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981.
Bringas E Köysüren Ö Quach DV Mahmoudi M Aznar E Roehling JD Marcos MD Martínez-Máñez R Stroeve P 《Chemical communications (Cambridge, England)》2012,48(45):5647-5649
We report here the on-command cargo controlled delivery using an alternating magnetic field (AMF) from magnetic silica mesoporous supports capped with a lipid bilayer. 相似文献
982.
An alternative synthesis of C‐monoacetylenic phosphaalkenes trans‐Mes*P=C(Me)(C≡CR) (Mes* = 2, 4, 6‐tBu3Ph, R = Ph, SiMe3) from C‐bromophosphaalkenes cis‐Mes*P=C(Me)Br using standard Sonogashira coupling conditions is described. Crystallographic studies confirm cis‐trans isomerization of the P=C double bond during Pd‐catalyzed cross coupling, leading exclusively to trans‐acetylenic phosphaalkenes. Crystallographic studies of all synthesized compounds reveal the extend of π‐conjugation over the acetylene and P=C π‐systems. 相似文献
983.
Eiji Tayama Ryota Sato Keisuke Takedachi Hajime Iwamoto Eietsu Hasegawa 《Tetrahedron》2012,68(24):4710-4718
Selective amine de-alkylation enables the conversion of Sommelet–Hauser rearrangement products into 2-aryl-2-bromoacetic acid derivatives. These compounds are valuable synthetic intermediates in the synthesis of α-aryl-α-amino or α-aryl-β-amino acid derivatives. The method presented herein is a formal de-N,N-dialkylation of Sommelet–Hauser rearrangement products. 相似文献
984.
La Mendola D Farkas D Bellia F Magrì A Travaglia A Hansson Ö Rizzarelli E 《Inorganic chemistry》2012,51(1):128-141
The angiogenin protein (hAng) is a potent angiogenic factor and its cellular activities may be affected by copper ions even if it is yet unknown how this metal ion is able to produce this effect. Among the different regions of hAng potentially able to bind copper ions, the N-terminal domain appears to be an ideal candidate. Copper(II) complexes of the peptide fragments encompassing the amino acid residues 4-17 of hAng protein were characterized by potentiometric, UV-vis, CD, and EPR spectroscopic methods. The results show that these fragments have an unusual copper(II) binding ability. At physiological pH, the prevailing complex species formed by the peptide encompassing the protein sequence 4-17 is [CuHL], in which the metal ion is bound to two imidazole and two deprotonated amide nitrogen atoms disposed in a planar equatorial arrangement. Preliminary spectroscopic (UV-vis, CD, and EPR) data obtained on the copper(II) complexes formed by the whole recombinant hAng protein, show a great similarity with those obtained for the N-terminal peptide fragments. These findings indicate that within the N-terminal domain there is one of the preferred copper(II) ions anchoring site of the whole recombinant hAng protein. 相似文献
985.
MARTIN PLATO HEINZ-JÜRGEN STEINHOFF CHRISTOPH WEGENER JENS T. TÖRRING ANTON SAVITSKY KLAUS MÖBIUS 《Molecular physics》2013,111(23):3711-3721
Semiempirical molecular orbital methods (PM3, INDO, ZINDO/S) have been used to calculate the effects of local electric fields and of hydrogen bonding on the g and hyperfine tensors of a nitroxide spin label model system. The results yield a linear correlation between the two principal tensor components g xx and A N zz at label sites of varying polarity. Hydrogen bonding with a single water molecule produces a constant shift of Δg xx ? ?4 × 10?4. These theoretical results are used to interpret recent high field (3.4 T, 95 GHz) electron paramagnetic resonance investigations on site-directed spin labelled bacteriorhodopsin. This protein reveals a close correlation between proticity and polarity at the various label sites. The slope of the g xx versus A N zz dependence is affected strongly by polarity induced structural strains of the spin label. 相似文献
986.
