Separation of alkylaminonaphthylenesulfonyl peptides and amin acids by high-performance liquid chromatography. Methods for measuring melanotropin inhibiting factor breakdown

N,N-Dimethyl diethyl, dipropyl, dibutyl, and N-monoisopropylaminoaphthylenesulfonyl derivatives of melanotropin inhibiting factor (MIF) and its metabolites were prepared, and their chromatographic behavior was investigated with thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC), using five solvent systems on polyamide layers and ten solvent systems on muBondapak C18 and muBondapak phenyl columns. A mixture of MIF and its metabolites derivatized with Dns chloride was adequately resolved by two-dimensional chromatography on polyamide layer with solvent systems, formic acid-water (3:97) and benzene-acetic acid (9:1). Bns-MIF and its metabolites were separated with muBondapak C18 column with the solvent system acetonitrile-0.01 M sodium sulphate buffer, pH 7 (50:50). They were separated into five groups: Gly and Bns acid; Pro-Leu, Leu-Gly and Leu; Pro; Gly-NH2; and MIF. The alkylaminonaphthylenesulfonyl derivates had strong fluorescence, which permitted their detection at the level of 10(-11) to 10(-9) mol. Dns-MIF and its derivatives had the lowest detectable amounts. HPLC with the aid of the Dns derivation is reliable and fast, and is the preferable method for study of neuropeptide breakdown.     

汽车制造商分时租赁模式采用及产品线策略研究

考虑自有平台和第三方平台两种分时租赁方式,将汽车质量划分为性能质量和环境质量,构建销售模式、纯分时租赁模式和混合模式下的产品线策略模型,研究制造商产品线策略与商业模式之间的相互作用。研究发现,同品牌产品间竞争和合并效应是分时租赁模式影响产品线策略的两个关键因素。同品牌产品间竞争的加剧和合并效应的增大都会激励企业选择性能更好的车型而忽略其环境表现。分时租赁模式能同时改进利润与产品环境表现,但存在条件:当消费者价格敏感性较低时,使用成本高且合并效应小是实现同时改进的条件;当消费者价格敏感较高时,使用成本低且合并效应小则是同时改进的条件。     

Macrocyclic polycther sulfide syntheses. The preparation of thia-crown-5, 6 and 7 compounds

Macroeyclic polyether sulfides have been prepared by reacting an oligoethylene glycol dichloride with a dimercaptan or sodium sulfide as reported in a previous paper (6). The following new compounds were prepared: 1,4,7-trithia(15-crown-5) (1); 1,4,10-trithia(15-crown-5) (II): 1,4,7,10-tetrathia(15-crown-5) (III); I-thia(18-crown-6) (IV); 1,4-dithia(18-crown-6) (V); 1,7-dithia(18-crown-6) (VI); 1,4,7-trithia(18-crown-6) (VII); 1,7-dithia(21-crown-7) (VIII); and 1,4,7-trithia(21-crown-7) (IX). The melting points of these and previously reported thia-crown compounds correlate with their structures. X-ray analyses of two thia-crown compounds indicate that the large sulfur atoms are directed away from the center of the ring.     

Melting behavior of one-dimensional zirconium nanowire

In this paper, we analyze the melting behavior of zirconium nanowire using the results of a series of molecular dynamics simulations. Our calculation employs a well-fitted, tight-binding many-body potential for zirconium atoms. The melting point of the nanowire is predicted by the root-mean-square displacements for inner and outer shells. Our simulations predict two melting behaviors: one is the inner melting and the other is the outer melting. Our results reveal that the melting of nanowire starts from the inner shell atoms. The melting point of zirconium nanowire is lower than the bulk value (2125 K). Moreover, the melting point of the inner shell is lower than that of the outer shell. A coexistence of crystal and liquid units is observed in the melting process of nanowire. An investigation of local clusters is carried out to further analyze the melting mechanism of the nanowire. The presence of the local clusters 1331, 1321, 1211, etc. is an indication of disordered structures. The pair and angular correlation functions are also presented for the analysis of the melting behavior. It is not only the diffusion of single atom but the diffusion of clusters result in the occurrence of the melting.     

A reliable ab initio potential energy surface and vibrational states for the ground electronic state of HgH2(X1Sigma+g)

A three-dimensional global potential energy surface for the ground (X (1)Sigma(+)(g))electronic state of HgH(2) is constructed from more than 13,00 ab initio points. These points are generated using an internally contracted multireference configuration interaction method with the Davidson correction and a large basis set. Low-lying vibrational energy levels of HgH(2), HHgD, and HgD(2) calculated using the Lanczos algorithm are found to be in good agreement with the available experimental band origins. The majority of the vibrational energy levels up to 9000 cm(-1) are assigned with normal mode quantum numbers. Our results indicate a gradual transition for the stretching vibrations from the normal mode regime at low energies to the local mode regime near 9000 and 8000 cm(-1) for HgH(2) and HgD(2), respectively, as evidenced by a decreasing energy gap between the (0,0,n(3)) and (1,0,n(3)-1) vibrational states and bifurcation of the corresponding wave functions.     

电化学合成铜配合物的研究

采用金属铜为"牺牲"阳极,首次在无隔膜电解槽中,电化学溶解金属铜一步制备了纳米CuO前体Cu(OEt)2, Cu(OBu)2, Cu(acac)2, Cu(OEt)(acac), Cu(OBu)(acac) (acac为乙酰丙酮基).产物通过红外光谱(FT-IR)、拉曼光谱(Raman spectrum)进行表征.同时讨论了影响电合成铜醇盐及其配合物的关键因素.实验表明,防止阳极钝化,温度控制在30～50 ℃,采用有机胺溴化物为导电盐, 电极电位控制在0.8～1.2 V之间,可以提高电合成效率.实验同时表明Cu(acac)2, Cu(OEt)(acac), Cu(OBu)(acac)可作为制备含铜纳米材料前驱体.     

Carbon anode materials from polysiloxanes for lithium ion batteries

Three kinds of silicon-containing disordered carbons have been prepared by pyrolysis of polysiloxanes with different amounts of phenyl side groups. X-ray powder diffraction, X-ray photoelectron spectroscopy and electrochemical capacity measurements were performed to study their behaviors. Graphite crystallites, micropores, and silicon species affect their electrochemical performances. All of them present high reversible capacities, >372 mAh/g. Since the graphite crystallites are very small, they contribute very little to reversible capacity. The number of micropores produced by gas emission during the heat-treatment process decides whether they exhibit reversible capacity. Si mainly exists in the form C–Si–O and influences the irreversible capacity. There is no evident capacity fading in the first ten cycles, indicating promising properties for these disordered carbons.     

Immunosuppressive ent‐Kaurene Diterpenoids from Isodon serra

Three new enmein‐type ent‐kaurenoids, i.e., the two pairs 1 and 2 of 20‐epimers and the (20R)‐isomer 3 , besides the seven known diterpenoids 4 – 10 , were isolated from the aerial parts of Isodon serra. Their structures were elucidated by spectroscopic techniques and X‐ray diffraction. The immunosuppressive effect for T‐lymphocytes proliferation induced by Con A in BALB/c mouse was evaluated for the isolates 1 – 10 . They all displayed a remarkable inhibitory effect, with multi‐glycosides of Tripterygium wilfordii as positive reference substance (Table 3).