198 research outputs found
Spatial and temporal control of regulated exocytosis by protein and lipid interactions
No full textCellular communication requires the transport of chemical messengers
between intracellular compartments and from cell to cell. The regulated exocytosis of
a secretory vesicle at the plasma membrane involves the merger of two bilayers, with
markedly different lipid composition, within a millisecond time scale. The spatial
and temporal control of the protein and lipid complement at these fusion sites is
essential. A highly conserved family of proteins are known to drive this fusion event;
SNAP-25 and syntaxin-1 (t-SNAREs) associate at the plasma membrane in a 1:1
stoichiometry to provide a binding site for the vesicle-membrane protein
synaptobrevin (v-SNARE). The formation of this complex and subsequent fusion
requires accessory proteins for efficient calcium-triggered exocytosis; which of these
proteins facilitate the initial attachment of vesicle to the plasma membrane prior to
fusion is still under debate. Specific sites for vesicle fusion have been proposed and
the organisation of lipids and proteins at these fusion sites has been extensively
investigated with limited spatial and temporal resolution; however the presence of
raft-forming lipids at these sites as well as the arrangement of SNARE proteins at the
molecular level is still under contention. The data presented within this thesis aims to
elucidate the protein and lipid environment at the fusion site using super-resolution
microscopy and advanced vesicle tracking. Under diffraction-limited microscopy the
t-SNAREs are visualised as 200 nm homogenous clusters; however I have used
single molecule localisation microscopy to reveal a more complex heterogeneous
molecular arrangement. Quantification of lipid order exclusively at the plasma
membrane provided insight into the influence of cholesterol-induced lipid
arrangement on SNAP-25 localisation. In addition the t-SNARE interaction was
investigated using TCSPC-FLIM identifying two lipid-order-dependent
conformations in distinct clusters at the plasma membrane. Extensive vesicle
tracking at optimum sampling rates demonstrated the ‘sampling’ behaviour of
LDCVs and allowed characterisation of vesicle fusion sites. In summary I find that
vesicles exhibit preference for residence and probably fusion at regions of plasma
membrane with a low t-SNARE density; these proteins appear to exert control over
exocytosis by adopting alternative conformations that are under cholesterol-induced
regulation
t-SNARE protein conformations patterned by the lipid microenvironment
No full textThe spatial distribution of the target (t-)SNARE proteins (syntaxin and SNAP-25) on the plasma membrane has been extensively characterized. However, the protein conformations and interactions of the two t-SNAREs in situ remain poorly defined. By using super-resolution optical techniques and fluorescence lifetime imaging microscopy, we observed that within the t-SNARE clusters syntaxin and SNAP-25 molecules interact, forming two distinct conformations of the t-SNARE binary intermediate. These are spatially segregated on the plasma membrane with each cluster exhibiting predominantly one of the two conformations, representing the two- and three-helical forms previously observed in vitro. We sought to explain why these two t-SNARE intermediate conformations exist in spatially distinct clusters on the plasma membrane. By disrupting plasma membrane lipid order, we found that all of the t-SNARE clusters now adopted a single conformational state corresponding to the three helical t-SNARE intermediates. Together, our results define spatially distinct t-SNARE intermediate states on the plasma membrane and how the conformation adopted can be patterned by the underlying lipid environment
Structural and magnetic properties of two branches of the tripod-kagome-lattice family A(2)R(3)Sb(3)O(14) (A = Mg, Zn; R = Pr, Nd, Gd, Tb, Dy, Ho, Er, Yb)
