用NMR方法研究杂多酸HPA-23与谷胱甘肽的作用

早在70年代初,人们就发现杂多酸具有抗病毒活性.例如钨锑酸钠[NaSb_9W_(21)O_(86)]~(18-)有可能成为潜在的抗病毒化合物.非常有趣的是最近报道[NH_4]_(18)[NaSb_9W_(21)O_(86)]·24H_2O(结构代号为HPA-23)具有很高的抗爱滋病病毒活性,在法国已进入临床应用.但从分子水平研究杂多酸化合物抗病毒的机理,目前尚未见到国内外报道.而作为病毒可以广义地看作由一个蛋白外壳包裹,内部则为核酸.爱滋病病毒同样由两层蛋白所包裹,与宿主细胞发生吸附作用主要是通过外层包络蛋白(GP120),该蛋白的活性组分是一个由8个氨基酸组成

用NMR方法研究稀土离子对DPPC脂质体构象的影响

随着稀土元素在工农业中的广泛应用,稀土进入机体内的作用机理是人们日益关心的问题.而稀土对生物体的作用,首先是通过生物膜.因此研究稀土与生物膜的作用是阐明其生理过程的重要环节.生物膜的结构比较复杂,而磷脂脂质体却能表现出生物膜膜脂结构的许

M(EGTA)配合物的NMR研究

乙二醇-双-(α-氨基乙基醚)四乙酸(EGTA)是一种Ca~(2+)高选择性螯合剂,结合Ca~(2+)能力比Mg~(2+)强10~6倍,被认为是钙结合蛋白钙结合位的理想配位模型。Ca(EGTA)的晶体结构虽已确定,但其溶液结构仍不清楚。考虑Ca~(2+)离子半径(0.99

SEQUENCE STRUCTURE OF ETHYLENE-VINYL SUBSTITUTED COPOLYMER WITH C-13 NMR .4.

The substituent chemical shift (SCS) has been applied to the assignment of the C-13 NMR spectrum of chlorinated polyethylene (CPE). CPE of different chlorine contents has been employed and their sequence structure discussed. The results show that characteristic of CPE with medium chlorine content is the dichloroethane structure in molecular chain. SCS parameters have been obtained from the C-13 NMR spectra. It was found that the effects of chlorine content and temperature on SCS are negligible, but the substituent parameter S1 reduced by 0.39 ppm when C2Cl4 was added to solvent ODCB.

KALMAN FILTERING FOR RESOLUTION OF OVERLAPPING LINES IN INDUCTIVELY COUPLED PLASMA ATOMIC EMISSION-SPECTROMETRY

A Kalman filter was developed for resolving overlapping lines in inductively coupled plasma atomic emission spectrometry (ICP-AES) and evaluated experimentally with the determination of La in the presence of Ho, and Cu in the presence of Pr. The whiteness of the innovation sequence for an optimal filter was explored to be the criterion for the correction of the wavelength positioning errors which may occur in spectral scans. Under the conditions of the medium-resolution spectrometer and 1.5 pm step size in scans, the filter effectively resolved the Cu/Pr line pair having a small peak separation of 4.8 pm. For the La/Ho line pair with a peak distance of 9.8 pm, an unbiased estimate for La concentration was still obtained even when the signal-to-background ratio was down to 0.048. Favourable detection limits for real samples were achieved. Unstructured backgrounds were modeled theoretically and all spectral scans therefore did not require the correction for solvent.

A HIGH-RESOLUTION SOLID-STATE NMR-STUDY OF THE MISCIBILITY, MORPHOLOGY, AND TOUGHENING MECHANISM OF POLYSTYRENE WITH POLY(2,6-DIMETHYL-1,4-PHENYLENE OXIDE) BLENDS

An extended Goldman-Shen pulse sequence was used to observe indirectly the proton spin diffusion in the blends of polystyrene (PS) with poly(2,6-dimethyl-1,4-phenylene oxides) (PPO). The results indicate that the average distance between PS and PPO is less than 5 angstrom in the intimately mixed phase, but there are heterogeneous domains on a 100-angstrom scale. The data of spin relaxation of carbons, T1(C), for homopolymers and their blends suggest that there is a strong pi-pi electron conjugation interaction between the aromatic rings of PS and those of PPO, while the aromatic rings of PPO drive the aromatic rings of PS to move cooperatively. It is the cooperative motion that markedly improves the impact strength of PS.

A STUDY OF ION KINETIC-ENERGY SPECTROMETRY OF ORTHO-DICHLORO, META-DICHLORO AND PARA-DICHLORO BENZENE DOUBLY CHARGED IONS [C6H4CL2]2+ AND [C6H3CL]2+ IN GAS-PHASE

The unimolecular Charge separation reactions of the doubly charged ions [C6H4Cl2]2+, [C6H3Cl]2+ produced in the ion source by electron impact from o-, m-, and p-dichloro benzene have been studied using mass analysed ion kinetic energy spectrometry. The values of kinetic energy releases (T) can be calculated from the energy dispersion of product ions. As T essentially reflects the release of coulombic energy, which can be used to calculate the approximate distances R between the two charges immediately before decomposition of the ions. From these data, some structural information about transiton states could be provided. The ECID and CID processes of above doubly charged ions, have also been studied. We found that the CID reactions of (C6H4Cl2)2+ could be used to distinguish three dichloro benzene isomers.

