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排序方式: 共有136条查询结果,搜索用时 31 毫秒
91.
Annik Bergeron Milton Furtado Fabio Garofolo 《Rapid communications in mass spectrometry : RCM》2009,23(9):1287-1297
Internal standards (IS) with similar physicochemical properties to the analyte provide multiple advantages in liquid chromatography/tandem mass spectrometric (LC/MS/MS) bioanalytical methods such as: reduction of the analysis run time, improvement in the intra‐injection reproducibility, impact reduction of matrix and ionization effects. However, it is important to evaluate the purity of the IS prior to their use. Indeed, a minor impurity in the IS may lead to an important issue during bioanalytical method development. Stable labelled internal standards are usually appropriate IS for bioanalysis. The use of oxycodone‐D3, ursodiol‐D5 and atovaquone‐D4 as internal standards in three different bioanalytical methods was evaluated. During oxycodone, oxymorphone and noroxycodone simultaneous quantification method development, oxymorphone was identified as a contaminant in oxycodone‐D3. Since the limit of quantification for oxymorphone was very low (10 pg/mL), the presence of an even low percentage of oxymorphone in oxycodone‐D3 leads to the change of the stable labelled IS for an analogue, ethylmorphine. 23‐Nordeoxycholic acid was preferred to ursodiol‐D5 as internal standard for the ursodiol, tauroursodiol and glycoursodiol simultaneous quantification method. Indeed, more than 7% of ursodiol was identified in the ursodiol‐D5 which could not be bypassed by decreasing the IS concentration without compromising the linearity. An atovaquone‐D4 reference standard revealed the non‐negligible presence of atovaquone‐D5 to atovaquone‐D8 that has a large impact on the method validation. Therefore, atovaquone‐D4 was sent for recertification since its isotopic purity was found to be much less than the isotopic purity mentioned on its certificate of analysis. Consequently, during bioanalytical method development, the purity of the IS should be scrutinized. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
92.
In this paper, we show how to endow the algebra of noncommutative symmetric functions with a natural structure of cochain complex which strongly relies on the combinatorics of ribbons, and we prove that the corresponding complexes are acyclic. 相似文献
93.
A Convenient Approach to Stereoisomeric Iminocyclitols: Generation of Potent Brain‐Permeable OGA Inhibitors
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Milan Bergeron‐Brlek Dr. Jake Goodwin‐Tindall Nevena Cekic Dr. Christian Roth Dr. Wesley F. Zandberg Dr. Xiaoyang Shan Dr. Vimal Varghese Sherry Chan Prof. Gideon J. Davies Prof. David J. Vocadlo Prof. Robert Britton 《Angewandte Chemie (International ed. in English)》2015,54(51):15429-15433
Pyrrolidine‐based iminocyclitols are a promising class of glycosidase inhibitors. Reported herein is a convenient epimerization strategy that provides direct access to a range of stereoisomeric iminocyclitol inhibitors of O‐GlcNAcase (OGA), the enzyme responsible for catalyzing removal of O‐GlcNAc from nucleocytoplasmic proteins. Structural details regarding the binding of these inhibitors to a bacterial homologue of OGA reveal the basis for potency. These compounds are orally available and permeate into rodent brain to increase O‐GlcNAc, and should prove useful tools for studying the role of OGA in health and disease. 相似文献
94.
95.
96.
R. F. Bergeron 《Studies in Applied Mathematics》1970,49(2):197-203
Some inviscid flows with the combined shear and periodic disturbance characteristic of the Kelvin “eat's eye” pattern are presented. The solutions have constant vorticity in each region of closed streamlines, with discontinuities in vorticity (but not velocity) allowed across boundaries. 相似文献
97.
Accurate quantum-mechanical wavepacket results are reported for two collinear A + BC → A + B + C dissociation models. Both systems are of the MO EXP (Morse oscillator, exponentially repulsive interaction) type and thus do not allow for the possibility of reaction. One of these models has been previously subjected to a semiclassical study by Rusinek and Roberts. In the present paper, dissociation probabilities from vibrational states υ = 0, 1 and 3 of the diatomic are reported in a wide energy range for both systems. Numerous state-to-state transition probabilities are also given and the results are compared to those of related studies. 相似文献
98.
The Grothendieck group of the tower of symmetric group algebras has a self-dual graded Hopf algebra structure. Inspired by this, we introduce by way of axioms, a general notion of a tower of algebras and study two Grothendieck groups on this tower linked by a natural paring. Using representation theory, we show that our axioms give a structure of graded Hopf algebras on each Grothendieck groups and these structures are dual to each other. We give some examples to indicate why these axioms are necessary. We also give auxiliary results that are helpful to verify the axioms. We conclude with some remarks on generalized towers of algebras leading to a structure of generalized bialgebras (in the sense of Loday) on their Grothendieck groups. 相似文献
99.
N. Bergeron 《Transformation Groups》2009,14(1):41-86
Let G be a connected semisimple group over . Given a maximal compact subgroup K ⊂ G() such that X = G()/K is a Hermitian symmetric domain, and a convenient arithmetic subgroup Γ ⊂ G(), one constructs a (connected) Shimura variety S = S(Γ) = Γ\X. If H ⊂ G is a connected semisimple subgroup such that H() / K is maximal compact, then Y = H()/K is a Hermitian symmetric subdomain of X. For each g ∈ G() one can construct a connected Shimura variety S(H, g) = (H() ∩ g
−1Γg)\Y and a natural holomorphic map j
g
: S(H, g) → S induced by the map H() → G(), h → gh. Let us assume that G is anisotropic, which implies that S and S(H, g) are compact. Then, for each positive integer k, the map j
g
induces a restriction map
In this paper we focus on classical Hermitian domains and give explicit criterions for the injectivity of the product of the
maps R
g
(for g running through G()) when restricted to the strongly primitive (in the sense of Vogan and Zuckerman) part of the cohomology. In the holomorphic
case we recover previous results of Clozel and Venkataramana [CV]. We also derive applications of our results to the proofs
of new cases of the Hodge conjecture and of new results on the vanishing of the cohomology of some particular Shimura variety. 相似文献
100.
The potential of five species of trees as historical monitors of heavy metal air pollution has been investigated. The study was carried out at a site 2 km from an industrial complex including several metal refineries. Using neutron activation, heavy metal concentrations were measured in the xylem as a function of the year of wood formation. The manganese concentrations were by far the highest. In maple trees the high natural level of this essential trace element masked any increases due to pollution. In ash and cedar increased Mn concentrations were found, relative to control trees, but there is evidence for radial translocation. In hemlock the time variations of the average Mn concentrations followed the production rates of the refineries but large variations among individual trees were observed. Hemlock was estimated to accumulate up to 0.3% of the atmospheric Mn input. 相似文献