Pyrene and anthracene dicarboxylic acids as fluorescent brightening comonomers for polyester

Diacids of fused arenes have been prepared for use as covalently bound fluorescent optical brightening agents in condensation polymers. The monomers: dimethyl 1,6‐pyrene dicarboxylate, dimethyl 1,8‐pyrenedicarboxylate, dimethyl 2,7‐pyrenedicarboxylate, 1,8‐bis(2‐carboxybenzoyl)pyrene dimethyl ester, dimethyl 2,6‐anthracenedicarboxylate, dimethyl 2,7‐anthracenedicarboxylate and dimethyl 9,10‐anthracenedicarboxylate are copolymerized with poly(ethylene terephthalate) and their optical properties are assessed. All of the polymers give blue fluorescence, with the copolymer containing dimethyl 1,6‐pyrenedicarboxylate being the brightest. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1291–1301, 2000     

Generation and detection of gaseous W12O 41 −· and other tungstate anions by laser desorption ionization mass spectrometry

The presence of a peak centered near m/z 2862, observed for the first time for the caged dodecatungstate radical-anion, [W₁₂O₄₁]^−·, enables distinguishing WO₂ from WO₃ by Laser Desorption Ionization mass spectrometry (LDI-MS). In addition to WO₂, laser irradiation of dry deposits made from aqueous ammonium paratungstate, and calcium and lead orthotungstate also produce the [W₁₂O₄₁]^−·. In contrast, spectra recorded from deposits made from aqueous Na₂WO₄, sodium metatungstate, and WO₃, or non-aqueous calcium and lead orthotungstate, and ammonium paratungstate, failed to show the m/z 2862 peak cluster. These observations support the hypothesis that polycondensation reactions to form [W₁₂O₄₁]^−· occur solely in the presence of water. Although dry spots are irradiated for ionization, the solvent used for sample preparation plays an important role on the chemical composition endowed to ions detected. For example, the m/z 2862 peak seen from deposits made from aqueous ammonium paratungstate, and calcium and lead orthotungstate, is absent in the spectra recorded either from pristine deposits or those derived from solutions made with organic solvents such as acetonitrile or ethanol.     

Local angular momentum-local impact parameter analysis: derivation and properties of the fundamental identity, with applications to the F+H2, H+D2, and Cl+HCl chemical reactions

The technique of local angular momentum-local impact parameter (LAM-LIP) analysis has recently been shown to provide valuable dynamical information on the angular scattering of chemical reactions under semiclassical conditions. The LAM-LIP technique exploits a nearside-farside (NF) decomposition of the scattering amplitude, which is assumed to be a Legendre partial wave series. In this paper, we derive the "fundamental NF LAM identity," which relates the full LAM to the NF LAMs (there is a similar identity for the LIP case). Two derivations are presented. The first uses complex variable techniques, while the second exploits an analogy between the motion of the scattering amplitude in the Argand plane with changing angle and the classical mechanical motion of a particle in a plane with changing time. Alternative forms of the fundamental LAM-LIP identity are described, one of which gives rise to a CLAM-CLIP plot, where CLAM denotes (Cross section) x LAM and CLIP denotes (Cross section) x LIP. Applications of the NF LAM theory, together with CLAM plots, are reported for state-to-state transitions of the benchmark reactions F+H2-->FH+H, H+D2-->HD+D, and Cl+HCl-->ClH+Cl, using as input both numerical and parametrized scattering matrix elements. We use the fundamental LAM identity to explain the important empirical observation that a NF cross section analysis and a NF LAM analysis provide consistent (and complementary) information on the dynamics of chemical reactions.     

Use of the filter diagonalization method in the study of space charge related frequency modulation in Fourier transform ion cyclotron resonance mass spectrometry

The filter diagonalization method (FDM) is a recently developed computational technique capable of extracting resonance frequencies and amplitudes from very short transient signals. Although it requires stable resonance frequencies and is slower than the fast Fourier transform (FFT), FDM has a resolution and accuracy that is unmatched by the FFT or any other comparable techniques. This unique feature of FDM makes it an ideal tool for tracing space charge induced frequency modulations in Fourier transform ion cyclotron resonance (FT-ICR) cells, which are shown to reach +/-400 ppm even for such simple spectra as Substance P.     

