Electron–Neutron Detector Array (ENDA)

Physics of Atomic Nuclei - By accurate measurement of components and energy spectrum in the knee region, problem of origin of cosmic ray can be solved. In one extensive air shower (EAS), high...     

Influence of Fine Ligand Substitution Modification of the Isocyanidometal Bridge on Metal-to-Metal Charge Transfer Properties in Class II–III Mixed Valence Complexes

The synthesis and characterization of Class II–III mixed valence complexes have been an interesting topic due to their special intermediate behaviour between localized and delocalized mixed valence complexes. To investigate the influence of the isocyanidometal bridge on metal-to-metal charge transfer (MMCT) properties, a family of new isocyanidometal-bridged complexes and their one-electron oxidation products cis-[Cp(dppe)Fe−CN−Ru(L)₂-NC−Fe(dppe)Cp][PF₆]_n (n=2, 3) (Cp=1,3-cyclopentadiene, dppe=1,2-bis(diphenylphosphino)ethane, L=2,2’-bipyridine (bpy, 1[PF₆]_n ), 5,5’-dimethyl-2,2’-bipyridyl (5,5’-dmbpy, 2[PF₆]_n ) and 4,4’-dimethyl-2,2’-bipyridyl (4,4’-dmbpy, 3[PF₆]_n )) have been synthesized and fully characterized. The experimental results suggest that all the one-electron oxidation products may belong to Class II–III mixed valence complexes, supported by TDDFT calculations. With the change of the substituents of the bipyridyl ligand on the Ru centre from H, 5,5’-dimethyl to 4,4’-dimethyl, the energy of MMCT for the one-electron oxidation complexes changes in the order: 1³⁺ < 2³⁺ < 3³⁺ , and that for the two-electron oxidation complexes decreases in the order 1⁴⁺ > 3⁴⁺ > 2⁴⁺ . The potential splitting (ΔE_1/2(2)) between the two terminal Fe centres for N[PF₆]₂ are the largest potential splitting for the cyanido-bridged complexes reported so far. This work shows that the smaller potential difference between the bridging and the terminal metal centres would result in the more delocalized mixed valence complex.     

Hydrothermal Synthesis, Crystal Structure and Fluorescent Property of a New Zinc Carboxylate-phosphonate： [Zn3（O3PCH（CH3）COO）2（H2O）]

1 INTRODUCTION Many efforts have been devoted to the synthesis of metal organophosphonates during the past three decades because of their rich variety of structural chemistry as well as their practical or potential applications in the areas of adsorption/desorption[1, 2], catalysts[3, 4], meso-/microporous materials[5～7] and intercalation chemistry[8～16]. One encouraging deve- lopment direction is the use of phosphonic acids with bi- and trifunctional groups, such as amino, hydroxyl and…     

Colorimetric detection of lysozyme based on electrostatic interaction with human serum albumin-modified gold nanoparticles

In this study, an aqueous solution of 13-nm gold nanoparticles (AuNPs) covalently bonded with human serum albumin (HSA) was used for sensing lysozyme (Lys). HSA molecules were good stabilizing agents for AuNPs in high-salt solution and exhibited the ability to bond with Lys electrostatically. The aggregation of HSA-AuNPs was achieved upon the addition of high-pI proteins, such as Lys, alpha-chymotrypsinogen A, and conalbumin. Not the same was achieved, however, when low-pI proteins such as ovalbumin, bovine serum albumin, and alpha-lactalbumin were added. Matrix-assisted desorption/ionization mass spectrometry was used to demonstrate the interaction between HSA-AuNPs and Lys. It was found that the sensitivity of HSA-AuNPs for Lys was highly dependent on the HSA concentration. The Lys-induced aggregation of HSA-AuNPs was suggested based on the London-van der Waals attractive force. We further improved the selectivity of the probe by adjusting the pH solution to 8.0. Under the optimum conditions, the selectivity of this system for Lys over other proteins in high-salt solutions was remarkably high, even when their pI was very close to the Lys. The lowest detectable concentration of Lys in this approach was 50 nM. The applicability of the method was validated through the analyses of Lys in chicken egg white.     

