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In search for new methods aiming biomimetic synthesis of polyprenylated acylphloroglucinols (PPAPs), we now report the results of an evaluation of sulfonium salts as prenyl, geranyl, and isolavandulyl transfer agents towards benzoylphloroglucinol derivatives, in neutral conditions. As a result, conditions were found for rather efficient C-prenylation of these compounds. The corresponding trimethyl ether gave the best results, but the reaction was accompanied by a deacylation process. Geranyl transfer was also observed, but in low yield, and, interestingly, an isolavandulyl group could be introduced with an appreciable yield. 相似文献
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Dominique Bazin Arnaud Dessombz Christelle Nguyen Hang Korng Ea Frédéric Lioté John Rehr Christine Chappard Stephan Rouzière Dominique Thiaudière Solen Reguer Michel Daudon 《Journal of synchrotron radiation》2014,21(1):136-142
Osteoporosis represents a major public health problem through its association with fragility fractures. The public health burden of osteoporotic fractures will rise in future generations, due in part to an increase in life expectancy. Strontium‐based drugs have been shown to increase bone mass in postmenopausal osteoporosis patients and to reduce fracture risk but the molecular mechanisms of the action of these Sr‐based drugs are not totally elucidated. The local environment of Sr2+ cations in biological apatites present in pathological and physiological calcifications in patients without such Sr‐based drugs has been assessed. In this investigation, X‐ray absorption spectra have been collected for 17 pathological and physiological calcifications. These experimental data have been combined with a set of numerical simulations using the ab initioFEFF9 X‐ray spectroscopy program which takes into account possible distortion and Ca/Sr substitution in the environment of the Sr2+ cations. For selected samples, Fourier transforms of the EXAFS modulations have been performed. The complete set of experimental data collected on 17 samples indicates that there is no relationship between the nature of the calcification (physiological and pathological) and the adsorption mode of Sr2+ cations (simple adsorption or insertion). Such structural considerations have medical implications. Pathological and physiological calcifications correspond to two very different preparation procedures but are associated with the same localization of Sr2+versus apatite crystals. Based on this study, it seems that for supplementation of Sr at low concentration, Sr2+ cations will be localized into the apatite network. 相似文献
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Christelle Nguyen Hang Korng Ea Dominique Thiaudiere Solenn Reguer Didier Hannouche Michel Daudon Frédéric Lioté Dominique Bazin 《Journal of synchrotron radiation》2011,18(3):475-480
Calcium (Ca2+)‐containing crystals (CCs), including basic Ca2+ phosphate (BCP) and Ca2+ pyrophosphate dihydrate (CPPD) crystals, are associated with severe forms of osteoarthritis (OA). Growing evidence supports a role for abnormal articular cartilage mineralization in the pathogenesis of OA. However, the role of Ca2+ compounds in this mineralization process remains poorly understood. Six patients, who underwent total knee joint replacement for primary OA, have been considered in this study. Cartilage from femoral condyles and tibial plateaus in the medial and lateral compartments was collected as 1 mm‐thick slices cut tangentially to the articular surface. First, CCs presence and biochemical composition were assessed using Fourier transform infrared spectroscopy (FT‐IR). Next, Ca2+ compound biochemical form was further assessed using X‐ray absorption spectroscopy (XAS) performed at the Ca2+K‐absorption edge. Overall, 12 cartilage samples were assessed. Using FT‐IR, BCP and CPPD crystals were detected in four and three out of 12 samples, respectively. Ca2+ compound biochemical forms differed between areas with versus without CCs, when compared using XAS. The complete set of data shows that XANES spectroscopy can be used to accurately characterize sparse CCs in human OA cartilage. It is found that Ca2+ compounds differ between calcified and non‐calcified cartilage areas. In calcified areas they appear to be mainly involved in calcifications, namely Ca2+ crystals. 相似文献
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S. Reguer P. Dillmann F. Mirambet J. Susini P. Lagarde 《Applied Physics A: Materials Science & Processing》2006,83(2):189-193
Synchrotron-based micro-X-ray absorption spectroscopy is used in the present study to obtain chemical information at the microscopic
scale such as coordination and oxidation state of Fe atoms in phases constituting corrosion products within archaeological
iron artefacts buried in soil. This technique is required in order to answer questions about the iron corrosion process related
to the presence of chloride, particularly for restoration and conservation of metallic artefacts of the cultural heritage.
