Protofibril-Fibril Interactions Inhibit Amyloid Fibril Assembly by Obstructing Secondary Nucleation.

Amyloid-β peptides (Aβ) assemble into both rigid amyloid fibrils and metastable oligomers termed AβO or protofibrils. In Alzheimer's disease, Aβ fibrils constitute the core of senile plaques, but Aβ protofibrils may represent the main toxic species. Aβ protofibrils accumulate at the exterior of senile plaques, yet the protofibril-fibril interplay is not well understood.

Origin of metastable oligomers and their effects on amyloid fibril self-assembly.

Assembly of rigid amyloid fibrils with their characteristic cross-β sheet structure is a molecular signature of numerous neurodegenerative and non-neuropathic disorders. Frequently large populations of small globular amyloid oligomers (gOs) and curvilinear fibrils (CFs) precede the formation of late-stage rigid fibrils (RFs), and have been implicated in amyloid toxicity. Yet our understanding of the origin of these metastable oligomers, their role as on-pathway precursors or off-pathway competitors, and their effects on the self-assembly of amyloid fibrils remains incomplete.

Solvent specific persistence length of molecular type I collagen.

Type I collagen is a fibril-forming protein largely responsible for the mechanical stability of body tissues. The tissue level properties of collagen have been studied for decades, and an increasing number of studies have been performed at the fibril scale. However, the mechanical properties of collagen at the molecular scale are not well established.

The effect of cross-link distributions in axially-ordered, cross-linked networks.

Cross-linking between the constituent chains of biopolymers has a marked effect on their materials' properties. In certain of these materials, such as fibrillar collagen, increases in cross-linking lead to an increase in the melting temperature. Fibrillar collagen is an axially-ordered network of cross-linked polymer chains exhibiting a broadened denaturation transition, which has been explained in terms of the successive denaturation with temperature of multiple species.

Structure and opto-electrochemical properties of ZnO nanowires grown on n-Si substrate.

Zinc oxide (ZnO) nanostructures have attracted great attention as a promising functional material with unique properties suitable for applications in UV lasers, light emitting diodes, field emission devices, sensors, field effect transistors, and solar cells. In the present work, ZnO nanowires have been synthesized on an n-type Si substrate using a hydrothermal method where surfactant acted as a modifying and protecting agent. The surface morphology, electrochemical properties, and opto-electrochemical properties of ZnO nanowires are investigated by using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), cyclic voltammetry, and impedance spectroscopy techniques.

Amyloid protofibrils of lysozyme nucleate and grow via oligomer fusion.

The mechanisms linking deposits of insoluble amyloid fibrils to the debilitating neuronal cell death characteristic of neurodegenerative diseases remain enigmatic. Recent findings implicate transiently formed intermediates of mature amyloid fibrils as the principal toxic agent. Hence, determining which intermediate aggregates represent on-pathway precursors or off-pathway side branches is critical for understanding amyloid self-assembly, and for devising therapeutic approaches targeting relevant toxic species.

Quantitation of surface-reducing-end covalently bound polysaccharides via hydrazinolysis and deamination.

Depending on the method of deposition, reactive sites of polysaccharides on substrates may not be available when their reducing ends have been used to covalently bind them to the substrates. Here we present a method that allows surface density measurements of reducing-end covalently bound polysaccharides in a procedure that cleaves the polysaccharide chain from the surface via hydrazinolysis and deamination, leaving on the surface a disaccharide that is later radiolabeled with an aldehyde in a reaction with enamine formation. The method described has the advantage that it may be used with any polysaccharide patterned to any surface exposing an amino-terminated monolayer by reductive amination of their galactosamine or glucosamine repeating units.

Static adhesion of cancer cells to glass surfaces coated with glycosaminoglycans.

Using a previously described method for the functionalization of glass substrates with glycosaminoglycans (GAGs), in vitro experimental comparison of adhesion levels of cancer cells to glycosaminoglycan-modified substrates was performed with non-treated and heparin-treated human cancer cells of different metastatic activity. For both non-treated and heparin-treated cells, our results indicate that heparan sulfate is the preferred substrate for adhesion while keratan sulfate shows anti-adhesive properties. The observed net effect of heparin is a cell-dependent reduction in the adhesion figures.

Construction and characterization of soft-supported lipid bilayer membranes for biosensors application.

A model cell membrane can be ingeniously used to mimic biological processes with wide applications in the biomedical field. For instance, a model cell membrane can be used as a functionalized element integrated to a sensor for identification of specific proteins or other molecules in a biofluid. A special characteristic of the model membrane described in this work is the fluidic or surface mobility feature given by a thin film of grafted polymer that serves as a cushion layer to support lipid bilayers.

Size-Exclusion "capture and release" separations using surface-patterned poly(N-isopropylacrylamide) hydrogels.

Micrometer-scale poly(N-isopropylacrylamide) (poly-NIPAAm) hydrogel monolith patterns were fabricated on solid surfaces using soft lithography. At sufficiently high aspect ratios, the hydrogel monoliths swell and contract laterally with temperature. The spaces between the monoliths form a series of trenches that catch, hold, and release appropriately sized targets.

Deposition of patterned glycosaminoglycans on silanized glass surfaces.

We report the robust attachment of glycosaminoglycans (GAGs) on silanized glass surfaces. Depositions were performed both by immersion and by application of a pattern by means of microcontact printing. Immunofluorescence assays were performed to verify the deposition and the quality of the patterns.