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Dimerization Process (dimerization + process)

Distribution by Scientific Domains

Chemistry	75%

Selected Abstracts

Haplotype Analysis Confirms the Association Between the HCRTR2 Gene and Cluster Headache

HEADACHE, Issue 7 2008
Innocenzo Rainero MD
Background., Several studies suggested that genetic factors play a role in cluster headache (CH) susceptibility. We found a significant association between the 1246 G>A polymorphism of the hypocretin receptor-2 (HCRTR2) gene and the disease. This association was confirmed in a large study from Germany but was not replicated in a dataset of CH patients from Northern Europe. Objective., The purpose of this study was to further evaluate the association between CH and the HCRTR2 gene using new polymorphisms, estimating the frequency of different gene haplotypes, searching for gene mutations, and evaluating the effects of the examined polymorphisms on hypocretin binding sites. Methods., We genotyped 109 CH patients and 211 healthy controls for 5 new polymorphisms of the HCRTR2 gene and we inferred different gene haplotypes. Complete HCRTR2 sequencing was undertaken for 11 independent CH patients, 5 of whom had a positive family history. The effects of the 1246 G>A polymorphism on the hypocretin binding sites were evaluated using different computer-assisted analyses. Results., Three new polymorphisms of the HCRTR2 gene resulted significantly associated with CH. The GTAAGG haplotype resulted more frequent in cases than in controls (OR: 3.68; 95% CI: 1.85-7.67). No point mutation of the HCRTR2 gene was found. Binding analyses showed that the 1246 G>A polymorphism (substitution of valine at position 308 by isoleucine) has no effect on the hypocretin binding sites but could influence the dimerization process of the receptor. Conclusion., Our data confirm previous studies suggesting that the HCRTR2 gene or a linked locus significantly modulates the risk for CH. In addition, we suggest that the V308I substitution of the HCRTR2 may interfere with the dimerization process of the receptor, thereby influencing its functional activity. [source]

Thermal dimerization kinetics of 3-(p -bromo-phenyl)-pyridazinium benzoyl methylid in solutions

INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 5 2008
V. Melnig
3-(p -Bromo-phenyl)-pyridazinium-benzoyl methylid (BPPBM) participates in solution at 3 + 3 dipolar thermal dimerization that can be spectrally monitored by the extinction in its visible intramolecular charge transfer (ICT) band. The attenuation of ICT band intensity shows the decrease of the BPPBM concentration with the increasing of dimer concentration. The complex kinetics of light-assisted dimerization process was studied taking into account that the thermodynamic equilibrium is reached after more than 24 h. On the basis of general order of reaction theory, we found that the dimerization reaction must be described as a multistep mechanism. The rate constants of the dimerization reactions in ethanol (k = 0.00897 s,1) and benzene (k = 0.00774 s,1) solutions were correlated with the BPPBM and dimer structural features established by using the HyperChem 5.02 simulation program package. A kinetic mechanism of 3 + 3 dipolar thermal dimerization for the studied ylid is proposed. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 230,239, 2008 [source]

Supramolecular Photomagnetic Materials: Photoinduced Dimerization of Ferrocene-Based Polychlorotriphenylmethyl Radicals

CHEMISTRY - A EUROPEAN JOURNAL, Issue 3 2004
Imma Ratera
Abstract New ferrocenyl Schiff-base polychlorotriphenylmethyl radicals have been synthesized and characterized. The imino group of one such radical undergoes an irreversible trans to cis structural isomerization induced by light. Such photoinduced isomerization has been monitored by UV/Vis and ESR spectroscopy and also monitored by HPLC. ESR frozen solution experiments at low temperature revealed that the cis isomer dimerizes, showing a strong antiferromagnetic interaction. Although numerous photochromic supramolecular systems have been described, such a photoinduced self-assembly process represents the first example of a one-way photoswitchable magnetic system in which a conversion between a doublet and a singlet ground state species is promoted by a photoinduced dimerization process driven by the formation of hydrogen bonds. DFT calculations on the minimized structure and on the rotational barriers have been performed to establish the origin of such behavior. The effect of the substituents and the media polarity on the photoisomerization of this imine chromophore have also been studied. It has been observed that the efficiency of the process is markedly dependent on the presence and characteristics of electron-donor and electron-acceptor substituents of the ferrocenyl Schiff-base polychlorotriphenylmethyl radicals as well as on the polarity of the solvent. Han estat sintetitzats i caracteritzats nous radicals policlorotrifenilmetílics connectats a una unitat de ferrocè mitjançant una base de Schiff. El grup imino d,un d,aquests radicals experimenta una isomerització estructural irreversible de trans a cis mitjançant la llum. Aquesta isomerització fotoinduïda ha estat seguida amb les tècniques d, UV/Vis, espectroscòpia de RPE així com també mitjançant cromatografia d, HPLC. L,espectre de RPE d,una solució congelada revel.la que L,isòmer cis dimeritza mostrant una forta interacció antiferromagnètica entre monòmers. Malgrat els nombrosos sistemes supramoleculars fotocròmics que han estat descrits fins ara, aquest procés d,autoassemblatge fotoinduït representa el primer exemple d,interruptor magnètic fotoinduït d,un sol sentit en el qual té lloc una conversió de doblet a singlet de L,espècie en estat fonamental promoguda per un procés d,autoassemblatge mitjançant la formació d,enllaços d,hidrogen. S,han realitzat càlculs de DFT de les estructures minimitzades i de les barreres rotacionals per tal de poder establir L,origen d,aquest comportament. També s,ha estudiat L,efecte dels substituents i de la polaritat del medi en la fotoisomerizació d,aquests cromòfors d,imina. S,ha observat que L,eficiència del procés té una dependència molt marcada amb la presència de substituents electro donadors així com també amb la polaritat del dissolvent. [source]

Self-Assembly of Tris(2-ureidobenzyl)amines: A New Type of Capped, Capsule-Like Dimeric Aggregates Derived from a Highly Flexible Skeleton

CHEMISTRY - A EUROPEAN JOURNAL, Issue 6 2004
Mateo Alajarín Prof. Dr.
Abstract A set of tris(2-ureidobenzyl)amines 3 was prepared and their dimerization processes thoroughly investigated. In spite of their inherent flexibility, tris(ureas) 3 form dimeric aggregates both in the solid state and in solution. Evidence for the existence of these dimeric species was provided by a combination of techniques (X-ray analysis, NMR and IR spectroscopy, and ESI-MS). The association constants and thermodynamic parameters for the dimerization processes of selected tris(ureas) were determined and show that they are enthalpically driven. Heterodimerization experiments in solution reveal a high degree of self-recognition or narcissistic self-sorting. On the other hand, desymmetrized tris(ureas) derived from 3 self-assemble with modest regioselectivities depending on the terminal substituent of every urea functionality. [source]