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排序方式: 共有897条查询结果,搜索用时 15 毫秒
1.
Edward G. Sheetz Zhao Zhang Alyssa Marogil Minwei Che Dr. Maren Pink Dr. Veronica Carta Prof. Dr. Krishnan Raghavachari Prof. Dr. Amar H. Flood 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(60):e202201584
The recognition of boron compounds is well developed as boronic acids but untapped as organotrifluoroborate anions (R−BF3−). We are exploring the development of these and other designer anions as anion-recognition motifs by considering them as substituted versions of the parent inorganic ion. To this end, we demonstrate strong and reliable binding of organic trifluoroborates, R−BF3−, by cyanostar macrocycles that are size-complementary to the inorganic BF4− progenitors. We find that recognition is modulated by the substituent's sterics and that the affinities are retained using the common K+ salts of R−BF3− anions. 相似文献
2.
Solid‐state 31P NMR investigation on the status of guanine nucleotides in paclitaxel‐stabilized microtubules
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Ga Hyang Lee Su Young Oh Kwon Joo Yeo Taslima Ferdous Meeyeon Cho Younkee Paik 《Magnetic resonance in chemistry : MRC》2015,53(5):330-336
Microtubule dynamics is a target for many chemotherapeutic drugs. In order to understand the biochemical effects of paclitaxel on the GTPase activity of tubulin, the status of guanine nucleotides in microtubules was investigated by 31P cross‐polarization magic angle spinning (CPMAS) NMR. Microtubules were freshly prepared in vitro in the presence of paclitaxel and then lyophilized in sucrose buffer for solid‐state NMR experiments. A 31P CPMAS NMR spectrum with the SNR of 25 was successfully acquired from the lyophilized microtubule sample. The broadness of the 31P spectral lines in the spectrum indicates that the molecular environments around the guanine nucleotides inside tubulin may not be as crystalline as reported by many diffraction studies. Deconvolution of the spectrum into four spectral components was carried out in comparison with the 31P NMR spectra obtained from five control samples. The spectral analysis suggested that about 13% of the nucleotides were present as GTP and 37% as GDP in the β‐tubulin (E‐site) of the microtubules. It was found that most of the GDPs were present as GDP‐Pi complex in the microtubules, which seems to be one of the effects of paclitaxel binding. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
3.
A new sample business survey for agriculture, the REA survey, and a project of integration with the FADN network (RICA in
Italy) have significantly changed the production of statistical information nowadays available with reference to the agricultural
sector. On the basis of this relevant information, new economic analyses are being developed on farms’ performance, agricultural
households’ income and the Common Agricultural Policy (CAP). In this paper the authors estimate the relationship between the
levels of variables of interest and their sampling errors using models in order to improve the accessibility of the information
on estimates accuracy to the final users (agricultural analysts, policy makers).
The paper is the result of a joint research of the three authors. Sections 1–3 and 6 by Pizzoli, Sects. 4 and 5 by Rondinelli,
Sect. 7 by Filiberti, conclusions joint to the three authors. 相似文献
4.
Veronica Felli Susanna Terracini 《Calculus of Variations and Partial Differential Equations》2006,27(1):25-58
This paper deals with a class of nonlinear elliptic equations involving a critical power-nonlinearity as well as a potential featuring multiple inverse square singularities. When the poles form a symmetric structure, it is natural we wonder how the symmetry affects such mutual interaction. The present paper means to study this aspect from the point of view of the existence of solutions inheriting the same symmetry properties as the set of singularities.
Mathematics Subject Classification (2000) 35J60, 35J20, 35B33 相似文献
5.
Veronica?StigssonEmail author G?ran?Kloow Ulf?Germg?rd Niclas?Andersson 《Cellulose (London, England)》2005,12(4):395-401
Controlling the reduction in molecular weight of the cellulose chains is essential in the production of carboxymethyl cellulose
(CMC). Such a reduction can be achieved by the addition of cobalt during the process of cobalt(II) ions, which act as a catalyst
for oxidative cleavage, and the influence thereof has been studied under a variety of conditions. This study has resulted
in a model that summarises the effects of the added amount of cobalt, the time for the cobalt reaction, the temperature in
the mercerisation stage of the CMC-manufacturing process and finally the effect of the temperature in the etherification stage.
It is shown that it is important for cobalt to be present during the mercerisation stage in order to achieve the desired viscosity. 相似文献
6.
The bond dissociation enthalpies (BDE) of several phenols containing electron-withdrawing substituents in the para position have been determined by means of the EPR radical equilibration technique. It has been found that CN, NO(2), CHO, COOR, and COOH induce an increase of the BDE value of the O-H bond, thus producing a worsening of the antioxidant activity of phenols, while Cl, Ph, and CH[double bond]CHPh show an opposite effect. The contributions of these substituents for the calculation of the BDE values in polysubstituted phenols by using the group additivity rule have also been derived. It is shown that this rule provides quite reliable predictions of bond strengths, so that the method can be conveniently used to estimate new data on substituted phenols. 相似文献
7.
