不同Ce/Mn摩尔比对CeO_2-MnO_x催化剂低温NH_3选择性催化还原NO的影响

以高锰酸钾和硝酸锰为锰源,采用改进的共沉淀法制备了不同Ce/Mn摩尔比的Ce O2-Mn Ox催化剂.以NH3为还原剂,考察了催化剂低温(小于150℃)NH3选择性催化还原NO的性能.并采用XRD,BET,H2-TPR,NH3-TPD和XPS等手段对催化剂的物理化学性质进行表征.结果表明,Ce O2-Mn Ox催化剂在50~150℃温度区间内表现出了良好的催化活性.引入适量的Ce可以有效地改变催化剂的晶粒大小,增强其氧化还原能力;而Mn的加入,促进了其低温SCR活性.当Ce/Mn摩尔比为1∶3时(C1M3),低温活性最佳,在82~150℃温度区间内NO去除率达到90%以上,这主要是由于C1M3催化剂有较高含量的表面吸附氧、大量的弱酸性位点、良好的氧化还原性能以及表面较高含量的Mn4+物种.     

氮掺杂纳米管包覆金属钴催化苯甲醇和苯胺一步N-烷基化反应

通过直接热解三聚氰胺、硝酸钴和葡萄糖混合物制备氮掺杂碳纳米管包覆金属钴催化剂(Co@NCNT).Co@NCNT具有较大的比表面积、均匀的氮分布以及包覆结构.在苯甲醇和苯胺一步法N-烷基化反应中Co@N CNT具有较高的催化活性,且循环4次反应活性没有明显的变化.控制实验和中毒实验表明金属Co和N对催化活性起着重要的作用,同时金属Co是中间产物N-苄叉苯胺加氢的主要活性位.     

Identification of [PtCl2(phen)] binding modes in amyloid-β peptide and the mechanism of aggregation inhibition

Platinum phenanthroline complexes inhibit amyloid-β (Aβ) aggregation and reduce Aβ-caused neurotoxicity [Proc. Natl. Acad. Sci., 2008, 105, 6813-6818]. In this study, we investigated the interactions of Aβ(1-16) with [PtCl(2)(phen)] (phen=1,10-phenanthroline) using HPLC, ESI-MS, and NMR spectroscopy , and characterized the identity of products using tandem mass spectrometry. Results indicated that the phenanthroline ligand could induce noncovalent interactions between Aβ peptide and platinum complexes, leading to rapid Aβ platination. Multiple products were generated in the reaction, in which His6/His14 chelation was preferentially formed. Coordination of Asp7, His13, and Lys16 was also detected in other products. The majority of products were monoplatinated adducts with binding of the {Pt(phen)} scaffold, which impeded intermolecular interactions between Aβ peptides. Moreover, noncovalent interactions were confirmed by the interaction between Aβ peptide and [Pt(phen)(2)]Cl(2). The synergistic roles of the phen ligand and platinum(II) atom in the inhibition of Aβ aggregation are discussed.     

Highly trifluoromethylated platinum compounds

The homoleptic, square‐planar organoplatinum(II) compound [NBu₄]₂[Pt(CF₃)₄] ( 1 ) undergoes oxidative addition of CF₃I under mild conditions to give rise to the octahedral organoplatinum(IV) complex [NBu₄]₂[Pt(CF₃)₅I] ( 2 ). This highly trifluoromethylated species reacts with Ag⁺ salts of weakly coordinating anions in Me₂CO under a wet‐air stream to afford the aquo derivative [NBu₄][Pt(CF₃)₅(OH₂)] ( 4 ) in around 75 % yield. When the reaction of 2 with the same Ag⁺ salts is carried out in MeCN, the solvento compound [NBu₄][Pt(CF₃)₅(NCMe)] ( 5 ) is obtained in around 80 % yield. The aquo ligand in 4 as well as the MeCN ligand in 5 are labile and can be cleanly replaced by neutral and anionic ligands to furnish a series of pentakis(trifluoromethyl)platinate(IV) compounds with formulae [NBu₄][Pt(CF₃)₅(L)] (L=CO ( 6 ), pyridine (py; 7 ), tetrahydrothiophene (tht; 8 )) and [NBu₄]₂[Pt(CF₃)₅X] (X=Cl ( 9 ), Br ( 10 )). The unusual carbonyl–platinum(IV) derivative [NBu₄][Pt(CF₃)₅(CO)] ( 6 ) is thermally stable and has a ν_CO of 2194 cm^?1. The crystal structures of 2? CH₂Cl₂, 5 , [PPh₄][Pt(CF₃)₅(CO)] ( 6′ ), and 7 have been established by X‐ray diffraction methods. Compound 2 has shown itself to be a convenient entry to the chemistry of highly trifluoromethylated platinum compounds. To the best of our knowledge, compounds 2 and 4 – 10 are the organoelement compounds with the highest CF₃ content to have been isolated and adequately characterized to date.     

