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21.
Lancelot N Elbayed K Raya J Piotto M Briand JP Formaggio F Toniolo C Bianco A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(6):1317-1323
A tetra- and a hepta-homopeptide from the C(alpha)-tetrasubstituted Aib (alpha-aminoisobutyric acid) residue were covalently linked to the POEPOP resin by the fragment-condensation approach. The conformational preferences of the two model peptides were determined for the first time on a solid support by means of high-resolution magic angle spinning NMR spectroscopy. The results obtained indicate that the Aib homopeptides adopt a regular 3(10)-helical structure even when they are covalently bound to a polymeric matrix, and thus confirm the remarkable conformational stability of the peptides rich in this amino acid. An ATR-FTIR spectroscopic investigation, performed in parallel, also confirmed that these polymer-bound peptides do indeed adopt a helical conformation. The results of this study open the possibility to exploit the peptide-resin conjugates based on C(alpha)-tetrasubstituted alpha-amino acids as helpful, structurally organized templates in molecular recognition studies or as catalysts in asymmetric synthesis. 相似文献
22.
George N Pick H Vogel H Johnsson N Johnsson K 《Journal of the American Chemical Society》2004,126(29):8896-8897
The specific and covalent labeling of fusion proteins with synthetic molecules opens up new ways to study protein function in the living cell. Here we present a novel method that allows for the specific and exclusive extracellular labeling of proteins on the surfaces of live cells with a large variety of synthetic molecules including fluorophores, protein ligands, or quantum dots. The approach is based on the specific labeling of fusion proteins of acyl carrier protein with synthetic molecules through post-translational modification catalyzed by phosphopantetheine transferase. The specificity and versatility of the labeling should allow it to become an important tool for studying and manipulating cell surface proteins and for complementing existing approaches in cell surface engineering. 相似文献
23.
Patrick Gredin Gwenaël Corbel Jonathan P. Wright Nathalie Dupont Ariel de Kozak 《无机化学与普通化学杂志》2003,629(11):1960-1964
Ba3Cu2Al2F16 is monoclinic: a = 7.334(1)Å, b = 5.320(2)Å, c = 16.022(1)Å, β = 96.34(1)°, Z = 2. Its crystal structure was solved in the space group P21 (No. 4) from synchrotron X‐ray single crystal data using 2685 unique reflections (2639 with Fo/σ(Fo) > 4). The final R factor is 0.044. The structure consists of a succession along the c‐axis of the cell of three layers of two different kinds of sheets developing in the (a, b) plane. The first one, formulated [(AlF5)2]∞4— and hereafter named A, is built up from infinite cis‐chains of aluminium‐fluorine octahedra [AlF6], linked by two vertices and distanced by a. The second one, formulated [Cu2AlF11]∞4— and named B, is bidimensional. It is constituted of distorted copper‐fluorine octahedra [CuF6], linked by edges, which form infinite chains interconnected by three vertices of isolated [AlF6] octahedra. The stacking sequence of the sheets is (A, B, B)∞. The barium ions, 12‐coordinated, are inserted between the sheets. The crystal structure of Ba3Cu2Al2F16 is closely related to that of Ba4Cu2Al3F21. Only the proportion and the stacking sequence of the two kinds of sheets in the c‐direction differ, according to two different compositions and two different symmetries. 相似文献
24.
Trens P Tanchoux N Galarneau A Fajula F 《The journal of physical chemistry. B》2005,109(34):16415-16420
In the present work, the corresponding states principle is proposed as a new approach to clarify the comparison between adsorption-desorption isotherms obtained on porous solids. The applicability of this principle at the capillary critical point in adsorption-desorption isotherms is demonstrated. Deviations of the Clausius-Clapeyron curves in reduced coordinates are interpreted in terms of polarizability, and those are perfectly correlated using analogous Pitzer acentric factors in confined environments. New acentric factors are proposed to take confinement effects in mesoporous materials into account. Enthalpic excesses during capillary condensation could be predicted, and those are supported by calorimetric experiments. 相似文献
25.
Yam CM Pradier CM Salmain M Fischer-Durand N Jaouen G 《Journal of colloid and interface science》2002,245(1):204-207
Fourier transform infrared reflection-absorption spectroscopy (FT-IRRAS) was successively used to monitor the covalent immobilization of biotin molecules onto a planar gold substrate covered with a self-assembled monolayer of cystamine and to transduce the molecular recognition of avidin and biotin. This detection was greatly facilitated and made selective by the labeling of avidin and of biotin with various transition metal carbonyl probes. The binding of avidin to the surface was optimized by blocking the nonspecific binding sites by adsorption of an unrelated protein, bovine serum albumin. This work exemplifies the feasibility of detecting biomolecular associations involving molecules of any size at a liquid/solid interface by using a simple and accessible surface analysis technique. 相似文献
26.
