Influence of the β-sheet content on the mechanical properties of aggregates during amyloid fibrillization.

Amyloid fibrils associated with neurodegenerative diseases, such as Parkinson's and Alzheimer's, consist of insoluble aggregates of α-synuclein and Aβ-42 proteins with a high β-sheet content. The aggregation of both proteins occurs by misfolding of the monomers and proceeds through the formation of intermediate oligomeric and protofibrillar species to give the final fibrillar cross-β-sheet structure. The morphological and mechanical properties of oligomers, protofibrils, and fibrils formed during the fibrillization process were investigated by thioflavin T fluorescence and circular dichroism in combination with AFM peak force quantitative nanomechanical technique.

One-pot semisynthesis of exon 1 of the Huntingtin protein: new tools for elucidating the role of posttranslational modifications in the pathogenesis of Huntington's disease.

The natural enzymes involved in regulating many of the posttranslational modifications (PTMs) within the first 17 residues (Nt17) of Huntingtin exon 1 (Httex1) remain unknown. A semisynthetic strategy that allows the site-specific introduction of PTMs within Nt17 by using expressed protein ligation (EPL) was developed. This strategy was used to produce untagged wild-type (wt) and T3-phosphorylated (pT3) Httex1 containing 23 glutamine residues (Httex1-23Q).

Novel mechanistic insight into the molecular basis of amyloid polymorphism and secondary nucleation during amyloid formation.

The formation of amyloid β (Aβ) fibrils is crucial in initiating the cascade of pathological events that culminates in Alzheimer's disease. In this study, we investigated the mechanism of Aβ fibril formation from hydrodynamically well defined species under controlled aggregation conditions. We present a detailed mechanistic model that furnishes a novel insight into the process of Aβ42 fibril formation and the molecular basis for the different structural transitions in the amyloid pathway.

Measurement of intrinsic properties of amyloid fibrils by the peak force QNM method.

We report the investigation of the mechanical properties of different types of amyloid fibrils by the peak force quantitative nanomechanical (PF-QNM) technique. We demonstrate that this technique correctly measures the Young's modulus independent of the polymorphic state and the cross-sectional structural details of the fibrils, and we show that values for amyloid fibrils assembled from heptapeptides, α-synuclein, Aβ(1-42), insulin, β-lactoglobulin, lysozyme, ovalbumin, Tau protein and bovine serum albumin all fall in the range of 2-4 GPa.

Traceless cross-linker for photocleavable bioconjugation.

Photoresponsive bioconjugation empowers the development of novel methods for drug discovery, disease diagnosis, and high-throughput screening, among others. In this paper, we report on the characteristics of a traceless photocleavable cross-linker, di-6-(3-succinimidyl carbonyloxymethyl-4-nitro-phenoxy)-hexanoic acid disulfide diethanol ester (SCNE). The traceless feature and the biocompatibility of this photocleavable cross-linking reagent were corroborated.

Fingerprinting species and strains of Bacilli spores by distinctive coat surface morphology.

In this work, we applied high-resolution atomic force microscopy (AFM) to identify and characterize similarities and differences in the spore surface morphology of strains from four species of Bacilli: B. anthracis, B. cereus, B.