Synthesis and characterization of three tetranuclear clusters containing a [Mo3OS3Sn]6+ cubane-like core

Three heterometallic cubane-like clusters, [Mo3(mu 3-O)(mu 3-S)3(SnCl3)(dtp)3(py)3] (dtp = S2P(OC2H5)2-, py = C5H5N) (1), (PPN)[Mo3(mu 3-O)(mu 3-S)3(SnCl3)(dtp)3(mu-OAc)(py)] (OAc = CH3COO-, PPN = (C6H5)3PNP(C6H5)3+) (2), and (Et4N)[Mo3(mu 3-O)(mu 3-S)3(SnCl3)(dtp)2(mu-OAc)2(py)] (3) have been prepared by the reaction of [Mo3(mu 3-O)-(mu-S)3(dtp)4(H2O)] (4), [Mo3(mu 3-O)(mu-S)3(dtp)3(OAc) (py)] (5), and [Mo3(mu 3-O)(mu-S)3(dtp)2(OAc)2 (py)] (6) with SnCl2, respectively. They have been characterized by IR, UV-vis, 31P NMR, 95Mo NMR, and X-ray structure analysis. All of these heterometallic clusters have a [Mo3OS3Sn]6+ core but contain a different arrangement of peripheral ligands. As far as the neutral cluster 1 is concerned, there is no bridging OAc ligand, while only one bridging OAc ligand is observed for cluster 2 and two are for cluster 3. The Mo-Mo distances are about 0.03-0.04 A shorter than those of the starting trimolybdenum clusters. This indicates that the incorporation of SnCl3- fragment into (Mo3) clusters makes the Mo-Mo bonding enhanced. Crystal data for 1: triclinic, space group P-1, a = 10.7423(2) A, b = 14.0357(1) A, c = 16.9346(2) A, alpha = 84.054(1) degrees, beta = 87.095(1) degrees, gamma = 84.517(1) degrees, V = 2525.82(6) A3, Z = 2, R = 0.038 for 5584 reflections (I > 2.0 sigma(I)). Crystal data for 2: triclinic, space group P-1, a = 12.9529(1) A, b = 15.6324(2) A, c = 19.6355(1) A, alpha = 92.083(1) degrees, beta = 97.908(1) degrees, gamma = 110.337(1) degrees, V = 3677.41(6) A3, Z = 2, R = 0.034 for 8665 reflections (I > 2.0 sigma(I)). Crystal data for 3: monoclinic, space group P2(1)/n, a = 14.0852(5) A, b = 15.1324(5) A, c = 23.2691(7) A, beta = 97.371(1) degrees, V = 4918.7(3) A3, Z = 4, R = 0.049 for 4970 reflections (I > 2.0 sigma(I)).     

Controlled kinetics of non-enzymatic chemiluminescence reactions for simple imaging of DNA and protein

A robust and sensitive non-enzymatic chemiluminescence (CL) imaging method is presented. In the method a fast-emitting CL reaction is tuned to furnish a slower-emitting reaction suitable for simple CL imaging. Typically, non-enzymatic CL reactions between luminol or fluorescein and oxygen species generated by KCN as catalyst, were rather fast and unsuitable for CL imaging; the speed of the reactions could, however, be reduced substantially by changing KCN for CH(3)CN or benzonitrile. Light emission from the tuned CL reaction was intense and long-lived, and even with a simple arrangement high sensitivity could be achieved. The maximum CL peak was reached after approximately 1.5 min in the presence of 25% acetonitrile, and as little as 16 fmol commercial isoluminol-labeled streptavidin was detected and visualized on either microplate or membrane. The approach was further illustrated by imaging of DNA on a membrane and of antibody on a microplate by use of biotin-streptavidin chemistry. Overall, this simple, economical, and sensitive CL imaging system is expected to be very useful in biochemical analysis, and greatly complements currently used enzyme-based CL imaging methods, especially in routine applications.     

