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991.
Levchenko EV Evteev AV Kozubski R Belova IV Murch GE 《Physical chemistry chemical physics : PCCP》2011,13(3):1214-1221
Surface segregation in (110) B2-NiAl film approximately 3 nm thick is investigated by using molecular dynamics simulation with a reliable embedded-atom potential. The simulation is performed for the stoichiometric composition at a temperature of 1500 K, just below the melting temperature of the film model. It is found that the (110) surface is structurally stable but develops adatoms, vacancies and antisites. The coverage of an adatom layer is estimated to be ~0.07 ML (monatomic layers) and it contains on average ~95% of Al atoms. The top (surface) and second (subsurface) layers of the (110) surface is the most enriched in Ni relative to the bulk composition. These layers contain on average ~51% of Ni atoms. The Ni fraction in the third and forth layers of the film is estimated as ~50.5%. The deeper layers have essentially the bulk composition. Vacancies in the film model are found only on the Ni sublattice. The vacancy concentration on the Ni sublattice in the top layer is ~7.5%. The second layer almost does not contain vacancies. The next layers have essentially the constant bulk vacancy composition which can be estimated as ~1.3-1.4%. 相似文献
992.
Portnaya I Khalfin R Kesselman E Ramon O Cogan U Danino D 《Physical chemistry chemical physics : PCCP》2011,13(8):3153-3160
Amphiphilic block copolymers and mixtures of amphiphiles find broad applications in numerous technologies, including pharma, food, cosmetic and detergency. Here we report on the interactions between a biological charged diblock copolymer, β-casein, and a synthetic uncharged triblock copolymer, Lutrol F-127 (EO(101)PO(56)EO(101)), on their mixed micellization characteristics and the micelles' structure and morphology. Isothermal titration calorimetry (ITC) experiments indicate that mixed micelles form when Lutrol is added to monomeric as well as to assembled β-casein. The main driving force for the mixed micellization is the hydrophobic interactions. Above β-casein CMC, strong perturbations caused by penetration of the hydrophobic oxypropylene sections of Lutrol into the protein micellar core lead to disintegration of the micelles and reformation of mixed Lutrol/β-casein micelles. The negative enthalpy of micelle formation (ΔH) and cooperativity increase with raising β-casein concentration in solution. ζ-potential measurements show that Lutrol interacts with the protein micelles to form mixed micelles even below its critical micellization temperature (CMT). They further indicate that Lutrol effectively masks the protein charges, probably by forming a coating layer of the ethyleneoxide rich chains. Small-angle X-ray scattering (SAXS) and cryogenic-transmission electron microscopy (cryo-TEM) indicate relatively small changes in the oblate micellar shape, but do show swelling along the small axis of β-casein micelles in the presence of Lutrol, thereby confirming the formation of mixed micelles. 相似文献
993.
Vorobyeva DV Karimova NM Odinets IL Röschenthaler GV Osipov SN 《Organic & biomolecular chemistry》2011,9(21):7335-7342
A convenient strategy for the synthesis of isoxazole-containing α-CF(3)-substituted α-aminocarboxylates and α-aminophosphonates have been developed. The method is based on copper-catalyzed 1,3-dipolar cycloaddition of different aromatic nitrile oxides to functionalized acetylenes. 相似文献
994.
A new computational approach to calculating binding energies and spatial positions of small molecules, peptides, and proteins in the lipid bilayer has been developed. The method combines an anisotropic solvent representation of the lipid bilayer and universal solvation model, which predicts transfer energies of molecules from water to an arbitrary medium with defined polarity properties. The universal solvation model accounts for hydrophobic, van der Waals, hydrogen-bonding, and electrostatic solute-solvent interactions. The lipid bilayer is represented as a fluid anisotropic environment described by profiles of dielectric constant (ε), solvatochromic dipolarity parameter (π*), and hydrogen bonding acidity and basicity parameters (α and β). The polarity profiles were calculated using published distributions of quasi-molecular segments of lipids determined by neutron and X-ray scattering for DOPC bilayer and spin-labeling data that define concentration of water in the lipid acyl chain region. The model also accounts for the preferential solvation of charges and polar groups by water and includes the effect of the hydrophobic mismatch for transmembrane proteins. The method was tested on calculations of binding energies and preferential positions in membranes for small-molecules, peptides and peripheral membrane proteins that have been experimentally studied. The new theoretical approach was implemented in a new version (2.0) of our PPM program and applied for the large-scale calculations of spatial positions in membranes of more than 1000 peripheral and integral proteins. The results of calculations are deposited in the updated OPM database ( http://opm.phar.umich.edu ). 相似文献
995.
Shakhmaeva II Saifullina DV Sattarova LI Abdullin TI 《Analytical and bioanalytical chemistry》2011,401(8):2591-2597
We designed an electrochemical sensor based on a carbon nanotube modified electrode (ME) to analyze DNA-cleaving activity.
The cleavage of high molecular weight DNA resulted in an increase in the oxidation current from DNA guanine nucleotides due
to a change in DNA adsorptive behavior on the surface of the ME. DNA digestion with DNAse I was accompanied by a linear increase
in the DNA signal in proportion to the enzyme activity. We then proposed an assay based on the sensor for the direct assessment
of the total deoxyribonuclease activity of blood serum as well as the separate detection of DNAse I and DNA abzymes. The assay
was applied to analyze deoxyribonucleases in sera from 21 healthy donors and 17 patients with autoimmune thyroiditis. Our
results show that the response of the sensor to DNA cleavage by blood deoxyribonucleases is a promising diagnostic criterion
for autoimmune thyroiditis. This sensor can be implemented in a disposable screen-printed electrode format for application
in clinical laboratories. 相似文献
996.