The samples available for X-ray microprobe analyses are cross sections from corroded iron archaeological objects. Previously,
complementary techniques have been used such as μXRD and μRaman. This specific study applies micro-X-ray absorption spectroscopy
to determine the spatial variation of the predominant Fe oxidation state and to identify the corresponding crystallographic
phase. The analyses performed at Fe and Cl K-edges (μXANES) reveal the correlation between the valence distribution in the
corrosion products and the evolution of the chloride concentration. In addition to the presence of the well-known iron oxyhydroxide
β-FeOOH: akaganeite, we highlight the presence of another important phase, the β-Fe2(OH)3Clhydroxychloride. These important findings help to gain new insights concerning the influence of such phases in the iron
corrosion mechanism within their precise characterization.
PACS 61.10.Ht; 61.10.-i; 68.49.Uv 相似文献
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Dominique Bazin Xavier Carpentier Olivier Traxer Dominique Thiaudière Andrea Somogyi Solenn Reguer Glenn Waychunas Paul Jungers Michel Daudon 《Journal of synchrotron radiation》2008,15(5):506-509
This very first report of an X‐ray absorption spectroscopy experiment at Synchrotron SOLEIL is part of a long‐term study dedicated to pathological calcifications. Such biological entities composed of various inorganic and/or organic compounds also contain trace elements. In the case of urinary calculi, different papers already published have pointed out that these oligo‐elements may promote or inhibit crystal nucleation as well as growth of mineral. Use of this analytical tool specific to synchrotron radiation, allowing the determination of the local environment of oligo‐elements and thus their occupation site, contributes to the understanding of the role of trace elements in pathological calcifications. 相似文献
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F. Mirambet S. Reguer E. Rocca S. Hollner D. Testemale 《Applied Physics A: Materials Science & Processing》2010,99(2):341-349
Metallic artefacts of the cultural heritage are often stored in uncontrolled environmental conditions. They are very sensitive
to atmospheric corrosion caused by a succession of wet and dry periods due to variations of relative humidity and temperature.
To avoid the complete degradation of the metallic artefacts, new preventive strategies must be developed. In this context,
we have studied new compounds based on sodium carboxylates solutions CH3(CH2)
n−2COO−, Na+ hereafter called NaC
n
. They allow the formation of a passive layer at the metallic surface composed of a metal–carboxylate complex. To understand
the action of those inhibitors in the passivation process of iron we have performed electrochemical measurements and surface
characterisation. Moreover, to monitor in real time the growth of the coating, in situ X-ray absorption spectroscopy (XAS)
experiments at iron K-edge were carried out in an electrochemical cell. These analyses have shown that in the case of NaC10 solution, the protection of iron surface is correlated to the precipitation of a well-organised layer of FeC10. These experiments confirmed that this compound is a fully oxidised trinuclear Fe(III) complex containing decanoate anions
as ligands. Such information concerning the passive layer is a key factor to evaluate its stability and finally the long-term
efficiency of the protection treatment. 相似文献
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Jean‐Philippe Echard Loïc Bertrand Dr. Alex von Bohlen Dr. Anne‐Solenn Le Hô Dr. Céline Paris Dr. Ludovic Bellot‐Gurlet Dr. Balthazar Soulier Agnès Lattuati‐Derieux Dr. Sylvie Thao Laurianne Robinet Dr. Bertrand Lavédrine Prof. Stéphane Vaiedelich 《Angewandte Chemie (International ed. in English)》2010,49(1):1-1
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Jean‐Philippe Echard Loïc Bertrand Dr. Alex von Bohlen Dr. Anne‐Solenn Le Hô Dr. Céline Paris Dr. Ludovic Bellot‐Gurlet Dr. Balthazar Soulier Agnès Lattuati‐Derieux Dr. Sylvie Thao Laurianne Robinet Dr. Bertrand Lavédrine Prof. Stéphane Vaiedelich 《Angewandte Chemie (International ed. in English)》2010,49(1):197-201