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Welch G. State A. Ilie A. Kok-Lim Low Lastra A. Cairns B. Towles H. Fuchs H. Ruigang Yang Becker S. Russo D. Funaro J. van Dam A. 《Multimedia, IEEE》2005,12(3):22-35
Immersive electronic books (IEBooks) for surgical training will let surgeons explore previous surgical procedures in 3D. The authors describe the techniques and tools for creating a preliminary IEBook, embodying some of the basic concepts. 相似文献
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Kerry J. Adams Thomas D. McGrath Georgina M. Rosair Andrew S. Weller Alan J. Welch 《Journal of organometallic chemistry》1998,550(1-2)
Analysis of the structures of 8,8-(PPh3)2-8,7-nido-RhSB9H10 and 9,9-(PPh3)2-9,7,8-nido-RhC2B8H11 by RMS misfit calculations has confirmed that these rhodaheteroboranes possess nido 11-vertex cluster geometries in apparent contravention of Wade's rules. However, examination of the molecular structures of both species shows that the {RhP2} planes are inclined by ca. 66° with respect to the metal-bonded SB3 or CB3 faces, and that two weak ortho-CHRh agostic interactions occupy the vacant co-ordination position thereby created. As a consequence of these agostic bonds the Rh atom, and hence the overall cluster, is provided with an additional electron pair, meaning that their nido structures are now fully consistent with Wade's rules. The chelated diphosphine compound 8,8-(dppe)-8,7-nido-RhSB9H10 is similar to the PPh3 compound in showing the same agostic bonding. Attempts to prepare a bis-P(OMe)3 analogue result in ligand scavenging and the formation of 8,8,8-{P(OMe)3}3-8,7-nido-RhSB9H10. Similarly, reaction between Cs[6-arachno-SB9H12] and RhCl(dmpe)CO does not result in CO loss but in formation of 8,8-(dmpe)-8-(CO)-8,7-nido-RhSB9H10, shown to exist as a mixture of two of three possible rotamers. Deprotonation of 8,8-(PPh3)2-8,7-nido-RhSB9H10 and 8,8-(dppe)-8,7-nido-RhSB9H10 with MeLi yields the anions [1,1-(PPh3)2-1,2-closo-RhSB9H9]− and [1,1-dppe-1,2-closo-RhSB9H9]−, respectively, with octadecahedral cage structures. It is argued that anion formation causes the agostic bonding to be `switched-off' and results in the cluster adopting the closo architecture predicted by Wade's rules. This structural change is fully reversible on reprotonation, and if reprotonation of [1,1-(dppe)-1,2-closo-RhSB9H9]− is carried out in MeCN, the product 8,8-(dppe)-8-(MeCN)-8,7-nido-RhSB9H10 forms. Interestingly, 8,8-(dppe)-8-(MeCN)-8,7-nido-RhSB9H10 reconverts to 8,8-(dppe)-8,7-nido-RhSB9H10 on standing in CDCl3, suggesting that the agostic bonding is sufficiently strong to displace co-ordinated MeCN. All new compounds are fully characterised by multinuclear NMR spectroscopy and, in many cases, by single crystal X-ray diffraction. 相似文献
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Single p-toluic acid pendant groups were attached to 1,4,7,10,13-pentaazacyclopentadecane (15aneN5) and 1,4,8,11-tetraazacyclotetradecane (cyclam) to prepare bifunctional reagents for radiolabeling monoclonal antibodies with (64,67)Cu. The ligands are 1,4,7,10,13-pentaazacyclopentadecane-1-(alpha-1,4-toluic acid) (PCBA) and 1,4,8,11-tetraazacyclotetradecane-1-(alpha-1,4-toluic acid) (CPTA). For the parent macrocycles and their pendant arm derivatives, the 1:1 Cu(2+) complexes dissociate only below pH 2. At pH 0.0 and 25 degrees C the CPTA-Cu complex has a half-life toward complete dissociation of 24 days. A new approach was developed for the estimation of the Cu(2+) stability constant for the kinetically robust CPTA. All other formation constants were determined at 25.0 degrees C with batch spectrophotometric techniques. Potentiometric titrations were used to determine the protonation constants of the macrocyclic ligands as well as of the metal chelates. The protonation constants, stability constants, and pM's are discussed in terms of both molecular mechanics calculations and the ligands' potential applicability as copper(II) radiopharmaceuticals. 相似文献
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Alex Yashkin Josep Rayo Larson Grimm Martin Welch Michael M. Meijler 《Chemical science》2021,12(12):4570
In recent years, the world has seen a troubling increase in antibiotic resistance among bacterial pathogens. In order to provide alternative strategies to combat bacterial infections, it is crucial deepen our understanding into the mechanisms that pathogens use to thrive in complex environments. Most bacteria use sophisticated chemical communication systems to sense their population density and coordinate gene expression in a collective manner, a process that is termed “quorum sensing” (QS). The human pathogen Pseudomonas aeruginosa uses several small molecules to regulate QS, and one of them is N-butyryl-l-homoserine lactone (C4-HSL). Using an activity-based protein profiling (ABPP) strategy, we designed biomimetic probes with a photoreactive group and a ‘click’ tag as an analytical handle. Using these probes, we have identified previously uncharacterized proteins that are part of the P. aeruginosa QS network, and we uncovered an additional role for this natural autoinducer in the virulence regulon of P. aeruginosa, through its interaction with PhzB1/2 that results in inhibition of pyocyanin production.Short-chain reactive probes can be used as tools to shed new light on virulence mechanisms in bacterial pathogens. 相似文献
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Parameters for the commercially available modeling package SYBYL have been developed for Gd(3+) complexes allowing these to be studied with molecular mechanics. With these parameters and a technique termed the "coordination scan", the coordination numbers of Gd(III) based complexes can be predicted, and thus the hydration number q determined. Knowledge of q has allowed the prediction of molar relaxivities based on correlations to literature values. In addition, the calculated value DeltaE(coord) was found to successfully predict the thermodynamic stability constants for polyamino carboxylate ligands with Gd(3+). Gadolinium complexes are commonly utilized as MRI contrast agents, and thus the techniques utilized in this work should aid in the development of new contrast agents. 相似文献
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