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排序方式: 共有489条查询结果,搜索用时 218 毫秒
1.
Prof. Margaret A. Brimble Dr. Pat J. Edwards Dr. Paul W. R. Harris Dr. Gillian E. Norris Dr. Mark L. Patchett Tom H. Wright Dr. Sung‐Hyun Yang Dr. Sarah E. Carley 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(9):3556-3561
The first total synthesis of glycocin F, a uniquely diglycosylated antimicrobial peptide bearing a rare S‐linked N‐acetylglucosamine (GlcNAc) moiety in addition to an O‐linked GlcNAc, has been accomplished using a native chemical ligation strategy. The synthetic and naturally occurring peptides were compared by HPLC, mass spectrometry, NMR and CD spectroscopy, and their stability towards chymotrypsin digestion and antimicrobial activity were measured. This is the first comprehensive structural and functional comparison of a naturally occurring glycocin with an active synthetic analogue. 相似文献
2.
Radiofluorination of a Pre‐formed Gallium(III) Aza‐macrocyclic Complex: Towards Next‐Generation Positron Emission Tomography (PET) Imaging Agents 下载免费PDF全文
Dr. Rajiv Bhalla Prof. William Levason Dr. Sajinder K. Luthra Dr. Graeme McRobbie George Sanderson Prof. Gillian Reid 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(12):4688-4694
As part of a study to investigate the factors influencing the development of new, more effective metal‐complex‐based positron emission tomography (PET) imaging agents, the distorted octahedral complex, [GaCl(L)]?2 H2O has been prepared by reaction of 1‐benzyl‐1,4,7‐triazacyclononane‐4,7‐dicarboxylic acid hydrochloride (H2L?HCl) with Ga(NO3)3?9 H2O, which is a convenient source of GaIII for reactions in water. Spectroscopic and crystallographic data for [GaCl(L)]?2 H2O are described, together with the crystal structure of [GaCl(L)]?MeCN. Fluorination of this complex by Cl?/F? exchange was achieved in high yield by treatment with KF in water at room temperature over 90 minutes, although the reaction was complete in approximately 30 minutes if heated to 80 °C, giving [GaF(L)]?2 H2O in good yield. The same complex was obtained by hydrothermal synthesis from GaF3?3 H2O and Li2L, and has been characterised by single‐crystal X‐ray analysis, IR, 1H and 19F{1H} NMR spectroscopy and ESI+ MS. Radiofluorination of the pre‐formed [GaCl(L)]?2 H2O has been demonstrated on a 210 nanomolar scale in aqueous NaOAc at pH 4 by using carrier‐free 18F?, leading to 60–70 % 18F‐incorporation after heating to 80 °C for 30 minutes. The resulting radioproduct was purified easily by using a solid‐phase extraction (SPE) cartridge, leading to 98–99 % radiochemical purity. The [Ga18F(L)] is stable for at least 90 minutes in 10 % EtOH/NaOAc solution at pH 6, but defluorinates over this time scale at pH of approximately 7.5 in phosphate buffered saline (PBS) or human serum albumin (HSA). The subtle role of the Group 13 metal ion and co‐ligand donor set in influencing the pH dependence of this system is discussed in the context of developing potential new imaging agents for PET. 相似文献
3.
The Development of Appropriate Upscaling Procedures 总被引:1,自引:0,他引:1
Permeability upscaling should be carried out with careful attention to the nature of rock heterogeneities. While there are many large-scale features which must be taken into account, there are also important heterogeneities at the small-scale. Many sedimentary structures contain laminae at the mm–cm scale, and beds at the m-scale, which give rise to strong contrasts in permeability. We use a 2D model derived from a photo-panel of an aeolian outcrop, along with permeability measurements from a North Sea oil field, to demonstrate the effects of small-scale heterogeneity. This model is similar in size to a typical cell of a reservoir geological model. We take imaginary probe and core plug measurements from the model, average them, and compare these with the effective permeability for the model computed from a finite difference flow calculation. Although this procedure is standard practice, we show that it can lead to biased estimates of the permeabilities used in flow simulation. As an alternative we suggest using models of representative beds, and performing flow simulation to calculate effective permeabilities for both single-phase and two-phase flow. 相似文献
4.