Label-free molecular beacon system based on DNAs containing abasic sites and fluorescent ligands that bind abasic sites

A new class of label-free molecular beacon (MB) system based on DNA strands that contain abasic (AP) sites (AP-DNA) and adopt stem-loop structures, in combination with fluorescent ligands that bind these AP sites, has been developed. Unlike a conventional MB, which requires covalent labeling of the MB with a fluorophore and a quencher, the developed system (APMB) does not require covalent attachment of signal transduction units. Detailed sensing functions of a series of APMB systems were examined with the aid of the fluorescent ligand named ATMND to provide insight into the design strategy for APMB systems. The effects of the stem length and the position of the AP site in the stem moiety on the fluorescence response of the APMB system were examined. Genotyping of a G/C SNP of PCR amplification products was successfully demonstrated with the APMB system and blue-fluorescent ATMND as a ligand. The APMB system was further extended to a system that utilized green-fluorescent lumiflavin.     

A microenvironment-sensitive fluorescent pyrimidine ribonucleoside analogue: synthesis, enzymatic incorporation, and fluorescence detection of a DNA abasic site

Base-modified fluorescent ribonucleoside-analogue probes are valuable tools in monitoring RNA structure and function because they closely resemble the structure of natural nucleobases. Especially, 2-aminopurine, a highly environment-sensitive adenosine analogue, is the most extensively utilized fluorescent nucleoside analogue. However, only a few isosteric pyrimidine ribonucleoside analogues that are suitable for probing the structure and recognition properties of RNA molecules are available. Herein, we describe the synthesis and photophysical characterization of a small series of base-modified pyrimidine ribonucleoside analogues derived from tagging indole, N-methylindole, and benzofuran onto the 5-position of uracil. One of the analogues, based on a 5-(benzofuran-2-yl)pyrimidine core, shows emission in the visible region with a reasonable quantum yield and, importantly, displays excellent solvatochromism. The corresponding triphosphate substrate is effectively incorporated into oligoribonucleotides by T7 RNA polymerase to produce fluorescent oligoribonucleotide constructs. Steady-state and time-resolved spectroscopic studies with fluorescent oligoribonucleotide constructs demonstrate that the fluorescent ribonucleoside photophysically responds to subtle changes in its environment brought about by the interaction of the chromophore with neighboring bases. In particular, the emissive ribonucleoside, if incorporated into an oligoribonucleotide, positively reports the presence of a DNA abasic site with an appreciable enhancement in fluorescence intensity. The straightforward synthesis, amicability to enzymatic incorporation, and sensitivity to changes in the microenvironment highlight the potential of the benzofuran-conjugated pyrimidine ribonucleoside as an efficient fluorescent probe to investigate nucleic acid structure, dynamics, and recognition events.     

Crystallographic analysis of metal-ion binding to human ubiquitin

The metal-binding ability of human ubiquitin (hUb) towards a selection of biologically relevant metal ions and complexes has been probed. Different techniques have been used to obtain crystals suitable for crystallographic analysis. In the first type of experiments, crystals of hUb have been soaked in solutions containing copper(II) acetate and two metallodrugs, Zeise salt (K[PtCl(3)(η(2)-C(2)H(4))]·H(2)O) and cisplatin (cis-[PtCl(2)(NH(3))(2)]). The Zeise salt is used in a test for hepatitis, whereas cisplatin is one of the most powerful anticancer drugs in clinical use. The Zeise salt readily reacts with hUb crystals to afford an adduct with three platinum residues per protein molecule, Pt(3)-hUb. In contrast, copper(II) acetate and cisplatin were found to be unreactive for contact times up to one hour and to cause degradation of the hUb crystals for longer times. In the second type of experiments, hUb was cocrystallized with a solution of copper(II) or zinc(II) acetate or cisplatin. Zinc(II) acetate gives, at low metal-to-protein molar ratios (8:1), crystals containing one metal ion per three molecules of protein, Zn-hUb(3) (already reported in previous work), whereas at high metal-to-protein ratios (70:1) gives crystals containing three Zn(II) ions per protein molecule, Zn(3)-hUb. In contrast, once again, copper(II) acetate and cisplatin, even at low metal-to-protein ratios, do not give crystalline material. In the soaking experiment, the Zeise anion leads to simultaneous platination of His68, Met1, and Lys6. Present and previous results of cocrystallization experiments performed with Zn(II) and other Group 12 metal ions allow a comprehensive understanding of the metal-ion binding properties of hUb with His68 as the main anchoring site, followed by Met1 and carboxylic groups of Glu16, Glu18, Glu64, Asp21, and Asp32, to be reached. In the case of platinum, Lys6 can also be a binding site. The amount of bound metal ion, with respect to that of the protein, appears to be a relevant parameter influencing crystal packing.     

Effect of iridium loading on HZSM-5 for isomerization of n-heptane

The effect of iridium loading on the properties and catalytic isomerization of n-heptane over Ir-HZSM-5 is studied. Ir-HZSM-5 was prepared by impregnation method and subjected to isomerization process in the presence of flowing hydrogen gas. XRD and BET studies show that the presence of iridium stabilizes the crystalline structure of HZSM-5, leading to more ordered framework structure and larger surface area. TGA and FTIR results substantiate that iridium species interacts with OH group on the surface of HZSM-5. Pyridine FT-IR study verifies the interaction between iridium and surface OH group slightly increased the Bro¨nsted and Lewis acid sites without changing the lattice structure of HZSM-5. The presence of iridium and the increase of strong Lewis acid sites on HZSM-5 were found to bring an increase about 4.1%, 33.2% and 11.8% in conversion, selectivity and yield of n-heptane isomerization, respectively.     

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