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101.
Carbon,nitrogen and sulphur isotopic fractionation in captive juvenile hooded seal (Cystophora cristata): Application for diet analysis
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102.
Dr. Xiong‐Jie Jiang Dr. Janet T. F. Lau Dr. Qiong Wang Prof. Dennis K. P. Ng Prof. Pui‐Chi Lo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(24):8273-8281
A diiodo distyryl boron dipyrromethene (BODIPY) core was conjugated to two ferrocenyl quenchers through acid‐labile ketal and/or thiol‐cleavable disulfide linkers, of which the fluorescence and photosensitizing properties were significantly quenched through a photoinduced electron‐transfer process. The two symmetrical analogues that contained either the ketal or disulfide linkers could only be activated by a single stimulus, whereas the unsymmetrical analogue was responsive to dual stimuli. Upon interaction with acid and/or dithiothreitol (DTT), these linkers were cleaved selectively. The separation of the BODIPY core and the ferrocenyl moieties restored the photoactivities of the former in phosphate buffered saline and inside the MCF‐7 breast cancer cells, rendering these compounds as potential activable photosensitizers for targeted photodynamic therapy. The dual activable analogue exhibited the greatest enhancement in intracellular fluorescence intensity in both an acidic environment (pH 5) and the presence of DTT (4 mm ). Its photocytotoxicity against MCF‐7 cells also increased by about twofold upon preincubation with 4 mm of DTT. The activation of this compound was also demonstrated in nude mice bearing a HT29 human colorectal carcinoma. A significant increase in fluorescence intensity in the tumor was observed over 9 h after intratumoral injection. 相似文献
103.
104.
Loïc Quinton Denis Servent Emmanuelle Girard Jordi Molgó Jean-Pierre Le Caer Christian Malosse El Ali Haidar Alain Lecoq Nicolas Gilles Julia Chamot-Rooke 《Analytical and bioanalytical chemistry》2013,405(15):5341-5351
Nicotinic acetylcholine receptors (nAChRs) are one of the most important families in the ligand-gated ion channel superfamily due to their involvement in primordial brain functions and in several neurodegenerative pathologies. The discovery of new ligands which can bind with high affinity and selectivity to nAChR subtypes is of prime interest in order to study these receptors and to potentially discover new drugs for treating various pathologies. Predatory cone snails of the genus Conus hunt their prey using venoms containing a large number of small, highly structured peptides called conotoxins. Conotoxins are classified in different structural families and target a large panel of receptors and ion channels. Interestingly, nAChRs represent the only subgroup for which Conus has developed seven distinct families of conotoxins. Conus venoms have thus received much attention as they could represent a potential source of selective ligands of nAChR subtypes. We describe the mass spectrometric-based approaches which led to the discovery of a novel α-conotoxin targeting muscular nAChR from the venom of Conus ermineus. The presence of several posttranslational modifications complicated the N-terminal sequencing. To discriminate between the different possible sequences, analogs with variable N-terminus were synthesized and fragmented by MS/MS. Understanding the fragmentation pathways in the low m/z range appeared crucial to determine the right sequence. The biological activity of this novel α-conotoxin (α-EIIA) that belongs to the unusual α4/4 subfamily was determined by binding experiments. The results revealed not only its selectivity for the muscular nAChR, but also a clear discrimination between the two binding sites described for this receptor. 相似文献
105.
Isotope labeling liquid chromatography–mass spectrometry (LC–MS) is a major analytical platform for quantitative proteome analysis. Incorporation of isotopes used to distinguish samples plays a critical role in the success of this strategy. In this work, we optimized and automated a chemical derivatization protocol (dimethylation after guanidination, 2MEGA) to increase the labeling reproducibility and reduce human intervention. We also evaluated the reagent compatibility of this protocol to handle biological samples in different types of buffers and surfactants. A commercially available liquid handler was used for reagent dispensation to minimize analyst intervention and at least twenty protein digest samples could be prepared in a single run. Different front-end sample preparation methods for protein solubilization (SDS, urea, Rapigest™, and ProteaseMAX™) and two commercially available cell lysis buffers were evaluated for compatibility with the automated protocol. It was found that better than 94% desired labeling could be obtained in all conditions studied except urea, where the rate was reduced to about 92% due to carbamylation on the peptide amines. This work illustrates the automated 2MEGA labeling process can be used to handle a wide range of protein samples containing various reagents that are often encountered in protein sample preparation for quantitative proteome analysis. 相似文献
106.
Thomas W. Gero Larry W. Jaques Richard P. Mays Debra H. Reid Dwight A. Shamblee Young S. Lo 《合成通讯》2013,43(3-4):553-559
A convenient method to prepare 5-halo-2-hydroxy-nicotinic acid is described. 相似文献
107.
