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排序方式: 共有484条查询结果,搜索用时 15 毫秒
111.
Cho KB Chen H Janardanan D de Visser SP Shaik S Nam W 《Chemical communications (Cambridge, England)》2012,48(16):2189-2191
DFT calculated barriers for C-H activation of 1,4-cyclohexadiene by nonheme iron(IV)-oxo and iron(III)-superoxo species show that the experimental trends can be explained if the spin inversion probability of the TMC iron(IV)-oxo is assumed to be poor. Also, the TMC iron(III)-superoxo reaction proceeds with an endothermic O(2)-binding energy followed by an intrinsically reactive quintet state. 相似文献
112.
Gonzalez-Ovalle LE Quesne MG Kumar D Goldberg DP de Visser SP 《Organic & biomolecular chemistry》2012,10(28):5401-5409
Density functional theory (DFT) calculations are presented on biomimetic model complexes of cysteine dioxygenase and focus on the effect of axial and equatorial ligand placement. Recent studies by one of us [Y. M. Badiei, M. A. Siegler and D. P. Goldberg, J. Am. Chem. Soc. 2011, 133, 1274] gave evidence of a nonheme iron biomimetic model of cysteine dioxygenase using an i-propyl-bis(imino)pyridine, equatorial tridentate ligand. Addition of thiophenol, an anion - either chloride or triflate - and molecular oxygen, led to several possible stereoisomers of this cysteine dioxygenase biomimetic complex. Moreover, large differences in reactivity using chloride as compared to triflate as the binding anion were observed. Here we present a series of DFT calculations on the origin of these reactivity differences and show that it is caused by the preference of coordination site of anion versus thiophenol binding to the chemical system. Thus, stereochemical interactions of triflate and the bulky iso-propyl substituents of the ligand prevent binding of thiophenol in the trans position using triflate. By contrast, smaller anions, such as chloride, can bind in either cis or trans ligand positions and give isomers with similar stability. Our calculations help to explain the observance of thiophenol dioxygenation by this biomimetic system and gives details of the reactivity differences of ligated chloride versus triflate. 相似文献
113.
Bente A. Somsen Fenna W. B. Craenmehr Wei-Hong W. Liu Auke A. Koops Marloes A. M. Pennings Emira J. Visser Christian Ottmann Peter J. Cossar Luc Brunsveld 《Chemical science》2022,13(44):13122
Molecular glues represent an evolution in drug discovery, however, targeted stabilization of protein complexes remains challenging, owing to a paucity of drug design rules. The functional mapping of hotspots has been critical to protein–protein interaction (PPI) inhibitor research, however, the orthogonal approach to stabilize PPIs has not exploited this information. Utilizing the hub protein 14-3-3 as a case study we demonstrate that functional mapping of hotspots provides a triage map for 14-3-3 molecular glue development. Truncation and mutation studies allowed deconvoluting the energetic contributions of sidechain and backbone interactions of a 14-3-3-binding non-natural peptide. Three central 14-3-3 hotspots were identified and their thermodynamic characteristics profiled. In addition to the phospho-binding pocket; (i) Asn226, (ii) Lys122 and (iii) the hydrophobic patch formed by Leu218, Ile219 and Leu222 were critical for protein complex formation. Exploiting this hotspot information allowed a peptide-based molecular glue that elicits high cooperativity (α = 36) and selectively stabilizes the 14-3-3/ChREBP PPI to be uniquely developed.The functional mapping of a 14-3-3 protein complex, by means of peptide truncations and point mutations, as an approach to identify critical hotspots regions for 14-3-3 molecular glue drug design. 相似文献
114.
