Unique intermolecular reaction of simple porphyrins at a metal surface gives covalent nanostructures

Deposition of a porphyrin onto metallic copper followed by heating leads to an unprecedented type of linking of the molecules giving a mixture of covalent multiporphyrin nanostructures at the surface.     

Direct visualization of chirality in two dimensions

Surface science techniques have been used to investigate 2D chirality induced by molecular adsorption at the Cu(1 1 0) surface. Particular emphasis has been devoted to presenting molecular resolution scanning tunnelling microscope images which provide direct, real-space access to chiral behaviour at the nanoscale. The systems chosen demonstrate the gamut of chiral organization: conglomerates, racemates and solid solutions. They show the creation of chirality from achiral adsorbates, and the enantiospecific hosting of an intrinsic chiral guest. In short, chirality at surfaces manifests its full range of behaviours, and STM provides the means by which that behaviour can be captured.     

Tailoring homochirality at surfaces: going beyond molecular handedness

Chirality can be bestowed upon a surface by the adsorption of molecules and is usually discussed in terms of the molecular handedness. However, the adsorption process often leads to a new manifestation of chirality in the form of the adsorption footprint, which can also be chiral and generate mirror-images in 2-D. Therefore, in describing the chirality of the interface, one must consider both the handedness and the adsorption 'footedness' of the system. Specifically, the creation of a truly homochiral surface must ensure that a single chirality is expressed for each aspect, and requires not only the control of molecule handedness but also direct control over footedness. Here, we demonstrate the ability to engineer homochiral footedness by a structural modification of enantiopure (S)-proline, which normally creates a (4 × 2) organization on a Cu(110) surface with heterochiral footedness. This modification of proline via the addition of a double bond within the pyrrolidine ring, yielding 3-pyrroline-2-carboxylic acid (PCA), is sufficient to drive the footprints of the entire (4 × 2) assembly from heterochiral to homochiral, leading to the creation of a truly homochiral interface The effects of modifications upon the footprint arrangements were characterized at the single-molecule level by scanning tunnelling microscopy, reflection absorption infrared spectroscopy and periodic density functional theory calculations. The control of adsorption footprints is not only pivotal to tailoring chirality at surfaces but also plays a key role in dictating the organization, the outward facing functionalities and the response of the organic-inorganic interface.     

Tracking Injectable Microspheres in Dynamic Tissues With Encapsulated Superparamagnetic Iron Oxide Nanoparticles

Trackable spheres of similar size to those typically used for sustained protein delivery are prepared by incorporating superparamagnetic iron oxide (SPIO) nanoparticles into the core of poly(lactide‐co‐glycolide) microspheres. The visibility of injections in static and temporally in dynamic tissue systems is demonstrated. This method improves upon other, less sensitive imaging modalities in their ability to track injectable delivery systems. The results obtained confirm the localization of microspheres to the injected target area and highlight the novelty of tracking delivery vehicles for other applications.

     

MRI of the skull

Thirty-four patients with a wide variety of benign and malignant incidental skull findings on routine magnetic resonance (MR) imaging of the brain were reviewed. In most instances detection of the lesions was not difficult. However, recognition of various patterns of skull involvement in different disease processes is important. This is particularly true in differentiating benign from malignant lesions, which may be a critical factor in patient management.     

Feasibility of fast MR imaging of the liver at 1.5 T

A phantom with T1 and T2 relaxation times encompassing normal liver and liver lesions was constructed to evaluate fast magnetic resonance pulse sequences using TR from 21-100 milliseconds, TE 12-60 milliseconds and flip angles from 5 degrees-90 degrees. Ten of these fast MR sequences were then selected and compared with conventional spin-echo sequences in normal volunteers (n = 3) and in patients with liver lesions (n = 6). Subjectively, the fast MR sequences eliminated motion artefacts. Objectively, 8 of 10 fast sequences had signal-to-noise ratios comparable to spin-echo imaging whereas only 2 of 10 had contrast-to-noise ratios that were similar to spin-echo imaging. This preliminary study, performed at 1.5 Tesla, does not show any clear-cut advantage of fast imaging over spin-echo imaging in the detection of liver lesions. The use of a liver tissue equivalent phantom provides a rapid, practical approach in evaluation of fast scans.     

Dynamic chiral flipping within strongly chemisorbed molecular monolayers at surfaces

Unexpected local chiral switching events are shown to occur within strongly chemisorbed homochiral domains, in which a pair of surface-bonded molecules dynamically switches their chiral configuration for a short period of time.     

Reactivity at Line Defects in Antimony in Etchants with Dextro- and Levo Tartaric Acid

The (111) cleavage faces of antimony single crystals were etched in aqueous mixtures of fuming nitric acid plus dextro tartaric acid and fuming nitric acid plus levo tartaric acid. Triangular, crystallographically oriented etch pits were observed at sites of dislocations. The activation energies for lateral motion of ledges and the frequency factors were calculated for both types of etchants which were found to be higher in levo tartaric acid containing etchants than in dextro tartaric acid containing etchants. The results are explained in terms of antimony complexes and the difference in the shape of dextro tartaric acid and levo tartaric acid molecular structures.