Ultrasensitive detection of indoleamines by combination of nanoparticle-based extraction with capillary electrophoresis/laser-induced native fluorescence

For the first time, citrate-capped gold nanoparticles (citrate-AuNPs) have been used for the selective extraction of indoleamines – 5-hydroxytryptophan (5-HTP), tryptophan (Trp), tryptamine (TA), 5-hydroxytryptamine (5-HT), and 5-hydroxyindoleacetic acid (5-HIAA) – prior to their analysis by capillary electrophoresis/laser-induced native fluorescence (CE/LINF). The extinction spectra obtained for the citrate-AuNPs in the presence of indoleamines revealed that 5-HTP, 5-HT, and 5-HIAA were extracted mainly because of van der Waals interactions between the indole ring and the citrate-AuNPs (hydrophobic surface), while 5-HT and TA were extracted by electrostatic attractions between the amine group of the indoleamines and the citrate ligands adsorbed on the AuNP surface. The extracted indoleamines could be liberated from the AuNP surface by the addition of high concentrations of 2-mercaptoethanol (2-ME), which binds strongly to the AuNPs. The sensitivity of this method to indoleamines could be significantly enhanced by increasing the AuNP concentration, incubation time, and sample volume. Under optimal extraction and separation conditions, the combination of NP-based extraction and CE-LINF provided 48-, 4077-, 985-, 920-, and 4030-fold improvements in the limits of detection (signal-to-noise ratio of 3) for 5-HTP, Trp, TA, 5-HT, and 5-HIAA as compared to the analysis of five indoleamines by CE-LINF. In addition, this proposed method was successfully used for the determination of TA and 5-HT in urine.     

Designed Syntheses and Crystal Structures of Two Cis-cyanide Bridged Trinuclear Complexes

Two cyanide bridged trinuclear compounds [Fe（bpy）2（CN）2]·[Cu（Cyclam）]2（ClO4）4·DMF 1 and [Fe（Phen）2（CN）2]·[Cu（Cyclam）]2（ClO4）4·2CH3CN·4H2O 2 （Bpy = 2,2＇- bipyridine, Phen = 1,10-phenanthroline, Cyclam = 1,4,8,11-tetraaza-cyclotetradecane, and DMF = N,N-dimethylformamide） have been synthesized by using mononuclear [Fe（Phen）2（CN）2]·2H2O and [Fe（bpy）2（CN）2]·3H2O as precursors. These two complexes crystallize in monoclinic space groups P21/c and C2/c, respectively. For 1, a = 25.164（2）, b = 12.0405（11）, c = 20.4433（15） A, β = 91.948（3）°, V = 6190.5（9） A^3, Z = 4, Mr = 1418.90, Dc = 1.522 g/cm^3, F（000） = 2936, μ = 1.161 mm^-1, the final R = 0.0722 and wR = 0.2011 for 10779 observed reflections （I 〉 2σ（I））. For 2, a = 43.5945（0）, b = 11.8447（0）, c = 29.5637（2）A, β = 120.430（11）o, V = 13162.76（9） A^3, Z = 8, Mr = 1518.48, Dc = 1.533 g/cm^3, F（000） = 6288, μ = 1.101 mm^-1, the final R = 0.0711 and wR = 0.1783 for 11262 observed reflections （I 〉 2σ（I））.     

An activity-based near-infrared glucuronide trapping probe for imaging β-glucuronidase expression in deep tissues

