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Hirotoshi Sakaino Brigitte A. G. Lamers Stefan C. J. Meskers E. W. Meijer Ghislaine Vantomme 《Journal of polymer science. Part A, Polymer chemistry》2021,59(12):1131-1141
Materials with highly ordered nanoscale structures can translate molecular processes to macroscopic function. Here we report on the photo-controlled organization of achiral alternating copolymers composed of discrete length blocks showing well-defined sub-10 nm morphologies. These alternating copolymers consist of main-chain azobenzene building blocks alternating with discrete oDMS blocks of various precise lengths. Remarkably, we demonstrate the imprinting of a stable helical molecular arrangement in spin-casted thin films by irradiation with circularly polarized light, without chiral dopant or plasticizer required. By following the out-of-equilibrium photo-switching process over irradiation time, the mechanism of molecular reorganization is unraveled and rationalized with the nature of the morphology. Linear photo-organization is preferentially reached with flexible and symmetric cylindrical structures while helical photo-organization is most easily obtained with robust but rotatable lamella structures. These findings suggest that precision in the synthesis and assembly of alternating copolymers can lead to complete control over molecular organization and main-chain motion. 相似文献
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Van Elslande E Guérineau V Thirioux V Richard G Richardin P Laprévote O Hussler G Walter P 《Analytical and bioanalytical chemistry》2008,390(7):1873-1879
Microsamples of pink cosmetic powders from the Greco–Roman period were analyzed using two complementary analytical approaches
for identification of the colouring agents (lake pigments originally manufactured from madder plants with an inert binder,
usually a metallic salt) present in the samples. The first technique was a methanolic acidic extraction of the archaeological
samples with an additional ethyl acetate extraction of the anthraquinone-type colouring agents which were identified using
high performance liquid chromatography coupled to electrospray ionization with high resolution mass spectrometry (LC–ESI–HRMS),
and the second was direct analysis of a microsample by laser desorption ionization–mass spectrometry (LDI–MS). The latter
technique is well suited when the quantity of samples is very low. This soft ionization technique enables the detection of
very small quantities of compounds using the combination of positive and negative-ion modes. It was also successfully applied
for the direct analysis of some laboratory-made reference compounds. However, the presence of lead in one of these ancient
samples induced a spectral suppression phenomenon. In this case and conditional on a sufficient quantity of available sample,
the former method is better adapted for the characterization of these anthraquinone-type molecules. This study also confirmed
that purpurin, munjistin, and pseudopurpurin are the principal colouring agents present in these ancient cosmetic powders
constituted from madder plants.
Presented at the Annual French National Symposium on Mass Spectrometry, Electrophoresis and Proteomics, 20–23 September 2007
in Pau, France. 相似文献
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Dr. Lars Ratjen Dr. Ghislaine Vantomme Prof. Dr. Jean‐Marie Lehn 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(28):10070-10081
The displacement of molecular structures from their thermodynamically most stable state by imposition of various types of electronic and conformational constraints generates highly strained entities that tend to release the accumulated strain energy by undergoing either structural changes or chemical reactions. The latter case amounts to strain‐induced reactivity (SIR) that may enforce specific chemical transformations. A particular case concerns dynamic covalent chemistry which may present SIR, whereby reversible reactions are activated by coupling to a high‐energy state. We herewith describe such a dynamic covalent chemical (DCC) system involving the reversible imine formation reaction. It is based on the formation of strained macrocyclic bis‐imine metal complexes in which the macrocyclic ligand is in a high energy form enforced by the coordination of the metal cation. Subsequent demetallation generates a highly strained free macrocycle that releases its accumulated strain energy by hydrolysis and reassembly into a resting state. Specifically, the metal‐templated condensation of a dialdehyde with a linear diamine leads to a bis‐imine [1+1]‐macrocyclic complex in which the macrocyclic ligand is in a coordination‐enforced strained conformation. Removal of the metal cation by a competing ligand yields a highly reactive [1+1]‐macrocycle, which then undergoes hydrolysis to transient non‐cyclic aminoaldehyde species, which then recondense to a strain‐free [2+2]‐macrocyclic resting state. The process can be monitored by 1H NMR spectroscopy. Energy differences between different conformational states have been evaluated by Hartree–Fock (HF) computations. One may note that the stabilisation of high‐energy molecular forms by metal ion coordination followed by removal of the latter, offers a general procedure for producing out‐of‐equilibrium molecular states, the fate of which may then be examined, in particular when coupled to dynamic covalent chemical processes. 相似文献
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Ghislaine Heathcote 《组合设计杂志》1993,1(5):359-378
There are 398 nonisomorphic nontrivial linear spaces on 16 points having no lines of size two. In addition, there are 157,151 proper linear spaces on 17 points having one line of size five and 42 lines of size three. © 1993 John Wiley & Sons, Inc. 相似文献
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Colette C Denier Andrée A Brisson-Lougarre Ghislaine G Biasini Jean J Grozdea Didier D Fournier 《BMC biochemistry》2002,3(1):2-8
Background
In humans, there are four alkaline phosphatases, and each form exibits a characteristic pattern of tissue distribution. The availability of an easy method to reveal their activity has resulted in large amount of data reporting correlations between variations in activity and illnesses. For example, alkaline phosphatase from neutrophils of mothers pregnent with a trisomy 21 fetus (Down's syndrome) displays significant differences both in its biochemical and immunological properties, and in its affinity for some specific inhibitors. 相似文献19.
Embryogenic calli of pedunculate oak (Quercus robur L.) were cryopreserved using direct immersion in liquid nitrogen. The pretreatment consisted of culture on a solid medium with increasing sucrose concentrations (0.25 M for 1 day, 0.5 M for 1 day, 0.75 M for 2 days, and 1.0 M for 3 days), followed by air desiccation of embryogenic calli to 17.3 percent (fresh weight basis). This method of cryoprotection was compared to a liquid cryoprotection treatment using high concentrations of sucrose solutions, followed by glycerol solutions. Regrowth of frozen tissue pretreated on a solid medium was significantly higher than those pretreated in the liquid solutions. 相似文献
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Ghislaine Ariane Fozing Mekeuo Christelle Despas Charles Péguy Nanseu-Njiki Alain Walcarius Emmanuel Ngameni 《Electroanalysis》2022,34(4):667-676
Fine particles of Ayous sawdust (AS) were successfully modified by maleic anhydride to increase their accumulation capability towards carbendazim (Cbz). For a more efficient use of the biosourced material as electrode modifier for electrochemical detection, the functionalized particles were mixed with carbon nanotubes to yield a conductive composite. After electrochemical characterization, the modified GCE was applied to Cbz detection. A sensitivity of (2.61±0.08) μA M−1 and a detection limit of 0.04 μM were obtained under optimized experimental conditions. Moreover, the designed sensor was found efficient for Cbz determination in real samples (spring water and commercial pesticide product). 相似文献