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131.
de Graaf AJ Boere KW Kemmink J Fokkink RG van Nostrum CF Rijkers DT van der Gucht J Wienk H Baldus M Mastrobattista E Vermonden T Hennink WE 《Langmuir : the ACS journal of surfaces and colloids》2011,27(16):9843-9848
We present experimental proof that so-called "flowerlike micelles" exist and that they have some distinctly different properties compared to their "starlike" counterparts. Amphiphilic AB diblock and BAB triblock copolymers consisting of poly(ethylene glycol) (PEG) as hydrophilic A block and thermosensitive poly(N-isopropylacrylamide) (pNIPAm) B block(s) were synthesized via atom transfer radical polymerization (ATRP). In aqueous solutions, both block copolymer types form micelles above the cloud point of pNIPAm. Static and dynamic light scattering measurements in combination with NMR relaxation experiments proved the existence of flowerlike micelles based on pNIPAm(16kDa)-PEG(4kDa)-pNIPAm(16kDa) which had a smaller radius and lower mass and aggregation number than starlike micelles based on mPEG(2kDa)-pNIPAm(16kDa). Furthermore, the PEG surface density was much lower for the flowerlike micelles, which we attribute to the looped configuration of the hydrophilic PEG block. (1)H NMR relaxation measurements showed biphasic T(2) relaxation for PEG, indicating rigid PEG segments close to the micelle core and more flexible distal segments. Even the flexible distal segments were shown to have a lower mobility in the flowerlike micelles compared to the starlike micelles, indicating strain due to loop formation. Taken together, it is demonstrated that self-assemblies of BAB triblock copolymers have their hydrophilic block in a looped conformation and thus indeed adopt a flowerlike conformation. 相似文献
132.
Beretta G Artali R Caneva E Maffei Facino R 《Magnetic resonance in chemistry : MRC》2011,49(3):132-136
1,2,3,4,6-Penta-O-galloyl-β-D-glucopyranose (PGG) is a polyphenolic compound found in substantial amounts in a number of medicinal herbs. We report (i) its conformational analysis by solution NMR and molecular dynamics calculation and (ii) theoretical study of its interaction with a model membrane bilayer. The galloyl groups B and E appear to play important roles in the interaction with the phospholipid bilayer. 相似文献
133.
Secco Andrea Carniato Fabio Gatti Giorgio Marabello Domenica Sappa Enrico 《Journal of Sol-Gel Science and Technology》2011,58(2):564-571
Abstract
The triruthenium complexes containing alkynols ligands have been reacted with 2(diphenylphosphino)ethyl-triethoxysilane (dpts), obtaining novel chemically stable disubstituted complexes. The same disubstituted Ru complexes above described were also synthesized following another approach based on the reaction from the phosphine substituted complex Ru3(CO)10(dpts)2 and the same alkynols ligands used to obtain the above triruthenium complexes. One of these stable complexes, the HRu3(CO)7[C≡C(Me)2(OH)](dpts)2 compound was grafted on the mesoporous silica SBA-15 and on γ-Al2O3 surface in order to obtain novel hybrid materials to employ in heterogeneous catalysis. The resulting materials have been characterized by multidisciplinary approach based on inductively coupled plasma-mass spectrometry (ICP-MS), FT-IR, XRD, physisorption measurements and DR-UV–Visible spectroscopy. 相似文献134.
Banert K Meier B Penk E Saha B Würthwein EU Grimme S Rüffer T Schaarschmidt D Lang H 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(4):1128-1136
Substituted 1-azidocyclopentenes and 1-azidocyclohexenes were photolyzed to generate 2,3-bridged 2H-azirines. In the case of bridgehead azirines with a six-membered carbocycle, detection by NMR spectroscopic analysis was possible, whereas even kinetically stabilized bridgehead azirines with a five-membered ring could not be characterized by low-temperature NMR spectroscopic analysis. Thus, a recent report on the latter heterocycles was corrected. Depending on the substitution pattern, irradiation of 1-azidocyclopentenes either led to products that can be explained on the basis of short-lived 2,3-bridged 2H-azirines, or gave secondary products generated from triplet nitrenes. The diverse photoreactivity of 2,3-bridged 2H-azirines was also studied by quantum chemical methods (DFT, CCSD(T), CASSCF(6,6)) with respect to the singlet and triplet energy surfaces. The ring-opening processes leading to the corresponding vinyl nitrenes were identified as key steps for the observed reactivity. 相似文献
135.