A rapid and sensitive high-performance liquid chromatographic method for the analysis of beta- and gamma-cyclodextrin in aqueous biological fluids such as plasma, urine, or tissue homogenate is described. The chromatographic system consists of a microBondapak Phenyl column as stationary phase and a mobile phase of water with 10% methanol. After post-column addition of an alkaline solution of phenolphthalein, negative colorimetric detection is used. The elution solvent and post-column reagent were mixed in a capillary tubing of 1.5 m (1.0 mm I.D.). Two methods of sample treatment are given, one for large (1.0 ml) and one for small (0.1 ml) sample volumes. Both methods were shown to be linear and reproducible. The detection limit for beta-cyclodextrin was 1.0 microgram/ml (0.77 nmol/ml). The method was used in the determination of some pharmacokinetic parameters of beta-cyclodextrin in rats after intravenous injection. 相似文献
115.
116.
A. R. Ball D. Gignoux F. E. Kayzel D. Schmitt A. de Visser 《Journal of magnetism and magnetic materials》1992,110(3):337-342
Magnetization measurements in fields up to 38 T performed at low temperature on single crystals of the hexagonal Pr(Ni1-xCox)5 compounds for x = 0, 0.05, 0.10 and 0.20 are presented. In PrNi5 we observe highly original behaviour predicted by the knowledge of the Crystalline Electric Field parameters and arising from the existence of a non-magnetic singlet ground state; namely transitions associated with the field induced “anticrossing” and “crossing” of the two lowest states along the [100] and [120] directions, respectively. The measurements performed on the other compounds have allowed us to study the dependence of this behaviour on Co substitutions. 相似文献
117.
Theodorus W. J. Gadella Arie van Hoek Antonie J. W. G. Visser 《Journal of fluorescence》1997,7(1):35-43
The construction of a homodyne frequency domain fluorescence lifetime imaging microscope is described. The system consists
of (i) an intensity-modulated laser excitation source, (ii) an epifluorescence microscope, (iii) a gain-modulated microchannel
plate (MCP) image intensifier, and (iv) a slow-scan CCD camera. The phase and modulation homogeneity of the MCP image intensifier
were determined at frequencies of 40, 100, 160, and 240 MHz. The detected modulation depths were 65, 52, 32, and 23%, respectively,
and were highly homogeneously distributed. The phasedistribution image revealed iris effects at frequencies of 160 and 240
MHz but was homogeneous at lower frequencies. Lifetime imaging of a solution of the fluorescent flavoprotein lipoamide dehydrogenase
demonstrated (i) the accuracy of the determined lifetimes (< 60 ps), (ii) the time resolution of the instrument (< 50 ps),
and (iii) the average precision for single pixel fluorescence lifetimes (50 ps is feasible). The imaging of tiny fluorescent
microspheres revealed that even in a volume of 0.3 x 10-15 L, the standard error in the lifetimes can be as low as 79 ps. The spatial resolution of the instrument is estimated to be
< 400 nm in the object plane at a 100 x magnification. 相似文献
118.
Matt Visser 《Physics letters. [Part B]》1985,159(1):22-25
We discuss an exotic class of Kaluza-Klein models in which the internal space is neither compact nor even of finite volume. Rather than using the usual compact internal space we consider the case where particles are gravitationally trapped near a four-dimensional submanifold of the higher-dimensional spacetime. A specific model exhibiting this phenomenon is constructed in five dimensions. 相似文献
119.
O. Visser L. Visscher P. J. C. Aerts W. C. Nieuwpoort 《Theoretical chemistry accounts》1992,81(6):405-416
Summary Results and details of molecular Fock-Dirac-(Breit) calculations on CH4, SiH4, GeH4, SnH4, and PbH4 obtained with the MOLFDIR© program package are presented and compared with other calculations and experimental results. The relativistic ground state energies (including the Breit interaction) of the atoms C, Si, Ge, Sn, and Pb, necessary for reference purposes, have been calculated using a small relativistic CI. One of our findings is that for the heavier systems perturbation theory over-estimates the relativistic bond length contraction. The Breit interaction has only a small effect on the bond lengths. 相似文献
120.