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1.
The spatial structure of a covalent adduct — the product of intracomplex alkylation at N-3-position of dC-8 nucleoside residue of target octanucleotide pd[TGTTTGGC] by means of 4-[N-methyl-N-(2-chloroethyl)amino]benzyl-5′-phosphamido derivative of heptanucleotide pd[CCAAACA] — has been investigated in aqueous solution by two-dimensional (2D)1H-NMR spectroscopy and restrained molecular mechanics calculations. By using COSY, COSY-DQF and NOESY experiments the assignment of oligonucleotide protons as well as protons of modifying group was carried out. The correlation times of benzylamide fragment protons and those of neighbouring nucleotide residues dC-1 and dC-8 were shown to be equal and shorter thanτ c of intraduplex nucleotides. The analysis of proton-proton coupling constants for H1′, H2′a, H2′b and H3′ protons showed all sugar residues to be in 2′-endo conformation. The distances between protons closed in the space were determined by means of a set of one-dimensional (1D) NOE experiments. The experimental distances were used as the constraints for energy minimization by molecular mechanics calculations. Eight conformations of benzylamide fragment of the covalent adduct differed with orientations of 4-N-methyl residue of the alkylating group and 1-methyleneamide linker function were constructed as starting structures in energy minimization procedure. Among of the resulting optimized structures only one S(Alk)8* was found to satisfy both experimental data and energetic criteria. The benzylamide fragment in conformation S(Alk)8* has been shown to localize in the region of lacked nucleoside residue of the duplex at the end of heptanucleotide chain less than 5 Å apart from the residues dC-1 and alkylated dC-8.  相似文献   

2.
With the help of an SU(3) dynamicalalgebraic structure, we ~nd an exact solutionof the Milburn equationfor the system of a three-levelatom in the [1] configuration interacting with one quantized field mode with arbitrary detuning ,The exact solution is then used to discuss the influence of the intrinsic decoherence on the nonclassical properties of the system,such as collapes and revivals of the atomic populations,oscillations of the photon number distribution,and squeezing of the radiation field.  相似文献   

3.
The effect of micrestructure on the glass temperature Tg of poly (α-methyl styrene) has been investigated. It has been observed that Tg increases as the syndiotacticity of the molecule increases-thus Tg = 446 ± 2°K for polymer with 67% syndiotactic placements, while a value of Tg = 453 ± 2°K is found for a sample with 95% syndiotactic placements. Coefficients of expansion for the liquid and glassy states have been calculated and from these a chain stiffness parameter δε/k has been estimated using the Gibbs-DiMarzio theory. The result indicates that the flex energy of the α-methyl styrene chain is 20% larger than for the polystyrene chain.  相似文献   

4.
5.
The stable isotope content of samples of precipitation and of the river water throughout the Piracicaba basin in Brazil was measured over a two-year period. The isotope values of precipitation follow a consistent pattern of relatively depleted values of both deuterium and oxygen 18 during the rainy summers and enriched ones during the dry winters, with all values aligned slightly above the Global Meteoric Water Line. The isotopic composition of the river water throughout the basin shows a remarkable spatial coherence and much smaller scatter of data than those of the precipitation. The isotope composition of river water is close to that of the precipitation in the rainy season, however, with a consistent lower d-excess value by 1‰–2‰. This is attributed to evaporative water loss in the basin, in part an expression of the recycling of water due to the anthropogenic activity in the region. The more divergent values are recorded during high-water stages in the rivers. In many cases, the floods during the beginning of the rainy season are characterized by an enrichment of the heavy isotopes and lower d-excess values when compared to the precipitation, with the opposite situation later in the rainy season. This is interpreted as resulting from the watershed/riverflow interaction pattern, and it thus suggests that the isotope composition can monitor the hydrologic situation in the basin and its changes.  相似文献   

6.
7.
B. Syed  D. Catoor  R. Mishra 《哲学杂志》2013,93(12):1499-1522
Magnesium bicrystals were grown with symmetric and asymmetric tilt boundaries about the [10–10] axis using the vertical Bridgman technique. Isothermal constant load tensile tests were conducted on these bicrystals in the temperature range 300–500°C and relative displacements of the two grains were measured to obtain an appreciation for grain boundary motion characteristics. Coupled grain boundary motion was noted in almost all cases with the degree of tangential motion versus migration changing with tilt misorientation, temperature and applied stress. Specifically, within the family of symmetric bicrystals evaluated, a minimum in grain boundary displacement in the specimen plane was observed at a tilt misorientation of 20°. In specific stress/temperature regimes, rigid body sliding was observed for the particular case of a 35° asymmetric tilt misorientation. The ease of basal and prism slip in magnesium at the temperatures considered and the consequential impingement of intragranular dislocations on the bicrystal boundary and their decomposition and motion along the boundary are thought to play an important role in the observed coupled motion of these tilt boundaries.  相似文献   

