Novel nitration of estrone by metal nitrates

Nitration of estrone has been investigated with different types of metal salts in the presence of solid surfaces under various conditions.     

Diameter control of electrospun polyacrylonitrile/iron acetylacetonate ultrafine nanofibers

Electrospinning is the process of producing ultrafine fibers by overcoming the surface tension of a polymer solution using high voltage. In this work, the effects of both solution properties (viscosity, conductivity, and surface tension) and operational conditions (voltage, feed rate, and spinneret‐collector distance), on the structure of electrospun polyacrylonitrile nanofibers, were systematically investigated. Iron acetylacetonate was added to the electrospinning solution to control fiber diameter by selectively adjusting solution properties. It was found that, with increased salt concentration, the fiber diameter increases and then passes through a maximum due to changes in solution viscosity, conductivity, and surface tension. In addition, the fiber diameter increases with increase in voltage, feed rate, and spinneret‐collector distance. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1611–1618, 2008     

The use of acrylic acid-co-nylon substrates for immobilizing enzymes

A number of poly(acrylic acid)-co-nylon graft copolymers were prepared. Two approaches were used. The first involved the direct, radiation-induced grafting of acrylic acid onto the nylon, while the second involved the hydrolysis of polyacrylonitrile-co-nylon graft copolymers. All the resulting poly(acrylic acid)-co-nylon graft copolymers coupled large amounts of protein when the carbodimides CMC and EDAC were used as coupling agents. However, when the enzymes β-galactosidase and trypsin were immobilized, the retention of activity was relatively low. A number of reasons for this effect can be postulated, some of which were investigated. From the evidence, it would appear that the major reason is that the carboxylic acid groups are fixed to a “rigid” backbone, which allows them to interact with the enzyme after the establishment of an initial covalent attachment. Additionally, with acid phosphatase, it was observed that the enzyme interacted with immobilized carboxylic acid groups before coupling occurred.     

Analysis of ochres from Clearwell Caves: the role of particle size in determining colour

Three ochre samples (A (orange-red in colour), B (red) and C (purple)) from Clearwell Caves, (Gloucestershire, UK) have been examined using an integrated analytical methodology based on the techniques of IR and diffuse reflectance UV-visible-NIR spectroscopy, X-ray diffraction, elemental analysis by ICP-AES and particle size analysis. It is shown that the chromophore in each case is haematite. The differences in colour may be accounted for by (i) different mineralogical and chemical composition in the case of the orange ochre, where higher levels of dolomite and copper are seen and (ii) an unusual particle size distribution in the case of the purple ochre. When the purple ochre was ground to give the same particle size distribution as the red ochre then the colours of the two samples became indistinguishable. An analysis has now been completed of a range of ochre samples with colours from yellow to purple from the important site of Clearwell Caves.     

Comparison of the discriminating power of Raman and surface‐enhanced Raman spectroscopy with established techniques for the examination of liquid and gel inks

The ability to discriminate between inks is important for forensic document analysis. Here, Raman spectroscopy (RS) and surface‐enhanced RS have been compared to the traditional document examination techniques of video spectral comparison and thin layer chromatography on a population of blue and black‐coloured liquid and gel inks. It was found that in most cases, the Raman techniques provided a similar or better discriminating power than the conventional methods. Importantly, this study allowed us to determine whether the same underlying changes in composition were being exploited by the different methods to discriminate between samples. It was found that there was indeed a high degree of commonality in the sample pairs being discriminated by the various techniques. This work can therefore underpin introduction of Raman methods into standard operating procedures for ink analysis since it not only measures the extent of discrimination between samples but can also explain the origin of the spectral changes that are used to distinguish between them. © 2013 John Wiley & Sons Ltd and Crown copyright     

Next-generation quantum theory of atoms in molecules for the photochemical ring-opening reactions of oxirane

The conical intersections corresponding to the C─O and C─C ring opening were optimized and the reaction paths traversing these intersections were obtained. Investigation of the C─O ring opening revealed that when traversing the lowest energy conical intersection, the reaction path returns to the closed ring geometry. The C─O path traversing the intersection featuring torsion of terminal CH₂ group however, led to a ring-opened geometry, an H-shift and the formation of acetaldehyde that can undergo further dissociation. The observation of different reaction paths was explained by the 3-D paths from quantum theory of atoms in molecules (QTAIM) that defined the most preferred direction of electronic motion that precisely tracked the mechanisms of bond breaking and formation throughout the photo-reactions. The size, orientation, and location of these most preferred 3-D paths indicated the extent and direction of motion of atoms, bonds, and the degree of torsion or planarity of a bond indicating a predictive ability.     

Ruthenium‐Containing Linear Helicates and Mesocates with Tuneable p53‐Selective Cytotoxicity in Colorectal Cancer Cells

The ligands L¹ and L² both form separable dinuclear double‐stranded helicate and mesocate complexes with Ru^II. In contrast to clinically approved platinates, the helicate isomer of [Ru₂( L¹ )₂]⁴⁺ was preferentially cytotoxic to isogenic cells (HCT116 p53^?/?), which lack the critical tumour suppressor gene. The mesocate isomer shows the reverse selectivity, with the achiral isomer being preferentially cytotoxic towards HCT116 p53^+/+. Other structurally similar Ru^II‐containing dinuclear complexes showed very little cytotoxic activity. This study demonstrates that alterations in ligand or isomer can have profound effects on cytotoxicity towards cancer cells of different p53 status and suggests that selectivity can be “tuned” to either genotype. In the search for compounds that can target difficult‐to‐treat tumours that lack the p53 tumour suppressor gene, [Ru₂( L¹ )₂]⁴⁺ is a promising compound for further development.     

A rapid method for the quantification of artemisinin in Artemisia annua L. plants cultivated for the first time in Burundi

We describe a simple, rapid combined method for extracting the antimalarial compound artemisinin from the leaves of Artemisia annua L. cultivated for the first time in Burundi, and quantitating the active principle by high-performance liquid chromatography-electrospray mass spectrometry.     

Semisynthesis of new D-seco-C-nor-taxane derivatives containing a polyfunctionalized furanosyl or cyclopentenyl or cyclopentyl C-ring

The synthesis of new D-seco-C-nor-taxane derivatives in which the D-ring has been deleted and the C-ring has been transformed into a new pentatomic ring, i.e., the polyfunctionalized tetrahydrofuranosyl and cyclopentenyl or cyclopentyl ring, was performed starting from baccatin III derivatives. The synthetic strategy adopted took advantage of the oxetane ring opening and disconnection of the C4-C5 bond, followed by an intramolecular condensation. The formation of furanosyl or cyclopentyl rings is strictly dependent on the presence of unprotected or protected oxygen at C-7 in the starting material. The reactions proceeded with good diastereoselectivity with control of the stereochemistry of one or two stereocenters.