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61.
Li Jingkun Liu Yaxi Su Hao Elaine Wong Y.-L. Chen Xiangfeng Dominic Chan T.-W. Chen Qingfeng 《Mikrochimica acta》2017,184(10):3809-3815
Microchimica Acta - The authors describe the in-situ hydrothermal growth of a porphyrinic zirconium metal-organic framework (MOF), referred to as PCN-222(Zr), on stainless steel fibers. The... 相似文献
62.
63.
Chen X Fung YM Chan WY Wong PS Yeung HS Chan TW 《Journal of the American Society for Mass Spectrometry》2011,22(12):2232-2245
Electron capture dissociation (ECD) of model peptides adducted with first row divalent transition metal ions, including Mn2+, Fe2+, Co2+, Ni2+, Cu2+, and Zn2+, were investigated. Model peptides with general sequence of ZGGGXGGGZ were used as probes to unveil the ECD mechanism of
metalated peptides, where X is either V or W; and Z is either R or N. Peptides metalated with different divalent transition
metal ions were found to generate different ECD tandem mass spectra. ECD spectra of peptides metalated by Mn2+ and Zn2+ were similar to those generated by ECD of peptides adducted with alkaline earth metal ions. Series of c-/z-type fragment ions with and without metal ions were observed. ECD of Fe2+, Co2+, and Ni2+ adducted peptides yielded abundant metalated a-/y-type fragment ions; whereas ECD of Cu2+ adducted peptides generated predominantly metalated b-/y-type fragment ions. From the present experimental results, it was postulated that electronic configuration of metal ions
is an important factor in determining the ECD behavior of the metalated peptides. Due presumably to the stability of the electronic
configuration, metal ions with fully-filled (i.e., Zn2+) and half filled (i.e., Mn2+) d-orbitals might not capture the incoming electron. Dissociation of the metal ions adducted peptides would proceed through
the usual ECD channel(s) via “hot-hydrogen” or “superbase” intermediates, to form series of c-/z
•- fragments. For other transition metal ions studied, reduction of the metal ions might occur preferentially. The energy liberated
by the metal ion reduction would provide enough internal energy to generate the “slow-heating” type of fragment ions, i.e.,
metalated a-/y- fragments and metalated b-/y- fragments. 相似文献
64.
Chen X Chan WY Wong PS Yeung HS Chan TW 《Journal of the American Society for Mass Spectrometry》2011,22(2):233-244
Peptides adducted with different divalent Group IIB metal ions (Zn2+, Cd2+, and Hg2+) were found to give very different ECD mass spectra. ECD of Zn2+ adducted peptides gave series of c-/z-type fragment ions with and without metal ions. ECD of Cd2+ and Hg2+ adducted model peptides gave mostly a-type fragment ions with M+• and fragment ions corresponding to losses of neutral side chain from M+•. No detectable a-ions could be observed in ECD spectra of Zn2+ adducted peptides. We rationalized the present findings by invoking both proton-electron recombination and metal-ion reduction
processes. As previously postulated, divalent metal-ions adducted peptides could adopt several forms, including (a) [M + Cat]2+, (b) [(M + Cat – H) + H]2+, and (c) [(M + Cat – 2H) + 2H]2+. The relative population of these precursor ions depends largely on the acidity of the metal–ion peptide complexes. Peptides
adducted with divalent metal-ions of small ionic radii (i.e., Zn2+) would form predominantly species (b) and (c); whereas peptides adducted with metal ions of larger ionic radii (i.e., Hg2+) would adopt predominantly species (a). Species (b) and (c) are believed to be essential for proton-electron recombination
process to give c-/z-type fragments via the labile ketylamino radical intermediates. Species (c) is particularly important for the formation of
non-metalated c-/z-type fragments. Without any mobile protons, species (a) are believed to undergo metal ion reduction and subsequently induce
spontaneous electron transfer from the peptide moiety to the charge-reduced metal ions. Depending on the exothermicity of
the electron transfer reaction, the peptide radical cations might be formed with substantial internal energy and might undergo
further dissociation to give structural related fragment ions. 相似文献
65.
