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61.
Siwei Wang Jesse Ward Sven Leyffer Stefan M. Wild Chris Jacobsen Stefan Vogt 《Journal of synchrotron radiation》2014,21(3):568-579
A novel approach to locate, identify and refine positions and whole areas of cell structures based on elemental contents measured by X‐ray fluorescence microscopy is introduced. It is shown that, by initializing with only a handful of prototypical cell regions, this approach can obtain consistent identification of whole cells, even when cells are overlapping, without training by explicit annotation. It is robust both to different measurements on the same sample and to different initializations. This effort provides a versatile framework to identify targeted cellular structures from datasets too complex for manual analysis, like most X‐ray fluorescence microscopy data. Possible future extensions are also discussed. 相似文献
62.
Anthony D. Appelhans John E. Olson David A. Dahl Michal B. Ward Troy A. Robinson James E. Delmore 《Journal of Radioanalytical and Nuclear Chemistry》2018,315(2):207-209
A new isotope separator has been designed, constructed, and put into routine operation for separation of 133Xe providing a major advancement and significant cost reduction in preparation of this radioactive isotope. The design features and advantages are discussed that expedite high purity separation of relatively small quantities of this isotope. These advantages could be easily used to expedite separation of other shorter-lived radioactive isotopes. 相似文献
63.
8E,10E-Dodecadienyl-tri-n-butylamonium and -tri-n-butylphosphonium methanesulfonates were prepared and shown to be effective phase transfer catalysts. After reaction the catalysts can be removed quantitatively from the organic phase by addition of a silica gelimmobilized triazolinedione dienophile followed by filtration. 相似文献
64.
N. H. Ladizesky Y. Chaoting I. M. Ward 《Journal of Macromolecular Science: Physics》2013,52(1-2):185-213
Isotropic monofilaments of linear polyethylene were subjected to electron irradiation in different atmospheres at a range of dose levels. It was found that the gel content remained very small up to a dose of about 2.5 Mrad (the gel point), and thereafter increased with irradiation dose in a manner similar to that found by other workers. Drawing of the irradiated filaments was very dependent on dose level, and high draw ratios of 30:1 could not be obtained above the gel point. Although irradiation of the spun monofilaments increased the initial tensile modulus of the drawn material to a small extent, neither the tensile strength nor the shear strength of the monofilaments (the latter measured with a pull-out adhesion technique) was significantly affected. On the other hand, the tensile strain at failure decreased dramatically as the irradiation dose was increased. The results are discussed in terms of our present state of knowledge regarding the structure and properties of highly drawn linear polyethylene, taking into consideration the cross-linking produced by the irradiation. 相似文献
65.
Dr. Renata Kaczmarek Samuel Ward Dipra Debnath Taisiya Jacobs Alexander D. Stark Dariusz Korczyński Prof. Dr. Anil Kumar Prof. Dr. Michael D. Sevilla Dr. Sergey A. Denisov Dr. Viacheslav Shcherbakov Dr. Pascal Pernot Prof. Dr. Mehran Mostafavi Prof. Dr. Roman Dembinski Prof. Dr. Amitava Adhikary 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(43):9495-9505
The directionality of the hole-transfer processes between DNA backbone and base was investigated by using phosphorodithioate [P(S−)=S] components. ESR spectroscopy in homogeneous frozen aqueous solutions and pulse radiolysis in aqueous solution at ambient temperature confirmed initial formation of G.+-P(S−)=S. The ionization potential of G-P(S−)=S was calculated to be slightly lower than that of guanine in 5′-dGMP. Subsequent thermally activated hole transfer from G.+ to P(S−)=S led to dithiyl radical (P-2S.) formation on the μs timescale. In parallel, ESR spectroscopy, pulse radiolysis, and density functional theory (DFT) calculations confirmed P-2S. formation in an abasic phosphorodithioate model compound. ESR investigations at low temperatures and higher G-P(S−)=S concentrations showed a bimolecular conversion of P-2S. to the σ2-σ*1-bonded dimer anion radical [-P-2S 2S-P-]− [ΔG (150 K, DFT)=−7.2 kcal mol−1]. However, [-P-2S 2S-P-]− formation was not observed by pulse radiolysis [ΔG° (298 K, DFT)=−1.4 kcal mol−1]. Neither P-2S. nor [-P-2S 2S-P-]− oxidized guanine base; only base-to-backbone hole transfer occurs in phosphorodithioate. 相似文献
66.
