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排序方式: 共有1605条查询结果,搜索用时 17 毫秒
1.
Daniel Cardenas Anna Turyanskaya Mirjam Rauwolf Arash Panahifar David Cooper Gregory R. Wohl Christina Streli Peter Wobrauschek Ana Pejović-Milić 《X射线光谱测定》2020,49(3):424-433
Strontium-based medications, such as strontium ranelate, have been suggested to have therapeutic effects in patients with osteoporosis. Strontium salts available off-shelf in stores across North America are assumed to provide similar effects as strontium ranelate and thus should lead to similar distributions of elemental strontium incorporated in bone. The objective of this study was to compare the spatial distribution of strontium in animal bones following the administration of strontium ranelate and strontium citrate. Seventeen-week-old Sprague–Dawley rats were split into three groups over 10 weeks and given 625 mg/kg/day of strontium ranelate and 676 mg/kg/day of strontium citrate; the control group received no additional supplementary strontium. The humeri were collected from all animals, and strontium distribution was mapped using 2D micro-XRF and 3D dual energy K-edge subtraction (KES) imaging. 2D and 3D elemental mapping methods demonstrated that strontium delivered during treatment by both salts had the same spatial distribution. 3D elemental strontium maps of treated animal bones showed that strontium was largely observed in the trabecular regions under the epiphyseal (growth) plate. The thickness of the strontium layers in both the strontium ranelate and strontium citrate sample was not significantly different (p = .9201). 2D micro-XRF and 3D dual-energy KES images effectively elucidated the spatial distribution of elemental strontium in calcified tissue. These methods provide a novel approach to evaluating the potential efficacy of strontium supplements in the treatment of osteoporosis. 相似文献
2.
3.
Dr. Rebecca L. Greenaway Dr. Valentina Santolini Dr. Filip T. Szczypiński Dr. Michael J. Bennison Dr. Marc A. Little Andrew Marsh Dr. Kim E. Jelfs Prof. Andrew I. Cooper 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(17):3718-3722
Molecular dumbbells with organic cage capping units were synthesised via a multi-component imine condensation between a tri-topic amine and di- and tetra-topic aldehydes. This is an example of self-sorting, which can be rationalised by computational modelling. 相似文献
4.
5.
Sven Heiles Richard J. Cooper Matthew J. DiTucci Evan R. Williams 《Chemical science》2015,6(6):3420-3429
Hydration of gaseous guanidinium (Gdm+) with up to 100 water molecules attached was investigated using infrared photodissociation spectroscopy in the hydrogen stretch region between 2900 and 3800 cm–1. Comparisons to IR spectra of low-energy computed structures indicate that at small cluster size, water interacts strongly with Gdm+ with three inner shell water molecules each accepting two hydrogen bonds from adjacent NH2 groups in Gdm+. Comparisons to results for tetramethylammonium (TMA+) and Na+ enable structural information for larger clusters to be obtained. The similarity in the bonded OH region for Gdm(H2O)20
+
vs. Gdm(H2O)100
+ and the similarity in the bonded OH regions between Gdm+ and TMA+ but not Na+ for clusters with <50 water molecules indicate that Gdm+ does not significantly affect the hydrogen-bonding network of water molecules at large size. These results indicate that the hydration around Gdm+ changes for clusters with more than about eight water molecules to one in which inner shell water molecules only accept a single H-bond from Gdm+. More effective H-bonding drives this change in inner-shell water molecule binding to other water molecules. These results show that hydration of Gdm+ depends on its local environment, and that Gdm+ will interact with water even more strongly in an environment where water is partially excluded, such as the surface of a protein. This enhanced hydration in a limited solvation environment may provide new insights into the effectiveness of Gdm+ as a protein denaturant. 相似文献
6.
Caitlin E. Shields Dr. Xue Wang Dr. Thomas Fellowes Rob Clowes Dr. Linjiang Chen Prof. Graeme M. Day Prof. Anna G. Slater Dr. John W. Ward Dr. Marc A. Little Prof. Andrew I. Cooper 《Angewandte Chemie (International ed. in English)》2023,62(34):e202303167
Hydrogen-bonded organic frameworks (HOFs) with low densities and high porosities are rare and challenging to design because most molecules have a strong energetic preference for close packing. Crystal structure prediction (CSP) can rank the crystal packings available to an organic molecule based on their relative lattice energies. This has become a powerful tool for the a priori design of porous molecular crystals. Previously, we combined CSP with structure-property predictions to generate energy-structure-function (ESF) maps for a series of triptycene-based molecules with quinoxaline groups. From these ESF maps, triptycene trisquinoxalinedione (TH5) was predicted to form a previously unknown low-energy HOF (TH5-A) with a remarkably low density of 0.374 g cm−3 and three-dimensional (3D) pores. Here, we demonstrate the reliability of those ESF maps by discovering this TH5-A polymorph experimentally. This material has a high accessible surface area of 3,284 m2 g−1, as measured by nitrogen adsorption, making it one of the most porous HOFs reported to date. 相似文献
7.
Donglin He Chengxi Zhao Dr. Linjiang Chen Dr. Marc A. Little Dr. Samantha Y. Chong Rob Clowes Katherine McKie Mark G. Roper Graeme M. Day Dr. Ming Liu Prof. Andrew I. Cooper 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(41):10589-10594
Ethyl acetate is an important chemical raw material and solvent. It is also a key volatile organic compound in the brewing industry and a marker for lung cancer. Materials that are highly selective toward ethyl acetate are needed for its separation and detection. Here, we report a trianglimine macrocycle ( TAMC ) that selectively adsorbs ethyl acetate by forming a solvate. Crystal structure prediction showed this to be the lowest energy solvate structure available. This solvate leaves a metastable, “templated” cavity after solvent removal. Adsorption and breakthrough experiments confirmed that TAMC has adequate adsorption kinetics to separate ethyl acetate from azeotropic mixtures with ethanol, which is a challenging and energy-intensive industrial separation. 相似文献
8.
Stephen P. Cooper Kevin I. Booker‐Milburn 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(22):6596-6600
Polyheterocycles are found in many natural products and are useful moieties in functional materials and drug design. As part of a program towards the synthesis of Stemona alkaloids, a novel palladium(II)‐catalyzed C H activation strategy for the construction of such systems has been developed. Starting from simple 1,3‐dienyl‐substituted heterocycles, a large range of polycyclic systems containing pyrrole, indole, furan and thiophene moieties can be synthesized in a single step. 相似文献
9.
10.
Dr. Aleksander Rebane Geoffrey Wicks Dr. Mikhail Drobizhev Dr. Thomas Cooper Aleksander Trummal Dr. Merle Uudsemaa 《Angewandte Chemie (International ed. in English)》2015,54(26):7582-7586
We present a new approach for determining the strength of the dipolar solute‐induced reaction field, along with the ground‐ and excited‐state electrostatic dipole moments and polarizability of a solvated chromophore, using exclusively one‐photon and two‐photon absorption measurements. We verify the approach on two benchmark chromophores N,N‐dimethyl‐6‐propionyl‐2‐naphthylamine (prodan) and coumarin 153 (C153) in a series of toluene/dimethyl sulfoxide (DMSO) mixtures and find that the experimental values show good quantitative agreement with literature and our quantum‐chemical calculations. Our results indicate that the reaction field varies in a surprisingly broad range, 0–107 V cm?1, and that at close proximity, on the order of the chromophore radius, the effective dielectric constant of the solute–solvent system displays a unique functional dependence on the bulk dielectric constant, offering new insight into the close‐range molecular interaction. 相似文献