Ultrathin silica-based nanosheets with a thickness of ~1 nm are fabricated in a low-cost and high-yield system excluding alkali metal ions. Unlike the Na-zeolites with a long capillary and microporous structure, the ultrathin nanosheets exhibit highly effective surface and active sites. As a result, the 0.4 wt% Pt-loaded nanosheets exhibit superior catalytic activity in H(2)O(2) decomposition with an O(2) evolution rate of 342.5 mL g(-1) min(-1) in a clean aqueous system. 相似文献
66.
Dr. Felipe Gándara Dr. Fernando J. Uribe‐Romo Dr. David K. Britt Dr. Hiroyasu Furukawa Dr. Liao Lei Rui Cheng Prof. Xiangfeng Duan Prof. Michael O'Keeffe Prof. Omar M. Yaghi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(34):10595-10601
A new family of porous crystals was prepared by combining 1H‐1,2,3‐triazole and divalent metal ions (Mg, Mn, Fe, Co, Cu, and Zn) to give six isostructural metal‐triazolates (termed MET‐1 to 6). These materials are prepared as microcrystalline powders, which give intense X‐ray diffraction lines. Without previous knowledge of the expected structure, it was possible to apply the newly developed charge‐flipping method to solve the complex crystal structure of METs: all the metal ions are octahedrally coordinated to the nitrogen atoms of triazolate such that five metal centers are joined through bridging triazolate ions to form super‐tetrahedral units that lie at the vertexes of a diamond‐type structure. The variation in the size of metal ions across the series provides for precise control of pore apertures to a fraction of an Angstrom in the range 4.5 to 6.1 Å. MET frameworks have permanent porosity and display surface areas as high as some of the most porous zeolites, with one member of this family, MET‐3, exhibiting significant electrical conductivity. 相似文献
67.
Xue T Jiang S Qu Y Su Q Cheng R Dubin S Chiu CY Kaner R Huang Y Duan X 《Angewandte Chemie (International ed. in English)》2012,51(16):3822-3825
Well supported: stable hemin-graphene conjugates formed by immobilization of monomeric hemin on graphene, showed excellent catalytic activity, more than 10 times better than that of the recently developed hemin-hydrogel system and 100 times better than that of unsupported hemin. The catalysts also showed excellent binding affinities and catalytic efficiencies approaching that of natural enzymes. 相似文献
68.
The fixation of carbon dioxide with epoxide catalysed by a series of carboxylic acidic functionalised ionic liquids (ILs) catalysts is investigated by density functional theory method. Except for the catalysts reported by the experiment, the catalytic activity of a new designed catalyst (4c see Scheme 1) is also explored. These ILs are categorised into four groups according to the different cation structures and number of functional groups. The effects of different chain length, anion, and cation structure on the catalytic activity are explored. The elongation of alkyl chain length in cation will increase the product yield, while increasing the chain bulk has almost negligible effect on the enhancement of catalytic activity. Utilisation of imidazole group as the cation is better than pyridine group. And the cation with two functional groups will have a better catalytic activity than that with one functional group. 相似文献
69.
70.
A new OFF-ON fluorescent chemosensor (H1) composed of a naphthalimide fluorophore and a 6-[(quinolin-8-yloxy)methyl]pyridin-2-ylmethanamine receptor has been synthesized and characterized by infra-red, (1)H NMR, (13)C NMR and mass spectrometry. The developed chemosensor H1 exhibited good turn-on and reversible responses toward Hg(2+), with excellent selectivity and sensitivity, in a neutral buffered aqueous solution. Other common metal ions did not interfere with the fluorescence-enhancement response to Hg(2+). Furthermore, the chemosensor H1, at a concentration of 10?μM, showed a rapid and linear response toward Hg(2+) in the concentration range 0-10?μM. On addition of 10?μM Hg(2+), the fluorescence intensity of H1 was enhanced about 4-fold. The detection limit was calculated to be 63?nM. The association constant was 1.11?×?10(5)?M(-1). The fluorescence quantum yield and lifetime of H1/Hg(2+) were 0.42 and 3.83?ns, respectively. 相似文献