RESUMO
In deuterium NMR spectra of phosphatidylethanolamine bilayers with an extremely high content of saturated fatty acids, each C1 deuteron of the glycerol backbone gave rise to a doublet [Yoshikawa et al., (1988) Biochim. Biophys. Acta 944, 321-328]. This suggests the presence of two backbone conformations, the exchange between which is slow on an NMR time-scale. The origin of the two conformations has been investigated in this work using saturated 1,2-diacyl-sn-glycero-3-phosphoethanolamine specifically deuterated in the glycerol backbone. The results showed that the two conformations originate from different domains, which have different fatty acid compositions. The differential scanning calorimetry of the bilayers suggested that the size of the domain is not large enough to show an independent phase transition. Thus, the formation of microdomains in the phosphatidylethanolamine bilayers has been concluded. Conformational difference in different domains was shown to be restricted to the C1 position of the glycerol backbone. The microdomains of phosphatidylethanolamine were retained even in the presence of other phospholipids.
Assuntos
Bicamadas Lipídicas/química , Fosfatidiletanolaminas/química , Varredura Diferencial de Calorimetria , Escherichia coli/química , Espectroscopia de Ressonância Magnética , Conformação Molecular , TemperaturaAssuntos
Corpos Estranhos , Perfuração Intestinal/etiologia , Adulto , Idoso , Animais , Feminino , Peixes , Humanos , Intestinos , Masculino , Pessoa de Meia-IdadeAssuntos
Perfuração Intestinal/etiologia , Adulto , Idoso , Animais , Osso e Ossos , Feminino , Peixes , Humanos , Masculino , Pessoa de Meia-IdadeRESUMO
The conformation of the polar head group of phosphatidylcholine in a bilayer in the liquid-crystalline state was deduced by analyzing the deuterium quadrupole splittings of the choline group and the phosphorus chemical shift anisotropy of the phosphate group in combination with the restriction of the choline conformation determined in laser Raman studies. The latter efficiently reduced the number of candidates for the actual conformation. A family of conformations was obtained for both the dynamic-structure and rigid-structure models, respectively. The polar head group is oriented roughly parallel to the membrane surface in both models. Furthermore, they are close to conformation A of the crystal structure of 1,2-dimyristoyl-sn-glycero-3-phosphocholine. The dynamic-structure model was concluded to be more reasonable in view of the fact that the polar head-group structures in most crystals comprise two conformations, which are nearly mirror images of each other. Conformational analysis was also carried out for the polar head group in the presence of multivalent cations. A possible conformational change of the polar head group induced by cations is discussed in the light of the present results.
Assuntos
Bicamadas Lipídicas/química , Fosfatidilcolinas/química , Cátions/química , Deutério , Dimiristoilfosfatidilcolina/química , Espectroscopia de Ressonância Magnética , Modelos Moleculares , Conformação Molecular , Solubilidade , Análise Espectral Raman , Difração de Raios XRESUMO
Selective transcatheter arterial embolization, using Gelfoam, was performed in 2 patients with bleeding from tongue arteries due to carcinoma. Though the patients were in poor general condition, being in the terminal stage of cancer, there were no complications and the bleeding was successfully controlled. This method was effective in controlling haemorrhage from the tongue due to carcinoma of the tongue.
