RESUMEN
Iron, an essential element for most living organism, participates in a wide variety of physiological processes. Disturbance in iron homeostasis has been associated with numerous pathologies, particularly in the heart and brain, which are the most susceptible organs. Under iron-overload conditions, the generation of reactive oxygen species leads to impairment in Ca2+ signaling, fundamentally implicated in cardiac and neuronal physiology. Since iron excess is accompanied by increased expression of iron-storage protein, ferritin, we examined whether ferritin has an effect on the ryanodine receptor - isoform 2 (RYR2), which is one of the major components of Ca2+ signaling. Using the method of planar lipid membranes, we show that ferritin induced an abrupt, permanent blockage of the RYR2 channel. The ferritin effect was strongly voltage dependent and competitively antagonized by cytosolic TEA+, an impermeant RYR2 blocker. Our results collectively indicate that monomeric ferritin highly likely blocks the RYR2 channel by a direct electrostatic interaction within the wider region of the channel permeation pathway.
Asunto(s)
Ferritinas/metabolismo , Canal Liberador de Calcio Receptor de Rianodina/metabolismo , Animales , Calcio/metabolismo , Bloqueadores de los Canales de Calcio/farmacología , Humanos , Membrana Dobles de Lípidos/metabolismo , Masculino , Potenciales de la Membrana/efectos de los fármacos , Ratas Wistar , Tetraetilamonio/farmacologíaRESUMEN
BACKGROUND: Isometric gene tree reconciliation is a gene tree/species tree reconciliation problem where both the gene tree and the species tree include branch lengths, and these branch lengths must be respected by the reconciliation. The problem was introduced by Ma et al. in 2008 in the context of reconstructing evolutionary histories of genomes in the infinite sites model. RESULTS: In this paper, we show that the original algorithm by Ma et al. is incorrect, and we propose a modified algorithm that addresses the problems that we discovered. We have also improved the running time from [Formula: see text] to [Formula: see text], where N is the total number of nodes in the two input trees. Finally, we examine two new variants of the problem: reconciliation of two unrooted trees and scaling of branch lengths of the gene tree during reconciliation of two rooted trees. CONCLUSIONS: We provide several new algorithms for isometric reconciliation of trees. Some questions in this area remain open; most importantly extensions of the problem allowing for imprecise estimates of branch lengths.
RESUMEN
The synthesis and structure of a new flexible metal-organic framework Ni(2)(2,6-ndc)(2)(dabco) (DUT-8(Ni), DUT = Dresden University of Technology, 2,6-ndc = 2,6-naphthalenedicarboxylate, dabco = 1,4-diazabicyclo[2.2.2]octane) as well as its characterization by gas adsorption and (129)Xe NMR spectroscopy is described. The compound shows reversible structural transformation without loss of crystallinity upon solvent removal and physisorption of several gases. Xenon adsorption studies combined with (129)Xe NMR spectroscopy turn out to be favorable methods for the detection and characterization of the so-called "gate-pressure" effect in this novel MOF material. The linewidth and chemical shift of the (129)Xe NMR signal are shown to be very sensitive parameters for the detection of this structural transition from a narrow pore system with low porosity to a wide pore state. The transition and threshold temperature is clearly detected.
Asunto(s)
Espectroscopía de Resonancia Magnética/métodos , Níquel/química , Compuestos Organometálicos/química , Xenón/química , Adsorción , Modelos Moleculares , Estructura Molecular , Nitrógeno/química , Compuestos Organometálicos/síntesis químicaRESUMEN
Microporous hydrophobic polysilanes with high specific surface areas (700-1100 m2 g(-1)) for applications in gas adsorption are obtained using an organolithiation route.
Asunto(s)
Polímeros/química , Silanos/química , Adsorción , Interacciones Hidrofóbicas e Hidrofílicas , Estructura Molecular , Nitrógeno/química , Tamaño de la Partícula , Polímeros/síntesis química , Porosidad , Silanos/síntesis química , Propiedades de Superficie , Agua/químicaRESUMEN
129Xe NMR measurements of adsorbed xenon are shown for the first time to be a suitable tool to characterize the porosity and the properties of the metal-organic framework Cu3(BTC)2(H2O)3 (BTC = benzene 1,3,5-tricarboxylate). The NMR experiments are performed at room temperature and over a wide range of xenon pressure and on two different synthesized Cu3(BTC)2 samples. 129Xe NMR results reveal that in dependence on the kind of the synthesis pathway either one or two signals are observed which can be attributed to two kinds of fast exchange of xenon atoms in two pores with different pore sizes. Coadsorption experiments of xenon and ethylene demonstrate that the xenon atoms prefer to fill the greater pores of the material because the smaller pores are occupied with residual molecules from the synthesis procedure and additionally adsorbed ethylene. Besides the NMR experiments a series of electron paramagnetic resonance (EPR) measurements are performed to estimate the state of copper having a strong influence on the chemical shift of the adsorbed xenon. The EPR experiments demonstrate that spin exchange between the interconnected copper dimers is taking place across the BTC linker molecules in the Cu3(BTC)2 framework.
RESUMEN
The title complex, [Zn(2)(C(7)H(5)O(2))(4)(C(20)H(21)NO(4))(2)], forms dimers of the paddle-wheel cage type located at crystallographic inversion centres. The two Zn atoms [Zn.Zn = 3.0533 (4) A] are connected by four syn-syn benzoate ligands. The apical positions of the square-pyramidal zinc coordination polyhedra are occupied by the N atoms of the papaverine ligand. Upon coordination, the mutual orientation of the phenyl and isoquinoline rings in papaverine is changed compared with that in the uncoordinated ligand.