Direct imaging of o-carborane molecules within single walled carbon nanotubes

Ortho-carborane molecules have been inserted into single walled carbon nanotubes (SWNTs) and imaged directly by high resolution transmission electron microscopy (HRTEM); both discrete molecules and 'zig-zag' 1D chains of o-carborane 'petit pois' were observed to pack into the tubule capillaries.     

A solid-phase route to N-cyanoamides

[reaction: see text] A new method for the solid-phase synthesis of cyanamides is described. The attachment of a secondary amine to solid support is accomplished using Merrifield resin. After functionalization, cleavage is readily achieved with cyanogen bromide to afford the desired cyanamide.     

Extended wedge covariance for wetting and filling transitions

Fluid adsorption on nonplanar and heterogeneous substrates is studied using a simple interfacial model. For systems with short-ranged forces, we find that, by tuning the local strength of the substrate potential, it is possible to find the exact equilibrium interfacial profile as a functional of the wall shape psi x. The tuning of the local substrate potential takes the form of a gauge condition theta x=+/-psi x, where theta x can be interpreted as a local effective contact angle. For wedgelike geometries with asymptotic tilt angle alpha, the midpoint interfacial height and roughness satisfy the same covariance relations previously found for simple linear wedges. For troughlike geometries satisfying the gauge condition, covariance is also found for the two-point correlation function. Predictions for more microscopic Landau and Ising models are also discussed.     

A stereospecific synthesis of vitamin A from 2,2,6-trimethyl-cyclohexanone.

An efficient synthesis of all-(E) vitamin A acetate from 2,2,6-trimethyl-cyclohexanone has been achieved via the intermediacy of 1-(9-acetoxy-3, 7-dimethyl-nona-3,5,7-trien-1-ynyl)-2,2,6-trimethyl-cyclohexanol ( 25 ), readily prepared in high yield by allylic rearrangement of tertiary propenols with glacial acetic acid. The key step in the synthesis is the transformation of 25 to the unsaturated ketone 27 (9-acetoxy-3,7-dimethyl-1-(2,6,6-trimethyl-cyclohex-1-enyl)-nona-3,5,7-trien- 2-one) using a novel vanadium(V)-catalysed rearrangement reaction. The carbonyl in 27 affords the means for the essential isomerization of the adjacent double bond to the (E) isomer and the product is readily transformed into the polyene by reduction and elimination. An overall yield of 18–31% of vitamin A acetate from 2,2,6-trimethyl-cyclohexanone has been realized.     

Detection of ammonium in geological materials by evolved gas analysis

The association of anomalously high levels of ammonium with both metallic and energy mineral deposits is of potential use in mineral exploration. Conventional geochemical methods for detecting NH₄ often provide only whole-rock NH₄ values and do not identify the specific minerals hosting NH₄. They may also lack sensitivity or be prone to interference. Evolved NH₃ analysis is shown to be capable of distinguishing between different NH₄-bearing minerals and can detect NH₄ values down to 120 ppm in rocks hosting silver-gold vein mineralization. Fully quantitative determination of NH₄ by this method is not possible as the NH₃ evolved from minerals during heating partially oxidised; however, amounts of evolved NH₃ do show a moderate positive linear correlation with NH₄ content determined by a modified Kjeldahl method.     

Effects of amine modifiers on retention and peak shape in reversed-phase high-performance liquid chromatography

A systematic evaluation of the effects of 15 different amine modifiers on the retention and peak symmetry of three solutes, a primary, a secondary, and a tertiary amine, is presented. Using automated experimentation, mobile phase combinations for each modifier over a pH range of 2.5 to 8 were investigated. The effect of changing the sodium ion concentration of the mobile phase was also examined. The importance of hydrophobic, ion exchange, and hydrogen bonding interactions as mechanisms for retention and peak symmetry of positively charged solutes is discussed.     

