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1.
Karam Asad Dr. Anastasios Stergiou Dr. Andreas Kourtellaris Prof. Nikos Tagmatarchis Prof. Nikos Chronakis 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(55):13879-13886
The multiaddition chemistry of azafullerene C59N has been scarcely explored, and the isolation of pure bisadducts is in its infancy. Encouraged by the recent regioselective synthesis of the inherently chiral equatorialface bisadduct of C59N, we focused on the isolation of the first trans-4 bisadduct in a simple two-step approach. The first regioselective synthesis of the trans-4 bisadduct of C59N by using cyclo-[2]-dodecylmalonate as a tether is now reported. The newly synthesized bisadduct has C1 symmetry, as evidenced by 13C NMR, while X-ray crystallography validated the trans-4′ addition pattern. Furthermore, the inherently chiral trans-4′ C59N bisadduct was enantiomerically resolved, and the mirror-image relation of the two enantiomers was probed by circular dichroism spectroscopy. Finally, UV-Vis and redox assays suggested that the addition pattern has a reflection in the light-harvesting and redox properties of the bisadduct. 相似文献
2.
Xiaoli Liu Michelle M. T. Jansman Peter W. Thulstrup Ana C. Mendes Ioannis S. Chronakis Leticia Hosta‐Rigau 《Macromolecular bioscience》2020,20(2)
Despite all the attempts to create advanced hemoglobin (Hb)‐based oxygen carriers (HBOCs) employing an encapsulation platform, major challenges including attaining a high Hb loading and long circulation times still need to be overcome. Herein, the fabrication, for the first time, of nanoparticles fully made of Hb (Hb‐NPs) employing the electrospray technique is reported. The Hb‐NPs are then coated by antioxidant and self‐polymerized poly(dopamine) (PDA) to minimize the conversion of Hb into nonfunctional methemoglobin (metHb). The PDA shell is further functionalized with poly(ethylene glycol) (PEG) to achieve stealth properties. The results demonstrate that the as‐prepared Hb‐NPs are hemo‐ and biocompatible while offering antioxidant protection and decreasing the formation of metHb. Additionally, decoration with PEG results in decreased protein adsorption onto the Hb‐NPs surface, suggesting a prolonged retention time within the body. Finally, the Hb‐NPs also preserve the reversible oxygen‐binding and releasing properties of Hb. All in all, within this study, a novel HBOCs with high Hb content is fabricated and its potential as an artificial blood substitute is evaluated. 相似文献
3.
Witte P Beuerle F Hartnagel U Lebovitz R Savouchkina A Sali S Guldi D Chronakis N Hirsch A 《Organic & biomolecular chemistry》2007,5(22):3599-3613
Over the past decade, surface-modified, water soluble fullerenes have been shown by many different investigators to exhibit strong antioxidant activity against reactive oxygen species (ROS) in vitro and to protect cells and tissues from oxidative injury and cell death in vivo. Nevertheless, progress in developing fullerenes as bona fide drug candidates has been hampered by three development issues: 1) lack of methods for scalable synthesis; 2) inability to produce highly purified, single-species regioisomers compatible with pharmaceutical applications; and 3) inadequate understanding of structure-function relationships with respect to various surface modifications (e.g., anionic versus cationic versus charge-neutral polarity). To address these challenges, we have designed and synthesized more than a dozen novel water soluble fullerenes that can be purified as single isomers and which we believe can be manufactured to scale at reasonable cost. These compounds differ in addition pattern, lipophilicity and number and type of charge and were examined for their water solubility, antioxidant activity against superoxide anions and binding of cytochrome C. Our results indicate that dendritic water soluble fullerene[60] monoadducts exhibit the highest degree of antioxidant activity against superoxide anions in vitro as compared with trismalonate-derived anionic fullerenes as well as cationic fullerenes of similar overall structure. Among the higher adducts, anionic derivatives have a higher antioxidant activity than comparable cationic compounds. To achieve sufficient water solubility without the aid of a surfactant or co-solvent at least three charges on the addends are required. Significantly, anionic in contrast to cationic fullerene adducts bind with high affinity to cytochrome C. 相似文献
4.
Muzafar A. Kanjwal Faheem A. SheikhNasser A.M. Barakat Xiaoqiang LiHak Yong Kim Ioannis S. Chronakis 《Applied Surface Science》2012,258(8):3695-3702
In this study, a new hierarchical nanostructure that consists of zinc oxide (ZnO) was produced by the electrospinning process followed by a hydrothermal technique. First, electrospinning of a colloidal solution that consisted of zinc nanoparticles, zinc acetate dihydrate and poly(vinyl alcohol) was performed to produce polymeric nanofibers embedding solid nanoparticles. Calcination of the obtained electrospun nanofiber mats in air at 500 °C for 90 min produced pure ZnO nanofibers with rough surfaces. The rough surface strongly enhanced outgrowing of ZnO nanobranches when a specific hydrothermal technique was used. Methylene blue dihydrate was used to check the photocatalytic ability of the produced nanostructures. The results indicated that the hierarchical nanostructure had a better performance than the other form. 相似文献
5.