线性非理想条件下液相色谱柱末端峰形规律

 色谱流出曲线的二阶中心矩μ２和三阶中心矩μ３以及描述峰形非对称程度的偏态系数∑ｋ＝μ３／μ１．５２是反映色谱峰形的重要参数。从液相色谱过程动力学方程出发，运用电子计算机证明了在线性非理想条件下高效液相色谱体系中不同保留值组分在柱末端峰形的分布基本一致的结论。     

Kinetics of solvolysis of 1-acetyl-4-(1-ethoxycarbonyl-1-cyano) methylene-1,4-dihydroquinoline in undried DMSO-d6· formation of Acetic Anhydride as an intermediate

The kinetics of solvolysis of the title compound (QAc) in undried DMSO-d₆ to give 4-(1-ethoxycarbonyl-1-cyano)methylquinoline (QH) and HOAc at ambient temperature were investigated by ¹H nmr spectrometry. With a limited excess of water the solvolysis follows a three-step process of $ {\rm QAc} + {\rm H}_2 {\rm O}\mathop \to \limits^{k_1} {\rm QH} + {\rm HOAc}, $ , and $ {\rm Ac}_{\rm 2} {\rm O} + {\rm H}_2 {\rm O}\mathop \to \limits^{k_3} {\rm 2\,HOAc}, $ where k₂ > k₁ and k₃ < k₁. Addition of pyridine-d₅ to the reaction mixture markedly catalyzes the overall solvolysis, while addition of CF₃CO₂D to the reaction mixture simplifies the kinetics to pseudo first-order in [QAc] with k = 4.3 × 10^?3 min^?1.     

Synthesis and properties of conjugated bimetallic ruthenium complexes with σ,σ-bridging azobenzene chains

A versatile synthetic route to conjugated bimetallic ruthenium complexes with σ,σ-bridging azobenzene chains was developed, and new ruthenium complexes with various ligands were synthesized and characterized. These bimetallic complexes showed a remarkable absorption in the visible region (λ_max: 452-483 nm), and undergo trans-to-cis isomerization under UV light irradiation for short time. Electrochemical study showed that the metal centers in bimetallic complexes containing the CHCHC₆H₄NNC₆H₄CHCH bridge interact with each other.     

Optical properties of nanocrystalline Y2O3:Eu depending on its odd structure

The structure of nanocrystalline Y2O3:Eu prepared by a combustion reaction was analyzed by XRD and high-resolution electron microscopy. Compared with a large-scale particles, 5-nm Y2O3:Eu particles presented as distorted crystallite and rough surfaces. Luminescent and absorption properties of nano-Y2O3:Eu showed remarkably particle size effects. At Y2O3:Eu particle sizes smaller than 10 nm some new results were observed: (a) a red shift of the charge-transfer-state absorption; (b) new emission bands of Eu3+ in the 5D0 --> 7F2 region; (c) luminescent decay of energy level 5D0 of Eu3+ turning to a two-step exponential; and (d) a pronounced increase in quenching concentration and much lower phonon density compared with those of the bulk material. All these phenomena can be attributed to the effect of the softened lattice and surface state of the nanomaterial. The latter was confirmed by stronger excitation by the host absorption after the surface modification.     

High extraction ability of 1,3-dialkynyl calixarene towards mercury（Ⅱ） ion

The reaction of 1,3-dipropyn-2-yloxycalix[4]arene with mercury(II)acetate could give mercury-containing alkynyl calixarenepolymer.The extraction behavior of 1,3-dipropyn-2-yl-oxycalix[4]arene towards mercury(II)ion was examined.When the moleratio of Hg~(2 )/calixarene was 1:1,the extractive percent can reach to 99.1%,and the extraction capacity was up to 431 mg/g.It couldalso decrease the Hg~(2 )concentration from 5 to 0.85 mg/L,which was only 17%of the national standard of effluent and satisfied thenational standard of drinking water.The extraction process included chemical reaction.     