Comparison of photodynamic targets in a carcinoma cell line and its mitochondrial DNA-deficient derivative

The relative contribution, to cell death, of photodynamic damage to respiratory proteins (known targets of photodynamic therapy with many photosensitizers) and other cellular sites was examined. The models were a human ovarian carcinoma cell line 2008, and its mitochondrial DNA-deficient derivative ET3, which lacks several key respiratory protein subunits. Phototoxicity was compared in the two cell lines with photosensitizers that localized to different cellular compartments. Photosensitizers included Victoria Blue BO (VBBO; mitochondria); Photofrin with a short incubation, (plasma membrane) or a long incubation (intracellular membranes including mitochondria); and Nile Blue A (NBA; lysosomes). Photosensitizer content and localization did not differ between the 2008 and ET3 cells. For sensitizers without a primary mitochondrial localization (NBA and Photofrin with a short incubation), there was no significant difference between 2008 and ET3 toxicity. Consistent with a mitochondrial localization of VBBO and independence from respiratory-chain damage, ET3 cells were less susceptible than 2008 to both dark- and light-activated VBBO-mediated damage. Statistical analysis of the data demonstrated minimal photobleaching of VBBO and a significant difference between the phototoxicity curves of ET3 and 2008. For Photofrin with a long incubation, dark- and phototoxicity effects were similar for both cell lines. Inhibition of respiratory enzymes is thus only a minor component of Photofrin-mediated (long incubation) phototoxicity in these cell lines and is overwhelmed by more significant damage elsewhere, whereas it is a major but not the exclusive element of death mediated by VBBO.     

Solid-state glycation of beta-lactoglobulin by lactose and galactose: localization of the modified amino acids using mass spectrometric techniques

The Maillard reaction is commonly encountered during food processing or storage, and also in human nutrition, hence there is a need for analytical methodologies to identify and characterize the modified proteins. This paper reports specific methods using mass spectrometric techniques to localize protein modifications induced by lactose and galactose on beta-lactoglobulin (beta-Lg) under solid-state glycation conditions. The extent of glycation was first determined by liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS). The specific identification of lactose-modified amino acid residues was realized using both NanoESI-MS, NanoESI-MS/MS (neutral loss scanning modes) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) (with and without guanidination of lysine residues) on unfractionated digests. The results indicated that, after 8.25 h of incubation, the lysine residues were the main targets of lactose-induced modification. In addition to the 15 lysine residues, Leu1 (NH2 terminal) and the Arg124 were also found to be modified, thus leading to a total of 17 different modified amino acid residues (versus 15 found by LC/ESI-MS measurement). In a second set of experiments, different strategies consisting of constant neutral loss and precursor ion scanning were compared to characterize galactose-induced modifications. Owing to the high level of beta-Lg glycation, the combined use of these different strategies appeared to be necessary for determining the galactose-modified sites after 8.25 h of incubation. Thus, among the 22 galactose adducts deduced from the LC/ESI-MS measurement, apart from the N-terminal and classical lysine residues, we also observed a few arginine residues (Arg40, Arg124 and Arg148) that were modified, and also dialkylations on specific lysine residues (Lys47, Lys75).     

Stabilization of Aliphatic Phosphines by Auxiliary Phosphine Sulfides Offers Zeptomolar Affinity and Unprecedented Selectivity for Probing Biological CuI

Full elucidation of the functions and homeostatic pathways of biological copper requires tools that can selectively recognize and manipulate this trace nutrient within living cells and tissues, where it exists primarily as Cu^I. Buffered at attomolar concentrations, intracellular Cu^I is, however, not readily accessible to commonly employed amine and thioether‐based chelators. Herein, we reveal a chelator design strategy in which phosphine sulfides aid in Cu^I coordination while simultaneously stabilizing aliphatic phosphine donors, producing a charge‐neutral ligand with low‐zeptomolar dissociation constant and 10¹⁷‐fold selectivity for Cu^I over Zn^II, Fe^II, and Mn^II. As illustrated by reversing ATP7A trafficking in cells and blocking long‐term potentiation of neurons in mouse hippocampal brain tissue, the ligand is capable of intercepting copper‐dependent processes. The phosphine sulfide‐stabilized phosphine (PSP) design approach, which confers resistance towards protonation, dioxygen, and disulfides, could be readily expanded towards ligands and probes with tailored properties for exploring Cu^I in a broad range of biological systems.