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1.
Guanidine‐Based Polymer Brushes Grafted onto Silica Nanoparticles as Efficient Artificial Phosphodiesterases 下载免费PDF全文
Claudia Savelli Riccardo Salvio 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(15):5856-5863
Polymer brushes grafted to the surface of silica nanoparticles were fabricated by atom‐transfer radical polymerization (ATRP) and investigated as catalysts in the cleavage of phosphodiesters. The surfaces of silica nanoparticles were functionalized with an ATRP initiator. Surface‐initiated ATRP reactions, in varying proportions, of a methacrylate moiety functionalized with a phenylguanidine moiety and an inert hydrophilic methacrylate species afforded hybrid nanoparticles that were characterized with potentiometric titrations, thermogravimetric analysis, and SEM. The activity of the hybrid nanoparticles was tested in the transesterification of the RNA model compound 2‐hydroxypropyl para‐nitrophenylphosphate (HPNP) and diribonucleoside monophosphates. A high catalytic efficiency and a remarkable effective molarity, thus overcoming the effective molarities previously observed for comparable systems, indicate the existence of an effective cooperation of the guanidine/guanidinium units and a high level of preorganization in the nanostructure. The investigated system also exhibits a marked and unprecedented selectivity for the diribonucleoside sequence CpA. The results presented open up the way for a novel and straightforward strategy for the preparation of supramolecular catalysts. 相似文献
2.
In this paper, the authors deal with bifunctions defined on complete metric spaces and with values in locally convex spaces ordered by closed convex cones. The aim is to provide a vector version of Ekeland’s theorem related to equilibrium problems. To prove this principle, a weak notion of continuity of a vector-valued function is considered, and some of its properties are presented. Via the vector Ekeland’s principle, existence results for vector equilibria are proved in both compact and noncompact domains. 相似文献
3.
Summary Campaign results of high-repetition ionospheric soundings, performed at the ionospheric station of Rome using a Digisonde
128P, are presented. We introduce an index derived from run rapid ionograms that can be used to detect oscillations of isodensity
surfaces ofF ionospheric region started by morning solar terminator. 相似文献
4.
5.
Riccardo De Arcangelis 《Annali dell'Universita di Ferrara》1989,35(1):135-145
Summary Letf: (x, z)∈R
n×Rn→f(x, z)∈[0, +∞] be measurable inx and convex inz.
It is proved, by an example, that even iff verifies a condition as|z|
p≤f(x, z)≤Λ(a(x)+|z|q) with 1<p<q,a∈L
loc
s
(R
n),s>1, the functional
that isL
1(Ω)-lower semicontinuous onW
1,1(Ω), does not agree onW
1,1(Ω) with its relaxed functional in the topologyL
1(Ω) given by inf
Riassunto Siaf: (x, z)∈R n×Rn→f(x, z)∈[0, +∞] misurabile inx e convessa inz. Si mostra con un esempio che anche sef verifica una condizione del tipo|z| p≤f(x, z)≤Λ(a(x)+|z|q) con 1<p<q,a∈L loc s (R n),s>1, il funzionale , che èL 1(Ω)-semicontinuo inferiormente suW 1,1(Ω), non coincide suW 1,1(Ω) con il suo funzionale rilassato nella topologiaL 1(Ω) definito da inf相似文献
6.
Beverina L Abbotto A Landenna M Cerminara M Tubino R Meinardi F Bradamante S Pagani GA 《Organic letters》2005,7(19):4257-4260
[graph: see text] Condensation of squaric acid with a number of differently substituted 2-pyrrolyl derivatives afforded three new classes of squaraines. Their sharp and intense absorption bands in the biological window (700-900 nm), inherent singlet oxygen generation capabilities, together with proper functionalization allowing good water solubility make them suitable candidates as new non-porphyrinic singlet oxygen photosensitizers for photodynamic therapy (PDT). 相似文献
7.
Franco Piacenti Mario Bianchi Piero Frediani Ugo Matteoli 《Journal of organometallic chemistry》1975,87(3):C54-C55
Both normal and secondary alkylcobalt carbonyls are shown not to undergo isomerization under catalytic “oxo” conditions, and the relevance of this obervation for the mechanism of the “oxo” reaction is discussed. 相似文献
8.
9.
Mario Bianchi Ugo Matteoli Piero Frediani Gloria Menchi Franco Piacenti 《Journal of organometallic chemistry》1982,236(3):375-380
Hydrogen transfer from racemic alcohols to prochiral ketones in the presence of H4Ru4(CO)8[(?)-DIOP]2 has been examined. The enantiomer-discrimination is influenced by the structure of the reactants, temperature and the excess of phosphine present. 相似文献
10.
[structure: see text] The conventional interpretation of proton NMR chemical shifts is supported by large basis set ab initio quantum mechanical calculations. The benzene protons are predicted to lie within the deshielding zone defined in terms of the out-of-plane magnetic shielding domain. However, ring currents by themselves are not sufficient to account quantitatively for the observed benzene proton downfield chemical shift. sigma-Electron contributions must also be taken into account. The conventional explanation for the ethyne proton chemical shift is valid. 相似文献