Dr. Hong‐Peng Jia Dr. Jie Ding Dr. Ying‐Fen Ran Dr. Shi‐Xia Liu Dr. Carmen Blum Dr. Irina Petkova Prof. Andreas Hauser Prof. Silvio Decurtins 《化学:亚洲杂志》2011,6(12):3312-3321
An efficient synthetic approach to a symmetrically functionalized tetrathiafulvalene (TTF) derivative with two diamine moieties, 2‐[5,6‐diamino‐4,7‐bis(4‐pentylphenoxy)‐1,3‐benzodithiol‐2‐ylidene]‐4,7‐bis(4‐pentylphenoxy)‐1,3‐benzodithiole‐5,6‐diamine ( 2 ), is reported. The subsequent Schiff‐base reactions of 2 afford large π‐conjugated multiple donor–acceptor (D–A) arrays, for example, the triad 2‐[4,9‐bis(4‐pentylphenoxy)‐1,3‐dithiolo[4,5‐g]quinoxalin‐2‐ylidene]‐4,9‐bis(4‐pentylphenoxy)‐1,3‐dithiolo[4,5‐g]quinoxaline ( 8 ) and the corresponding tetrabenz[bc,ef,hi,uv]ovalene‐fused pentad 1 , in good yields and high purity. The novel redox‐active nanographene 1 is so far the largest known TTF‐functionalized polycyclic aromatic hydrocarbon (PAH) with a well‐resolved 1H NMR spectrum. The electrochemically highly amphoteric pentad 1 and triad 8 exhibit various electronically excited charge‐transfer states in different oxidation states, thus leading to intense optical intramolecular charge‐transfer (ICT) absorbances over a wide spectral range. The chemical and electrochemical oxidations of 1 result in an unprecedented TTF?+ radical cation dimerization, thereby leading to the formation of [ 1 ?+]2 at room temperature in solution due to the stabilizing effect, which arises from strong π–π interactions. Moreover, ICT fluorescence is observed with large solvent‐dependent Stokes shifts and quantum efficiencies of 0.05 for 1 and 0.035 for 8 in dichloromethane. 相似文献
997.
A set of highly concentrated water-in-oil emulsions with supersaturated dispersed phase were investigated in this work to verify and/or develop the models that have been presented both in the literature and in this work. The material used to form emulsions consisted of supersaturated oxidiser solution, hydrocarbon oil and PIBSA-based surfactants. The interfacial characteristics for different surfactant types were first examined. Then, the rheology of samples was studied, and different scaling methods and fitting of experimental data were studied. On the basis of flow curve measurements and observed $\tau _\emph{v} \sim \dot {\gamma }^{1/2}$ scaling, a modified version of Windhab model was suggested which showed excellent fitting of experimental results. The linear dependences of ?? y0/?? versus 1/d 32 for studied emulsions showed non-zero intercept which implies a non-linear dependence (resulting from interdroplet interaction) to fulfil the zero-intercept requirement. It was established that the zero intercept condition was fulfilled in the $\tau _{y0} \sim \sigma /d_{32}^2 $ scaling, although the experimental results for different surfactants were not superimposed. 相似文献
998.
Petr K. Sazonov Yuri F. Oprunenko Irina P. Beletskaya 《Journal of fluorine chemistry》2011,132(9):587-595
The C-F?M+ interaction in anionic σ-(α-fluorovinyl)rhenium oxycarbene complexes, [RCFCFReC(O)R′(CO)4]M (1-6), M = Na, Li, K is studied by 19F NMR in THF and Et2O. The coordination of α-F to M+ results in an upfield shift of the corresponding 19F NMR signal and a decrease of 1JCF. The maximum shift is found for the Li salt of complex 4 in Et2O (ΔδFα = 36.4 ppm), in which case a 7Li-19F spin-spin coupling is also observed (JLiF = 40 Hz). The ΔE of C-F?M+ interaction and its effect on 19F shielding was further studied by DFT calculations using β-fluoroenolates as models, which confirmed a strong impact of CF-bond environment on the coordination ability of fluorine in these F,O-chelates. A compound with a β-fluoroenolate backbone but without rhenium, o-(α-fluorovinyl)phenolate 12, was prepared and studied by 19F NMR, and similarly showed indications of C-F?M+ interaction in THF solution. It is concluded that the donor ability of fluorine in the studied system is enhanced because of the conjugation of α-fluorovinyl group with the enolate π-system and back donation from the transition metal. 相似文献
999.
Romanova IP Bogdanov AV Mironov VF Shaikhutdinova GR Larionova OA Latypov SK Balandina AA Yakhvarov DG Gubaidullin AT Saifina AF Sinyashin OG 《The Journal of organic chemistry》2011,76(8):2548-2557
The reactions of such cyclic α-diketones as acenaphthenequinone, aceanthrenequinone, and N-alkylisatins, with hexaethyltriaminophosphine in the presence of the fullerene C(60), lead to the formation of methanofullerene derivatives under mild conditions. This process proceeds via deoxygenation of the dicarbonyl compound by the P(III) derivative and is likely to involve the intermediate formation of α-ketocarbenes. The structure of some methanofullerenes has been confirmed by NMR and XRD. The electrochemical behavior of the methanofullerenes was also investigated. 相似文献
1000.
Peter?NymanEmail author Irina?Basieva 《International Journal of Theoretical Physics》2011,50(12):3864-3881
We study the problem of representing statistical data (of any origin) by a complex probability amplitude. This paper is devoted
to representation of data collected from measurements of two trichotomous observables. The complexity of the problem eventually
increases compared to the case of dichotomous observables. We see that only special statistical data (satisfying a number
of nonlinear constraints) have the quantum-like representation. 相似文献