Nanometer linear focusing of hard x rays by a multilayer Laue lens

We report on a type of linear zone plate for nanometer-scale focusing of hard x rays, a multilayer Laue lens (MLL), produced by sectioning a multilayer and illuminating it in Laue diffraction geometry. Because of its large optical depth, a MLL spans the diffraction regimes applicable to a thin Fresnel zone plate and a crystal. Coupled wave theory calculations indicate that focusing to 5 nm or smaller with high efficiency should be possible. Partial MLL structures with outermost zone widths as small as 10 nm have been fabricated and tested with 19.5 keV synchrotron radiation. Focal sizes as small as 30 nm with efficiencies up to 44% are measured.     

Coordination and hydrogen bonded network structures of Cu(II) with mixed ligands: a hybrid hydrogen bonded material, an infinite sandwich arrangement, and a 3-D net

Mixed-ligand Cu(II) complexes with deprotonated trimesic acid and phenanthroline-type ligands were synthesised by solvothermal methods to form 2-D infinite hexagonal hydrogen bonded structures with additional trimesic acid (H3tma) molecules. The complex [Cu(phendione)2(H2tma)2].2(H3tma).1.65(CF3CH2OH).2.5(H2O), where phendione = 1,10-phenanthroline-5,6-dione, has hydrogen bonded networks of [Cu(phendione)2(H2tma)2] complexes interspersed with layers of H3tma with a topologically identical hydrogen bonding network. Whereas in [Cu(1,10-phenanthroline)(H2tma)2]2.2(H3tma), a dimeric Cu(II) complex hydrogen bonds directly to additional H3tma molecules to form a three-layered 2-D network resembling an infinite sandwich. The synthesis and structures of simple Cu(II) complexes of the phendione ligand are also reported. One of these, [Cu(phendione)2Br2] shows a particularly polar packing arrangement.     

Synthesis and reactions of some heterobimetallic and multimetallic complexes containing η-arene-ruthenium(II), -osmium(II) and η-Pentamethylcyclopentadienyl-rhodium(III) moieties

Heterobimetallic complexes such as [η-areneMCl(SPPh₂)₂Pt(S₂CNEt₂)] (I, M = Ru, Os) and [η-C₅Me₅RhCl(SPPh₂)₂Pt(S₂CNEt₂)] (II) have been synthesised by reaction of NEt₂H₂[Pt(S₂CNEt₂)(Ph₂PS)₂] with either [M(η-arene)Cl₂]₂ or [Rh(η-C₅Me₅)Cl₂]₂ (2/1) molar ratio). Further reactions of I include facile chloride displacement with a range of neutral ligands L to give [η-areneML(SPPh₂)₂Pt(S₂CNEt₂)⁺ (III) cations and formation of tri- and penta-metallic species on treatment with more [Pt(S₂CNEt₂)(Ph₂PS)₂]^?.     

Synthetic studies with iron carbonyl complexes. Versatile synthesis of olefinic side-chains to a tricarbonyl(cyclohexadiene)iron(0) ring

Tricarbonyl(cyclohexadiene)iron(0) complexes bearing olefinic side-chains at the 2- or the 5-position have been prepared by a versatile route. Terminal olefins are isomerised to internal isomers. The presence of a methoxy substituent at the 2-position prevents isomerisation of the coordinated diene into conjugation with the olefin, so locking the side-chain at the 5-exo-position.     

Ion/Ion reactions for oligopeptide mixture analysis: application to mixtures comprised of 0.5–100 kDa components

Oligopeptide mixtures have been subjected to electrospray ionization, accumulated within a quadrupole ion trap, and subjected to ion/ion proton transfer reactions with anions derived from perfluoro-1,3-dimethylcyclohexane. Various mixtures were studied with approximate molecular weight ranges of 0.5–8.5, 12–30, 45–100, and 0.5–100 kDa. Mixtures of known composition were studied to evaluate the mixture complexity amenable to electrospray combined with ion/ion reactions to reduce spectral complexity associated with multiple charging. Mixture analysis with at least 40 components of low and medium molecular weight and roughly comparable solution concentrations appears to be straightforward. No matrix effects upon ionization were implicated in the data for the low and medium molecular weight mixtures but bovine albumin appeared to inhibit signals from bovine transferrin and chicken conalbumin in the high molecular weight mix. Furthermore, the presence of abundant low mass-to-charge ions appeared to inhibit signals from high molecular weight proteins (>40 kDa) in the 0.5–100 kDa mix. Such an observation is consistent with dynamic range limitations that can arise from discrimination based on ion space charge effects, although an ionization matrix effect could not be precluded from the data reported here. The results reported here indicate that the limitation to mixture complexity amenable to electrospray mass spectrometry imposed by spectral congestion associated with multiple charging can be significantly reduced via ion/ion reactions. The use of ion/ion reactions can therefore facilitate the study of other factors that can impose limitations to mixture analysis, such as matrix effects upon ionization and differences in ion transmission, accumulation, storage, and detection efficiencies.     