8.
We have obtained the Raman spectra of the Calix[n]arene C60 complex of anti-conformation.Very different interactions between C60 and calix[n]arene (n=4,8) have been found from the vibratory spectroscopy,which are more complicated than those reported in previous works.It is interesting to find three low frequency modes,i.e.the spheroidal,torsional and E2 clearly shown at 39,130 and 208cm^-1,respectively.It is primarily interpreted as a relaxation effect of calix[8]arene framework for C60 where the intramolecular bridge between C60 and calix[8]arene are partly packed and two axes of c60([100] and [101]) are changed from the original configuration.The change of the vibratory environment of the carbon atom of C60 created some new modes.The Hg5 mode(at 1101cm^-1) and Hg2(at 431cm^-1) have been split and some modes (Ag2 and other six Hg modes) were hidden.  相似文献   

9.
Macroscopic, microscopic, goniometric, qualitative spectrographic and quantitative chemical data of kettnerite [2] with some new observations are given. The unit cell dimensions determined from the powder and rotating crystal photographs area 0=b 0=5.36±0.02 Å,c 0=13.59±0.03 Å. There are four molecules in the unit cell. The crystal structure of kettnerite was studied from the ordinary and generalized projections of the Patterson function along the [010] axis. Direct evidence of tetragonal layers (Ca. 2 F, Ca) and (Bi, 2 O, Bi) parallel to the basal face was found. The spatial arrangement of these layers corresponds to the symmetry of the space groupP 4/nmm. These layers alternate in the [001] direction being interleaved by single CO3 layers. Both the biaxial character of the mineral and the uncertainty concerning the rotation of the CO3 groups indicate a lower, most probably an orthorhombic symmetry. The highest possible symetry is that ofCmma. The structure is related to that of the typeX 1 found by Sillén et al. for several bismuth oxyhalides and especially to that of bismutite.
CaBi[OF¦ CO3]
, , , [2] . , :a 0=b 0=5,36±0,02 Å, 0=13,59±0,03 Å;Z=4. [010]. (Ca, 2 F, ) (Bi, 2 O, Bi), (010). 4/. , 3. 3 . C. , , 1, .


We wish to express gratitude to our colleagues Dr. A. Línek and Ing. C. Novák (Institute of Technical Physics, Czech. Acad. Sci.) for the use of the M1 equipment [11]. We are also very grateful to Mr. Z. iký for carrying out most of the numerical calculations.  相似文献   

10.
For the biosynthetic preparation of 14C-erucic acid (C21H41COOH) by means of rape plants cv. sollux the plants were supplied with 14CO2 and additionally fed with 14C-Sodium acetate after anthesis. After saponification of the extracted lipids the erucic acid was isolated and purified. The substance was identified by gas chromatography. The incorporation of the applied radioactivity (34 MBq 14CO2; 37 MBq14C-natrium acetate) into the fatty acids amounted to 1,2 per cent. The eruric acid could be isolated from the fatty acids mixture with a specific radioactivity of 1,001 MBq/mmol and a purity of 97,2 per cent.  相似文献   

11.
The fluorescence behavior of a calix[6]arene with a dansyl group as fluorescence marker (C6-DA) was investigated with respect to the inclusion properties of alkaloids as atropine and cocaine. A strong hypsochromic shift of the fluorescence band and a strong increase in fluorescence intensity is connected with the interaction of atropine to the lower rim of the C6-DA. The fluorescence increase is saturated at an atropine concentration above the 1:1 complex formation. Addition of cocaine to the complexed atropine-C6-DA leads to a decrease of the fluorescence intensity which could be explained by an exchange mechanism of the complexed molecules. The complexation of the atropine (the “belladonna effect”) is interpreted by electrostatic interaction (proton transfer from the carboxylic group to the nitrogen) with important contribution from hydrogen bonding by the guest OH-group.  相似文献   