Alexander Mutschke Annika Schulz Marko Bertmer Clemens Ritter Antti J. Karttunen Gregor Kieslich Nathalie Kunkel 《Chemical science》2022,13(26):7773
The four compounds A3MO4H (A = Rb, Cs; M = Mo, W) are introduced as the first members of the new material class of the transition oxometalate hydrides. The compounds are accessible via a thermal synthesis route with carefully controlled conditions. Their crystal structures were solved by neutron diffraction of the deuterated analogues. Rb3MoO4D, Cs3MoO4D and Cs3WO4D crystallize in the antiperovskite-like K3SO4F-structure type, while Rb3WO4D adopts a different orthorhombic structure. 2H MAS NMR, Raman spectroscopy and elemental analysis prove the abundance of hydride ions next to oxometalate ions and experimental findings are supported by quantum chemical calculations. The tetragonal phases are direct and wide band gap semiconductors arising from hydride states, whereas Rb3WO4H shows a unique, peculiar valence band structure dominated by hydride states.The synthesis, structures and electronic properties of the first four heteroanionic compounds containing both hydride and transition oxometalate ions are reported. 相似文献
27.
Alain Valla Nathalie Méheux Dominique Cartier Benoist Valla Laurent Dufossé 《合成通讯》2013,43(2):184-190
A synthesis of a new C-15 phosphorus ylide from a C-14 enaminone is reported. This reagent, which undergoes selective 1,2- or 1,4-additions with saturated and unsaturated aldehydes, may find some synthetic use for the preparation of β-end-group retinoid derivatives. 相似文献
28.
29.
Gérald Lemonnier Nathalie Van HijfteMuriel Sebban Thomas PoissonXavier Pannecoucke 《Tetrahedron》2014
Herein, an efficient access to fluorinated homoallylic alcohol is reported. The fluorinated alcohols were obtained in good to excellent yield using indium and halo-fluorinated allylic derivatives. The developed methodology using γ-substituted halo-fluorinated allylic derivatives gave the corresponding α-substituted fluorinated homoallylic alcohol in good yields and good diastereoselectivities up to 86:14. 相似文献
30.
Nathalie A. Desrosiers Garry Milman Damodara R. Mendu Dayong Lee Allan J. Barnes David A. Gorelick Marilyn A. Huestis 《Analytical and bioanalytical chemistry》2014,406(17):4117-4128
Oral fluid (OF) enables non-invasive sample collection for on-site drug testing, but performance of on-site tests with occasional and frequent smokers’ OF to identify cannabinoid intake requires further evaluation. Furthermore, as far as we are aware, no studies have evaluated differences between cannabinoid disposition among OF collection devices with authentic OF samples after controlled cannabis administration. Fourteen frequent (≥4 times per week) and 10 occasional (less than twice a week) adult cannabis smokers smoked one 6.8 % ?9-tetrahydrocannabinol (THC) cigarette ad libitum over 10 min. OF was collected with the StatSure Saliva Sampler, Oral-Eze, and Draeger DrugTest 5000 test cassette before and up to 30 h after cannabis smoking. Test cassettes were analyzed within 15 min and gas chromatography–mass spectrometry cannabinoid results were obtained within 24 h. Cannabinoid concentrations with the StatSure and Oral-Eze devices were compared and times of last cannabinoid detection (t last) and DrugTest 5000 test performance were assessed for different cannabinoid cutoffs. 11-nor-9-Carboxy-THC (THCCOOH) and cannabinol concentrations were significantly higher in Oral-Eze samples than in Stat-Sure samples. DrugTest 5000 t last for a positive cannabinoid test were median (range) 12 h (4–24 h) and 21 h (1–?≥?30 h) for occasional and frequent smokers, respectively. Detection windows in screening and confirmatory tests were usually shorter for occasional than for frequent smokers, especially when including THCCOOH ≥20 ng L?1 in confirmation criteria. No differences in t last were observed between collection devices, except for THC ≥2 μg L?1. We thus report significantly different THCCOOH and cannabinol, but not THC, concentrations between OF collection devices, which may affect OF data interpretation. The DrugTest 5000 on-site device had high diagnostic sensitivity, specificity, and efficiency for cannabinoids. 相似文献