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221.
222.
α‐Peptide–Oligourea Chimeras: Stabilization of Short α‐Helices by Non‐Peptide Helical Foldamers
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Dr. Juliette Fremaux Laura Mauran Dr. Karolina Pulka‐Ziach Dr. Brice Kauffmann Dr. Benoit Odaert Dr. Gilles Guichard 《Angewandte Chemie (International ed. in English)》2015,54(34):9816-9820
Short α‐peptides with less than 10 residues generally display a low propensity to nucleate stable helical conformations. While various strategies to stabilize peptide helices have been previously reported, the ability of non‐peptide helical foldamers to stabilize α‐helices when fused to short α‐peptide segments has not been investigated. Towards this end, structural investigations into a series of chimeric oligomers obtained by joining aliphatic oligoureas to the C‐ or N‐termini of α‐peptides are described. All chimeras were found to be fully helical, with as few as 2 (or 3) urea units sufficient to propagate an α‐helical conformation in the fused peptide segment. The remarkable compatibility of α‐peptides with oligoureas described here, along with the simplicity of the approach, highlights the potential of interfacing natural and non‐peptide backbones as a means to further control the behavior of α‐peptides. 相似文献
223.
Targeting the Two Oncogenic Functional Sites of the HPV E6 Oncoprotein with a High‐Affinity Bivalent Ligand
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Dr. Manjeet Kumar Dr. Thomas Simonson Dr. Gilles Ohanessian Dr. Carine Clavaguéra 《Chemphyschem》2015,16(3):658-665
The association of Mg2+ and H2PO4? in water can give insights into Mg:phosphate interactions in general, which are very widespread, but for which experimental data is surprisingly sparse. It is studied through molecular dynamics simulations (>100 ns) by using the polarizable AMOEBA force field, and the association free energy is computed for the first time. Explicit consideration of outer‐sphere and two types of inner‐sphere association provides considerable insight into the dynamics and thermodynamics of ion pairing. After careful assessment of the computational approximations, the agreement with experimental values indicates that the methodology can be extended to other inorganic and biological Mg:phosphate interactions in solution. 相似文献
226.
Theoretical and experimental research on the self‐assembled system of molecularly imprinted polymers formed by salbutamol and methacrylic acid
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The quantum chemical method was applied for screening functional monomers in the rational design of salbutamol‐imprinted polymers. Salbutamol was the template molecule, and methacrylic acid was the single functional monomer. The LC‐WPBE/6–31G(d,p) method was used to investigate the geometry optimization, active sites, natural bond orbital charges, binding energies of the imprinted molecule, and solvation energy. The mechanism of action between salbutamol and methacrylic acid was also discussed. The theoretical results show that salbutamol interacts with functional monomers by hydrogen bonds, and the salbutamol‐imprinted polymers with a ratio of 1:4 (salbutamol/methacrylic acid) in acetonitrile had the highest stability. The salbutamol‐imprinted polymers were prepared by precipitation polymerization. The experimental results indicated that the maximum adsorption capacity for salbutamol toward molecularly imprinted polymers was 7.33 mg/g, and the molecularly imprinted polymers had a higher selectivity for salbutamol than for norepinephrine and terbutaline sulfate. Herein, the studies can provide theoretical and experimental references for the salbutamol molecular imprinted system. 相似文献
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228.
Dr. Wei Wang Guo‐Ping Li Shao‐Feng Wang Dr. Zi‐Fa Shi Prof. Xiao‐Ping Cao 《化学:亚洲杂志》2015,10(2):377-382
Daphenylline, a novel daphniphyllum alkaloid, boasts a fused and bridging ring system coupled with six stereogenic centers. Here we present a direct and short construction of the ACDE ring system of daphenylline from the known 3‐(2‐bromophenyl)propanal in 10 steps and 17 % overall yield. The synthesis features an iron(III)‐catalyzed aza‐Cope‐Mannich reaction, a self‐terminating 6‐exo‐trig aryl radical‐alkene cyclization and an intramolecular Friedel–Crafts acylation. 相似文献
229.
Damien Cornut Steven Moerkerke Prof. Johan Wouters Prof. Gilles Bruylants Prof. Ivan Jabin 《化学:亚洲杂志》2015,10(2):440-446
The efficient synthesis of calix[6]cryptothiourea 6 was achieved through a two‐step sequence that involves a key [1+1] macrocyclization step. It was shown by NMR spectroscopy that this heteroditopic receptor can bind zwitterions in protic media with an outstanding selectivity for β‐alanine betaine G5 , which is likely due to a high complementarity between the two partners. This result constitutes a rare example of cavity complexation of a zwitterion by a calix[6]arene. In comparison with the parent urea‐based receptors, 6 behaves as a much more efficient host for betaines. This strengthening of the binding properties is due to the better preorganization of the tripodal hydrogen‐bonding cap as well as to the higher acidity of the thiourea groups and their poor ability to self‐associate. Remarkably, host 6 is able to perform solid–liquid as well as liquid–liquid extraction of G5 . Finally, 6 provides an excellent structural model for the binding site of glycine betaine G4 encountered in natural systems. 相似文献
230.
The rate constant of the comparably slow bimolecular NCN radical reaction NCN + O2 has been measured for the first time under combustion relevant conditions using the shock tube method. The thermal decomposition of cyanogen azide (NCN3) served as a clean high‐temperature source of NCN radicals. NCN concentration–time profiles have been detected by narrow‐bandwidth laser absorption at cm?1. The experiments behind incident shock waves have been performed with up to 17% O2 in the reaction gas mixture. At such high O2 mole fractions, it was necessary to take O2 relaxation into account that caused a gradual decrease of the temperature during the experiment. Moreover, following fast decomposition of NCN3 and collision‐induced intersystem crossing of the initially formed singlet NCN to its triplet ground state, an unexpected and slow additional formation of triplet NCN has been observed on a 100‐μs timescale. This delayed NCN formation was attributed to a fast recombination of 1NCN with O2 forming a 3NCNOO adduct acting as a reservoir species for NCN. Rate constant data for the reaction NCN + O2 have been measured at temperatures between 1674 and 2308 K. They are best represented by the Arrhenius expression . No pressure dependence has been observed at pressures between 216 and 706 mbar. 相似文献