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51.
Y Aye EJ Brignole MJ Long J Chittuluru CL Drennan FJ Asturias J Stubbe 《Chemistry & biology》2012,19(7):799-805
Highlights? Expression/isolation of active human RNR-α from mammalian cells is developed ? Strategy unveils Clofarabine mechanism and in-cell-relevance of α-oligomerization ? Independent biochemical and structural methods document in-cell-assembled α-hexamers ? Drug-induced hexameric states have remarkable kinetic stability 相似文献
52.
The reaction of the fluorescent macrocyclic ligand 1,8-bis(anthracen-9-ylmethyl)-1,4,8,11-tetraazacyclotetradecane with copper(II) salts leads to formation of the Cu(DAC)2+ cation (I), which is not luminescent. However, when aqueous methanol solutions of I are allowed to react with NO, fluorescence again develops, owing to the formation of the strongly luminescent N-nitrosated ligand DAC-NO (II), which is released from the copper center. This reaction is relatively slow in neutral media, and kinetics studies show it to be first order in the concentrations of NO and base. In these contexts, it is proposed that the amine nitrosation occurs via NO attack at a coordinated amine that has been deprotonated and that this step occurs with concomitant reduction of the Cu(II) to Cu(I). DFT computations at the BP/LACVP* level support these mechanistic arguments. It is further proposed that such nitrosation of electron-rich ligands coordinated to redox-active metal centers is a mechanistic pathway that may find greater generality in the biochemical formation of nitrosothiols and nitrosoamines. 相似文献
53.
INDO parameterized calculations of nJ(19F15N) are reported where n=1, 2, 3, 4 and 5. The calculations are performed within the sum-over-states perturbation and self-consistent perturbation frameworks. In general, satisfactory agreement between both sets of calculated results and the available experimental data is obtained. All of the 1 J(19F15N) and 4J(19F15N) couplings can be of either sign. Most of the couplings considered are dominated by the contact contribution but the non-contact interactions can be very important in certain cases. 相似文献
54.
Here we report a fast and effective method to visualize interactive proteins across intact mammalian cells via on-site formation of fluorescence using instant reaction of non-fluorescent fluorescamine with primary amines on proteins. Without interference by fluorescence background, this fluorogenic labelling opens a way for selective identification of primary amine-rich interacting proteins, efficient mapping and real-time monitoring of their spatial distribution in assemblies/network, and fast differentiation of cellular types. Without adverse effect on biological functions, this labelling method also provides new insights to comprehend important aspects of cellular functions of organelles and their relation to health imperfections for disease diagnostics and imaging-guided therapy. 相似文献
55.
Noriyuki Fujima Daisuke Yoshida Tomohiro Sakashita Akihiro Homma Akiko Tsukahara Khin Khin Tha Kohsuke Kudo Hiroki Shirato 《Magnetic resonance imaging》2014
Purpose
To investigate the correlation between perfusion-related parameters obtained with intravoxel incoherent motion (IVIM) and classical perfusion parameters obtained with dynamic contrast-enhanced (DCE) magnetic resonance imaging in patients with head and neck squamous cell carcinoma (HNSCC), and to compare direct and asymptotic fitting, the pixel-by-pixel approach, and a region of interest (ROI)-based approach respectively for IVIM parameter calculation.Materials and methods
Seventeen patients with HNSCC were included in this retrospective study. All magnetic resonance (MR) scanning was performed using a 3 T MR unit. Acquisition of IVIM was performed using single-shot spin-echo echo-planar imaging with three orthogonal gradients with 12 b-values (0, 10, 20, 30, 50, 80, 100, 200, 400, 800, 1000, and 2000). Perfusion-related parameters of perfusion fraction ‘f’ and the pseudo-diffusion coefficient ‘D*’ were calculated from IVIM data by using least square fitting with the two fitting methods of direct and asymptotic fitting, respectively. DCE perfusion was performed in a total of 64 dynamic phases with a 3.2-s phase interval. The two-compartment exchange model was used for the quantification of tumor