Search results for "oie"
showing 10 items of 1669 documents
Redox-active crown ethers derived from biphenyl. Electrochemical and spectroscopic study of binding processes with alkali, alkali-earth and mercury s…
1998
Abstract Three new electroactive ligands, 3a, 3b and 3c, that contain the biphenyl frameworks in their structure were prepared. These new ligands presented three interesting characteristics: 1) they exhibited a reversible oxidation, 2) the oxidation induced a conformational change in the crown moiety and 3) they had two different coordination centers, the crown ether and the dimethylamino groups. Electrochemical and spectroscopic studies using alkali, alkali-earth and mercury salts were carried out.
Biphenyl macrolactams in anion complexation. Selective naked-eye fluoride recognition
2004
Two colorimetric anion sensors 1 and 2 allow for the selective differentiation of fluoride in the presence of other anions. Two different types of species have been observed in the complexation process, one of them is a co-ordination complex and the other is a salt generated by ligand deprotonation. The deprotonation reaction induces a conformational change, giving rise to a symmetrical species. This species is responsible for colour development. Ligand 3 has a similar structure and does not give rise to any colour modification due to presence of the dimethylamino groups in the biphenyl moiety. The X-ray structure of ligand 2 is also reported and compared with that of ligand 1, that had bee…
Polyazapodands Derived from Biphenyl. Study of their Behaviour as Conformationally Regulated Fluorescent Sensors
2004
Eight new polyazapodands containing a 4,4′-substituted biphenyl moiety have been synthesised. Four (7, 8, 9 and 11) are functionalised on positions 4 and 4′ with a nitro group and four (1, 2, 3 and 10) with a dimethylamino substituent. Comparison of the emission behaviour of 1, 2, 3 with that of the reference compounds 10 and tetramthylbenzidine, clearly suggests that a modification in the dihedral angle between the biphenyl rings is an important factor in determining the fluorescent response of the molecule. The fluorescence is pH dependent, due to the formation of intramolecular hydrogen bonds between protonated aliphatic nitrogens and a carbonyl oxygen, which influences the aforementione…
N-Biphenyl thioureas as carboxylate receptors. Effect of the ligand substituents on the geometry of the complexes
2006
Abstract Six new biphenyl thiourea derivatives have been prepared to be used in carboxylate sensing. Experiments carried out with these ligands have demonstrated that the type of interaction with TBA carboxylates is strongly dependent on the substituents in the thiourea moiety. These interactions go from the formation of 1:1 hydrogen-bonded complexes to acid–base reactions. In addition, different geometries have been observed for the complexes being dependent on the conformations of the free ligands in solution.
Biphenyl-4-yl 4-methylbenzenesulfonate
2017
Molecules of the title compound, C19H16O3S, are composed of a biphenyl moiety substituted with a toluene-4-sulfonate group. The dihedral angle between the two coplanar biphenyl rings and the toluene ring is 52.72 (6)°.
Comparison of the crystal structures of 4,4′-bis[3-(4-methylpiperidin-1-yl)prop-1-yn-1-yl]-1,1′-biphenyl and 4,4′-bis[3-(2,2,6,6-tetramethylpiperidin…
2015
The crystal structures of the two title compounds display chair conformations of the piperidine rings in their molecules. In compound (I), the biphenyl system has a twisted conformation with a dihedral angle of 26.57 (6)° while in compound (II) the two phenyl rings are exactly coplanar.
Differential roles of cAMP and cGMP in megakaryocyte maturation and platelet biogenesis
2012
The cyclic nucleotides cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) regulate the activity of protein kinase A (PKA) and protein kinase G (PKG), respectively. This process helps maintain circulating platelets in a resting state. Here we studied the role of cAMP and cGMP in the regulation of megakaryocyte (MK) differentiation and platelet formation. Cultured, platelet-producing MKs were differentiated from fetal livers harvested from 13.5 days postcoital mouse embryos. MK development was accompanied by a dramatic increase in cAMP production and expression of soluble guanylate cyclase, PKG, and PKA as well as their downstream targets vasodilator-stimulated ph…
Change in Protein Phenotype without a Nucleus: Translational Control in Platelets
2004
For most cells the nucleus takes center stage. Not only is it the largest organelle in eukaryotic cells, it carries most of the genome and transcription of DNA to RNA largely takes place in the nucleus. Because transcription is a major step in gene regulation, the absence of a nucleus is limiting from a biosynthetic standpoint. Consequently, the anucleate status of platelets has stereotyped it as a cell without synthetic potential. It is now clear, however, that this viewpoint is far too simplistic. In response to physiologic stimuli, platelets synthesize biologically relevant proteins that are regulated via gene expression programs at the translational level. This process does not require …
Eltrombopag in chronic hepatitis C
2014
Chronic hepatitis C is a public health problem worldwide. Unfortunately, not all patients may benefit from antiviral therapy due to thrombocytopenia. Its causes are represented by portal hypertension and platelet sequestration in the spleen, decreased serum levels or activity of thrombopoietin, the bone marrow suppression induced by hepatitis C virus and a possible adverse effect of interferon. Thrombopoietin receptor analogs may contribute to increase platelet counts in these patients. Eltrombopag binds to another region of the thrombopoietin receptor compared to endogenous thrombopoietin and stimulates the proliferation and maturation of megakaryocytes and the platelet production in a dos…
Non-steroidal Anti-inflammatory Agents, Part 19:E-2-Pyrrolizin-5-yl Acrylic Acids as Potent Dual or Selective Inhibitors of Bovine Cyclooxygenase and…
1995
The pyrrolizinyl substituted acrylic acid derivatives represent another class of dual and selective inhibitors of cyclooxygenase and 5-lipoxygenase. By modifying their substitution pattern at the phenyl moiety of C-6 the balance between the activity against cyclooxygenase and against 5-lipoxygenase can be shifted. Structure-activity relationships are discussed. Compound 6k is the most potent and well-balanced dual inhibitor of both enzymes, while the highest selectivity of lipoxygenase inhibition was found for 6j. The activity and selectivity of compounds with an additional sulfur moiety depend on the oxidation status of this atom, giving an indication of the discussed coupling between pero…