LaPO4纳米微粒的制备及表征

Surface-modified LaPO4 nanoparticales were synthesized in the mixture solvent of water-ethanol with the surface modification age of dialkylphosphate. The conditions of synthesis and characterization were discussed. The results indicated that nanoparticle core of LaPO4 and surface-modified layer were formed. The surface-modified nanoparticles of LaPO4 can be dispersed in organic solvent and has better lubricating properties.     

系数倍率导数分光光度法测定邻氯苯亚甲基丙二腈和邻氯苯甲醛

本文提出一种新的光度法——系数倍率导数分光光度法,用于邻氯苯亚甲基丙二腈和邻氯苯甲醛的测定,回收率分别为97.6～102.0％和97.5～104.2％。实验结果表明方法快速、准确、可靠。     

Synthesis,characterization, and theoretical studies of group 4 amido hydrotris(pyrazolyl)borate complexes

Titanium and zirconium amido complexes containing a hydrotris(pyrazolyl)borate (Tp) or hydrotris(3,5-dimethylpyrazolyl)borate (Tp*) ligand TpM(NMe(2))(3) (M = Ti, 1; M = Zr, 2) and Tp*M(NMe(2))(3) (M = Ti, 3; M = Zr, 4) were prepared by the reactions of M(NMe(2))(3)Cl (M = Ti, Zr) with sodium hydridotris(pyrazol-1-yl)borate and potassium hydridotris(3,5-dimethylpyrazol-1-yl)borate, respectively. The structures of 1, 2, and 4.CH(2)Cl(2) were determined by X-ray diffraction and show octahedral coordination geometry around the metal centers. Density functional theory calculations at the B3PW91 level were performed to understand the orientations and the rotational behavior of amido ligands in these metal complexes.     

The determination of calcium in yttrium oxide by alpha-particle activation analysis

The determination of calcium in yttrium oxide through the⁴⁰Ca(α, p)⁴³Sc reaction was studied, using a post-irradiation radiochemical separation procedure. The half-life of⁴³Sc was determined to be 3.87 hr. The chemical recovery was about 70%. The detection limit was about 10 ppb, for a 30 min irradiation at an alpha-particle beam current of 1 μA (E_α=13.4 MeV) and γ−γ coincidence counting (background counts being<1, cpm), with counting starting at 4 hours after the end of irradiation. Four samples of a batch of yttrium oxide (A.R.) were analyzed, and found to contain 13.9±1.0 ppm of calcium.     

Structural Determination of Bis-histidinopeptide Zinc Complexes by 15N NMR (HMBC) Spectra

Polynitrogen receptors such as bis-histidine peptides possess strong ability to bind metals, which play much important roles in medicinal, bioinorganic, bioorganic, biomimetic and supramolecular chemistry. In order to investigate the interaction of these hosts with a variety of neutral, cationic and anionic guests, several techniques, for example, NMR,potentiometric tirations and monocrystal X-ray diffraction have been employed. Among them NMR is a powerful technique for unraveling the structure of polynitrogen receptors as long as they are in solution where the rapid tumbling of molecules averages out the anisotropies such as chemical shift and dipole-dipole interactions. General 1H NMR approach has been widely used for the study of host-guest interaction, but it is difficult for the accurate measurement in complexes structures, particularly metal complexes structures in which how the polynitrogen receptors bind metal, and which nitrogen binds metal and so on.     

Structural Features of a Polysaccharide from Centella asiatica

Centella asiatica has been used as remedy for sodation, stabilization and against lepra, anabrosis1 in the oriental countries. The low-molecular-weight constituents in Centella asiatica have been investigated1. However, no polysaccharides have been reported. 1BI was the first polysaccharide isolated from C. asiatica, which had immunostimulating activity in vitro. In present study, we report the structural features of 1BI. Experimental Extraction, isolation and purification Dried C.…     

DNA-mediated coordinative assembly of upconversion hetero-nanostructures for targeted dual-modality imaging of cancer cells

We reported a simple and universal strategy for DNA-mediated assembly of CdTe quantum dots (QDs) and lanthanide-doped upconversion nanoparticles (UCNPs). Such DNA-QD/UCNPs heterostructures not only maintains both fluorescent properties of QDs and upconversion luminescence behaviors of UCNPs, but also offers a polyvalent DNA surface, allowing for targeted dual-modality imaging of cancer cells using an aptamer     

混合金属氧化物柱撑α-磷酸锆的研究

制备、表征了混合铝/铬金属氧化物柱撑α-磷酸锆(Al/Cr-ZrP),并对胶体化使用有机胺的种类、柱化液金属离子浓度以及金属离子用量等因素进行了研究。研究表明以乙醇胺为胶体化有机胺比使用正丙胺为胶体化有机胺所得到的产物的层间距更大;采用较低金属离子浓度、较高金属离子用量有利于Al/Cr-ZrP的合成。在Al/Cr比为1、以正丙胺为胶体化有机胺、金属离子浓度为0.067mol·L^-1、金属离子用量为6.67CEC的条件下,制备出了混合金属氧化物柱撑α-磷酸锆,其层间距可达3.60nm,     

Efficient synthesis of complex glycopeptides based on unprotected oligosaccharides

N-Glycopeptides containing 1 to 4 trisaccharide chains, with the carbohydrates vicinal to each other in the multivalent glycopeptides, were efficiently synthesized by using the glycosylated Fmoc-asparagine as a key building block. While the couplings of amino acids with glycopeptides could be achieved in the homogeneous solutions in N-methylpyrrolidinone (NMP) to give excellent yields, all products were conveniently isolated from the reaction mixtures through a precipitation method by using the free carbohydrate chains as phase tags. Commercially available pentafluorophenyl (Pfp) esters of amino acids were employed for the glycopeptide elongation. Longer glycopeptides were constructed by means of a highly convergent synthetic design that is based on the coupling of glycopeptide/peptide fragments. Hydrogen bond interactions between free oligosaccharides were proposed to explain the exceptionally high efficiency of the couplings between two glycosylated building blocks.     

Asymmetric synthesis of trans-2,3-piperidinedicarboxylic acid and trans-3,4-piperidinedicarboxylic acid derivatives

Asymmetric syntheses of (2S,3S)-3-(tert-butoxycarbonyl)-2-piperidinecarboxylic acid (1b), (3R,4S)-4-(tert-butoxycarbonyl)-3-piperidinecarboxylic acid (2b), and their corresponding N-Boc and N-Cbz protected analogues 8a,b and 17a,b are described. Enantiomerically pure 1b has been synthesized in five steps starting from L-aspartic acid beta-tert-butyl ester. Tribenzylation of the starting material followed by alkylation with allyl iodide using KHMDS produces the key intermediate 5a in a 6:1 diastereomeric excess. Upon hydroboration, the alcohol 6a is oxidized, and the resulting aldehyde 7 is subjected to a ring closure via reductive amination, providing 1b in an overall yield of 38%. Optically pure 2b has been synthesized beginning with N-Cbz-beta-alanine. The synthesis involves the induction of the first stereogenic center using Evans's chemistry and sequential LDA-promoted alkylations with tert-butyl bromoacetate and allyl iodide. Further elaboration by ozonolysis and reductive amination affords 2b in an overall yield of 28%.