We present a general method for the linear least-squares solutionof overdetermined and underdetermined systems. The method isparticularly efficient when the coefficient matrix is quasi-square,that is when the number of rows and number of columns is almostthe same. The numerical methods for linear least-squares problemsand minimum-norm solutions do not generally take account ofthis special characteristic. The proposed method is based onLU factorization of the original quasi-square matrix A, assumingthat A has full rank. In the overdetermined case, the LU factorsare used to compute a basis for the null space of AT. The right-handside vector b is then projected onto this subspace and the least-squaressolution is obtained from the solution of this reduced problem.In the case of underdetermined systems, the desired solutionis again obtained through the solution of a reduced system.The use of this method may lead to important savings in computationaltime for both dense and sparse matrices. It is also shown inthe paper that, even in cases where the matrices are quite small,sparse solvers perform better than dense solvers. Some practicalexamples that illustrate the use of the method are included. 相似文献
6.
Kotsiris SG Vasil'ev YV Streletskii AV Han M Mark LP Boltalina OV Chronakis N Orfanopoulos M Hungerbühler H Drewello T 《European journal of mass spectrometry (Chichester, England)》2006,12(6):397-408
A variety of derivatized fullerenes have been studied by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. Of particular emphasis has been the evaluation of a recently introduced solvent-free sample/target preparation method. Solvent-free MALDI is particularly valuable in overcoming adverse solvent-related effects, such as insolubility and/or degradation of the sample. The method was applied to fullerene derivatives susceptible to decomposition under insufficiently "soft" MALDI conditions. Analytes included the hydrofullerene: C(60)H(36), fluorofullerenes: C(60)F(x) where x = 18, 36, 46, 48 and C(70)F(x) where x = 54, 56, methano-bridged amphiphilic ligand adducts to C(60) and the [4 + 2] cycloadduct of tetracene to C(60). The new solvent-free sample preparation is established as an exceedingly valuable addition to the repertoire of preparation protocols within MALDI. The MALDI mass spectra were of very high quality throughout, providing a testimony that "soft" MALDI conditions could be achieved. Using the [4 + 2] cycloadduct of tetracene to C(60) as the model analyte for direct comparison with solvent-based MALDI, the solvent-free approach led to less fragmentation and more abundant analyte ions. Applying solvent-free sample preparation, different matrix compounds have been examined for use in the MALDI of derivatized fullerenes, including sulfur, tetracyanoquinodimethane (TCNQ), 9-nitroanthracene (9-NA) and trans-2-[3-(4-tert-butylphenyl)-2-methyl-2- propenylidene]malononitrile (DCTB). DCTB was confirmed as the best performing matrix, reducing unwanted decomposition and suppression effects. 相似文献
7.
The [4 + 2] cycloaddition of trans,trans-2,4-hexadiene with C(60) proceeds via a concerted mechanism with retention of stereochemistry in the cycloadduct 1a. However, when cis,trans-2,4-hexadiene reacts with C(60), isomerization of the cis,trans to the thermodynamically more stable trans,trans isomer occurs. Subsequently, the cis,trans diene isomerized to the trans,trans isomer and cycloadds to C(60), to form adduct 1a. When the reaction is carried out at higher temperatures, the formation of cycloadduct 1b is also obtained. This result is consistent with a concerted cycloaddition of cis,trans-2,4-hexadiene with C(60), which is more reactive at elevated temperatures and leads to the formation of the Diels-Alder adduct 1b. 相似文献
8.
[reaction: see text] The Diels-Alder reaction of rigid s-cis dienes with C(60) occurs by a concerted mechanism, via a symmetrical transition state. 相似文献
9.
Manos MJ Markoulides MS Malliakas CD Papaefstathiou GS Chronakis N Kanatzidis MG Trikalitis PN Tasiopoulos AJ 《Inorganic chemistry》2011,50(22):11297-11299
The initial use of a novel elongated tricarboxylic acid H(3)hmpib in metal-organic framework (MOF) chemistry resulted in a [Zn(4)O(hmpib)(2)] MOF (UCY-1) with pyrite topology. The compound displays a remarkably high internal surface area despite its double-interpenetrated structure as well as high CO(2) uptake and selective adsorption for it over CH(4). 相似文献
10.
[reaction: see text] The reaction between the C(59)N(+) carbocation and the electron-rich aromatic compounds toluene and anisole has been mechanistically studied. The measured intermolecular kinetic isotope effects are consistent with an electrophilic aromatic substitution mechanism in which the arenium cation is formed by electrophilic attack of C(59)N(+) on the aromatic ring in the first step of the reaction, followed by hydrogen abstraction in a rate-determining second step. 相似文献