Biophysical Society Thematic Meeting | Tutzing 2026

Single-Molecule FRET: The Next 30 Years

Poster Abstracts

74-POS

Board 37

SINGLE-MOLECULE FLUORESCENCE SPECTROSCOPY IN H1-DNA DROPLETS Matti Valdimarsson 1 ; Nicola Galvanetto 1 ; Aritra Chowdhury 1 ; Daniel Nettels 1 ; Ben Schuler 1 1 University of Zurich, Department of Biochemistry, Zurich, Switzerland Abstract: Biomolecular condensates formed by highly charged intrinsically disordered proteins (IDPs) are a widespread principle of cellular organization, yet the behaviour of individual chains inside the dense phase remains difficult to access experimentally. We previously showed that the oppositely and highly charged IDPs prothymosin α (ProT α ) and linker histone H1 form a biomolecular condensate in which both partners remain fully disordered and exceptionally dynamic. Since most cellular condensates also contain nucleic acids, a central open question is how the presence of a polyanion such as DNA alters the structure and dynamics of the dense phase. Here we extend this system to ternary ProT α /H1/DNA condensates, enabling a direct comparison between purely protein-based and protein–nucleic acid condensates. We combine single-molecule fluorescence spectroscopy and solution NMR to characterize partitioning, chain dimensions, conformational and translational dynamics. Our results show that short DNA of comparable molecular weight and charge to ProT α outcompetes it and leads to greatly slowed diffusive processes at all length scales.

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