We investigated the biomaterial and pharmaceutical utility of pure silk fibroin (SF) protein as a possible for separation, using Sephadex G-25 gel filtration chromatography and simply preparing SF microsphere particles (SFMP) by spray dryer. Also, some of its physicochemical properties and morphology were investigated. Obtaining microspheres and/or submicronic particles by spray dryer method was accelerated or completed with the transition from the random coil to the β-sheet structure during spray dryer treatment. It was identified by the basic Fourier transform infrared spectroscopy of SFMP. The various pH range of SFMP’s swelling ratio is dependent on the pH of the solution, not on the occurred gelation. Morphologically, SFMP was spherical in shape, and particles, average 2±10 μm in size, were observed by scanning electron microscope and particle analyzer, respectively. The average molecular weight (MW) of pure SF protein dissolved in calcium chloride is about 61,500 g/mol as measured by gel permeation chromatography. 相似文献
8.
Jeong JO Byun J Jeon ES Gwon HC Lim YS Park J Yeo SJ Lee YJ Kim S Kim DK 《Experimental & molecular medicine》2002,34(4):278-284
Direct injection of the vascular endothelial growth factor (VEGF) gene plasmid DNA into the myocardium was shown to induce development of new blood vessels to increase the circulation in the heart of patients with coronary artery diseases. However, such angiogenic gene therapy (via naked DNA) was limited by low level of gene expression. Furthermore, the temporal and spatial characteristics of VEGF gene transfer in the heart are not known. In this study, we demonstrated that a plasmid vector, containing the human cytomegalovirus immediate early (HCMV IE) promoter and enhancer, induces greater expression of gene in the rat heart monitored by gene fused to the chloramphenicol acetyl transferase (CAT) reporter, than four different viral and cellular promoters. Interestingly, expression of VEGF121 protein showed an earlier peak, a shorter duration, and a wider distribution than that of CAT only. Therefore, a plasmid vector with an HCMV IE promoter/enhancer provides clear advantages over other previously developed plasmids. Furthermore, expression profile of VEGF121 gene may provide useful information in the design of angiogenic gene therapy in the heart. 相似文献
9.
An organopalladium complex containing ortho-metalated (S)-(1-(dimethylamino)ethyl)naphthalene as the chiral auxiliary has been used to promote the asymmetric hydrophosphination reactions between diphenylphosphine and (E)- or (Z)-diphenyl-1-propenylphosphine in high regio- and stereoselectivities under mild conditions. Hydrophosphination of (Z)-diphenyl-1-propenylphosphine with diphenylphosphine gave (S)-(-)-prophos as the major product. Using the same chiral metal template, the corresponding hydrophosphination reaction with (E)-diphenyl-1-propenylphosphine gave (R)-(+)-prophos predominantly. The hydrophosphination reactions generated the asymmetric diphosphines as bidentate chelates on the chiral naphthylamine palladium templates. The template products obtained undergo cis-trans isomerization in solution to form an equilibrium mixture of regioisomers. X-ray analysis of the major template products obtained from the hydrophosphination of (Z)-diphenyl-1-propenylphosphine reveals that the two regioisomers are cocrystallized in a 1:1 ratio. The naphthylamine auxiliary could be removed chemoselectively from the template products by treatment with concentrated hydrochloric acid to form the corresponding optically pure neutral complexes [(R)- or (S)-(prophos)PdCl(2)]. Subsequently, the (R)- and (S)-dichloro complexes undergo ligand displacement with aqueous cyanide to generate the corresponding optically pure diphosphine ligands in high yields. Mechanistic pathways explaining the stereoselectivity of the chiral organopalladium template promoted hydrophosphination reactions are also proposed. 相似文献
10.
Roman E. Enrique Castro W. Veronica Camus O. Margarita 《Journal of organometallic chemistry》1985,293(1):93-101
The reactions between the phosphine-organoiron [CpFeII-η6-C6Me5CH2PPh2]+ PF6? (1) and [RhCl(η4-diolefin)(μ-Cl)]2 in CH2Cl2 at reflux give the new heterobinuclear air-stable crystalline complexes [CpFeII-η6-C6Me5CH2)P(Ph)2Rh(η4-diene)Cl]PF6,(D'*-diene=cyclooctadiene (COD): 65%, 2; trimethylfluorobenzobicyclo[2.2.2]octadiene (Me3TFB): 48%, 3). Complexes 2 and 3 have been studied by 1H, 13C and 31P NMR spectroscopy and they are carbonylated (CO, 1 atm). Cyclic voltammetry experiments with addition of MeOH show electron transfer FeIRhI → FeIIRh0, the presence of a catalytic wave FeI/FeII and the possible formation of Rh hydrides. Under normal conditions 2 is a catalyst for hydrogenation of cyclohexene, but it is less efficient than the known mononuclear Rh1 analogues. 相似文献