Travaglia A Arena G Fattorusso R Isernia C La Mendola D Malgieri G Nicoletti VG Rizzarelli E 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(13):3726-3738
There is a significant overlap between brain areas with Zn(2+) and Cu(2+) pathological dys-homeostasis and those in which the nerve growth factor (NGF) performs its biological role. The protein NGF is necessary for the development and maintenance of the sympathetic and sensory nervous systems. Its flexible N-terminal region has been shown to be a critical domain for TrkA receptor binding and activation. Computational analyses show that Zn(2+) and Cu(2+) form pentacoordinate complexes involving both the His4 and His8 residues of the N-terminal domain of one monomeric unit and the His84 and Asp105 residues of the other monomeric unit of the NGF active dimer. To date, neither experimental data on the coordination features have been reported, nor has one of the hypotheses according to which Zn(2+) and Cu(2+) may have different binding environments or the Ser1 α-amino group could be involved in coordination been supported. The peptide fragment, encompassing the 1-14 sequence of the human NGF amino-terminal domain (NGF(1-14)), blocked at the C terminus, was synthesised and its Cu(2+) and Zn(2+) complexes characterized by means of potentiometric and spectroscopic (UV/Vis, CD, NMR, and EPR) techniques. The N-terminus-acetylated form of NGF(1-14) was also investigated to evaluate the involvement of the Ser1 α-amino group in metal-ion coordination. Our results demonstrate that the amino group is the first anchoring site for Cu(2+) and is involved in Zn(2+) coordination at physiological pH. Finally, a synergic proliferative activity of both NGF(1-14) and the whole protein on SHSY5Y neuroblastoma cell line was found after treatment in the presence of Cu(2+). This effect was not observed after treatment with the N-acetylated peptide fragment, demonstrating a functional involvement of the N-terminal amino group in metal binding and peptide activity. 相似文献
136.
Luciano Lepori Paolo Gianni Andrea Spanedda Enrico Matteoli 《The Journal of chemical thermodynamics》2011,43(10):1453-1462
Excess molar volumes VE at 298.15 K were determined by means of a vibrating tube densimeter for binary mixtures of {heptane + open chain secondary (diethyl to dibutyl) and tertiary (triethyl to tripentyl) amines} as well as for cyclic imines (C2, C3, C4, C6, and C7) and primary cycloalkylamines (C5, C6, C7, and C12). The VE values were found positive for mixtures involving small size amines, with VE decreasing as the size increases. Negative VE’s were found for tributyl- and tripentylamine, heptamethylenimine, and cyclododecylamine. Mixtures of heptane with cycloheptylamine showed an s-shaped curve.Partial molar volumes of amines at infinite dilution in heptane were obtained from VE and compared with of hydrocarbons and other classes of organic compounds taken from literature. An additivity scheme, based on the intrinsic volume approach, was applied to estimate group (CH3, CH2, CH, C, NH2, NH, N, OH, O, CO, and COO) contributions to . These contributions, the effect of cyclization on , and the limiting slope of the apparent excess molar volumes were discussed in terms of solute–solvent and solute–solute interactions. 相似文献
137.
从原子到大分子体系的计算机模拟——计算化学50年 总被引:2,自引:0,他引:2
本文综述并修订了从20世纪50年代末至今,我们在计算化学领域所做的一些有意义的工作。序言部分把我们的工作置于当代科学的背景之下。然后我们以一种经典的基准测试体系——一种新的单粒子表象(即替代传统的原子和分子自旋轨道的化学自旋轨道)所构建的氢分子(H2)波函数——作为开始。用Hartree-Fock-Heitler-Lo... 相似文献
138.
