Search results for "Thioflavin T"

Design and synthesis of new trehalose-conjugated pentapeptides as inhibitors of Aβ(1-42) fibrillogenesis and toxicity

2009

Aggregation of the amyloid A? peptide and its accumulation into insoluble deposits (plaques) are believed to be the main cause of neuronal dysfunction associated with Alzheimer's disease (AD); small molecules that can interfere with the A? amyloid fibril formation are therefore of interest for a potential therapeutic strategy. Three new trehalose-conjugated peptides of the well known ?-sheet breaker peptide iA?5p,were synthesized. The disaccharide was covalently attached to different sites of the LPFFD peptide chain, i.e. at the N-terminus, C-terminus or at the Asp side chain. CD spectroscopy in different solvents was used to assess changes in the peptide conformation of these compounds. Th…

Thioflavin T Hydroxylation at Basic pH and Its Effect on Amyloid Fibril Detection

2008

The fluorescent dye thioflavin T (ThT) is commonly used for in situ amyloid fibril detection. In this work, we focused on the spectroscopic properties and chemical stability of ThT in aqueous solution as a function of pH, temperature, and dye concentration. A reversible hydroxylation process occurs in alkaline solutions, which was characterized using a combination of UV-vis absorption spectroscopy, proton NMR, and density functional theory (DFT). On the basis of these studies, we propose a chemical structure for the hydroxylated form. Finally, by means of fluorescence spectroscopy, ThT hydroxylation effects on in situ amyloid detection have been investigated, providing new insights on the e…

Secondary nucleation and accessible surface in insulin amyloid fibril formation.

2008

At low pH insulin is highly prone to self-assembly into amyloid fibrils. The process has been proposed to be affected by the existence of secondary nucleation pathways, in which already formed fibrils are able to catalyze the formation of new fibrils. In this work, we studied the fibrillation process of human insulin in a wide range of protein concentrations. Thioflavin T fluorescence was used for its ability to selectively detect amyloid fibrils, by mechanisms that involve the interaction between the dye and the accessible surface of the fibrils. Our results show that the rate of fibrillation and the Thioflavin T fluorescence intensity saturate at high protein concentration and that, surpr…

Amyloid fibrils formation and amorphous aggregation in Concanavalin A

2007

We here report an experimental study on the thermal aggregation process of concanavalin A, a protein belonging to the legume lectins family. The aggregation process and the involved conformational changes of the protein molecules were followed by means of fluorescence techniques, light scattering, circular dichroism, zeta potential measurements and atomic force microscopy. Our results show that the aggregation process of concanavalin A may evolve through two distinct pathways leading, respectively, to the formation of amyloids or amorphous aggregates. The relative extent of the two pathways is determined by pH, as amyloid aggregation is favored at high pH values ( approximately 9), while th…

Protective Effects of L- and D-Carnosine on R-Crystallin Amyloid Fibril Formation: Implications for Cataract Disease

2009

Mildly denaturing conditions induce bovine ?-crystallin, the major structural lens protein, to self-assemble into fibrillar structures in vitro. The natural dipeptide L-carnosine has been shown to have potential protective and therapeutic significance in many diseases. Carnosine derivatives have been proposed as potent agents for ophthalmic therapies of senile cataracts and diabetic ocular complications. Here we report the inhibitory effect induced by the peptide (L- and D-enantiomeric form) on ?-crystallin fibrillation and the almost complete restoration of the chaperone activity lost after denaturant and/or heat stress. Scanning force microscopy (SFM), thioflavin T, and a turbidimetry ass…

AMYLOID AGGREGATION IN CONCANAVALIN A AT HIGH PH STUDIED BY LIGHT SCATTERING, FLUORESCENCE AND CIRCULAR DICHROISM SPECTROSCOPY

2008

Amyloid Fibrils Formation in Concanavalin A studied by Dynamic Light Scattering and Fluorescence techniques

2007

Phasor FLIM analysis of Thioflavin T fluorescence in protein amyloid aggregates: Mapping molecular interactions.

Thioflavin T (ThT) is a worldwide used dye to monitor protein aggregation as it stains with a certain specificity amyloid structures. The interactions between ThT and its hosts are largely studied suggesting that fluorescence properties of this dye critically depend both on the environment rigidity, electrostatic and hydrophobic properties as well as on molecular details binding site structure. Here FLIM and phasor approach analysis are used to exploit ThT amyloid interactions and, in turn, to address polymorphism and structural heterogeneity of amyloid species mapping aggregate-to-aggregate structural differences and revealing details of molecular architecture within the same aggregate.

Probing ensemble polymorphism and single aggregate structural heterogeneity in insulin amyloid self-assembly.

2020

Ensembles of protein aggregates are characterized by a nano- and micro-scale heterogeneity of the species. This diversity translates into a variety of effects that protein aggregates may have in biological systems, both in connection to neurodegenerative diseases and immunogenic risk of protein drug products. Moreover, this naturally occurring variety offers unique opportunities in the field of protein-based biomaterials. In the above-mentioned fields, the isolation and structural analysis of the different amyloid types within the same ensemble remain a priority, still representing a significant experimental challenge. Here we address such complexity in the case of insulin for its relevance…

Phasor-FLIM analysis of Thioflavin T self-quenching in Concanavalin amyloid fibrils

2020

The formation of amyloid structures has traditionally been related to human neurodegenerative pathologies and, in recent years, the interest in these highly stable nanostructures was extended to biomaterial sciences. A common method to monitor amyloid growth is the analysis of Thioflavin T fluorescence. The use of this highly selective dye, diffused worldwide, allows mechanistic studies of supramolecular assemblies also giving back important insight on the structure of these aggregates. Here we present experimental evidence of self-quenching effect of Thioflavin T in presence of amyloid fibrils. A significant reduction of fluorescence lifetime of this dye which is not related to the propert…