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RISS 인기검색어
- 검색키워드
- 저자 : Sciacca, Michele F. M. (검색결과 3 건)
- 무료
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Phosphatidylethanolamine Enhances Amyloid Fiber-Dependent Membrane Fragmentation
Sciacca, Michele F. M.,Brender, Jeffrey R.,Lee, Dong-Kuk,Ramamoorthy, Ayyalusamy American Chemical Society 2012 Biochemistry Vol.51 No.39
<P>The toxicity of amyloid-forming peptides has been hypothesized to reside in the ability of protein oligomers to interact with and disrupt the cell membrane. Much of the evidence for this hypothesis comes from in vitro experiments using model membranes. However, the accuracy of this approach depends on the ability of the model membrane to accurately mimic the cell membrane. The effect of membrane composition has been overlooked in many studies of amyloid toxicity in model systems. By combining measurements of membrane binding, membrane permeabilization, and fiber formation, we show that lipids with the phosphatidylethanolamine (PE) headgroup strongly modulate the membrane disruption induced by IAPP (islet amyloid polypeptide protein), an amyloidogenic protein involved in type II diabetes. Our results suggest that PE lipids hamper the interaction of prefibrillar IAPP with membranes but enhance the membrane disruption correlated with the growth of fibers on the membrane surface via a detergent-like mechanism. These findings provide insights into the mechanism of membrane disruption induced by IAPP, suggesting a possible role of PE and other amyloids involved in other pathologies.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/bichaw/2012/bichaw.2012.51.issue-39/bi3009888/production/images/medium/bi-2012-009888_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/bi3009888'>ACS Electronic Supporting Info</A></P>
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Two-Step Mechanism of Membrane Disruption by Aβ through Membrane Fragmentation and Pore Formation
Sciacca, Michele F.M.,Kotler, Samuel A.,Brender, Jeffrey R.,Chen, J.,Lee, D.k.,Ramamoorthy, A. Biophysical Society ; Published for the Biophysica 2012 Biophysical journal Vol.103 No.4
Disruption of cell membranes by Aβ is believed to be one of the key components of Aβ toxicity. However, the mechanism by which this occurs is not fully understood. Here, we demonstrate that membrane disruption by Aβ occurs by a two-step process, with the initial formation of ion-selective pores followed by nonspecific fragmentation of the lipid membrane during amyloid fiber formation. Immediately after the addition of freshly dissolved Aβ<SUB>1-40</SUB>, defects form on the membrane that share many of the properties of Aβ channels originally reported from single-channel electrical recording, such as cation selectivity and the ability to be blockaded by zinc. By contrast, subsequent amyloid fiber formation on the surface of the membrane fragments the membrane in a way that is not cation selective and cannot be stopped by zinc ions. Moreover, we observed that the presence of ganglioside enhances both the initial pore formation and the fiber-dependent membrane fragmentation process. Whereas pore formation by freshly dissolved Aβ<SUB>1-40</SUB> is weakly observed in the absence of gangliosides, fiber-dependent membrane fragmentation can only be observed in their presence. These results provide insights into the toxicity of Aβ and may aid in the design of specific compounds to alleviate the neurodegeneration of Alzheimer's disease.
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Origin of a localized vibrational mode in a GaSb substrate with a MBE-grown ZnTe epilayer
Kim, Hyunjung,Tarhan, E,Chen, G,Ramdas, A K,Sciacca, M Dean,Gunshor, R L Institute of Physics 2006 Semiconductor science and technology Vol.21 No.9
<P>A localized vibrational mode (LVM) with a remarkable fine structure is observed in the infrared transmission spectrum of a ZnTe epilayer grown with molecular beam epitaxy (MBE) on a GaSb substrate. On the basis of the Zn and Te deposited on the GaSb substrate during the MBE growth of ZnTe, and assuming diffusion of Zn and Te into GaSb, the LVM is attributed to Zn, substitutionally replacing either the cation, Ga (Zn<SUB>Ga</SUB>), or the anion, Sb (Zn<SUB>Sb</SUB>). The frequency of the LVM and its fine structure can then be interpreted in terms of the infrared active modes of <SUP>64</SUP>Zn substituting for Sb as an anti-site impurity and treating the centre as an XY<SUB>4</SUB> quasimolecule. With X≡<SUP>64</SUP>Zn and Y≡<SUP>69</SUP>Ga and <SUP>71</SUP>Ga, occupying the nearest-neighbour sites reflecting all the possible combinations and permutations as well as the natural isotopic abundance of Ga, the fine structure of the LVM can be accounted for quantitatively.</P>
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