23 research outputs found
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Effect of trehalose on the interaction of Alzheimer's Aβ-peptide and anionic lipid monolayers
The interaction of amyloid β-peptide (Aβ) with cell membranes is believed to play a central role in the pathogenesis of Alzheimer's disease. In particular, recent experimental evidence indicates that bilayer and monolayer membranes accelerate the aggregation and amyloid fibril formation rate of Aβ. Understanding that interaction could help develop therapeutic strategies for treatment of the disease. Trehalose, a disaccharide of glucose, has been shown to be effective in preventing the aggregation of numerous proteins. It has also been shown to delay the onset of certain amyloid-related diseases in a mouse model. Using Langmuir monolayers and molecular simulations of the corresponding system, we study several thermodynamic and kinetic aspects of the insertion of Aβ peptide into DPPG monolayers in water and trehalose subphases. In the water subphase, the insertion of the Aβ peptide into the monolayer exhibits a lag time which decreases with increasing temperature of the subphase. In the presence of trehalose, the lag time is completely eliminated and peptide insertion is completed within a shorter time period compared to that observed in pure water. Molecular simulations show that more peptide is inserted into the monolayer in the water subphase, and that such insertion is deeper. The peptide at the monolayer interface orients itself parallel to the monolayer, while it inserts with an angle of 50° in the trehalose subphase. Simulations also show that trehalose reduces the conformational change that the peptide undergoes when it inserts into the monolayer. This observation helps explain the experimentally observed elimination of the lag time by trehalose and the temperature dependence of the lag time in the water subphase.Fil: Izmitli, Aslin. University of Wisconsin Madison; Estados UnidosFil: Schebor, Carolina Claudia. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: McGovern, Michael P.. University of Wisconsin Madison; Estados UnidosFil: Reddy, Allam S.. University of Wisconsin Madison; Estados UnidosFil: Abbott, Nicholas L.. University of Wisconsin Madison; Estados UnidosFil: De Pablo, Juan J.. University of Wisconsin Madison; Estados Unido
Diffusion-Weighted PFGNMR Study of Molecular Level Interactions of Loops and Direct Bridges of HEURs on Latex Particles
Viscosity building in latex coatings
to provide desirable shear
thinning rheological properties is a key property commercially achieved
with hydrophobically modified ethylene oxide urethane (HEUR) rheology
modifiers (RMs). Prior studies focused on the aqueous solution properties
of HEURs, resulting in the well-known transient network model that
describes solution rheology reasonably well. Relatively fewer studies
have probed the molecular level interactions between the hydrophobe
groups of HEUR and latex surfaces under conditions of realistic latex
volume fractions and HEUR concentration. The presence of ubiquitous
surfactant and oligomer molecules in the latex aqueous phase makes
it difficult to detect these interactions directly for any off-the-shelf
(industrial) materials. In this work, we outline the use of pulsed
field gradient (PFG) NMR spectroscopy as diffusion-weighted filter
to remove the signals of low molecular weight species in order to
detect hydrophobe end groups and urethane linkers. This in situ approach
does not have any perturbation issues that are inherent in prior methods
involving centrifugation and avoids the questions raised by the use
of custom pyrene hydrophobes in fluorescence spectroscopy. From this
study we conclude that there are no HEUR transient network structures
present in HEUR–latex composites with less than about 2% HEUR
and 30% latex relevant for coatings applications. Our results explain
the shear thinning rheology of latex–HEUR composites based
on molecular level interactions between hydrophobe end groups and
urethane linkers of HEURs and latex particles to produce HEUR PEO
loops on latex and direct bridges between pairs of latex particles