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91.
Corre C Landreau CA Shipman M Lowden PA 《Chemical communications (Cambridge, England)》2004,(22):2600-2601
Isotopically labelled intermediates in a proposed biosynthesis of the naphthoate fragment of azinomycin B have been made and successfully incorporated by the azinomycin producing organism. 相似文献
92.
Agarose sols have been seen for long as solutions of flexible chains that, on cooling, produce thermoreversible gels through double-helix formation. Investigations of the chain conformation in the sol state by small-angle neutron scattering reveals instead a rigid chain with a very large persistence length (lp > 9 nm). The chain cross-section radius and mass per unit length correspond to characteristics of helices as those described by Foord and Atkins. These results lead one to a reappraisal of the occurrence of double helices in the gelation process, as they rather suggest a transition of the type loose-single helix⇒tight single helix. Studies of gels from agarose/water/cosolvent where the cosolvent is Dimethyl Sulfoxide (DMSO), Dimethyl Formamide (DMF), and Methyl Formamide (MF) have led one to conclude on the formation of agarose/water/ cosolvent ternary complexes. The contrast variation method by neutron scattering gives further support to this assumption. Finally, determination of the gel nanostructure allows one to account for the two regimes observed for the variation of the elastic modulus vs concentration. 相似文献
93.
Inside Back Cover: Non‐Aqueous Sol–Gel Synthesis of Ultra Small Persistent Luminescence Nanoparticles for Near‐Infrared In Vivo Imaging (Chem. Eur. J. 20/2015) 下载免费PDF全文
94.
Alain Guinault Cyrille Sollogoub Violette Ducruet Sandra Domenek 《European Polymer Journal》2012,48(4):779-788
The helium and oxygen gas barrier properties of poly(lactide) were investigated as a function of stereochemistry and crystallinity degree. Poly(l-lactide) and poly(d,l-lactide) films were obtained by extrusion and thermally cold crystallized in either α′- or α-crystalline form with increasing crystallinity degree. Annealing of the films at low temperatures yielded to α′-crystals as well as the creation of a rigid amorphous fraction in the amorphous phase. Unexpectedly, the quantity of the rigid amorphous fraction was highest in poly(l-lactide) crystallized under α′-form. Unexpectedly, the gas permeability increased with increasing quantity of α′-crystals in poly(l-lactide) and remained constant with increasing quantity of α′-crystals in poly(d,l-lactide). A gain in gas barrier properties was obtained upon crystallization at higher temperatures yielding α-crystals. The analysis of the oxygen transport parameters, in particular the diffusion and the solubility coefficient showed that the diffusion was accelerated upon crystallization, while the solubility coefficient decreased in an expected manner which led to conclude that it remained constant in the amorphous phase. The acceleration of the diffusion seems to be correlated to the occurrence of the rigid amorphous fraction, which holds larger free volume. To conclude, for optimization of poly(lactide) gas barrier properties by focussing on the decrease of the diffusion coefficient it can be suggested to work with poly(d,l-lactide) and to aim a crystallization in α-form avoiding the formation of a rigid amorphous fraction. 相似文献
95.
Non‐Aqueous Sol–Gel Synthesis of Ultra Small Persistent Luminescence Nanoparticles for Near‐Infrared In Vivo Imaging 下载免费PDF全文
Dr. Thomas Maldiney Nicole Lièvre Dr. Guillaume Yangshu Wang Prof. Laurence Motte Dr. Cyrille Richard Dr. Yoann Lalatonne 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(20):7350-7354
Ultra‐small ZnGa2O4:Cr3+ nanoparticles (6 nm) that exhibit near‐infrared (NIR) persistent luminescence properties are synthesized by using a non‐aqueous sol–gel method assisted by microwave irradiation. The nanoparticles are pegylated, leading to highly stable dispersions under physiological conditions. Preliminary in vivo studies show the high potential for these ultra‐small ZnGa2O4:Cr3+ nanoparticles to be used as in vivo optical nanotools as they emit without the need for in situ excitation and, thus, avoid the autofluorescence of tissues. 相似文献
96.
Fluorogenic Behaviour of the Hetero‐Diels–Alder Ligation of 5‐Alkoxyoxazoles with Maleimides and their Applications 下载免费PDF全文
Kévin Renault Dr. Laurie‐Anne Jouanno Antoine Lizzul‐Jurse Prof. Dr. Pierre‐Yves Renard Dr. Cyrille Sabot 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(51):18522-18531
Fluorogenic reactions are largely underrepresented in the toolbox of chemoselective ligations despite their tremendous potential, particularly in chemical biology and biochemistry. In this respect, we have investigated in full detail the fluorescence behaviour of the azaphthalamide, a scaffold which is generated through a hetero‐Diels–Alder reaction of 5‐alkoxyoxazole and maleimide derivatives under mild conditions that are compatible with, among others, peptide chemistry. The scope and limitations of such a fluorogenic labelling strategy were examined through four distinct applications, which target enzymatic activities or bioorthogonal reactions. 相似文献
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Cover Picture: Theoretical and Experimental Study on Boron β‐Diketonate Complexes with Intense Two‐Photon‐Induced Fluorescence in Solution and in the Solid State (ChemPhysChem 14/2016) 下载免费PDF全文
100.
Dr. Jean Rouillon Dr. Cyrille Monnereau Dr. Chantal Andraud 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(30):8003-8007
Although tetraphenylethylene (TPE) and its derivatives have been the most commonly used building blocks in the construction of molecules with aggregation-induced emission (AIE) properties, no absolute consensus exists regarding the mechanisms at the origin of the phenomenon. Restriction of intramolecular rotations (RIR) of peripheral phenyls has historically been a dominant paradigm, which has served as a valuable guideline in the molecular engineering of AIEgens. Yet, an increasing number of recent works have established that photoisomerization or photocyclization may actively participate in the nonradiative dissipation of the excitation energy. In this paper, the first experimental evaluation of the quantum efficiencies of these different processes is reported, and photoisomerization is shown to be by far the dominant photophysical pathway in solution, accounting for virtually all nonradiative decay of the molecule‘s excited state in degassed solution. 相似文献