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921.
表面活性剂与金属离子的相互作用 总被引:1,自引:0,他引:1
烷基硫酸盐(CnS)的抗盐能力很差,在其中引进氧乙烯基(Eo)以后,形成的烷基聚氧乙烯基醚硫酸盐(CnEnS)的抗盐能力明显增强。把CnEnS加到CnS中,形成混合表面活性剂的低温抗盐能力也将明显改善。Doscher、Schott等人认为,CnEnS中的Eo与高价金属阳离子形成了一种“复合物”,这使得CnEnS具有很强的抗盐能力。Chiu则没有发现这种“复合物”。显然,了解CnEmS的抗盐机理,对于该类表面活性剂的理论研究和实际应用,都有重要的意义。 相似文献
922.
新型糠醛加氢制糠醇催化剂研究 总被引:8,自引:0,他引:8
新型糠醛加氢制糠醇催化剂研究林培滋,黄世煜,周焕文,赵彤彤,刘崇早,罗洪原,梁东白(中国科学院大连化学物理研究所,大连116023)关键词铜催化剂,糠醛,加氢,糠醇糠醇是重要的化工原料,糖醇树脂是耐酸、碱腐蚀的材料,在工业发达的国家中,铸造工业广泛采... 相似文献
923.
924.
Manganese (Mn), iron (Fe), copper (Cu), and zinc (Zn) concentrations were determined in the brain regions of normal 1-, 3-, 5-, 7-, 14-, 21-, 42-, 77-, and 147-day-old Wistar rats using inductively coupled plasma mass spectrometry (ICP-MS), and their maps were illustrated in color to visually compare the distribution of the elements at various stages of the growth process. Sagittal slices (1-mm thickness) sectioned at the level of the substantia nigra were divided into 18 regions, and the small slice samples were digested in microwave-assisted closed vessels for ICP-MS measurement. Mn, Fe, Cu, and Zn concentrations increased region-specifically with age, and their distributional maps showed some characteristics. These findings are discussed in terms of needs for these trace elements in the normal brain. Among new findings about their brain distribution, it is especially noteworthy that higher concentrations of Mn, Fe, and Zn were observed in the substantia nigra compared with those in neighboring regions. The mapping method in this work is expected to open up possibilities for screening of the in vivo element–element interrelationships among these essential elements. 相似文献
925.
926.
Ejnik JW Todorov TI Mullick FG Squibb K McDiarmid MA Centeno JA 《Analytical and bioanalytical chemistry》2005,382(1):73-79
Urine uranium concentrations are the best biological indicator for identifying exposure to depleted uranium (DU). Internal exposure to DU causes an increased amount of urine uranium and a decreased ratio of 235U/238U in urine samples, resulting in measurements that vary between 0.00725 and 0.002 (i.e., natural and depleted uraniums 235U/238U ratios, respectively). A method based on inductively coupled plasma dynamic reaction cell mass spectrometry (ICP-DRC-MS) was utilized to identify DU in urine by measuring the quantity of total U and the 235U/238U ratio. The quantitative analysis was achieved using 233U as an internal standard. The analysis was performed both with and without the reaction gas oxygen. The reaction gas converted ionized 235U+ and 238U+ into 235UO2+ (m/z=267) and 238UO2+ (m/z=270). This conversion was determined to be over 90% efficient. A polyatomic interference at m/z 234.8 was successfully removed from the 235U signal under either DRC operating conditions (with or without oxygen as a reaction gas). The method was validated with 15 urine samples of known uranium compositions. The method detection limit for quantification was determined to be 0.1 pg U mL–1 urine and an average coefficient of variation (CV) of 1–2% within the sample measurements. The method detection limit for determining 235U/238U ratio was 3.0 pg U mL–1 urine. An additional 21 patient samples were analyzed with no information about medical history. The measured 235U/238U ratio within the urine samples correctly identified the presence or absence of internal DU exposure in all 21 patients.The opinions and assertions expressed herein are those of the authors and are not to be construed as official or as representing the views of the Armed Forces Institute of Pathology, the Department of the Army, or the Department of Defense 相似文献
927.
We report the synthesis and physical studies of a novel porphyrazine (pz) dimer [1[Ni,Cu]]2, which has Ni(II) ions incorporated into the pz cores and is linked by two Cu(II) ions coordinated to bis(picolinamide) chelates attached to the pz periphery. [1[Ni,Cu]]2 was prepared from precursor pz 2 with a selenodiazole ring fused to the pz core. This ring was deprotected to form the diamino-pz 3, which reacted with 2 mol of picolinoyl chloride hydrochloride to form pz 1[2H,2H], with peripheral bis(picolinamide) chelates; this was metalated to form [1[Ni,Cu]]2. The crystal structures of 1[2H,2H] and [1[Ni,Cu]]2 are presented. The latter is a dimer in which parallel, face-to-face pz's with an average separation of 3.30 angstroms are linked through the peripheral picolinamide ligands by a pair of peripheral Cu(II) ions. Each Cu(II) is coordinated with distorted square-planar geometry by a picolinamide from each pz. In this report, we focus on the interaction of these two peripheral Cu(II) ions. We discuss the preparation and magnetic properties of the pz dimer complex [1[Ni,Cu]]2 with two Cu(II) ions in the peripheral chelate but a diamagnetic metal ion Ni(II) in the pz core. Although [1[Ni,Cu]]2 contains two Cu(II) ions (S = 1/2), we could detect no electron paramagnetic resonance signal, which suggests very strong antiferromagnetic exchange between those two Cu(II) ions. Temperature-dependent magnetic susceptibility measurement gives an exchange splitting between the S = 0 ground state and the excited triplet state of delta = 660 cm(-1). 相似文献
928.
A simple and efficient one-step, regioselective, enzymatic glucosylation of arbutin by α-glucosidase
4-Hydroxyphenyl-β-isomaltoside has been synthesized by α-glucosidase assisted transglycosylation between arbutin as acceptor and sucrose as donor molecules, respectively. Optimum conditions for the transglucosylation reaction were 40 °C for 20 h with 10 mM arbutin and 1.5 M sucrose in a 100 mM sodium citrate/phosphate buffer at pH 5.0. The new glucoside was obtained in a 50% molar yield with respect to arbutin. 相似文献
929.
Cooper TJ Talaty ER Van Stipdonk MJ 《Journal of the American Society for Mass Spectrometry》2005,16(8):1305-1310
We report a new fragmentation pathway for the CID of (b3 - 1 + Cat)+ product ions derived from the model peptide AXAG, where X = beta-alanine, gamma-aminobutyric acid, epsilon-amino-n-caproic acid, or 4-aminomethylbenzoic acid. By changing the amino acid to the C-terminal side of the amino acid X, and incorporating 15N and 13C labeled residues at the same position, we conclude that the dissociation pathway most likely leads to a metal cationized nitrile. With respect to the various amino acids at position X, the putative nitrile product becomes more prominent, relative to the conventional (a3 - 1 + Cat)+ species, in the order beta-alanine < gamma-aminobutyric acid < epsilon-aminocaproic acid < 4-aminomethylbenzoic acid. The pathway is not observed for peptides with alpha-amino acids at position X. The product ion is observed most prominently during the CID of Li+ and Na+ cationized peptides, only to a small extent for Ag+ cationized peptides, and not at all from protonated analogues. 相似文献
930.