Ultraviolet photodissociation at 266 nm of phosphorylated peptide cations

Ultraviolet (UV) photodissociation (PD) experiments using 266 nm light were performed for a series of phosphopeptide cations in a Fourier transform mass spectrometer. The objective of the experiments was to determine whether 266 nm UV irradiation on the phosphopeptide cations would induce unique peptide backbone dissociation. In addition, the general behavior of the phosphate loss (?80 or ?98 Da) was monitored, particularly for those phosphopeptides with a phosphotyrosine residue that itself is a UV chromophore. For phosphopeptides with a UV chromophore, their photodissociation behavior was very similar to that of low‐energy sustained off‐resonance irradiation collisionally activated dissociation (SORI‐CAD), with a few exceptions. For example, b‐ and y‐type peptide backbone fragments were prevalent, and their dephosphorylation behavior was consistent with that of the SORI‐CAD results. For phosphoserine peptides, the loss of a phosphate group was always observed. On the other hand, for phosphotyrosine peptides, the phosphate loss was found to be dependent on the presence of a basic amino group in the sequence and the charge state of the precursor ions, in agreement with the CAD results in the literature. However, hydrogen atom loss or aromatic side chain loss, which is known to be the excited state specific fragmentation pathway, was rarely observed in our 266 nm UV PD experiments, in contrast to the previous UV PD literature (particularly at 220 nm). The mechanism for these observations is described in terms of dominant internal conversion followed by intramolecular vibrational energy redistribution (IVR). Copyright © 2009 John Wiley & Sons, Ltd.     

A method for structured linear total least norm on blind deconvolution problem

The regularized structured total least norm (RSTLN) method finds an approximate solutionx and error matrixE to the overdetermined linear system (H+E)x≈b, preserving structure ofH. A new separation scheme by parts of variables for the regularized structured total least norm on blind deconvolution problem is suggested. A method combining the regularized structured total least norm method with a separation by parts of variables can be obtain a better approximated solution and a smaller residual. Computational results for the practical problem with Block Toeplitz with Toeplitz Block structure show the new method ensures more efficiency on image restoration.     

Hydrodechlorination of chlorophenols over Pd catalysts supported on zeolite Y,MCM-41 and graphene

Hydrodechlorination (HDC) reaction of chlorophenols was carried out using Pd catalysts supported over zeolite Y, MCM-41 or graphene. Pd-MCM-41 and Pd-Y zeolite were prepared by impregnation and ion-exchange method, respectively. Pd-graphene (Pd-G) was prepared by hydrazine hydrate reduction of palladium ion dispersed on graphene oxide. The catalysts were characterized by several analytical tools such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS). These catalysts were subjected to HDC reaction of chlorophenols, such as 4-chlorophenol (4-CP), 2,4-dichlorophenol (2,4-DCP), 2,6-dichlorophenol (2,6-DCP) and 3,4-dichlorophenol (3,4-DCP). The reaction rate of HDC of chlorophenols catalyzed by Pd catalysts with various solid bases, such as KF/Al₂O₃ (alumina), sodium acetate (NaOAc) and K₂CO₃ was compared. First, Pd-MCM-41 and Pd-Y catalysts were compared. 2,4- and 3,4-DCPs were completely decomposed within 6 h, in the case of Pd-MCM-41 with NaOAc. Using Pd-Y instead of Pd-MCM-41 with NaOAc, much faster decomposition was observed. Faster decomposition of 4-CP and DCPs was observed with NaOAc base than K₂CO₃ or KF/Al₂O₃ under the same condition. In the case of Pd-Y with KF/Al₂O₃, slower decomposition of 4-CP and DCPs was observed. These base effects were interpreted using the solubility of NaCl and KCl in alcohol and the basic sites of KF/Al₂O₃. Because the solubility of NaCl is known to be larger than KCl solubility in alcohol, byproduct NaCl could be easily dissolved and ionized in solvents. For Pd-Y with KF/Al₂O₃, the small pore size of Y zeolite can interfere with the diffusion of HCl to KF/Al₂O₃ basic site. Second, three catalysts, including Pd-graphene, were compared. 2,4-DCP was decomposed within 2 h using Pd-G with either K₂CO₃, NaOAc or KF/Al₂O₃. Pd-G catalyst showed the highest catalytic activity among Pd-G, Pd-MCM-41 and Pd-Y catalysts. The high activity and stability of the Pd-G could be attributed to the strong metal–support interaction with an electron-deficient site and a critical Pd particle size (ca. 3.5 nm) of Pd-G nanocatalyst with a stronger resistance to the deactivation and good affinity toward aromatic organic molecules, especially phenols. The progress of HDC reaction was monitored by gas chromatography with flame ionization detection (GC/FID), and a feasible degradation process could be explained by analyzing the degradation products such as phenol, cyclohexanone and cyclohexanol from resulting GC chromatograms. The effect of reaction temperature on HDC in Pd-G catalyst was also discussed. In conclusion, Pd-G is an efficient catalyst for decomposition of chlorophenols and can be applied to remediation of chlorophenol-contaminated water under mild conditions.     

