Use of amorphous zirconium phosphate for the treatment of radioactive waste

Ion-exchange experiments were carried out for the removal of¹³⁷Cs, and⁹⁰Sr/⁹⁰Y radioisotopes by different cationic forms of amorphous zirconium phosphate. The effect of temperature and concentration on the percent uptake and distribution coefficients (K _d ) values (milli-equivalents of ion per gram of exchanger/milli-equivalents of ion per ml of solution) were determined. Experiments were made in simulated pond water at pH 11.4.     

Synthesis and structure of phosphatidylinositol dimannoside

(R)-tuberculostearic acid (2) was synthesized in seven steps from (S)-citronellol (5). The carbon chain of 2 was assembled by copper-catalyzed cross coupling of (S)-citronellol tosylate (6) and hexylmagnesium bromide; subsequent ozonolysis and reaction with 6-benzyloxyhexylmagnesium bromide furnished alcohol 10. Functional group manipulation afforded (R)-2 in 49% overall yield from 5. DCC coupling of (R)-2 with 3-O-benzyl-1-O-palmitoyl-sn-glycerol (16), followed by hydrogenolytic removal of the benzyl group and treatment with benzyl bis(diisopropyl)phosphoramidite, afforded phosphoramidite 20. Tetrazole-mediated coupling of 20 with PIM1 head group 21 gave 22, and subsequent debenzylation afforded phosphatidylinositol mono-mannoside, PIM1 (23). Similarly, coupling of 20 and 24 and removal of the benzyl protecting groups gave PIM2 (1c). Both 23 and 1c have a clearly defined acylation pattern, which was confirmed by mass spectrometry, with sn-1 palmitoyl and sn-2 tuberculostearoyl groups on the glycerol moiety. Both 23 and 1c were shown to modulate the release of the pro-inflammatory cytokine, IL-12, in a dendritic cell assay.     

Duplex stability of DNA.DNA and DNA.RNA duplexes containing 3'-S-phosphorothiolate linkages

3'-S-Phosphorothiolate (3'-SP) linkages have been incorporated into the DNA strand of both a DNA.RNA duplex and a DNA.DNA duplex. Thermal melting (T(m)) studies established that this modification significantly stabilises the DNA.RNA duplex with an average increase in T(m) of about 1.4 degrees C per modification. For two or three modifications, the increase in T(m) was larger for an alternating, as compared to the contiguous, arrangement. For more than three modifications their arrangement had no effect on T(m). In contrast to the DNA.RNA duplex, the 3'-S-phosphorothiolate linkage destabilised the DNA.DNA duplex, irrespective of the arrangement of the 3'-SP linkages. The effect of ionic strength on duplex stability was similar for both the phosphorothiolate-substituted and the unmodified RNA.DNA duplexes. The results are discussed in terms of the influence that the sulfur atom has on the conformation of the furanose ring and comparisons are also drawn between the current study and those previously conducted with other modifications that have a similar conformational effect.     

Preference for a C3 conformation in tris-dimethylaminophosphonium cations: a comparison of the reactions of (Me2N)3P with I-X (X = Cl, Br, I, CN)

Tris-(dimethylamino)phosphine reacts with I(2) to form (Me(2)N)(3)PI(2), which when recrystallised from acetonitrile displays a structure of overall stoichiometry [{(Me(2)N)(3)PI}I](6).CH(3)CN . The asymmetric unit of consists of four different [(Me(2)N)(3)PI](+) cations, one of these exhibits a cation-anion interaction to an iodide ion, with an I-I contact distance of 3.6378(14) A, the longest yet observed for an R(3)PI(2) compound. Two of the other three cations display no interactions, whilst a cation-solvent interaction is observed for the fourth. When (Me(2)N)(3)PI(2) is recrystallised from dichloromethane the molecule abstracts chlorine from the solvent to form [(Me(2)N)(3)PCl]I this latter compound can also be synthesised directly from (Me(2)N)(3)P and ICl. The reaction of (Me(2)N)(3)P with IBr forms [(Me(2)N)(3)PBr]I, which when recrystallised from chlorinated solvents forms [(Me(2)N)(3)PCl(0.5)Br(0.5)]I. The analogous [(Me(2)N)(3)PCN]I, does not display CN-Cl exchange and can be recrystallised from dichloromethane. The structures of and have all been determined by X-ray diffraction. All of the (Me(2)N)(3)P groups in the cations in, and exhibit a C(3) conformation, in contrast to the majority of (R(2)N)(3)P systems where a C(s) conformation is usually preferred. This C(3) conformation appears to be favoured where there is increased positive charge on phosphorus, as is the case in the phosphorus(v) ionic species described herein. This conformation allows greater P-N pi-bonding, and as a result the P-N bonds are shortened, varying between 1.566(10) and 1.624(10) A in these compounds.     

A simple and economical method for the production of 13C,18O-labeled Fmoc-amino acids with high levels of enrichment: applications to isotope-edited IR studies of proteins

Isotope-edited IR of proteins has generated considerable interest. Double labeling with 13C and 18O with high levels of isotopic enrichment is required for residue-specific resolution. Current methods for the preparation of doubly labeled amino acids give modest 18O enrichment, limiting the utility of the approach. We report a simple and economical method for preparing 13C,18O-doubly labeled N-(9-fluorenylmethoxycarbonyl)amino acids with high levels of enrichment for residues that do not require acid-labile side-chain protecting groups.     