No full textWe present a systematic study of the structural and magnetic properties of two branches of the rare-earth tripod-kagome-lattice (TKL) family A(2)R(3)Sb(3)O(14) (A= Mg, Zn; R= Pr, Nd, Gd, Tb, Dy, Ho, Er, Yb; here, we use abbreviation A-R, as in MgPr for Mg2Pr3Sb3O14), which complements our previously reported work on MgDy, MgGd, and MgEr [Z. L. Dun et al., Phys. Rev. Lett. 116, 157201 (2016)]. The present susceptibility (chi(dc), chi(ac)) and specific-heat measurements reveal various magnetic ground states, including the nonmagnetic singlet state for MgPr, ZnPr; long-range orderings (LROs) for MgGd, ZnGd, MgNd, ZnNd, and MgYb; a long-range magnetic charge ordered state for MgDy, ZnDy, and potentially for MgHo; possible spin-glass states for ZnEr, ZnHo; the absence of spin ordering down to 80 mK for MgEr, MgTb, ZnTb, and ZnYb compounds. The ground states observed here bear both similarities as well as striking differences from the states found in the parent pyrochlore systems. In particular, while the TKLs display a greater tendency towards LRO, the lack of LRO in MgHo, MgTb, and ZnTb can be viewed from the standpoint of a balance among spin-spin interactions, anisotropies, and non-Kramers nature of single-ion state. While substituting Zn for Mg changes the chemical pressure, and subtly modifies the interaction energies for compounds with larger R ions, this substitution introduces structural disorder and modifies the ground states for compounds with smaller R ions (Ho, Er, Yb).National Natural Science Foundation of China [11275012]; NSAF [U1530402]; NSFC [21501162]; State of Florida; DOE; NHMFL User Collaboration Grant Program; [NSF-DMR-1350002]; [NSF-DMR 1534741]; [NSF-DMR-1157490]SCI(E)ARTICLE109
Transformation of BPEL processes to Petri nets
No full textWeb service composition involves the combination of a number of existing web services to create a value-added service in ways that may not be foreseen at the time when a web service is written. BPEL is a promising language which describes web service composition in form of business processes. However, BPEL is an XML-based language and may suffer from ambiguities or some erroneous properties. It is necessary to analyze business processes specified in BPEL with a formal tool. In this paper we put forward an approach to model and verify BPEL based on ServiceNet, a special class of Petri nets. We present some transformation rules of BPEL business processes into ServiceNet. Then the throughness of a BPEL business process can be verified by reducing the corresponding ServiceNet based on some reduction rules.Computer Science, Software EngineeringComputer Science, Theory & MethodsEICPCI-S(ISTP)
decent work and employees' innovative behaviour
No full textThis data set is a revised version of the earlier published one entitled as V1 and V2. Several variables are dropped and the structural models are made more parsimonious.The data set contains 529 supervisor-employee dyads collected from XL, a large state holding company group with over 20 independent business units. The data is used to test the effects of Decent Work (DW) on Employees' Innovative Behaviour (EIB) through multiple mediation of Job Self-Efficacy (JSE), Intrinsic Motivation (IM), and Work Engagement (WE).SEM analysis tested that DW promotes EIB through two paths: the "expertise & self-efficacy" path and the "intrinsic motivation & engagement path". Along the former path, DW promotes EIB via mediation of JSE, with education (EDU) and company tenure (TENURE) conducive to JSE. Along the latter path, decent work promotes EIB via the serial partial mediation of IM and WE.The uploaded data set contains demographic data of the correspondents, value of each manifest items of the variable measures, and processed (e.g. by summation or average) value of variable measures. Following Farmer, Tierney, and Kung-Mcintyre (2003, p. 623), we created three manifest indicators for each latent variable by randomly assigning items to composites to reduce the parameters assessed, thus improving the ratio between sample size and estimator. Thus, for the rearranged manifest items, the letter "r" was added to the end of its variable name. In other words, items ended with "r" are inputs of SEM analysis.Along with the original dataset, we've also uploaded the data coding and major AMOS working models of the SEM analysis. Reviewers can reproduce results by directly running the models with AMOS. For quick reviewers who have not installed AMOS or feel bothered to run the software by themselves, the author also uploaded the AMOS output of hypotheses testing pasted in word documents
Design of controller for Lur'e systems guaranteeing dichotomy
