SNAREs, 14-3-3 proteins and cholesterol dependent membrane domains

Lipid rafts are suggested to be sphingolipid and cholesterol rich domains that segregate out from the bulk plasma membrane by forming a more ordered lipid phase. Lipid raft-like domains have been described as cell signalling platforms and have been implicated in the regulation of an array of signal transduction events. This study investigates the association of two classes of protein, 14-3-3 proteins and plasma membrane SNAREs, with lipid raft-like domains. The 14-3-3 family of proteins are important regulators of numerous cell signalling pathways and are essential for cell survival; recently there has been some interest in the roles of these soluble proteins at the membrane, though this area remains poorly characterised. 14-3-3 has also been linked to CJD progression, which is directed by the lipid raft associated prion protein. SNAREs are essential mediators of exocytosis, a process that is also reported to depend on cholesterol, implying lipid raft involvement. SNAREs have also been isolated in detergent resistant membranes (DRMs) that are believed to represent clustered lipid rafts.To examine the association of 14-3-3 and SNAREs with lipid raft-like domains in N2a and PC 12 cells two approaches were taken. Initially, detergent resistant membranes were isolated and analysed for protein association. The second approach involved quantitative analysis of the colocalisation of 14-3-3 and SNAREs with membrane domains in intact cells by confocal microscopy, using the lipid raft marker cholera toxin B subunit (CTXB). Discrepancies between results from these two methods add to evidence implying that DRMs do not necessarily represent pre¬ existing membrane domains. Cholesterol depletion, which affects the integrity of lipid raft-like domains, caused a rearrangement CTXB labelled clusters in N2a and PC 12 cells. The colocalisation of 14-3-3 with CTXB was unaffected by cholesterol depletion, a result which does not support the localisation of 14-3-3 to lipid raft-like domains. Interestingly however, the membrane distribution of the lipid raft marker Thy-1, a GPI-anchored protein, was also unaltered when cholesterol was depleted. In contrast to previous reports, disruption of SNAP-25 or syntaxinla (SNARE) clusters was not observed following cholesterol depletion. However, in N2a cells, the colocalisation of SNAP-25 with CTXB was reduced, though this was not the case in PC 12 cells. Taken together these results suggest that cholesterol depletion may affect various raft-associated proteins and cell types in different ways. The findings from N2a cells indicate a role for lipid raft-like domains in controlling the spatial distribution of SNAP-25 on the plasma membrane. The membrane distribution of syntaxinla appears to be differently regulated from that of SNAP-25, which may have implications for the regulation of exocytosis

Examining Roberts County Mathematics Teachers\u27 Beliefs Regarding the Nature of Mathematics and Their Classroom Learning Environment

The purpose of this study was to examine the relationship of mathematics teachers beliefs regarding the nature of mathematics and their classroom learning environment in Roberts County (fictional). The study investigated 165 kindergarten through twelfth grade mathematics teachers that taught at least one segment of mathematics a day. The researcher administered three surveys: the Teacher Beliefs Survey (developed by Beswick, 2005), the Constructivist Learning Environment Survey (developed by Taylor, Fraser, and Fisher, 1997) and a demographics survey to mathematics teachers at 35 schools. Data analysis included calculating the sub-scale means of each survey, a Pearson correlation, and Analysis of Variance (ANOVA). Data analysis found that Roberts County mathematics teachers held beliefs consistent with a problem-solving (or student-centered) view of mathematics however they were undecided (did not agree or disagree) with the instrumentalists\u27 view of mathematics. Teachers favored a classroom environment that allowed students to communicate about mathematics and to express their concerns about their own learning. Teachers\u27 beliefs about the nature of mathematics and their classroom learning environment were found to be statistically, positively significant with regard to the problem-solving view of mathematics (TBS sub-scale) and the CLES subscales. Elementary, middle, and high school teachers\u27 beliefs differed. Elementary teachers were more likely to have problem-solving oriented beliefs and had classrooms which supported a constructivist learning environment. Elementary teachers supported mathematics by making connections to mathematics outside of school, encouraging students to communicate about mathematics, providing a safe learning environment that allowed students to express concerns about their learning and to share control of their learning. Recommendations to further Roberts Countys mathematics teachers towards a more problem-solving and constructivist classroom learning environments are guided by the ideals of the National Council of Teachers of Mathematics publications and the Georgia Performance Standards for mathematics

Spin-enhanced magnetocaloric effect in molecular nanomagnets

An unusually large magnetocaloric effect for the temperature region below 10 K is found for the Fe-14 molecular nanomagnet. This is to large extent caused by its extremely large spin S ground state combined with an excess of entropy arising from the presence of low-lying excited S states. We also show that the highly symmetric Fe-14 cluster core, resulting in small cluster magnetic anisotropy, enables the occurrence of long-range antiferromagnetic order below T-N=1.87 K

Руководство по применению внутриматочных контрацептивов

ВНУТРИМАТОЧНЫЕ УСТРОЙСТВАКОНТРАЦЕПТИВНЫЕ СРЕДСТВА ЖЕНСКИ

Bridging the Gap: International Organizations as Organizations

http://deepblue.lib.umich.edu/bitstream/2027.42/51108/1/340.pd

Influence of antisymmetric exchange interaction on quantum tunneling of magnetization in a dimeric molecular magnet Mn6

We present magnetization measurements on the single molecule magnet Mn6, revealing various tunnel transitions inconsistent with a giant-spin description. We propose a dimeric model of the molecule with two coupled spins S=6, which involves crystal-field anisotropy, symmetric Heisenberg exchange interaction, and antisymmetric Dzyaloshinskii-Moriya exchange interaction. We show that this simplified model of the molecule explains the experimentally observed tunnel transitions and that the antisymmetric exchange interaction between the spins gives rise to tunneling processes between spin states belonging to different spin multiplets.Comment: 5 pages, 4 figure

The importance of being exchanged: [Gd III 4M II 8(OH) 8(L) 8(O 2CR) 8] 4+ clusters for magnetic refrigeration

El pdf del artículo es la versión post-print.-- et al.Playing it cool: Almost all of the constituent parts of the complex [Ln III 4M II 8(OH) 8(L) 8(O 2CR) 8]X 4, namely the lanthanide ions Ln 3+, the transition-metal ions M 2+, the bridging ligand L, the carboxylates, and the counterions X can be exchanged, thus allowing a thorough understanding of the individual contributions to the magnetocaloric effect. Example in picture: Gd purple, Cu green, O red, N blue. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.E.K.B. wishes to thank the EPSRC for funding. M.E. acknowledges contracts MAT2009-13977-C03 and CSD2007-00010. S.P. thanks the Danish Natural Science Research Council for a Sapere Aude Fellowship (10-081659).Peer Reviewe