstract

Problems concerning GPC band spreading effects and their elimination were discussed, reference being also made to particular requirements to be met in the case of copolymer studies. GPC analysis optimization experiments were performed in order to minimize instrumental spreading for a multicolumn set operated in carbon tetrachloride. Results of experiments carried out at mobile phase flow rates of 1.0, 0.3 and 0.1 cm³/min for narrow MWD solutes were used to compute the values of the degree of polydispersity and other MWD obtainable parameters determining the extent of spreading minimization attained. The GPC data generated for runs conducted at the lowest flow rate employed were shown to have been rendered sufficiently accurate for the raw chromatograms to represent the polymers being analyzed without the need of performing mathematical corrections for imperfect GPC resolution.     

Approaches for the development of potential dengue inhibitors

Abstract

Dengue is the most severe mosquito borne viral disease for several decades in tropical and subtropical countries. Dengue virus (DENV) is a part of the Flaviviridae family with single positive stranded RNA genetic material encoding a single polyprotein, which is cleaved into structural and nonstructural proteins. Lethal consequences of DENV infections range from fever to hemorrhagic manifestations, volume depletion. Until now, no strategies are accessible for specific therapeutic measures for dengue fever, although it is the most rapidly spreading mosquito-borne viral infection in the world. Global disease burden caused by DENV infections is considerable, as neither specific antiviral drugs nor vaccines exist. The present synthetic literature provides interesting information in order to design novel drugs that mostly target viral processes. This review article reviews potential anti-dengue activities possessed by synthetic and plant based molecules.     

A new isoflavanone from the trunk of Horsfieldia pandurifolia

A new isoflavanone, 2,2′-epoxy-4′-methoxy-3,7-dihydroxyisoflavanone (1), and a new natural coumaranone, 2-hyroxy-2-(4′-methoxybenzyl)-6-methoxy-3-coumaranone (2), along with 26 known compounds, were first isolated from the trunk of Horsfieldia pandurifolia. Their structures were elucidated by the means of spectroscopic analysis. Compound 1 was assessed for its cytotoxicity against five human tumour lines (HL-60, SMMC-7721, A-549, MCF-7 and SW-480), and the result showed that it has no activity.     

ON THE ANIONS OF DIPHENYL 1-(4-NITROPHENYLAMINO)-1-ARYLMETHANE PHOSPHONATES1

Abstract

By means of UV spectroscopy it is shown that the anions derived of diphenyl 1-(4-nitrophenylamino)-1-arylmethane phosphonates are carbanions and not nitranions. This spectroscopical finding is corroborated by alkylation of the anions to give almost quantitatively the C-alkylated products.     

Models of virus capsids containing 72 pentameric capsomeres

A simple model for describing the non-quasi-equivalent icosahedral virus capsid composed of 72 pentameric capsomeres is developed. By means of six-step operations, a new 4-gons polyhedron P is obtained which contains 72 pentagons, 80 trigons and 210 quadrilaterals. More importantly, it bears icosahedral symmetry. The rationality of the existence of the 4-gons polyhedron P is further discussed. The results show that this model can be used to represent the capsids of papovaviruses.     

Dilution Methods in Flow Injection Analysis. Evaluation of Different Approaches as Exemplified for the Determination of Nitrosyl in Concentrated Sulphuric Acid

Abstract

Instigated by developing a flow injection procedure for assay of nitrosyl in concentrated sulphuric acid, different approaches for reliable and robust on-line dilution in FIA were evaluated. These comprised the application of mixing tees in conjunction with mixing coils (including knotted reactors) of different internal diameter, zone sampling, the use of a mixing chamber, micro-sampling, and sample injection by means of pseudo-hydrodynamic injection. The individual approaches are described in detail, their advantages and disadvantages being emphasized in regard to their practical applicability. For each approach the criteria stipulated were that the procedure should allow a dilution factor of approximately 100, yet without excessive zone spreading, so that it, on one hand, could effectively eliminate the pronounced Schlieren effect encountered when mixing concentrated sulphuric acid with an aqueous diluent, and, on the other hand, would permit the sample material to be appropriately conditioned for the ensuing chemical derivatization procedure. It was found that this most reliably could be effected by a combination of pseudo-hydrodynamic injection comprising a mixing point and the use of mixing tees in conjunction with knotted reactors of relatively large internal diameter (1.5 mm). The optimized FI-manifold was used with the Griess method for the spectrophotometric assay of nitrosyl (nitrite) in standards prepared in the matrix of concentrated sulphuric acid (detection limit 0.16 mg/1 NO⁺-N (3[sgrave])) and in practical WSA-samples.     

Solvent Composition Effects in the Chromatography of Alkaloids in the Systems Water + Methanol/Silanized Silica

Abstract

For systems of the type silanized silica/binary aquo-organic solvent, linear log k'vs. % H₂O plots are often obtained, the lines spreading fanwise in the direction of increased concentration of water. An example of such plots for a group of barbiturates is reported. For solutes which have more differentiated structures (especially in terms of the number and type of hydrophilic groups) less regular relationships can be obtained, as illustrated by log k' vs. % H₂O plots of eight alkaloids.     

An Improved Instrument for Measuring the Ultrasonic Absorption of Metal Chelate Adducts

Abstract

The purpose of this instrument is to provide a means to measure the rates of exchange, ΔG, ΔS, and ΔH of water and organic solvent adducts on metal chelates.

The instrument employs a pulsed ultrasonic technique which perturbs the equilibrium of a metal chelate and then measures the rate at which it returns to equilibrium.

This instrument is 10 times more sensitive than a previous instrument and was tested by examining the vanadium(V) benzo-hydroxamic acid chelate in n-butanol.     