Synthesis and separation of mellitic acid and graphite oxide colloid through electrochemical oxidation of graphite in deionized water

Electrochemical oxidation of graphite anode in deionized water at galvanostatic mode is investigated. It is found that mellitic acid and graphite oxide colloid (>20 nm) are coexisted as main products, as identified by XRD and TEM, FTIR and XPS. They can be separated successfully through several procedures. A few amounts of graphene and graphene rolls are also appeared as co-products.     

Field‐effect transistors based on PPV derivatives as a semiconducting layer

A series of modified thiophene groups containing PPV‐based semiconducting materials, poly[(2,5‐bis(octyloxy)‐1,4‐phenylenevinylene)‐alt‐(2,2′bithienylenevinylene)] ( PPBT ), poly[(2,5‐bis(octyloxy)‐1,4‐phenylenevinylene)‐alt‐(5,5‐thiostilylenevinylene)] ( PPTVT ), have been synthesized through a Horner coupling reaction. From the FTIR and ¹H NMR spectroscopy, the configuration of the vinylene groups in the polymers was all trans (E) geometry. The weight‐average molecular weights (M_w) of PPBT and PPTVT were found to be 11,700 and 11,800, with polydispersity indices of 2.51 and 2.53, respectively. PPBT and PPTVT thin films exhibit UV–visible absorption maxima at 538 and 558 nm, respectively, and the strong absorption shoulder peaks at 578 and 602 nm, respectively. Solution processed field‐effect transistors (FET) fabricated using all the polymers showed p‐type OTFT characteristics. The field‐effect mobility of the PPTVT was obtained up to 2.3 × 10^?3 cm² V^?1 s^?1, an on/off ratio of 1.0 × 10⁵ with ambient air stability. Studies of the atomic force microscopy (AFM) and X‐ray diffraction (XRD) analysis of the polymer thin films revealed that all the polymers were amorphous structure. The greater planarity and rigidity of PPTVT compared to PPBT results in elongation of conjugation length and better π–π stacking of polymer chains in amorphous region, which leads to improved FET performance. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 111–120, 2009     

A novel method for separating Cs<Superscript>+</Superscript> from liquid radioactive waste using ionic liquids and a selective extractant

Selective separation of Cs ⁺ from liquid radioactive waste by “precipitation” was observed in a hydrophobic ionic liquid containing the Cs ⁺ -selective extractant dicyclohexano-18-crown-6. The precipitate was formed by the cation exchange mechanism, which simplified the treatment of Cs ⁺ after extraction. Solid–liquid extraction is a more economical extraction system than liquid–liquid extraction because it uses smaller quantities of ionic liquids. This work showed the possibility of developing a new method for removing Cs ⁺ from liquid radioactive waste using solid–liquid phase separation instead of the conventional liquid–liquid separation in an ionic liquid extraction system.