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Protein misfolding and aggregation into oligomeric and fibrillar structures is a common feature of many neurogenerative disorders. Single-molecule techniques have enabled characterization of these lowly abundant, highly heterogeneous protein aggregates, previously inaccessible using ensemble averaging techniques. However, they usually rely on the use of recombinantly-expressed labeled protein, or on the addition of amyloid stains that are not protein-specific. To circumvent these challenges, we have made use of a high affinity antibody labeled with orthogonal fluorophores combined with fast-flow microfluidics and single-molecule confocal microscopy to specifically detect α-synuclein, the protein associated with Parkinson's disease. We used this approach to determine the number and size of α-synuclein aggregates down to picomolar concentrations in biologically relevant samples.
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http://dx.doi.org/10.1002/anie.202216771 | DOI Listing |
Proc Natl Acad Sci U S A
August 2025
Department of Chemistry and Center for Nanoscience, Ludwig-Maximilians-Universität Munich, Munich 81377, Germany.
The human Fic enzyme FicD plays an important role in regulating the Hsp70 homolog BiP in the endoplasmic reticulum: FicD reversibly modulates BiP's activity through attaching an adenosine monophosphate to the substrate binding domain. This reduces BiP's chaperone activity by shifting it into a conformation with reduced substrate affinity. Crystal structures of FicD in the apo, adenosine triphosphate (ATP)-bound, and BiP-bound states suggested significant conformational variability in the tetratricopeptide repeat (TPR) motifs.
View Article and Find Full Text PDFBiophys J
September 2025
Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland. Electronic address:
Three-color single-molecule Förster resonance energy transfer (FRET) is a valuable tool to study conformational dynamics of macromolecules. In this work, we present a maximum likelihood method for analyzing three-color fluorescence bursts collected from freely diffusing molecules in confocal microscopy. In three-color single-molecule FRET measurements, the third dye with the longest wavelength typically has a much lower quantum yield than the other two dyes, which leads to significantly reduced brightness, particularly for molecular states with high energy transfer to the third dye.
View Article and Find Full Text PDFCurr Opin Struct Biol
August 2025
Department of Chemistry and Center for Nanoscience, Ludwig-Maximilians-Universität Munich, 81377, Munich, Germany. Electronic address:
Förster resonance energy transfer (FRET) is a powerful tool for studying protein conformations, interactions, and dynamics at the single-molecule level. Multicolor FRET extends conventional two-color FRET by incorporating three or more fluorophores and thereby enabling a more comprehensive view of complex biomolecular processes. This technique allows for the simultaneous tracking of multiple structural changes, detecting intermediate states, and resolving heterogeneous population distributions.
View Article and Find Full Text PDFSingle-molecule localization microscopy (SMLM) breaks the diffraction limit, significantly enhancing optical resolution and providing a powerful tool for imaging complex biological structures in life sciences. However, imaging biological structures below 10 nm and studying protein-protein interactions remains a challenge for optical super-resolution microscopy. Here, we introduce a microscopy based on two-color single-molecule localization microscopy, we call it molecular Imaging by two-color imaging (MITI), which improves resolution to the molecular level, reaching several nanometers.
View Article and Find Full Text PDFNat Commun
May 2025
Max Planck Institute for Solid State Research, Stuttgart, Germany.
Probing and manipulating the spatiotemporal dynamics of hot carriers in nanoscale metals is crucial to a plethora of applications ranging from nonlinear nanophotonics to single-molecule photochemistry. The direct investigation of these highly non-equilibrium carriers requires the experimental capability of high energy-resolution (~ meV) broadband femtosecond spectroscopy. When considering the ultimate limits of atomic-scale structures, this capability has remained out of reach until date.
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