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151.
Abstract— The absorption spectroscopic study of retinyl polyenes, i.e. all- trans retinal, 9- cis retinal, 13- cis retinal, all- trans retinol, 13- cis retinol and all- trans retinyl acetate in solid films is discussed. The spectra of the films with low surface coverages obtained from dilute solutions are red shifted relative to their solution spectra. This shift is interpreted as due to the weak interaction between the surface and polyene molecules. With increased surface coverages, i.e. the films obtained from concentrated solutions, the retinals show a large red shift whereas a blue shift is observed with the retinols. Chromophore–chromophore interactions in addition to the surface effects are believed to be responsible for such observations. Effect of surface causing permanent changes in molecule is also discussed. 相似文献
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153.
DNA‐Templated [2+2] Photocycloaddition: A Straightforward Entry into the Aplysinopsin Family of Natural Products 下载免费PDF全文
Nicolas Duchemin Adam Skiredj Justine Mansot Karine Leblanc Dr. Jean‐Jacques Vasseur Dr. Mehdi A. Beniddir Dr. Laurent Evanno Prof. Dr. Erwan Poupon Prof. Dr. Michael Smietana Dr. Stellios Arseniyadis 《Angewandte Chemie (International ed. in English)》2018,57(36):11786-11791
Biosynthetic considerations inspired us to harness the templating properties offered by DNA to promote a [2+2] photoinduced cycloaddition. The method was developed based on the dimerization of (E)‐aplysinopsin, which was previously shown to be unproductive in solution. In sharp contrast, exposure of this tryptophan‐derived olefin to light in the presence of salmon testes DNA (st‐DNA) reproducibly afforded the corresponding homo‐dimerized spiro‐fused cyclobutane in excellent yields. DNA provides unique templating interactions enabling a singular mimic of the solid‐state aggregation necessary for the [2+2] photocycloaddition to occur. This method was ultimately used to promote the prerequisite dimerizations leading to both dictazole B and tubastrindole B, thus constituting the first example of a DNA‐mediated transformation to be applied to the total synthesis of a natural product. 相似文献
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Jonathan Leblanc Mathilde Mercier Christian Fonteix Fernand Pla 《Macromolecular Symposia》2007,259(1):85-93
Summary: This work deals with the development of the dispersed phase morphology in immiscible blends of poly(ethylene glycol)/polyamide 66 (PEG/PA) with an extremely low viscosity ratio. The blends were obtained, under different operating conditions, by melt blending in an internal mixer. The objective was to examine the influence of the main processing parameters on the particles size of the minor phase (PEG). A model was elaborated to describe the dependence of the particle size on interfacial tension, PEG concentration, shear rate and viscosity ratio between the two blend components. 相似文献
158.
ClaudiaM. Cardona StephanH. Jannach Hao Huang Yukiko Itojima RogerM. Leblanc RobertE. Gawley GaryA. Baker EricB. Brauns 《Helvetica chimica acta》2002,85(10):3532-3558
Second and third generation Newkome‐type trifurcated dendrimers, containing either a coumarin or dansyl fluorescent probe at the dendrimer core, have been synthesized and attached to ArgoGel ® solid‐phase‐synthesis beads. Subsequent reaction with rhodamine dye shows that the dye can penetrate throughout the beads to acylate the remaining sites. Thus, it is possible to achieve a spatially resolved microdomain for library formation at the core of the dendrimer, primarily on the bead's periphery, and a second microdomain suitable for derivatization by other reagents such as encoding tags and fluorescent sensors. 相似文献
159.
RM. Murugappan M. Karthikeyan A. Aravinth MR. Alamelu 《Applied biochemistry and biotechnology》2012,168(8):2170-2183
In the present study, siderophore produced by the marine yeast Aureobasidium pullulans was characterized as hydroxamate by chemical and bioassays. The hydroxamate assignment was supported by the appearance of peaks at 1,647.21?C1,625.99?cm?1 and at 1,435.04?cm?1 in the infrared spectrum. The purified siderophore exhibited specific growth-promoting activity under iron-limited conditions for siderophore auxotrophic probiotic bacteria. Cross-utilization of siderophore indicates a symbiotic relationship between the yeast A. pullulans and the selected probiotic bacterial strains. Statistical optimization of medium components for improved siderophore production in A. pullulans was depicted by response surface methodology. The shift in UV?CVis spectroscopy indicates the photoreactive property and subsequent oxidative cleavage of purified siderophore on exposure to sunlight. 相似文献
160.
K. S. Pramod V. Vijayasundaram N. Krishnakumar PL. RM. Palaniappan 《Journal of Thermal Analysis and Calorimetry》2012,108(1):133-139
This article presents the changes in the thermal properties of the control and titanium dioxide (TiO2), both nano and bulk exposed Zebrafish bones by using thermo analytical techniques. The result shows that the mass loss due
to the thermal decomposition occurs in three distinct steps due to loss of water, organic and inorganic materials. The titanium
dioxide exposed bones present a different thermal behaviour compared to the control bones. The residue masses are found to
be increased due to titanium dioxide exposure. In particular, nano titanium dioxide exposure increases the residue mass level
significantly (three fold) when compared to titanium dioxide bulk exposure. These thermal characteristics can be used as a
qualitative method to check the metal oxide intoxication in biological samples. 相似文献