blood volume (TBV) and tumor blood flow (TBF). Each tumor was delineated with a polygonal ROI for the calculation of f, f ? D* performed using both the pixel-by-pixel approach and the ROI-based approach. In the pixel-by-pixel approach, after fitting each pixel to obtain f, f ? D* maps, the mean value in the delineated ROI on these maps was calculated. In the ROI-based approach, the mean value of signal intensity was calculated within the ROI for each b-value in IVIM images, and then fitting was performed using these values. Correlations between f in a total of four combinations (direct or asymptotic fitting and pixel-by-pixel or ROI-based approach) and TBV were respectively analyzed using Pearson's correlation coefficients. Correlations between f ? D* and TBF were also similarly analyzed.Results
In all combinations of f and TBV, f ? D* and TBF, there was a significant correlation. In the comparison of f and TBV, a moderate correlation was observed only between f obtained by direct fitting with the pixel-by-pixel approach, whereas a good correlation was observed in the comparisons using the other three combinations. In the comparison of f ? D* and TBF, a good correlation was observed only with f ? D* obtained by asymptotic fitting with the ROI-based approach. In contrast, moderate correlations were observed in the comparisons using the other three combinations.Conclusion
IVIM was found to be feasible for the analysis of perfusion-related parameters in patients with HNSCC. Especially, the combination of asymptotic fitting with the ROI-based approach was better correlated with DCE perfusion. 相似文献56.
For the Σ–Σ–α system we theoretically look into the possible existence of a quasi-bound state in the framework of Faddeev calculations. We are particularly interested in the state of total iso-spin T=2, because there is no strong conversion between Ξ–N–α and ${\Lambda-\Lambda-\alpha}$ . An analytic continuation using the point method is applied to search the eigenvalue in the complex energy plane. In our results the Σ–Σ–α three-body system has two quasi-bound states (J π = 0+) where, depending on the potential parameters in the Nijmegen NSC97 model potential, the energy ranges between ?1.4 and ?2.4 MeV and the level width is about 0.4 MeV for the ground state. In addition, we obtained the excited state at ?0.15 MeV (width 4 MeV). 相似文献
57.
Than Sint Khin 《Journal of Mathematical Analysis and Applications》2009,354(1):220-228
We consider propagation property for anisotropic diffusion equation with convection in 2 dimension,
t∂(um)−x1∂(|x1∂u|p1−1x1∂u)−x2∂(|x2∂u|p2−1x2∂u)+uα−1x1∂u=0, 相似文献
58.
Synthesis, characterization and cell-biomarker applications for a novel series of comb-copolymers featuring hydrophobic amide side groups, carboxylates and other functionalities such as polymerizable side chains and PEG oligomers are reported. When used as polymer ligand shell for trioctylphosphine oxide (TOPO) coated quantum dots (QDs) these copolymers effectively solubilise CdSe/ZnS QDs in water. A systematic study was carried out to find the relation between the molecular structure of the copolymers, their ability to coat the QDs, and to suspend the nanocrystals in water. To demonstrate potential applications, highly luminescent QD/polymer assemblies were internalized into living and fixed cells. 相似文献
59.
Self-consistent perturbation calculations of 70 1J(CC) values are reported within the INDO framework. A least-squares agreement between the calculated and observed couplings, for a variety of bond multiplicities, provides values of 13.503 au?6 and 5.072 au?6 for (SC2(O))2 and 〈r?3〉C2, respectively. The non-contact terms are found to be important in cases of multiple bonding. 相似文献
60.
Self-consistent perturbation calculations within the INDO framework are reported for 63 15N? 13C coupling constants. Examples are presented for which each of the contact, orbital and dipolar terms provides the dominant contribution to the observed coupling constant. In general, good agreement with the experimental data is obtained when the integral products SN2(O)SC2(O) and 〈r?3〉N〈r?3〉C take the values 14.480 au?6 and 2.446 au?6 for 1J(15N? 13C), and the corresponding values of 10.444 au?6 and 17.664 au?6 for 1J(15N?13C). All 19 of the 1J(15N?13C) couplings considered are predicted to have a negative sign. 相似文献