12.
13.
Infrared and Raman spectra of CO[dbnd] 3 ions are different in the two crystallographic forms of CaCO3 Calcite and Aragonite owing to their different site symmetries. Due to this fact, i.r. has been used to assess the reversible Calcite ← → Aragonite transformation which occurs upon grinding of CaCO3, and much work has been done in this field in the last few years(1-4). In the present paper data are reported on Raman spectra of Calcite and Aragonite forms of CaCO3 produced by the above mechanical procedure.  相似文献   

14.
《Ultrasonics sonochemistry》2014,21(4):1451-1460
A convenient one-pot protocol was developed for the synthesis of 1H-spiro[furo[3,4-b]pyridine-4,3′-indoline]-3-carbonitrile derivatives. This reaction was carried out through a three component condensation reaction of isatins, malononitrile, and anilinolactones in the presence of a catalytic amount of Et3N as an inexpensive and available basic catalyst in THF under ultrasound irradiation. The products were obtained in high yields and short reaction times. The main advantage of this synthetic method is that the obtained products in ultrasonic irradiations are different from classical heating.  相似文献   

15.
利用同步辐射角分辨光电子能谱(SRARPES)对6H-SiC(0001)-6[KF(]3[KF)]×6[KF(]3[KF)] R30°重构表面的电子结构和表面态进行了研究.通过鉴别价带谱中来自于体态的信息,可以推断出重构表面的费米能级位于体态价带顶之上(2.1±0.1)eV处.实验测出的体能带结构与理论计算的结果较为符合.在重构表面上发现三个表面态,分别位于结合能-0.48 eV(S0),-1.62 eV(S1)和-4. 关键词: 角分辨光电子能谱 碳化硅(SiC) 电子结构 表面态  相似文献   

16.
The dynamic shear behavior of poly (ethylene terephthalate) (PET) has been investigated in the 4.2—300°K temperature region using a freely oscillating torsion pendulum at frequencies of 0.4 to 2 cps. Uniaxial stretching (draw ratio 3:1) of an amorphous specimen resulted in the appearance of a definite maximum in both the damping, δ, and the loss modulus, G', at 30°K (0.7 cps). Filled unstretched PET samples exhibited small loss maxima in the 50—90°K region. For biaxially stretched heat-set specimens the splitting of the β-damping peak (220°K, 1 cps) is found to depend on the orientations of molecular chain axes with respect to the torsion axis.  相似文献   

17.
In the framework of applying econophysics ideas in religious topics, the finances of the Antoinist religious movement organised in Belgium between 1920 and 2000 are studied. The interest of investigating financial aspects of such a, sometimes called, sect stems in finding characteristics of conditions and mechanisms under which definitely growth andand decay features of communities can be understood. The legally reported yearly income and expenses between 1920 and 2000 are studied. A three wave asymmetric regime is observed over a trend among marked fluctuations at times of crises. The data analysis leads to the proposition of a general mechanistic model taking into account an average GDP growth, oscillatory monetary inflation and a logistic population drift.  相似文献   

18.
19.
Recently,fundamental properties and practical applications of two-dimensional(2D)materials have attracted tremendous interest.Micro/nanostructures and functional devices in 2D materials have been fabricated by various methods.Ultrafast direct laser writing(DLW)with the advantages of rich light-matter interactions;unique three-dimensional processing capability;arbitrary-shape design flexibility;and minimized thermal effect,which enables high fabrication accuracy resolution,has been widely applied in the fabrication of 2D materials for multifunctional devices.This timely review summarizes the laser interactions with 2D materials and the advances in diverse functional photonics devices by DLW.The perspectives and challenges in designing and improving laser-fabricated 2D material photonic devices are also discussed.  相似文献   

20.
Electronic bands belonging to the [20.4]3Φ→(1)3Δ system have been observed in the emission spectrum of lanthanum monofluoride at high temperature in the presence of the Ar+ 457.9-nm laser line: the (0-0), (1-1), (2-2), and (3-3) bands of the 3Φ43Δ3 subsystem and the (0-0) bands of the 3Φ33Δ2 and 3Φ23Δ1 subsystems. Rotational structures which are well developed in these experimental conditions were analyzed. The data were treated using a polynomial expression for the upper levels term-values, directly at equilibrium for 3Φ4, whereas a previous Hamiltonian matrix representation of the (1)3Δ state was assumed. A Hund's case (a) representation of the [20.4]3Φ state at v=0 was also considered. Perturbations affecting 3Φ2 levels at v=0 were observed; the energy and rotational constant of the perturbing state and the interaction parameter were estimated.  相似文献   

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