Characterization of phosphopeptides from protein digests using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and nanoelectrospray quadrupole time-of-flight mass spectrometry

A two-step mass spectrometric method for characterization of phosphopeptides from peptide mixtures is presented. In the first step, phosphopeptide candidates were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) based on their higher relative intensities in negative ion MALDI spectra than in positive ion MALDI spectra. The detection limit for this step was found to be 18 femtomoles or lower in the case of unfractionated in-solution digests of a model phosphoprotein, beta-casein. In the second step, nanoelectrospray tandem mass (nES-MS/MS) spectra of doubly or triply charged precursor ions of these candidate phosphopeptides were obtained using a quadrupole time-of-flight (Q-TOF) mass spectrometer. This step provided information about the phosphorylated residues, and ruled out nonphosphorylated candidates, for these peptides. After [(32)P] labeling and reverse-phase high-performance liquid chromatography (RP-HPLC) to simplify the mixtures and to monitor the efficiency of phosphopeptide identification, we used this method to identify multiple autophosphorylation sites on the PKR-like endoplasmic reticulum kinase (PERK), a recently discovered mammalian stress-response protein.     

Assay of free ferulic acid and total ferulic acid for quality assessment of Angelica sinensis

Activity of Chinese Danggui (DG), the processed root of Angelica sinensis (Oliv.) Diels, is linked to the ferulic acid content but the stability of ferulic acid during extraction for medicinal use is not known. The stabilities of ferulic acid and coniferyl ferulate were evaluated in the extracts of DG using a variety of extraction solvents. These included various combinations and proportions of methanol, water, formic acid, 1 M aqueous hydrochloric acid and 2% sodium hydrogen carbonate (NaHCO3) in water. Coniferyl ferulate was found liable to hydrolyze into ferulic acid in neutral, strongly acidic and basic solvents, where heat and water could facilitate this hydrolysis. However, the hydrolysis was relatively resisted in weakly organic acid. Based on the stability evaluation, two new terms, namely: free ferulic acid and total ferulic acid, were suggested and defined. Free ferulic acid refers to the natural content of ferulic acid in herbs. Total ferulic acid means the sum of free ferulic acid plus the amount of related hydrolyzed components. Meanwhile, the high-performance liquid chromatographic (HPLC) method was developed to assay free ferulic acid and total ferulic acid in DG using methanol-formic acid (95:5) and methanol-2% NaHCO3 in water (95:5) as extraction solvents, respectively. Ten DG samples were investigated on their contents of free and total ferulic acid. The results indicated that the amount variety of free ferulic acid was larger than that of their counterparts, and the ratio of total ferulic acid to free ferulic acid was 4.07 +/- 2.73 (mean +/- SD, n = 10). The chemical assay of DG using total ferulic acid content would be a better choice to assess the herbal quality and was recommended.     

Study on the formation of the ketonic defects in the thermal degradation of ladder-type poly(p-phenylenes) by vibrational spectroscopy

We have investigated the thermal degradation in air by Fourier transform infrared spectroscopy of a ladder-type copolymer containing fluorene units in the backbone (Me-LPF), to reveal the formation of the ketonic defects. As thermal treatment of Me-LPF film at 200 degrees C in air proceeds, a new group of complex absorption bands due to degradation products arises in the range between 1800 and 1600 cm(-1). The observed overlapping bands were separated and assigned by utilizing the second-derivative IR spectral analysis, which can narrow the peak width to one-third of the originals and thereby eases the analysis. The degraded products were assigned as fluorenone (1718 cm(-1)) and benzophenone (Ar-(C=O)-Ar) (1665 cm(-1)), formed by the oxidation of the backbone, and acylphenone (Ar-(C=O)-R) (1685 cm(-1)) from the side chain. The fluorenone was found to be the major component among the degraded products in the main chain, and the time and temperature dependence indicated that the oxidation is a kind of autocatalytic radical-chain process. The oxidation can reach a very high degree (approximately 30% for 6 h oxidation at 240 degrees C estimated by absorption of the alkyl). Our results suggest the possibility of the oxidation of the 9-bialkylfluorene sites. We propose that the degradation of the alkyl in the side chain can help the radicals to propagate in the chain reaction.