Dendrimers as potential drug carriers; encapsulation of acidic hydrophobes within water soluble PAMAM derivatives

This paper describes the synthesis of three neutral water soluble poly(amidoamine) (PAMAM) dendrimer derivatives. The ability of the two larger dendrimers to bind small acidic hydrophobic molecules is reported. Spectroscopic data and pH behaviour suggested that the acidic hydrophobes were forming stable ion pairs with the dendrimer's internal, basic tertiary nitrogens. With respect to forming 1:1 and 2:1 substrate/dendrimer complexes, both of the larger dendrimers were equally efficient at binding. All dendrimer/substrate complexes were completely miscible with water in all proportions (i.e. infinitely water soluble). When the bound substrates are drug moieties, then the resulting complexes could be considered as potential drug delivery systems. Flow calorimetry demonstrated that the dendrimers were able to release their hydrophobic guests when in contact with a biological cell.     

In situ electrochemical ESR and voltammetric studies on the anodic oxidation of para-haloanilines in acetonitrile

An in situ electrochemical electron spin resonance (ESR) study on the electro-oxidation of para-chloroaniline, para-bromoaniline, and para-iodoaniline dissolved in acetonitrile at gold electrodes is reported. ESR spectra obtained using a tubular flow cell reveal the presence of a paramagnetic dimer product derived from para-aminodiphenylamine, during oxidative electrolysis, suggesting the coupling of reactive electrogenerated radical cations with neutral parent haloaniline molecules. The ESR signal intensity behaves in a manner expected for a radical species reacting with second-order kinetics, suggesting the paramagnetic dimer is, itself, unstable. The theory describing the ESR signal intensity flow rate behavior for this reaction mechanism is developed for the tubular arrangement and used to extract mechanistic and kinetic data from the experimental results for the cases of para-chloroaniline and para-bromoaniline. Further mechanistic aspects, including proton and halide ion expulsion during dimerization, are explored voltammetrically and with the aid of digital simulations using Digisim. Comparison of the ESR signal and voltammetric measurements suggests that an additional mechanism operates which does not lead to paramagnetic products. Additionally, the in situ electrolysis of N,N-dimethyl-para-bromoaniline is reported to generate the stable radical cation of N,N,N',N'-tetramethylbenzidine, and a mechanism of electro-oxidation is, thus, proposed.     

Differential inhibition of postnatal brain,spinal cord and body growth by a growth hormone antagonist

Background  

Growth hormone (GH) plays an incompletely understood role in the development of the central nervous system (CNS). In this study, we use transgenic mice expressing a growth hormone antagonist (GHA) to explore the role of GH in regulating postnatal brain, spinal cord and body growth into adulthood. The GHA transgene encodes a protein that inhibits the binding of GH to its receptor, specifically antagonizing the trophic effects of endogenous GH.     

Microwire Chronoamperometric Determination of Concentration,Diffusivity, and Salinity for Simultaneous Oxygen and Proton Reduction

A microwire chronoamperometric method is reported employing a 25 µm diameter platinum microwire for multi‐parameter electroanalysis with digital simulation‐based evaluation (employing DigiElch 4.F). Concentration and diffusion coefficient data are obtained for the reduction of oxygen and for the reduction of protons individually and simultaneously in saline (0.1 M to 4.0 M NaCl) electrolyte media. The diffusion coefficient and concentration data for oxygen allows salinity levels to be estimated. The microwire chronoamperometry method offers versatility and precision due to (i) a slow approach to steady state (when compared to microdisc methods) and (ii) insignificant viscosity effects (when compared to hydrodynamic methods).     

Raman spectroscopy of smithsonite

Raman spectroscopy at both 298 and 77 K has been used to study a series of selected natural smithsonites from different origins. An intense sharp band at 1092 cm⁻¹ is assigned to the CO₃²⁻ symmetric stretching vibration. Impurities of hydrozincite are identified by a band around 1060 cm⁻¹. An additional band at 1088 cm⁻¹ which is observed in the 298 K spectra but not in the 77 K spectra is attributed to a CO₃²⁻ hot band. Raman spectra of smithsonite show a single band in the 1405–1409 cm⁻¹ range assigned to the ν₃ (CO₃)²⁻ antisymmetric stretching mode. The observation of additional bands for the ν₃^g modes for some smithsonites is significant in that it shows distortion of the ZnO₆ octahedron. No ν₂ bending modes are observed for smithsonite. A single band at 730 cm⁻¹ is assigned to the ν₄ in phase bending mode. Multiple bands be attributed to the structural distortion are observed for the carbonate ν₄ in phase bending modes in the Raman spectrum of hydrozincite with bands at 733, 707 and 636 cm⁻¹. An intense band at 304 cm⁻¹ is attributed to the ZnO symmetric stretching vibration. Copyright © 2007 John Wiley & Sons, Ltd.     