Gabriele Saleh Dr. Raffaella Soave Dr. Leonardo Lo Presti Prof. Riccardo Destro 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(10):3490-3503
The accurate, experimental charge density distribution, ρ( r ), of the potent antimalarial drug dihydroartemisinin (DHA) has been derived for the first time from single‐crystal X‐ray diffraction data at T=100(2) K. Gas‐phase and solid‐state DFT simulations have also been performed to provide a firm basis of comparison with experimental results. The quantum theory of atoms in molecules (QTAIM) has been employed to analyse the ρ( r ) scalar field, with the aim of classifying and quantifying the key real‐space elements responsible for the known pharmacophoric features of DHA. From the conformational perspective, the bicyclo[3.2.2]nonane system fixes the three‐dimensional arrangement of the 1,2,4‐trioxane bearing the active O? O redox centre. This is the most nucleophilic function in DHA and acts as an important CH???O acceptor. On the contrary, the rest of the molecular backbone is almost neutral, in accordance with the lipophilic character of the compound. Another remarkable feature is the C? O bond length alternation along the O‐C‐O‐C polyether chain, due to correlations between pairs of adjacent C? O bonds. These bonding features have been related with possible reactivity routes of the α‐ and β‐DHA epimers, namely 1) the base‐catalysed hemiacetal breakdown and 2) the peroxide reduction. As a general conclusion, the base‐driven proton transfer has significant non‐local effects on the whole polyether chain, whereas DHA reduction is thermodynamically favourable and invariably leads to a significant weakening (or even breaking) of the O? O bond. The influence of the hemiacetal stereochemistry on the electronic properties of the system has also been considered. Such findings are discussed in the context of the known chemical reactivity of this class of important antimalarial drugs. 相似文献
108.
Prof. Giuseppe Alibrandi Dr. Valeria Amendola Dr. Greta Bergamaschi Dr. Riccardo Dollenz Prof. Luigi Fabbrizzi Prof. Maurizio Licchelli Dr. Carmelo Lo Vecchio 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(11):3729-3734
The combined activity of the 1.1.1‐cryptand and of a dicopper(II) bistren cryptate complex including chloride makes the Cl? ion be continuously and slowly delivered to the solution, without any external intervention. The 1.1.1‐cryptand slowly releases OH? ions, according to a defined kinetics, and each OH? ion displaces a Cl? ion from the cryptate. Chloride displacement induces a sharp colour change from bright yellow to aquamarine and can be conveniently monitored spectrophotometrically, even in diluted solutions. The 1.1.1‐cryptand is the motor of a molecular dispenser (the dicopper(II) cryptate) delivering chloride ion automatically, from the inside of the solution. 相似文献
109.
Chengshuo Shen Dr. Emmanuel Anger Dr. Monika Srebro Dr. Nicolas Vanthuyne Dr. Loïc Toupet Prof. Christian Roussel Prof. Jochen Autschbach Prof. Régis Réau Dr. Jeanne Crassous 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(49):16722-16728
Homochiral and heterochiral cis‐bis‐cycloplatinated‐[6]helicene derivatives 1 b1, 2 , as representative examples of platina[6]helicenes that share a common platinum center, have been prepared. A diastereo‐ and enantioselective synthesis, which combines CH activation and dynamic isomerization from heterochiral structure 1 b2 into homochiral structure 1 b1 , is also described. Overall, this isomerization process results in the transfer of chiral information from one helicene moiety to the other one. The chiroptical properties of homochiral (P)‐ and (M)‐ 1 b1 were greatly modified upon oxidation into their corresponding (P)‐ and (M)‐diiodo‐PtIV complexes ( 5 ). The changes were also analyzed by performing theoretical calculations. C? H activation in the synthesis of organometallic helicenes is further demonstrated by the preparation of cis‐bis‐cycloplatinated‐[8]helicene 1 c . 相似文献
110.
Azetidinium triflates were reacted in a one-pot two-steps sequence involving, generation of an azetidinium ylide, its alkylation with an halide, and final regioselective Hofmann elimination of the produced alkylated azetidinium ion to yield substituted α,β-unsaturated nitriles bearing an aminoethyl side-chain. The scope of this sequence was examined, and was found to depend both on the steric hindrance around the reactive center in the starting azetidinium salt, and on the nature of the reacting halide. Produced acrylonitriles were further used in DBU-catalyzed conjugate addition of amines, to yield 4-amino-2-aminomethyl-butyronitriles with fair diastereoselectivity, or, alternatively, to give C2 symmetrical cyclopropanes. 相似文献