Ariadna Lázaro Cristina Balcells Dr. Josefina Quirante Prof. Josefa Badia Prof. Laura Baldomà Dr. Jas S. Ward Prof. Kari Rissanen Dr. Mercè Font-Bardia Prof. Laura Rodríguez Dr. Margarita Crespo Prof. Marta Cascante 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(9):1947-1952
Platinum-based chemotherapy persists to be the only effective therapeutic option against a wide variety of tumours. Nevertheless, the acquisition of platinum resistance is utterly common, ultimately cornering conventional platinum drugs to only palliative in many patients. Thus, encountering alternatives that are both effective and non-cross-resistant is urgent. In this work, we report the synthesis, reduction studies, and luminescent properties of a series of cyclometallated (C,N,N′)PtIV compounds derived from amine–imine ligands, and their remarkable efficacy at the high nanomolar range and complete lack of cross-resistance, as an intrinsic property of the platinacycle, against multiplatinum-resistant colorectal cancer (CRC) and castration-resistant prostate cancer (CRPC) metastatic cell lines generated for this work. We have also determined that the compounds are effective and selective for a broader cancer panel, including breast and lung cancer. Additionally, selected compounds have been further evaluated, finding a shift in their antiproliferative mechanism towards more cytotoxic and less cytostatic than cisplatin against cancer cells, being also able to oxidize cysteine residues and inhibit topoisomerase II, thereby holding great promise as future improved alternatives to conventional platinum drugs. 相似文献
67.
C. K. Chang Brian Ward Richard Young Michail P. Kondylis 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(10-11):1307-1326
Heme reactivity in hemoproteins is governed by the microenvironment near the ligand binding site. In order to quantify polarity effects on heme ligand binding, the kinetics of O2 and CO binding have been measured for a series of synthetic heme models equipped with a range of groups of varying dipole moments positioned near the heme coordination site. For hemes with polar aprotic groups, both O2 on (k′) and off rates (k) are found to be dependent on the dipole moment. For model systems containing protic groups, the O2 off rate is substantially reduced due to hydrogen bonding with the coordinated O2. The hydrogen-bonding stabilization is estimated to be 0.7 and 1.6 kcal/mol for an alcohol and a secondary amide, respectively. CO binding displays little correlation with a polarity effect; instead it seems to depend upon the size and position of the polar group. 相似文献
68.
We report the synthesis of three new dipyrrinone imine analogues and the characterisation of their self-association properties. Based on vapour pressure osmometry and nuclear magnetic resonance studies, placing the imine functional group at C(9) of the dipyrrinone disrupts the native self-association of the dipyrrinone core in a manner that correlates with the conformational A-value of the imine N-substituent. 相似文献
69.
The syntheses, characterization and metal ion complexation and extraction capabilities of six new calix[4]arene Schiff base compounds, 5–10, are reported. The preparation of the compounds was achieved by the condensation of 5,17-diamino-11,23-di-tert-butyl-25,27-di-n-butoxy-26,28-dihydroxycalix[4]arene with the appropriate aldehyde (5-bromosalicylaldehyde for 5, 4-anisaldehyde for 6, 4-(dimethylamino)benzaldehyde for 7, 9-anthracenecarboxaldehyde for 8, 1-pyrenecarboxaldehyde for 9, and 9-fluorenecarboxaldehyde for 10) in refluxing ethanol. The compounds were characterized by 1H and 13C NMR spectroscopy, IR spectroscopy, high-resolution mass spectrometry and elemental analysis. The X-ray crystal structures of 7, 8 and 9 (as dichloromethane solvates) revealed that the calixarene molecules adopt H-bond stabilized, distorted-cone conformations and form centrosymmetric dimers in the solid state. Compounds 5–10 did not form host–guest complexes with NEt4[(bdt)MoO2(OSiPh3)] (bdt2–=benzene-1,2-dithiolate), a potential precursor for biologically relevant oxosulfido-Mo(VI/V) enzyme models; such host–guest complexes have the potential to stabilize these sought-after but highly reactive model compounds. In addition, the capabilities of 5–10 to extract selected metal ions (Ni2+, Co2+, Cu2+, Zn2+, Ag+, Pb2+, Cd2+ and Hg2+) from an aqueous into an organic phase have been assessed by picrate extraction experiments. Compound 5 displayed exceptional selectivity towards Ni2+, compound 7 exhibited enhanced extraction towards all of the metal ions tested and compounds 6, 9 and 10 showed very high selectivity towards Hg2+. On the other hand, compound 8 exhibited negligible capacity to extract any of the metal ions tested. 相似文献
70.
Gyula Dekany Karen Wright Peter Ward Istvan Toth 《Journal of carbohydrate chemistry》2013,32(4):383-398
Abstract Sialyl Lewis X (SLex) analogs 2a and 2b were synthesised, where the N-acetyl-D-glucose and the D-galactose units of SLex 1 were replaced with an alkyl and a heteroalkyl spacer. Sulphate ester 6i was also synthesised from alcohol 6b and chlorosulphonic acid. A novel promoter, silver mercaptoethanesulphonate, was used to synthesise α-sialosides 2c. 7b and 7c. 相似文献