Surface-charge differentiation of streptavidin and avidin by atomic force microscopy-force spectroscopy.

Chemical information can be obtained by using atomic force microscopy (AFM) and force spectroscopy (FS) with atomic or molecular resolution, even in liquid media. The aim of this paper is to demonstrate that single molecules of avidin and streptavidin anchored to a biotinylated bilayer can be differentiated by using AFM, even though AFM topographical images of the two proteins are remarkably alike. At physiological pH, the basic glycoprotein avidin is positively charged, whereas streptavidin is a neutral protein.

Tau aggregation followed by atomic force microscopy and surface plasmon resonance, and single molecule tau-tau interaction probed by atomic force spectroscopy.

Intracellular neurofibrillary tangles, composed mainly of tau protein, and extracellular plaques, containing mostly amyloid-beta, are the two types of protein aggregates found upon autopsy within the brain of Alzheimer's disease patients. Polymers of tau protein can also be found in other neurodegenerative disorders known as tauopathies. Tau is a highly soluble protein, intrinsically devoid of secondary or tertiary structure, as many others proteins particularly prone to form fibrillar aggregations.

Unbinding molecular recognition force maps of localized single receptor molecules by atomic force microscopy.

Atomic force microscopy is a technique capable to study biological recognition processes at the single-molecule level. In this work we operate the AFM in a force-scan based mode, the jumping mode, where simultaneous topographic and tip-sample adhesion maps are acquired. This approach obtains the unbinding force between a well-defined receptor molecule and a ligand attached to the AFM tip.

Biochemical, ultrastructural, and reversibility studies on huntingtin filaments isolated from mouse and human brain.

Huntington's disease (HD) and eight additional inherited neurological disorders are caused by CAG triplet-repeat expansions leading to expanded polyglutamine-sequences in their respective proteins. These triplet-CAG repeat disorders have in common the formation of aberrant intraneuronal proteinaceous inclusions containing the expanded polyglutamine sequences. These aggregates have been postulated to contribute to pathogenesis caused by conformational toxicity, sequestration of other polyglutamine-containing proteins, or by interfering with certain enzymatic activities.

Characterization by atomic force microscopy and cryoelectron microscopy of tau polymers assembled in Alzheimer's disease.

The structure of the Paired Helical filaments (PHF), a polymer of the microtubule associated protein tau, has been studied by Atomic Force Microscopy (AFM) and by cryoelectron microscopy. Mica and graphite were used as substrates in the AFM analysis with no differences in the results. A banding pattern of 8-12 nm width within the helical structure is found when detailed analysis of the data is performed.