883 research outputs found
Expectation values of single-particle operators in the random phase approximation ground state
We developed a method for computing matrix elements of single-particle
operators in the correlated random phase approximation ground state. Working
with the explicit random phase approximation ground state wavefunction, we
derived practically useful and simple expression for a molecular property in
terms of random phase approximation amplitudes. The theory is illustrated by
the calculation of molecular dipole moments for a set of representative
molecules.Comment: Accepted to J.Chem.Phy
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Isomeric triazines exhibit unique profiles of bioorthogonal reactivity.
Expanding the scope of bioorthogonal reactivity requires access to new and mutually compatible reagents. We report here that 1,2,4-triazines can be tuned to exhibit unique reaction profiles with biocompatible strained alkenes and alkynes. Computational analyses were used to identify candidate orthogonal reactions, and the predictions were experimentally verified. Notably, 5-substituted triazines, unlike their 6-substituted counterparts, undergo rapid [4 + 2] cycloadditions with a sterically encumbered strained alkyne. This unique, sterically controlled reactivity was exploited for dual bioorthogonal labeling. Mutually orthogonal triazines and cycloaddition chemistries will enable new multi-component imaging applications
A Comparison between the Zero Forcing Number and the Strong Metric Dimension of Graphs
The \emph{zero forcing number}, , of a graph is the minimum
cardinality of a set of black vertices (whereas vertices in are
colored white) such that is turned black after finitely many
applications of "the color-change rule": a white vertex is converted black if
it is the only white neighbor of a black vertex. The \emph{strong metric
dimension}, , of a graph is the minimum among cardinalities of all
strong resolving sets: is a \emph{strong resolving set} of
if for any , there exists an such that either
lies on an geodesic or lies on an geodesic. In this paper, we
prove that for a connected graph , where is
the cycle rank of . Further, we prove the sharp bound
when is a tree or a unicyclic graph, and we characterize trees
attaining . It is easy to see that can be
arbitrarily large for a tree ; we prove that and
show that the bound is sharp.Comment: 8 pages, 5 figure
Hypoxia modulates cholinergic but not opioid activation of G proteins in rat hippocampus
Intermittent hypoxia, such as that associated with obstructive sleep apnea, can cause neuronal death and neurobehavioral dysfunction. The cellular and molecular mechanisms through which hypoxia alter hippocampal function are incompletely understood. This study used in vitro [ 35 S]guanylyl-5′- O -(Γ-thio)-triphosphate ([ 35 S]GTPΓS) autoradiography to test the hypothesis that carbachol and DAMGO activate hippocampal G proteins. In addition, this study tested the hypothesis that in vivo exposure to different oxygen (O 2 ) concentrations causes a differential activation of G proteins in the CA1, CA3, and dentate gyrus (DG) regions of the hippocampus. G protein activation was quantified as nCi/g tissue in CA1, CA3, and DG from rats housed for 14 days under one of three different oxygen conditions: normoxic (21% O 2 ) room air, or hypoxia (10% O 2 ) that was intermittent or sustained. Across all regions of the hippocampus, activation of G proteins by the cholinergic agonist carbachol and the mu opioid agonist [D-Ala 2 , N-Met-Phe 4 , Gly 5 ] enkephalin (DAMGO) was ordered by the degree of hypoxia such that sustained hypoxia > intermittent hypoxia > room air. Carbachol increased G protein activation during sustained hypoxia (38%), intermittent hypoxia (29%), and room air (27%). DAMGO also activated G proteins during sustained hypoxia (52%), intermittent hypoxia (48%), and room air (43%). Region-specific comparisons of G protein activation revealed that the DG showed significantly less activation by carbachol following intermittent hypoxia and sustained hypoxia than the CA1. Considered together, the results suggest the potential for hypoxia to alter hippocampal function by blunting the cholinergic activation of G proteins within the DG. © 2007 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/57386/1/20312_ftp.pd
Synthesis of 5 : 6-hydroxy-flavonols - Part III
The synthesis of 3 : 5 : 6 : 3': 4'-pentahydroxy-flavone was already reported. The lower members of this group of 5 : 6-hydroxy flavonols with one and no hydroxyl group in the side-phenyl nucleus have now been prepared by Kostanecki's method. The characteristic properties are described
Conformational flexibility of longifolene
The flexibility of the bicyclo[2.2.1]heptane-based tricyclic bridged system in longifolene is analysed based on x-ray structural data. In this context, the molecular structure of three differently substituted longifolenes has been analysed. The highly substituentdependent conformation provides scope for the synthesis of a variety of commercially oriented products
Second-generation nitazoxanide derivatives: thiazolides are effective inhibitors of the influenza A virus
Aim: The only small molecule drugs currently available for treatment of influenza A virus (IAV) are M2 ion channel blockers and sialidase inhibitors. The prototype thiazolide, nitazoxanide, has successfully completed Phase III clinical trials against acute uncomplicated influenza. Results: We report the activity of seventeen thiazolide analogs against A/PuertoRico/8/1934(H1N1), a laboratory-adapted strain of the H1N1 subtype of IAV, in a cell culture-based assay. A total of eight analogs showed IC50s in the range of 0.14–5.0 μM. Additionally a quantitative structure–property relationship study showed high correlation between experimental and predicted activity based on a molecular descriptor set. Conclusion: A range of thiazolides show useful activity against an H1N1 strain of IAV. Further evaluation of these molecules as potential new small molecule therapies is justified
(2R*,3R*,4aS*,6aR*,11aS*,11bS*)-Methyl 2-acetoxy-11b-hydroxy-3,7-dimethyl-1,2,3,4,4a,5,6,6a,7,11,11a,11b-dodecahydrophenanthro[3,2-b]furan-3-carboxylate
In the title compound, C22H30O6, the conformation of the molecule is dictated by an intramolecular C—H⋯O contact. The crystal structure is stabilized via intermolecular C—H⋯O, O—H⋯O and C—H⋯π contacts
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