Galvanic exchange platinization reveals laser-inscribed pattern in 3D-LAM-printed steel

Galvanic exchange involving dissolution of iron and the simultaneous growth of platinum onto 316 L stainless steel was investigated for specimens manufactured by 3D-printing, and the behavior was compared to conventional stainless steel. Novel phenomena associated with the 3D-printed steel, but not conventional steel, reacting in three distinct phases were observed: first, with low platinum loading, a bright etching pattern linked to the laser-manufacturing process is revealed at the steel surface; second, a nanostructured pore pattern with platinum nano-deposits forms; and third, a darker platinum film coating of typically 500-nm thickness forms and then peels off the steel surface with further platinum growth underneath. Unlike the conventional steel (and mainly due to residual porosity), 3D-printed steel supports well-adhered platinum films for potential application in electrocatalysis, as demonstrated for alkaline methanol oxidation.

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Transfer measurements for the Ti+Ni systems at near barrier energies

Large enhancements have been observed in the sub-barrier fusion cross sections for Ti+Ni systems in our previous studies. Coupled channel calculations incorporating couplings to 2⁺ and 3⁻ states failed to explain these enhancements completely. A possibilty of transfer channels contributing to the residual enhancements had been suggested. In order to investigate the role of relevant transfer channels, measurements of one- and two-nucleon transfer were carried out for ^46,48Ti+⁶¹Ni systems. The present paper gives the results of these studies.     

A thermogravimetric study of the alunites of sodium, potassium and ammonium

Thermogravimetry in tandem with mass spectrometry has been used to characterise the thermal decomposition of synthetic alunites of potassium, sodium and ammonium. Three mechanisms of decomposition are observed (a) dehydration, (b) dehydroxylation and (c) desulphation. The thermal decomposition of the three alunites is different. For NH₄-alunite, an additional process of de-ammoniation is observed which occurs simultaneously with dehydration. Dehydroxylation takes place in a series of four steps. De-sulphation occurs for K-alunite at 680 °C in a single step in comparison with Na and NH₄ alunites where de-sulphation is observed in a series of four steps. The temperature of desulphation is cation dependent. The thermal decomposition is not completed until around 800 °C.     

Using FTIR spectroscopy to detect sericin on historic silk

Silks represent some of the most precious ancient and historic textile artefacts in collections worldwide.Their optimum preservation demands an appreciation of their characteristics.One important concern,especially with regard to ancient Chinese silks,is whether the fabrics have been degummed.Silks with remnant sericin gum coating the fibroin fibres would require different conservation protocol.In previous research on aged silks,the presence of sericin has been inferred from amino acid analysis of hydrolysa...     

Electrocatalytic reactions mediated by N,N,N',N'-Tetraalkyl-1,4-phenylenediamine redox liquid microdroplet-modified electrodes: chemical and photochemical reactions In, and At the surface of, femtoliter droplets

The electro-oxidation of electrolytically unsupported ensembles of N,N-diethyl-N',N'-dialkyl-para-phenylenediamine (DEDRPD, R = n-butyl, n-hexyl, and n-heptyl) redox liquid femtoliter volume droplets immobilized on a basal plane pyrolytic graphite electrode is reported in the presence of aqueous electrolytes. Electron transfer at these redox liquid modified electrodes is initiated at the microdroplet-electrode-electrolyte three-phase boundary. Dependent on both the lipophilicity of the redox oil and that of the aqueous electrolyte, ion uptake into or expulsion from the organic deposits is induced electrolytically. In the case of hydrophobic electrolytes, redox-active ionic liquids are synthesized, which are shown to catalyze the oxidation of l-ascorbic acid over the surface of the droplets. In contrast, the photoelectrochemical reduction of the anaesthetic reagent halothane proceeds within the droplet deposits and is mediated by the ionic liquid precursor (the DEDRPD oil).