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31.
Gd@C82(OH)40 has been developed as a new generation of MRI contrast agent. But recently, it was found that Gd@C82(OH) x with a larger number of OH (x>36) would lead to cage break and hence, release of highly toxic Gd ions. We synthesized the more stable Gd@C82(OH) x with less OH-number, Gd@C82(OH)16, and studied its proton relaxivity and MRI images. The results indicate that Gd@C82(OH)16 also gives high proton relaxivity, even higher than that of (NMG)2-Gd-DTPA. The bio-distribution indicated that Gd@C82(OH)16 tends to be entrapped in the liver and kidney and remained in tissue for about 2 hours. The results suggest that the more stable metallofullerene derivative Gd@C82(OH)16 can be the potential candidate of the new MRI contrast agent.  相似文献   
32.
Positron annihilation lifetime measurements of PMMA, PEMA, PiPMA, PnPMA and PnBMA were performed in the temperature range between 15 and 300 K, where , and relaxational transitions occur for these polyalkylmethacrylates. The variations of free volume size and content calculated from the longest lifetime component against temperature are correlated to the results obtained by dielectric, viscoelastic and dynamic mechanical relaxation data of the polymers. The variations of free volume sizes and contents, apparent free volume fraction and size distribution of the polyalkylmethacrylates are well correlated with the rotational transitions of side chains. The location of free volumes, in which positronium annihilates can be estimated near the vicinity of alkyl groups bound to oxygen atom of side ester chains.  相似文献   
33.
Qin WH  Cao CX  Li S  Zhang W  Liu W 《Electrophoresis》2005,26(16):3113-3124
The paper advanced the theoretical procedures for quantitative design on selective stacking of zwitterions in full capillary sample matrix by a cathodic-direction moving reaction boundary (MRB) in capillary electrophoresis (CE) under control of electroosmotic flow (EOF). With the procedures, we conducted the theoretical computations on the selective stacking of two test analytes of L-histidine (His) and L-tryptophan (Trp) by the MRB created with 30 mM pH 3.0 formic acid-NaOH buffer and 2-80 mM sodium formate. The results revealed the following three predictions. At first, the MRB cannot stack His and Trp plugs if less than 12.5 mM sodium formate is used to form the MRB and prepare the sample matrix. Second, the MRB can stack His and/or Trp sample plugs completely if higher than 50 mM sodium formate is chosen to form the MRB. Third, the MRB can only focus His plug completely, but stack Trp plug partially if 20-50 mM sodium formate is used; this implied the complete MRB-induced selective stacking to His rather than Trp. All the three predictions were quantitatively proved by the experiments. With great dilution of sample matrix and control of EOF, controllable, simultaneous and MRB-induced selective stacking and separation of zwitterions were achieved. The theoretical results hold evident significances to the quantitative design of selective stacking conditions and the increase of detection sensitivity of zwitterions in CE. In addition, the control of EOF by cetyltrimethylammonium bromide (CTAB) can evidently improve the stacking efficiency to both His and Trp.  相似文献   
34.
The synthesis, characterisation and polymerisation studies of a homologous series of α,ω-bis(pyrrolyl)alkanes are described. These α,ω-bis(pyrrolyl)alkanes were produced using Friedel-Crafts acylation followed by reduction of the carbonyl group using Red-Al®. Chemical polymerisation of the resultant dimers using FeCl3 produced poly(α,ω-bis(pyrrolyl)alkane) films, which were characterised by SEM, FTIR and tested for conductivity.  相似文献   
35.
This work highlights four different topics in modeling of DNA: (i) the importance of water and ions together with the structure and function of DNA; the hydration structure around the ions appears to be the determining factor in the ion coordination to DNA, as demonstrated in the results of our MD simulations; (ii) how MD simulations can be used to simulate single molecule manipulation experiments as a complement to reveal the structural dynamics of the studied biomolecules; (iii) how damaged DNA can be studied in computer simulations; and (iv) how repair of damaged DNA can be studied theoretically. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007  相似文献   
36.
Quantitative determination of ppb-order 10B was carried out in a small number of cultured tumor cells by particle tracks by the 10B(n,)7Li reactions using solid state nuclear track detector (SSNTD) for boron neutron capture therapy research. The detection limit of 10B concentration in tumor cells is less than 1·10-3 ppm under our experimental conditions which permits the quantitative determination of 10B in a small number of boronated tumor cells (105/ml = ca. 0.1 mg). Boron quantities in tumor cells determined were well compatible with the tumor cell killing effects of boron neutron capture therapy.  相似文献   
37.
Apple procyanidins were separated by high-speed counter-current chromatography using a type-J multilayer coil planet centrifuge. Several two-phase solvent systems with a wide range of hydrophobicities from a non-polar hexane system to polar n-butanol systems were evaluated their performance in terms of the partition coefficient and the retention of the phase. The best separation of procyanidins B and C was achieved with a two-phase solvent system composed of n-butanol-methyl tert.-butyl ether-acetonitrile-0.1% trifluoroacetic acid (2:4:3:8) using the lower phase as a mobile at a flow-rate of 1.0 ml/min.  相似文献   
38.
Hydrolysis procedure of N-phosphoryl phenylalanine (DIPP-Phe) was studied by HPLC-ESI-MS/MS. The results showed that (HO)(i-PrO)P(O)Phe was the main intermediate and the hydrolysis of DIPP-Phe also occurred through a penta-coordinate transition state.  相似文献   
39.
Two equivalents of the thermally stable silylene Si[(NCH2But)2C6H4-1,2] (1) react with pyridine to yield the 1-aza-2,3-disilacyclobutane derivative (2), which is labile and slowly rearranges via a 1,3-H shift to the 2-pyridyldisilane (3). A similar reaction of 1 with quinoline gives 1-aza-2,3-disilacyclobutane derivative (4), which is stable. The X-ray structures of 2 and 3 are discussed.  相似文献   
40.
采用示差脉冲伏安法,在乳酸脱氢酶(LDH)酶促体系“丙酮酸盐 + NADH +H+ (?) 乳酸盐 + NAD+”中,通过检测NAD+还原峰电流的变化,测定了不同条件下(不同酶用量、缓冲液pH值以及温度)LDH的活性、酶促体系的米氏常数KmNADH以及最大反应速率vmax。并且在最佳实验条件下,通过检测LDH活性的改变,实验考察了3种纳米物质(ZnS,TiO2(R)和TiO2(A))对乳酸脱氢酶酶促体系的影响。  相似文献   
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