Decompositions of odd- and even-electron anions derived from deoxy-polyadenylates

Radical anions have been formed via electron transfer from multiply charged 5′-d(AAA)-3′ and 5′-d(AAAA)-3′ anions to CCl₃ ⁺. These ions have been isolated in a quadrupole ion trap operated with helium bath gas at a pressure of 1 mtorr and subjected to resonance excitation (i. e., conventional ion trap collisional activation). Collisional activation of the even-electron species of the same charge state formed directly via electrospray was also performed by using essentially identical conditions. The collisional activation data can be compared directly without ambiguity arising from differences in parent ion internal energies and/or dissociation time frames. Both the odd- and even-electron anions yield extensive sequence-informative fragmentation but show significant differences in the extent of nucleobase loss and in the relative contributions from the various sequence diagnostic dissociation channels. The results of this study indicate that radical anions derived from multiply deprotonated oligo-deoxynucleotides that survive the electron transfer process are stable with respect to fragmentation in the ion trap environment under normal storage conditions and that the unimolecular dissociation behavior of these ions differs from the even-electron anions of the same charge state. These findings suggest, therefore, that odd- and even-electron anions might be used to provide complementary sequence information in cases in which neither ion type provides the full sequence.     

Ion-ion proton transfer reactions of bio-ions involving noncovalent interactions: Holomyoglobin

Multiply protonated horse skeletal muscle holomyoglobin and apomyoglobin have been subjected to ion-ion proton transfer reactions with anions derived from perfluoro-1,3-dimethylcyclohexane in a quadrupole ion trap operated with helium as a bath gas at 1 mtorr. Neither the apomyoglobin nor holomyoglobin ions show any sign of fragmentation associated with charge state reduction to the 1 + charge state. This is particularly noteworthy for the holomyoglobin ions, which retain the noncovalently bound heme group. For example, no sign of heme loss is associated with charge state reduction from the 9 + charge state of holomyoglobin to the 1 + charge state despite the eight consecutive highly exothermic proton transfer reactions required to bring about this charge change. This result is consistent with calculations that show the combination of long ion lifetime and the high ion-helium collision rate relative to the ion-ion collision rate makes fragmentation unlikely for high mass ions in the ion trap environment even for noncovalently bound complexes of moderate binding strength. The ion-ion proton transfer rates for holo- and apomyoglobin ions of the same charge state also were observed to be indistinguishable, which supports the expectation that ion-ion proton transfer rates are insensitive to ion structure and are determined primarily by the attractive Coulomb field.     

Characterization of partially transesterified poly(beta-hydroxyalkanoate)s using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) was used for the characterization of a partially transesterified poly(beta-hydroxyalkanoate), PHA, polymer produced by the bacterial strain Alcaligenes eutrophus using saponified vegetable oils as the sole carbon sources. The transesterification was carried out separately under acidic and basic conditions to obtain PHA oligomers weighing less than 10 kDa. The intact oligomers were detected in their cationized [M + Na](+) and [M + K](+) forms by MALDI-TOFMS. A composition analysis, using the MALDI-TOF spectra, indicate that the oligomers obtained via acid catalysis were terminated with a methyl 3-hydroxybutyrate end group, and those obtained by base catalysis had a methyl crotonate (olefinic) termination. In addition to HB (hydroxy butyrate), the oligomers were found to contain a small percentage of HV (hydroxy valerate). This was independently confirmed using gas chromatography/mass spectrometry (GC/MS). In comparison, the analysis of a commercial PHA polymer, transesterified under identical conditions, only showed the presence of HB, i.e. a pure PHB homopolymer. Copyright 1999 John Wiley & Sons, Ltd.