Bergamaschi G Boiocchi M Monzani E Amendola V 《Organic & biomolecular chemistry》2011,9(24):8276-8283
The influence of the positively charged N-methylpyridinium substituent on the anion binding tendencies of urea-based receptors has been investigated by comparing molecules 1 and 2. These receptors have been studied in acetonitrile, by performing UV-vis. and (1)H NMR titrations with several anions. UV-vis. titrations have also been performed in DMSO, MeOH and CHCl(3)/CH(3)CN mixture (1/1, v/v). In the case of 1, the presence of both H-donor and H-acceptor groups (urea and pyridine, respectively) favours aggregation and the formation of dimers in the solid state. In solution, this tendency to aggregate reduces affinity for anions with respect to the similar urea-based receptor 3. The methylation of the pyridyl group of 1 leads to the pyridinium-containing receptor 2. The pyridinium positive charge enhances the acidity of urea and increases anion affinity, as evidenced by the comparison of the binding constants. Both receptors (1-2) form stable adducts with all investigated anions. However, in the case of 2, the formation of 1?:?1 adducts with basic anions, such as acetate and fluoride, is followed by a proton transfer process. Quite interestingly, deprotonation does not involve the urea group, thus preserving the 1?:?1 adduct, as demonstrated by the (1)H NMR measurements. In particular, the proton transfer process takes place at the methylene group linking the pyridinium fragment to the receptor's skeleton. (1)H NMR studies indicate the formation of a stable neutral methine species, characterised by the loss of aromaticity by the pyridyl ring. These results open new perspectives in the field of anion recognition, as receptor 2 may by applied to the monitoring of both bound anion (through the urea unit) and excess anion in solution (through the development of the yellow methine species). 相似文献
139.
Mügge C Rothenburger C Beyer A Görls H Gabbiani C Casini A Michelucci E Landini I Nobili S Mini E Messori L Weigand W 《Dalton transactions (Cambridge, England : 2003)》2011,40(9):2006-2016
Twelve Pt(II) complexes with cis-PtP(2)S(2) pharmacophores (where P(2) refers to two monodentate or one bidentate phosphane ligand and S(2) is a dithiolato ligand) were prepared, characterized and evaluated as potential antiproliferative agents. The various compounds were first studied from the structural point of view; afterward, their solubility properties as well as their solution behaviour were analyzed in detail. Antiproliferative properties were specifically evaluated against A2780 human ovarian carcinoma cells, either resistant or sensitive to cisplatin. For comparison purposes similar studies were carried out on four parent cis-dichloro bisphosphane Pt(II)complexes. On the whole, the cis-PtP(2)S(2) compounds displayed significant antiproliferative properties while the cis-PtP(2)Cl(2) (cis-dichloro bisphosphane Pt(II)) compounds revealed quite poor biological performances. To gain further insight into the molecular mechanisms of these bisphosphane Pt(II) compounds, the reactions of selected complexes against the model protein cytochrome c were investigated by ESI-MS and their adduct formation explored. A relevant reactivity with cyt c was obtained only for cis-PtP(2)Cl(2) compounds, whereas cis-PtP(2)S(2) compounds turned out to be nearly unreactive. The obtained results are interpreted and discussed in the frame of the current knowledge of anticancer platinum compounds and their structure-activity-relationships. The observation of appreciable antiproliferative effects for the relatively inert cis-PtP(2)S(2) compounds strongly suggests that these compounds will undergo specific activation within the cellular environment. 相似文献
140.
Matteo Novaga Enrico Valdinoci 《Calculus of Variations and Partial Differential Equations》2011,40(1-2):37-49
Given a double-well potential F, a ${\mathbb{Z}^n}$ -periodic function H, small and with zero average, and ???>?0, we find a large R, a small ?? and a function H ?? which is ??-close to H for which the following two problems have solutions:
- Find a set E ?? ,R whose boundary is uniformly close to ? B R and has mean curvature equal to ?H ?? at any point,
- Find u = u ?? ,R,?? solving $$ -\delta\,\Delta u + \frac{F'(u)}{\delta} +\frac{c_0}{2} H_\varepsilon = 0, $$ such that u ??,R,?? goes from a ??-neighborhood of +?1 in B R to a ??-neighborhood of ?1 outside B R .