C-13 NMR CHARACTERIZATION OF SOLUBLE POLYANILINE

A high-resolution C-13 n.m.r. spectrum of soluble polyaniline in DMF-d7 solution was recorded. The assignment for the various resonance peaks in the spectrum was tentatively performed and the chain structure of polyaniline was analysed. It has been shown that the main chain of pristine state polyaniline is composed of alternating benzoid-quinoid and successive benzoid-quinoid sequences with the former being present in greater concentration. The sequence distribution is random. In addition to the benzoid-type and quinoid-type structures, there is a small amount of other structural units in the main chain.

EVALUATION OF THE RELIABILITY OF KALMAN FILTERING RESULTS IN INDUCTIVELY COUPLED PLASMA ATOMIC EMISSION-SPECTROMETRY

This paper deals with the evaluation of the reliability of the analytical results obtained by Kalman filtering. Two criteria for evaluation were compared: one is based on the autocorrelation analysis of the innovation sequence, the so-called NAC criterion; the other is the innovations number, which actually is the autocorrelation coefficient of the innovation sequence at the initial wavelength. Both criteria allow compensation for the wavelength positioning errors in spectral scans, but there exists a difference in the way they work. The NAC criterion can provide information about the reliability of an individual result, which is very useful for the indication of unmodelled emissions, while the innovations number should be incorporated with the normalization of the innovations or seek the help of the sequence itself for the same purpose. The major limitation of the NAC criterion is that it does not allow the theoretical modelling of continuous backgrounds, which, however, is convenient in practical analysis and can be taken with the innovations number criterion.

NMR-STUDIES ON THE COORDINATION OF RARE-EARTHS WITH GLYCYL-DL-VALINE AND THE CONFORMATION OF THEIR COMPLEX IN AQUEOUS-SOLUTION

In this paper lanthanide-induced shifts have been measured for C-13 and H-1 nuclei of glycyl-DL-valine in the presence of three lanthanide cations (La3+, Ho3+ and Yb3+) in aqueous solution. The stability constants of the coordination compounds of rare earths (Ho, Yb) with glycyl-DL-valine have been calculated. The coordination of rare earths with the ligand has been discussed. The simulation for conformation of lanthanide coordination compounds with glycyl-DL-valine shows that the ligand is coordinated to lanthanide ion through oxygen atoms of carboxyl group and the bond length of Ln-O is 0.226 nm. In the coordination compounds glycyl-DL-valine is in extended state with minimal steric hindrance.

SOLID-STATE C-13 NMR-STUDIES ON THE CONDENSATION AND SULFONATION OF FURFURYL ALCOHOL AND TRIS (2-HYDROXYETHYL) ISOCYANURATE

The condensation and sulfonation of furfuryl alcohol (FA) and FA with tris (2-hydroxyethyl) isocyanurate (THEIC) and the crosslinking product structures were studied by means of solid-state C-13 NMR. The reaction of formalin with FA linear oligomer terminated by 2-methyl furan took place in the presence of the phase transfer catalyst (C4H9)4N+I-. The reaction of the terminated oligomer with a large amount of sulfuric acid as well as the former reaction was examined. The effects of some main reaction conditions on the crosslinking condensation and sulfonation were also discussed.

C-13 AND H-1 NMR STUDIES OF SOLUTION STRUCTURE OF LANTHANIDE COMPLEX WITH GLYCYL-GLYCINE

C-13 and H-1 NMR technique was used to study the interaction of Gly-Gly with heavy lanthanide cations Dy3+, Ho3+, Er3+, Tm3+ and Yb3+ in aqueous solution. The stability constants for the 1:1 and 1:2 complexes of Gly-Gly with Ho3+ and Yb3+ were determined from the titration curves of chemical shift versus concentration ratio of lanthanide to Gly-Gly. The solution structure of the Ln-Gly-Gly complex was analyzed based upon the C-13 and H-1 lanthanide induced shifts and the results show that in the complex Gly Gly is coordinated to the lanthanide ion through the carboxyl oxygens with the backbone of the ligand in an extended state.

A STUDY OF ION KINETIC ENERGY SPECTROMETRY OF FERROCENE DOUBLY CHARGED IONS IN GAS PHASE

The unimolecular charge separation reactions of the doubly charged ions FeC10H102+, FeC10H theta 2+, FeC10H82+ produced in the ion source by electron impact from ferrocene have been studied using Mass analyzed Ion Kinetic Energy Spectrometry (MIKES) technique. From the values of the kinetic energy releases (T), the intercharge distances (R) of the exploding doubly charged ions in their transition structures have been estimated and some structural informations about the transition states can be obtained. The collision induced reactions of the FeC10H102+ ion with Ar have been studied using MIKES, we postulate a new type of continuing reaction which may be "collisional charge separation induced dissociation".

用NMR方法研究稀土离子对DPPC脂质体极性基团构象的影响

稀土对生物体的作用首先是通过生物膜,因此研究稀土与生物膜的作用是阐明其生理过程的重要环节.~2H四极劈裂和稀土位移试剂两种方法的研究结果表明,二棕榈酸磷酯酰胆碱(DPPC)的极性基团在金属离子的作用下,由原来的平行于膜平

环氧乙烷--四氢呋喃无规共聚醚结构研究 Ⅰ．液体共聚醚链结构的NMR分析

环氧乙烷(EO)与四氢呋喃(TO)的端羟基液体共聚醚(ETO),其流动性好,粘结性强,易固化,燃烧完全以及热稳定性较好,是固体推进剂的优质粘合剂。本工作对M_n为2000～6000不同组份的ETO,制备30%(V/V)的CDC13溶液,用Unity—400 NMR谱仪,定量测定了ETO链结构各组成参数及其序列分布。