No full textIn this paper, the problem of controller design for Lur'e systems guaranteeing dichotomy is investigated. On the basis of Kalman-Yakubovich-Popov (KYP) lemma and two frequency equalities, a new methodology for the dichotomy analysis of the Lur'e systems is proposed. A linear matrix inequality (LMI) based criterion is derived, which is equivalent to the Leonov's frequency-domain one, while for the dichotomy analysis and synthesis which is more straightforward than the frequency-domain one. In virtue of this result, a dynamic output feedback controller ensuring the dichotomy property for Lur'e systems is designed. Finally a numerical example is included to demonstrate the validity and the applicability of the proposed approach. Crown Copyright (C) 2011 Published by Elsevier Inc. All rights reserved.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000290902600007&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Mathematics, AppliedSCI(E)EI1ARTICLE228927-893521
The t-SNARE complex:a close up
No full textThe SNARE proteins, syntaxin, SNAP-25, and synaptobrevin have long been known to provide the driving force for vesicle fusion in the process of regulated exocytosis. Of particular interest is the initial interaction between SNAP-25 and syntaxin to form the t-SNARE heterodimer, an acceptor for subsequent synaptobrevin engagement. In vitro studies have revealed at least two different dynamic conformations of t-SNARE heterodimer defined by the degree of association of the C-terminal SNARE motif of SNAP-25 with syntaxin. At the plasma membrane, these proteins are organized into dense clusters of 50-60 nm in diameter. More recently, the t-SNARE interaction within these clusters was investigated in live cells at the molecular level, estimating each cluster to contain 35-70 t-SNARE molecules. This work reported the presence of both partially and fully zippered t-SNARE complex at the plasma membrane in agreement with the earlier in vitro findings. It also revealed a spatial segregation into distinct clusters containing predominantly one conformation apparently patterned by the surrounding lipid environment. The reason for this dynamic t-SNARE complex in exocytosis is uncertain; however, it does take us one step closer to understand the complex sequence of events leading to vesicle fusion, emphasizing the role of both membrane proteins and lipids. © 2010 Springer Science+Business Media, LLC.</p
Scientometric portrait of Nobel laureate Leland H. Hartwell
No full textLeland H. Hartwell was honoured with the Nobel Prize in Physiology or Medicine (2001) at his 62 years age and at 41 years of research publishing career. The first contribution of the author was in 1961 at the age of 22. The number of his contributions in a year peaked in 1997 when it touched 8. He had 108 publications during 1961 – 2001 in domains: Molecular Biology of Cell Cycle Regulation (43), Genetics of Cell Division (48), Genomic Re-arrangement and DNA Repair (9), Molecular Genetics of Yeast Cell Fission (5), and Drug Target Interaction (3) which were analysed for authorship pattern with his 101 collaborators. Most active researchers having number of publications with Leland H. Hartwell were : Weinert, T. A. (10), Garvik, B. M. (8), McLaughlin, C. S. (8), Jenness, D. D. (5). His productivity coefficient was 0.76 which clearly indicates that his productivity increased after 50 percentile age. Highest collaboration coefficient (1) for Leland H. Hartwell was found during 1963-1965, 1968-1969, 1977, 1981-1983, 1985-1990, 1996 and 1998-2001. Journals have been the most preferred channel of communication where, as many as 96 papers out of 108 have been published. The core journals publishing his papers were: Cell (14), Genetics (12), Mol. Cell Biol. (8), J. Bactariol. (7), J. Cell Biol. ( 7), Science (7) J. Mol. Biol.(6), Exp. Cell Res. (5), and Proc. Nat. Acad. Sci.(5). Publication density is 2.63 and Publication concentration is 14.63. Most prolific keywords in titles of publications were: Saccharomyces cerevisiae , Yeast , Cell division cycle , RAD9, DNA Damage , Genes , Cell cycle, Genetic control , Check point (s) , Cell division , Mutant of Yeast
Cyclical variability of changes of a investment outlays structure and, employment in Mid-Western Macroregion
No full textRegional cycles are a relatively r a r e topic in t h e literature on spatial problems. The observation
of changes occurring at a regional level have led the author to the supposition that regional
development may be characterized by a cyclical variability. The outcome of research presented in
the article confirmed in principle the hypotheses formulated by the author.Digitalizacja i deponowanie archiwalnych zeszytów RPEiS sfinansowane przez MNiSW w ramach realizacji umowy nr 541/P-DUN/201
fish and fishery products microbiology bacteria causing fish spoilage
No full textThis material describe bacteria which causing spoilage in fish and seafood products
- …
