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751.
Dr. Antoine Robert Dr. Guillaume Naulet Dr. Harald Bock Dr. Nicolas Vanthuyne Marion Jean Dr. Michel Giorgi Dr. Yannick Carissan Dr. Christie Aroulanda Antoine Scalabre Dr. Emilie Pouget Dr. Fabien Durola Dr. Yoann Coquerel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(63):14364-14369
Cyclobis[n]helicenes (n=3 or 5) are chiral D2-symmetric π-conjugated macrocycles with stable lemniscular, or figure-eight, shapes. The conformational analysis of five different cyclobis[n]helicenes revealed that these molecules can only exist as their lemniscular conformers with high barriers to enantiomerization (>200 kJ mol−1). The enantiomers of a cyclobis[5]helicene were resolved by HPLC and their unusual chiroptical properties were attributed to the inherent chirality of their macrocyclic figure-eight. 相似文献
752.
Sacha J. Pidot Marion Herisse Liam Sharkey Liselle Atkin Jessica L. Porter Torsten Seemann Benjamin P. Howden Mark A. Rizzacasa Timothy P. Stinear 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(12):4036-4041
The nargenicin family of antibiotics are macrolides containing a rare ether‐bridged cis‐decalin motif. Several of these compounds are highly active against multi‐drug resistant organisms. Despite the identification of the first members of this family almost 40 years ago, the genetic basis for the production of these molecules and the enzyme responsible for formation of the oxa bridge, remain unknown. Here, the 85 kb nargenicin biosynthetic gene cluster was identified from a human pathogenic Nocardia arthritidis isolate and this locus is solely responsible for nargenicin production. Further investigation of this locus revealed a putative iron‐α‐ketoglutarate‐dependent dioxygenase, which was found to be responsible for the formation of the ether bridge from the newly identified deoxygenated precursor, 8,13‐deoxynargenicin. Uncovering the nargenicin biosynthetic locus provides a molecular basis for the rational bioengineering of these interesting antibiotic macrolides. 相似文献
753.
Kenji Caprice Marion Pupier Antonio Bauz Antonio Frontera Fabien B. L. Cougnon 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(24):8137-8141
A molecular Solomon link adopts different conformations in acetonitrile ( 1 ) and in water ( 2 ). Contrary to expectations, the main driving force of the transformation is not the change in medium polarity, but the cooperative binding of about four molecules of water, forming a tiny droplet in the central cavity of 2 . Mechanistic studies reveal that the four binding sites can simultaneously switch between an inactive state (unable to bind water) and an active state (able to bind water) during the transformation. Spatial and temporal coordination of switching events is commonly observed in biological systems but has been rarely achieved in artificial systems. Here, the concerted activation of the four switchable sites is controlled by the topology of the whole molecule. 相似文献
754.
Marion Girod 《Rapid communications in mass spectrometry : RCM》2019,33(Z3):64-71
Mass spectrometry offers an arsenal of tools for diverse proteomic investigations. This perspective article reviews some of the recent developments in the field of coupling laser‐induced dissociation with mass spectrometry (LID‐MS). Strategies involving labelling with a chromophore to induce specific photo‐absorption properties are considered, with a focus on specific amino acid derivatization. Some of the opportunities and challenges of LID‐MS after targeted labelling for increasing specificity in complex sample analysis are discussed. 相似文献
755.
756.
Marion Pommet Andréas Redl Marie-Hélène Morel Sandra Domenek Stéphane Guilbert 《Macromolecular Symposia》2003,197(1):207-218
Proteins, as heteropolymers, offer a large range of possible interactions and chemical reactions. The thermoplastic behavior of proteins has been studied in order to produce bioplastics by thermal or thermomechanical processes such as mixing, extrusion or hot molding. The extrusion trials were performed by using a co-rotating twin-screw extruder, recording torque, temperature and die pressure. Batch mixing was done in a two blade counter-rotating mixer, with continuous recording of torque and product temperature. Proteins were alternatively extruded, mixed or hot molded under a large range of processing conditions. Protein aggregation during each process was estimated from the accumulation of SDS-insoluble protein fraction. Protein aggregation evidences a cross-linking reaction the activation energy of which was dependent on the thermoplastic process used. The increase in network density appears to be induced by the severity of the treatment: temperature and shear strongly affect the structural characteristics of the protein-based bioplastics. 相似文献
757.
Colorless lath-shaped single crystals of the title compound are obtained from a melt of Y2O3, YF3, and SiO2 (2:5:3 molar ratio) using CsCl as a flux (evacuated silica tube, 973 K, 9 d, 10 K/h cooling rate). 相似文献
758.
759.
Marion Helou Olivier Miserque Jean‐Michel Brusson Jean‐Franois Carpentier Sophie M. Guillaume 《Macromolecular rapid communications》2009,30(24):2128-2135
α,ω‐Dihydroxy‐telechelic poly(trimethylenecarbonate), HO‐PTMC‐OH, is synthesized from the controlled “immortal” ring‐opening polymerization (ROP) of trimethylene carbonate under mild conditions (bulk, 60 °C), using ZnEt2 or, more efficiently, [(BDI)Zn(N(SiMe3)2)] (BDI = CH(CMeNC6H3‐2,6‐iPr2)2) as catalyst precursor, in the presence of a diol HO‐R‐OH (R = (CH2)2 or CH2C6H4CH2; 0.5–10 equiv. vs Zn) acting both as co‐initiator and chain transfer agent. Alternatively, HO‐PTMC‐OH is prepared upon hydrogenolysis of HO‐PTMC‐OCH2Ph, initially prepared from the ROP of TMC using the [(BDI)Zn(N(SiMe3)2)]/PhCH2OH system, under smooth operating conditions using Pd/charcoal. Well‐defined dihydroxy‐functionalized PTMCs of molar mass ranging from = 2 000 to 109 500 g · mol−1 were thus quantitatively obtained and fully characterized by NMR, MALDI‐TOF‐MS and SEC analyses. The versatility of this “immortal” ROP allows the preparation of alike α,ω‐functional polyester such as linear HO‐poly(lactide)‐OH, as well as star polymers such as the glycerol‐based PTM‐OH3.