Algorithms for automatic interpretation of high resolution mass spectra

Automated interpretation of high-resolution mass spectra in a reliable and efficient manner represents a highly challenging computational problem. This work aims at developing methods for reducing a high-resolution mass spectrum into its monoisotopic peak list, and automatically assigning observed masses to known fragment ion masses if the protein sequence is available. The methods are compiled into a suite of data reduction algorithms which is called MasSPIKE (Mass Spectrum Interpretation and Kernel Extraction). MasSPIKE includes modules for modeling noise across the spectrum, isotopic cluster identification, charge state determination, separation of overlapping isotopic distributions, picking isotopic peaks, aligning experimental and theoretical isotopic distributions for estimating a monoisotopic peak's location, generating the monoisotopic mass list, and assigning the observed monoisotopic masses to possible protein fragments. The method is tested against a complex top-down spectrum of bovine carbonic anhydrase. Results of each of the individual modules are compared with previously published work.     

2D FT-ICR MS of Calmodulin: A Top-Down and Bottom-Up Approach

Two-dimensional Fourier transform ion cyclotron resonance mass spectrometry (2D FT-ICR MS) allows data-independent fragmentation of all ions in a sample and correlation of fragment ions to their precursors through the modulation of precursor ion cyclotron radii prior to fragmentation. Previous results show that implementation of 2D FT-ICR MS with infrared multi-photon dissociation (IRMPD) and electron capture dissociation (ECD) has turned this method into a useful analytical tool. In this work, IRMPD tandem mass spectrometry of calmodulin (CaM) has been performed both in one-dimensional and two-dimensional FT-ICR MS using a top-down and bottom-up approach. 2D IRMPD FT-ICR MS is used to achieve extensive inter-residue bond cleavage and assignment for CaM, using its unique features for fragment identification in a less time- and sample-consuming experiment than doing the same thing using sequential MS/MS experiments.

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Acetylene on Cu(111): imaging a molecular surface arrangement with a constantly rearranging tip

Acetylene on Cu(111) is investigated by scanning tunnelling microscopy (STM); a surface pattern previously derived from diffraction measurements can be validated, if the variation of the STM image transfer function through absorption of an acetylene molecule onto the tip apex is taken into account. Density functional theory simulations point to a balance between short-range repulsive interactions of acetylene/Cu(111) associated with surface stress and longer range attractive interactions as the origin of the ordering.     

Palladium‐Catalysed Cross‐Coupling of Vinyldisiloxanes with Benzylic and Allylic Halides and Sulfonates

The Hiyama cross‐coupling reaction is a powerful method for carbon–carbon bond formation. To date, the substrate scope of this reaction has predominantly been limited to sp²–sp² coupling reactions. Herein, the palladium‐catalysed Hiyama type cross‐coupling of vinyldisiloxanes with benzylic and allylic bromides, chlorides, tosylates and mesylates is reported. A wide variety of functional groups were tolerated, and the synthetic utility of the methodology was exemplified through the efficient total synthesis of the cytotoxic natural product bussealin A. In addition, the antiproliferative ability of bussealin A was evaluated in two cancer‐cell lines.     

Electron Capture Dissociation of Disulfide, Sulfur–Selenium, and Diselenide Bound Peptides

To examine the electron capture dissociation (ECD) behavior of disulfide (S?CS), sulfur?Cselenium (S?CSe), and diselenide (Se?CSe) bonds-containing peptides, a series of free cysteine (Cys) and selenocysteine (Sec) containing peptides were reacted to form interchain S?CS, S?CSe, and Se?CSe bonds, and then studied using ECD with Fourier transform ion cyclotron mass spectrometry (FTICR MS). These results demonstrate that the radical has higher tendency to stay at selenium rather than sulfur after the cleavage of Se?CS bonds by ECD. In addition, ?CSH (?C33), ?CS (?C32), and ?CS + H (?C31) small neutral losses were all observed from the cleavage of C?CS bonds of a disulfide bound peptide. Similar, but minor, fragments were also detected in S?CSe bound peptides. In contrast, the cleavage of C?CSe bonds of the Se?CSe species mainly forms fragments with neutral loss of ?CSe + H (?C78.90868), and the radical tends to stay on the selenium of its corresponding complementary pair. Although the electron affinities of S atom (2.07?eV) and Se atom (2.02?eV) are very close; they have very different reactivity towards electrons. The replacement of sulfur with selenium greatly increases the electron affinities of S?CSe and Se?CSe bonds comparing to S?CS bonds (with an increase of electron affinity by about 0.20?eV by replacing a sulfur with a selenium) (Int J Quantum Chem 110:513-523, 2010), which in turn leads to different ECD fragmentation behavior and mechanisms. Our results are in good agreement with previously published ab initio calculations on Se?CSe compounds by other groups.