Soil Contamination by some Organic Micropollutants Related to Sewage Sludge Spreading

Abstract

The aim of the present publication is to give some information on soil contamination by 4 different micropollutant classes due to sewage sludge spreading.

The soil under reserch shown an accumulation of light molecular weight PAHs and PCBs, DEHP and 4-NP just after spreading, but one month later the con-centration of these micropollutant groups fall to the concentration detected just before the sludge spreding.

As far as the soil concentration is concerned, only PAHs and PCBs are precipitation dependent.

Some test plots, enriched during 10 years with fertilisers, pig-dung or sewage sludges show only an increse of the PAH concentrations of the plots amended with sludges. In the same way, the sewage sludge is chiefly responsible for the increase of PCBs in the soils, but pig-dung seems to contain quantities of these micropollutants which have to be taken into consideration.     

Mn(III) and Cu(II) complexes of 1-((3-(dimethylamino)propylimino)methyl) naphthalen-2-ol): Synthesis,characterization, catecholase and phenoxazinone synthase activity and DFT-TDDFT study

Two new complexes, [MnL₂](ClO₄) (1) and [CuL₂] (2) (where LH = (E)-1-((3-(dimethylamino)propylimino)methyl)naphthalen-2-ol), have been synthesized and characterized by spectroscopic techniques and their molecular structures are established by single-crystal X-ray diffraction study. Complex 1 adopts an octahedral geometry around the central manganese atom which is in + 3 oxidation state, whereas in complex 2, the Cu⁺² ion preferred a square pyramidal environment around it through the ligand donor atoms. Both complexes were tested for catecholase and phenoxazinone synthase activity. Complex 1 catalyzes the oxidation of 3,5-ditertiary-butyl catechol with a k_cat value of 6.8424 × 10² h^?1 in acetonitrile whereas the same for complex 2 is 3.7485 × 10² h^?1 in methanol. Phenoxazinone synthase activity was shown only by complex 2 having k_cat = 74.225 h^?1. Structures of both the title complexes have been optimized by means of DFT calculations. Experimental electronic spectra of the complexes have been corroborated by TDDFT analysis. Electrochemical investigations by means of cyclic voltammetry have been carried out to study the electron transfer processes in the complexes.     

Kompressionsverhalten und Gleichgewichtsspreitungsdrucke binärer monomolekularer Dipalmitoylkephalin/Dimyristoylkephalin-Mischungen

1. The concentration dependence of theF/A-isotherms (premixed spreading, separate spreading) and the equilibrium spreading pressuresF ^e of the system dipalmitoylcephaline/dimyristoyl-cephaline were studied atT=298 K. The results were analysed and compared by means of thermodynamics with respect to miscibility of the components.
2. The spreading technique (pre-mixed spreading, separate spreading (with and without barrier), does not essentially influence the run of theF/A-isotherm. Alone, the collaps pressuresF _K differ.
3. The concentration dependence of theF/A-isotherms of premixed spread monolayers is analysed in terms of theA-x ^σ-diagram. The additivity of molecular areas at all surface pressures are assumed to indicate complete miscibility of the cephalins.
4. The phase rule according to Crisp was applied to analyse the spreading diagram in connection with the phase diagram of the mixtures in bulk. The results show that the cephalins are completely miscible in the monolayer.
5. The experimental collaps pressuresF _K of pre-mixed spread monolayers are very much larger than the equilibrium collapse presuresF _K calculated according to Garrett. The difference indicate the strong supercompression of mixed film during the compression.

     

Syntheses,crystal structures,and magnetic properties of RE(III)–Cu(II) heteronuclear complexes with α-methylacrylic acid

A series of carboxylate-bridged heteronuclear 3d–4f complexes have been prepared by reaction of REL₃ (HL = CH₂ = C(CH₃)COOH) with Cu(NO₃)₂. A family of air-stable 2-D complexes [RECuL₄(H₂O)₄] _n L _n (RE = La (1), Ce (2), Eu (3), and Gd (4)) have the same crystal system (monoclinic) and space group (P2₁/c). The chains which are made by the carboxylate-bridged alternating Cu(II)–RE(III) fragments spreading along the c-axis are linked through hydrogen bonds by uncoordinated carboxylates to form a 2-D network structure along the bc planes. Magnetic measurements showed that 1 and 2 have antiferromagnetic interaction between RE and Cu, but 4 exhibits ferromagnetic interaction. Eu ions show van Vleck behavior in 3.     

In plane and out of plane anisotropy in Langmuir-Blodgett films of discogenic molecules

Abstract

Langmuir-Blodgett films of a discotic mesogenic pyrylium tetrafluoroborate salt (1) have been investigated from the point of view of their in-plane anisotropy, i.e. considering the average molecular orientation with respect to the dipping direction. The molecules are found to stand on edge with their flat polycyclic core more or less perpendicular to the dipping direction. Mixing 1 with N(C₄H₉)₄ ⁺ TCNQ^? in the spreading solvent leads to a different behaviour of the monolayer at the air-water interface, involving the formation of the Pyrylium-TCNQ salt. In contrast to the films of pure 1, these films do not exhibit any in-plane anisotropy after deposition on a solid substrate. The temperature dependance of the molecular anisotropy of both films has also been investigated. The results are presented and discussed in the framework of their mesomorphic properties together with the influence of the anion associated with Pyrylium.     

A new galloyl glycoside from Lotus corniculatus

A new galloyl glucoside, 2,6-di-O-acetyl 1-O-galloyl β-D-glucose (1), along with five known phenolic compounds were isolated from the whole plants of Lotus corniculatus. Their structures were elucidated by means of extensive spectroscopic analysis. Compound 1 was assessed for its cytotoxicity against five human tumour lines (HL-60, SMMC-7721, A-549, MCF-7 and SW-480), and the result showed that it had no activity.