MATTHIAS BECHMANN STEPHAN DUSOLD HANS FÖRSTER ULRICH HAEBERLEN TADEUSZ LIS ANGELIKA SEBALD 《Molecular physics》2013,111(9):605-617
A 31P and 13C NMR study of powder and single crystal samples of two phosphoenolpyruvate (PEP) compounds, the tris-ammonium salt monohydrate (NH4)3(PEP)·H2O (1), and the mono-ammonium-salt (NH4)(H2PEP) (2) is presented. The P chemical shielding tensors in 1 are measured by 31P single crystal NMR on four minuscule samples and assigned without ambiguity by exploiting the orientation-dependent 31P-31p dipolar splittings of the resonance lines. The orientation of the 31P chemical shielding tensor is discussed in terms of the C2v — and C3-type distortions of the phosphate PO4-coordination sphere. From 13C MAS NMR experiments with 31P rotary resonance recoupling on polycrystalline powder samples the orientations of the 31P chemical shielding tensors in 1 and 2 are obtained, for 1 in very good agreement with the 31P single crystal NMR results. Only some of the orientational parameters of the three 13C chemical shielding tensors in the PEP moiety of 1 could be derived from 13C MAS NMR experiments with 31P rotary resonance recoupling. 相似文献
987.
FAHRETTIN GOGTAS HALIL OTURAK NIYAZI BULUT SINAN AKPINAR ALI KÖKCE 《Molecular physics》2013,111(12):1901-1909
The state-to-state and state-to-all reaction probabilities have been calculated for three-dimensional reactive and inelastic scattering of Ne + H+ 2 (v = 0, j = 0, 1, 2) at zero total angular momentum. The time-dependent Schrödinger equation is solved by means of Fourier grid and discrete variable representation techniques. The inelastic and reactive scattering probabilities for a broad range of energies are calculated. Although the system has an open reactive channel, the results show that a high fraction of the flux is reflected back due to endoergicity and potential barriers leading to inelastic scattering. 相似文献
988.
989.
JONNA STÅLRING MARTIN SCHÜTZ ROLAND LINDH GUNNAR KARLSTRÖM PER-OLOF WIDMARK 《Molecular physics》2013,111(21):3389-3399
The low-energy region of the intermolecular potential energy hypersurface (PES) of the ammonia dimer was studied at the level of second-order Moller-Plesset perturbation theory (MP2) using a very large basis set. Individual minima were located on the PES employing the counterpoise (CP) correction to account for the basis set superposition error (BSSE). Apart from these canonical MP2 calculations local MP2 (LMP2) calculations were performed. For the latter the BSSE at the correlated level is inherently absent by virtue of the local truncation of the virtual space. Results from canonical and local MP2 calculations are compared and the reliability of the LMP2 method for intermolecular complexes and clusters is discussed. The canonical MP2 calculations predicted five minimum structures, the four most stable ones lying energetically very close. For these four structures single point MP2 energy calculations with a further extended basis set (1024 functions for the ammonia dimer) were performed. The equilibrium dissociation energies so obtained are close to the one-particle basis set limit, as illustrated by a remaining BSSE of less than 0.2 kJ mol?1. The geometry optimizations at the LMP2 level, using the three most stable canonical MP2 structures as initial geometries, all collapsed to a single minimum corresponding to an asymmetric structural arrangement. A canonical MP2 single point calculation, at that geometry, revealed that the LMP2 minimum structure is virtually as stable as the lowest minima on the canonical MP2 PES. Based on these calculations the global minimum of the ammonia dimer was assigned to a part of the PES represented by an asymmetric structure with an equilibrium dissociation energy of 13.5±0.3 kJ mol?1 相似文献
990.
Dilara Özbakır Işın 《Molecular physics》2013,111(24):3578-3588
Anthraquinones are located in an important class of natural compounds having antioxidant properties. Quantum chemical calculations based on the density functional theory were employed to study the relationship between the structure and the antioxidant activity of four hydroxyanthraquinones. The solvation effects on the antioxidant activity were taken into account by using the conductor-like polarisable continuum model with different dielectric constants (ε = 2.25, C6H6; ε = 78.39, H2O). The three antioxidant action mechanisms, hydrogen atom transfer (HAT), single electron transfer-proton transfer and sequential proton loss electron transfer (SPLET) were elucidated. The reaction enthalpies related to the steps in these mechanisms were computed in gas phase and solvents. The calculated results are in line with experimental values. The results showed that HAT was the most favourable mechanism for describing the antioxidant activity of hydroxyanthraquinones in the gas phase and in benzene, whereas in aqueous solution, SPLET represented the most thermodynamically plausible reaction pathway. 相似文献