Search results for "bond"
showing 10 items of 3527 documents
Dimeres und Trimers 1-Methyl-1-aza-5-stannabicyclo[3.3.01,5]-octan sulfid [MeN(CH2CH2CH2)2SnS]n, Röntgenstrukturanalyse des Dimeren und Gleichgewicht…
1991
Abstract The crystal structure of the dimeric title compound has been determined and refined to R = 0.0266. The core of the nearly centrosymmetric dimer is formed by an almost perfect [SnS]2 rectangle (Sn-S 2.39 and 2.51 A). The two sulfur atoms of this rectangle establish the connecting edge of two distorted trigonal bipyramids around the two tin atoms (Sn … N 2.55 A). Solutions of the title compound contain in addition to the dimer (σ(119Sn) = −4.6 ppm) about 20% of the trimer (+ 10.3 ppm). By quick crystallization a mixture of both oligomers can be transferred into the solid state.
Chemical and Spectroscopical Properties of Medium Sizedtrans- andcis-Bicyclo[n.1.0]alk-2-ynes
1997
Chemical and spectroscopical properties of cis- and trans-cyclopropano-anellated cycloalkynes of medium ring size are investigated and compared with results from force field calculations. IR and 13C-NMR data of the alkynes reflect the deformation of the triple bond due to ring strain. Parallel to bending the reactivity increases with decreasing ring size, the trans fused alkynes prove to be nearly as reactive as the cis fused with a two carbon smaller ring size. The bicycloalkynes are complexed with silver triflate. 13C NMR reveals that the triple bond as well as the cyclopropane serve as ligands.
Nucleophilic substitutions on bromotriazolopyridines - an improved route to 2,6-disubstituted pyridines and to 1,3-disubstituted isoquinolines
1986
Abstract A regiospecific synthesis of 2,6-disubstituted pyridines and of 1,3-disubstituted isoquinolines is described.
A full conformational space analysis of bilirubin
2009
Ab initio methods were utilized in a gas-phase systematic conformational search of bilirubin conformers. The whole molecule was divided into four fragments. Most stable conformers of them were employed to build 196 conformers of the complete bilirubin molecule. Initial geometries were optimized using HF/3-21G level of theory and the minimum energy conformers were then reoptimized at B3LYP/6-31G(d) level. Ridge-tile conformer was the most stable one, in perfect agreement with X-ray data. We found that while tetrapyrrole backbone shows some flexibility, propionic acid side chains have a greater influence in bilirubin conformation because they can interact through different hydrogen bond patte…
Full and Partial Agonism of Ionotropic Glutamate Receptors Indicated by Molecular Dynamics Simulations
2011
Ionotropic glutamate receptors (iGluRs) are synaptic proteins that facilitate signal transmission in the central nervous system. Extracellular iGluR cleft closure is linked to receptor activation; however, the mechanism underlying partial agonism is not entirely understood. Full agonists close the bilobed ligand-binding domain (LBD), while antagonists prevent closure; the transmembrane ion channel either opens or stays closed, respectively. Although some bulky partial agonists produce intermediate iGluR-LBD closure, the available crystal structures also imply that the cleft can be shut with certain partial agonists. Recently, we have shown that the iGluR-LBD closure stage can be recreated b…
Halogen Bonded Analogues of Deep Cavity Cavitands
2014
The first examples of halogen bonded analogues of deep cavity cavitands with guest binding properties, formed between N-alkyl ammonium resorcinarene halides as acceptors and bromotrichloromethane as the donor, are reported in the solid state and in solution.
Synthesis of a New Disulfide Affinity Adsorbent for Purification of Human Uterine Progesterone Receptor
2005
For purification of the human uterine progesterone receptor, an affinity adsorbent was synthesized in which the specific ligand (16 alpha-ethyl-3-oxo-19nor-androst-4-ene 17 beta-carboxylic acid) was bound to derivatized celulose using a disulfide-group-containing spacer. The purified receptor protein, isolated by reductive cleavage of the disulfide bond, bound the synthetic gestagen R5020 with high affinity (Kd 12.2 nmol/l). The affinity gel was highly efficient. A 24000-fold purification of progesterone receptor with a recovery of 40% could be achieved in a single step within 6 h. By means of dodecyl sulphate/polyacrylamide gel electrophoresis two main polypeptides with molecular weights o…
Metallosupramolecular compounds based on Cu(ii)/oxalate/twisted NSSN ligands showing a new in situ S–C bond cleavage
2013
Four new complexes, [Cu2(C2O4) 2(SCS)]·3H2O (1), [Cu2(C 2O4)3(SCSH)2]·H2O (2), [Cu(C2O4)(SS)2]·3H2O (3) and [Cu(C2O4)(SS)]·6H2O (4) [where SCS = bis(4-pyridylthio)methane and SS = 4,4′-dipyridyldisulfide], have been synthesized by the reaction of the SS and SCS ligands with the corresponding copper(ii) oxalate salt. The different synthetic conditions allowed control of the preparation of a 3D open metal-organic framework in 1, a dinuclear zwitterionic molecular compound in 2 and one- and two-dimensional (1D and 2D) coordination polymers in 3 and 4, respectively. Compound 4 was also obtained by in situ transformation of the dithioether ligand (SCS) to the disulfide ligand (SS) under hydrothe…
The role of size and protein shells in the toxicity to algal photosynthesis induced by ionic silver delivered from silver nanoparticles
2019
Abstract Because of their biocide properties, silver nanoparticles (AgNPs) are present in numerous consumer products. The biocidal properties of AgNPs are due to both the interactions between AgNP and cell membranes and the release of dissolved silver (Ag+). Recent studies emphasized the role of different nanoparticle coatings in complexing and storing Ag+. In this study, the availability of dissolved silver in the presence of algae was assessed for three AgNPs with different silver contents (59%, 34% and 7% of total Ag), silver core sizes and casein shell thicknesses. The impact of ionic silver on the photosynthetic yield of Chlamydomonas reinhardtii was used as a proxy to estimate the amo…
1,5-Disubstituted 1,2,3-Triazoles as Amide Bond Isosteres Yield Novel Tumor-Targeting Minigastrin Analogs.
2021
[Image: see text] 1,5-Disubstituted 1,2,3-triazoles (1,5-Tz) are considered bioisosteres of cis-amide bonds. However, their use for enhancing the pharmacological properties of peptides or proteins is not yet well established. Aiming to illustrate their utility, we chose the peptide conjugate [Nle(15)]MG11 (DOTA-dGlu-Ala-Tyr-Gly-Trp-Nle-Asp-Phe-NH(2)) as a model compound since it is known that the cholecystokinin-2 receptor (CCK2R) is able to accommodate turn conformations. Analogs of [Nle(15)]MG11 incorporating 1,5-Tz in the backbone were synthesized and radiolabeled with lutetium-177, and their pharmacological properties (cell internalization, receptor binding affinity and specificity, pla…