Jikun Li Xinxin Feng Wei Zhu Nikita Oskolkov Tianhui Zhou Boo Kyung Kim Noman Baig Prof. Michael T. McMahon Prof. Eric Oldfield 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(1):264-271
Diamagnetic chemical exchange saturation transfer (CEST) contrast agents offer an alternative to Gd3+‐based contrast agents for MRI. They are characterized by containing protons that can rapidly exchange with water and it is advantageous to have these protons resonate in a spectral window that is far removed from water. Herein, we report the first results of DFT calculations of the 1H nuclear magnetic shieldings in 41 CEST agents, finding that the experimental shifts can be well predicted (R2=0.882). We tested a subset of compounds with the best MRI properties for toxicity and for activity as uncouplers, then obtained mice kidney CEST MRI images for three of the most promising leads finding 16 (2,4‐dihydroxybenzoic acid) to be one of the most promising CEST MRI contrast agents to date. Overall, the results are of interest since they show that 1H NMR shifts for CEST agents—charged species—can be well predicted, and that several leads have low toxicity and yield good in vivo MR images. 相似文献
5.
Andrew L. Hector William Levason Mark E. Light Gillian Reid Kripasindhu Sardar Wenjian Zhang 《无机化学与普通化学杂志》2013,639(6):906-910
Crystalline CrOCl3 contains [Cl2OCr(μ‐Cl)2CrOCl2] molecules with two square pyramidal CrOCl4 units sharing a common edge and with the Cr–O arranged anti, a new structure type for transition metal MOX3 compounds. Crystals are monoclinic with space group P21/c, Z = 4, with a = 5.735(5), b = 13.738(7), c = 11.318(4) Å, α = 90°, β = 98.346(6)°, γ = 90°. Its IR and UV/Vis spectra are reported and compared with those of the C3v monomer found in the gas phase. Structures are also reported for M2[CrOCl5] (M = Cs or Rb) and show a pseudo‐octahedral anion. Cs2[CrOCl5] adopts a K2PtCl6‐type structure with [CrOCl5]2– ions randomly orientated, but Rb2[CrOCl5] is orthorhombic with space group Pnma with a = 13.6471(7), b = 9.9175(5), and c = 6.9562(4) Å. Rietveld refinement of the data on the rubidium salt gave Cr–O = 1.628(1), Cr–CltransO = 2.652(7), Cr–CltransCl = 2.239(8)–2.342(3) Å. Corresponding CrV oxide bromide species do not form. 相似文献
6.
7.
William Levason Gillian Reid Wenjian Zhang 《Coordination chemistry reviews》2011,255(11-12):1319-1341
The coordination chemistry of silicon(IV) and (II) and germanium(IV) and (II) halides with neutral donor ligands from groups 15 (N, P or As) and 16 (O, S or Se) is reviewed; N-heterocyclic carbene complexes are also included. The focus is mainly on results published after 1990 and illustrates that significant recent developments have been made in the coordination chemistry of low-valent silicon and germanium halide complexes in particular; this is expected to pave the way for much new reaction chemistry both from a fundamental and application-driven perspective. 相似文献
8.
9.
Lixin Zhang W.E. McMahon Y. Liu Y. Cai M.H. Xie N. Wang S.B. Zhang 《Surface science》2012,606(21-22):1728-1738
The lattice-misfit InN/GaN (0001) interface supports a triangular network of α-core 90° partial misfit dislocations. These misfit dislocations provide excellent strain relief. However, in their unreconstructed form the dislocation contains numerous high-energy N dangling bonds, which must be eliminated by reconstructing the dislocation core. Existing single-period (SP) and double-period (DP) dislocation reconstruction models eliminate these dangling bonds via a like-atom dimerization, such as N-N dimers. However, we show that these N–N dimers are unstable for the III-N materials, so an entirely new reconstruction mechanism is needed. A “triple-period” (TP) structural model is developed which eliminates N dangling bonds via the formation of N vacancies instead of N-N dimers. The model contains no N–N (or III–III) bonds, fully bonds all N atoms to four group-III neighboring atoms, and satisfies the “electron counting rule” by transferring charge from In dangling bonds to Ga dangling bonds. 相似文献
10.
The synthesis and coordination chemistry of a saturated analogue of a “bulky‐yet‐flexible” N‐heterocyclic carbene (NHC) ligand are described. “SIPaul” is a 4,5‐dihydroimidazol‐2‐ylidene ligand with unsymmetrical aryl N‐substituents, and is one of the growing class of “bulky‐yet‐flexible” NHCs that are sufficiently bulky to stabilize catalytic intermediates, but sufficiently flexible that they do not inhibit productive chemistry at the central metal atom. Here, the synthesis of SIPaul.HCl and its complexes with copper, silver, iridium, palladium, and nickel, and its selenourea, are reported. The steric impact of the ligand is quantified using percent buried volume (% Vbur), whereas the electronic properties are probed and quantified using the Tolman Electronic Parameter (TEP) and δSe of the corresponding selenourea. This work shows that despite the often very different performance of saturated versus unsaturated carbenes in catalysis, the effect of backbone saturation on measurable properties is very small. 相似文献