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.     

Visible light photo-oxidation of model pollutants using CaCu3Ti4O12: an experimental and theoretical study of optical properties, electronic structure, and selectivity

Charge transfer between metal ions occupying distinct crystallographic sublattices in an ordered material is a strategy to confer visible light absorption on complex oxides to generate potentially catalytically active electron and hole charge carriers. CaCu3Ti4O12 has distinct octahedral Ti4+ and square planar Cu2+ sites and is thus a candidate material for this approach. The sol?gel synthesis of high surface area CaCu3Ti4O12 and investigation of its optical absorption and photocatalytic reactivity with model pollutants are reported. Two gaps of 2.21 and 1.39 eV are observed in the visible region. These absorptions are explained by LSDA+U electronic structure calculations, including electron correlation on the Cu sites, as arising from transitions from a Cu-hybridized O 2p-derived valence band to localized empty states on Cu (attributed to the isolation of CuO4 units within the structure of CaCu3Ti4O12) and to a Ti-based conduction band. The resulting charge carriers produce selective visible light photodegradation of 4-chlorophenol (monitored by mass spectrometry) by Pt-loaded CaCu3Ti4O12 which is attributed to the chemical nature of the photogenerated charge carriers and has a quantum yield comparable with commercial visible light photocatalysts.     

Tripodal imidazole frameworks: Reversible vapour sorption both with and without significant structural changes

A series of tripodal imidazole frameworks (TIFs) are reported based on a tripodal, cavity-containing tris(imidazole) derivative. In the case of [Co(3)Cl(6)(1)(2)]·n(solvent) (TIF-1) which possesses a doubly interpenetrated framework structure, the material exhibits rigid, permanent porosity and selectively absorbs CO(2). The non-interpenetrated [Co(1)(2)(H(2)O)(2)]Cl(2)·4H(2)O (TIF-2) also absorbs gases and vapours fully reversibly exhibiting a reversible phase change in the process and considerable conditioning and hysteresis. The very highly hydrated [Co(1)(2)]Cl(2)·22H(2)O (TIF-3) irreversibly dehydrates to the layered structure [Co(1)(2)]Cl(2)·H(2)O (TIF-4). A nickel analogue [Ni(1)(2)]Cl(2)·22H(2)O (TIF-5) closely related to TIF-3 is also reported along with two isostructural, non-porous materials [MCl(2)(1)] (M = Mn, TIF-6; M = Cd, TIF-7) based on d(5) and d(10) Mn(II) and Cd(II). Some of the materials may be prepared by mechanochemical as well as solution based methods. We liken TIF-1 to a gas cylinder, TIF-2 to a sponge and TIF-3 to a fragile soda can that is crushed on emptying to give TIF-4.     

Direct Laser Desorption Ionization of Endogenous and Exogenous Compounds from Insect Cuticles: Practical and Methodologic Aspects

We recently demonstrated that ultraviolet laser desorption ionization orthogonal time-of-flight mass spectrometry (UV-LDI o-TOF MS) could be used for the matrix-free analysis of cuticular lipids (unsaturated aliphatic and oxygen-containing hydrocarbons and triacylglycerides) directly from individual Drosophila melanogaster fruit flies (Yew, J. Y.; Dreisewerd, K.; Luftmann, H.; Pohlentz, G.; Kravitz, E. A., Curr. Biol. 2009, 19, 1245–1254). In this report, we show that the cuticular hydrocarbon, fatty acid, and triglyceride profiles of other insects and spiders can also be directly analyzed from intact body parts. Mandibular pheromones from the jaw of a queen honey bee are provided as one example. In addition, we describe analytical features and examine mechanisms underlying the methodology. Molecular ions of lipids can be generated by direct UV-LDI when non-endogenous compounds are applied to insect wings or other body parts. Current sensitivity limits are in the 10 pmol range. We show also the dependence of ion signal intensity on collisional cooling gas pressure in the ion source, laser wavelength (varied between 280–380 nm and set to 2.94 μm for infrared LDI), and laser pulse energy.     

Total Synthesis,Stereochemical Assignment,and Biological Activity of Chamuvarinin and Structural Analogues

A highly stereocontrolled synthesis of (+)‐chamuvarinin has been completed in 1.5 % overall yield over 20 steps. The key fragment coupling reactions were the addition of alkyne 8 to aldehyde 7 (under Felkin–Anh control), followed by the two step activation/cyclization to close the C20–C23 2,5‐cis‐substituted tetrahydrofuran ring and a Julia–Kocienski olefination at C8–C9 to introduce the terminal butenolide. The inherent flexibility of our coupling strategy led to a streamlined synthesis with 17 steps in the longest sequence (2.2 % overall yield), in which the key bond couplings are reversed. In addition, a series of structural analogues of chamuvarinin have been prepared and screened for activity against HeLa cancer cell lines and both the bloodstream and insect forms of Trypanosoma brucei, the parasitic agent responsible for African sleeping sickness.