β-glucuronidase is an attractive reporter and prodrug-converting enzyme. The development of near-IR (NIR) probes for imaging of β-glucuronidase activity would be ideal to allow estimation of reporter expression and for personalized glucuronide prodrug cancer therapy in preclinical studies. However, NIR glucuronide probes are not yet available. In this work, we developed two fluorescent probes for detection of β-glucuronidase activity, one for the NIR range (containing IR-820 dye) and the other for the visible range [containing fluorescein isothiocyanate (FITC)], by utilizing a difluoromethylphenol-glucuronide moiety (TrapG) to trap the fluorochromes in the vicinity of the active enzyme. β-glucuronidase-mediated hydrolysis of the glucuronyl bond of TrapG generates a highly reactive alkylating group that facilitates the attachment of the fluorochrome to nucleophilic moieties located near β-glucuronidase-expressing sites. FITC-TrapG was selectively trapped on purified β-glucuronidase or β-glucuronidase-expressing CT26 cells (CT26/mβG) but not on bovine serum albumin or non-β-glucuronidase-expressing CT26 cells used as controls. β-glucuronidase-activated FITC-TrapG did not interfere with β-glucuronidase activity and could label bystander proteins near β-glucuronidase. Both FITC-TrapG and NIR-TrapG specifically imaged subcutaneous CT26/mβG tumors, but only NIR-TrapG could image CT26/mβG tumors transplanted deep in the liver. Thus NIR-TrapG may provide a valuable tool for visualizing β-glucuronidase activity in vivo.     

Facile access to diverse all-carbon quaternary center containing spirobicycles by exploring a tandem Castro–Stephens coupling/acyloxy shift/cyclization/semipinacol rearrangement sequence

Efficient combination of two or more reactions into a practically useful purification free sequence is of great significance for the achievement of structural complexity and diversity, and an important approach for the development of new synthetic strategies that are industrially step-economic and environmentally friendly. In this work, a facile and efficient method for the construction of highly functionalized spirocyclo[4.5]decane derivatives containing a synthetically challenging quaternary carbon center has been successfully developed through the realization of a tandem Castro–Stephens coupling/1,3-acyloxy shift/cyclization/semipinacol rearrangement sequence. Thus a series of multi-substituted spirocyclo[4.5]decane and functionalized cyclohexane skeletons with a phenyl-substituted quaternary carbon center have been constructed using this method as illustrated by 24 examples in moderate to good yields. The major advantages of this method over the known strategies are better transformation efficiency (four consecutive transformations in one tandem reaction), product complexity and diversity. As a support of its potential application, a quick construction of the key tetracyclic diterpene skeleton of waihoensene has been achieved.

An efficient construction of spirocyclo[4.5]decane derivatives is developed via a Castro–Stephens coupling/1,3-acyloxy shift/cyclization/semipinacol rearrangement sequence.     

Syntheses and characterizations of a series of novel Ln6Cu24 clusters with amino acids as ligands

With glycine or L-alanine as ligands, a series of novel 3d-4f heterometallic Ln(6)Cu(24) clusters with the formulas of [Sm(6)Cu(24)(mu(3)-OH)(30)(Gly)(12)(Ac)(12)(ClO(4))(H(2)O)(16)].(ClO(4))(9).(OH)(2).(H(2)O)(31) (1) and [Ln(6)Cu(24)(mu(3)-OH)(30)(Ala)(12)(Ac)(6)(ClO(4))(H(2)O)(12)].(ClO(4))(10).(OH)(7).(H(2)O)(34) (2.Ln) (Ln = Tb, Gd, Sm, and La) were synthesized by self-assembly, among which 1 and 2.Tb were characterized by X-ray structure analysis. The metal skeleton of the clusters may be described as a huge [Ln(6)Cu(12)] octahedron (constructed with 6 Ln(III) ions located at the vertices and 12 inner Cu(II) ions located at the midpoints of the edges) connected by 12 additional Cu(II) ions (every 2 are connected to 1 Ln(III) vertex). The temperature dependence of the magnetic susceptibilities of 2.Ln was investigated and was found to vary with the central rare-earth ions. Impedance spectroscopic measurements of 2.Ln reveal that they are ionic conductors.     

聚硫醚醚酮(砜)芳香环状低聚物的合成与自由基开环聚合

在“拟高稀释”条件下,通过亲核缩聚反应高产率地合成了含硫醚键的芳香醚环状低聚物.应用核磁、GPC和激光质谱(MALDI-TOFMS)等手段对环状低聚物的结构进行了确认,并研究了环状低聚物的组分分布.聚硫醚醚酮环状低聚物在硫醚自由基的引发下进行快速熔融聚合,得到热稳定性很好的高分子量线性聚合物.