Biology subjects

van Wee, R.

Publications and source records attributed to van Wee, R..

7 recordsLinked to original sources

bioRxiv2026

Mass-specific single molecule pull-down from complex mixtures with bilayer-assisted mass photometry

Determining the identity, quantity and interactions of proteins is fundamental to studies of biomolecular function and (dis)regulation in disease. Here, we combine mass photometry with supported lipid bilayers (SLBs) to specifically recruit proteins of interest from complex mixtures such as cell lysate and demonstrate sensitive detection and mass measurement of single biomolecules and their complexes without prior purification. Extending to heterologously expressed proteins, we provide rapid information on oligomerisation and concentration in lysate. Introduction of polyethylene glycol in the SLBs passivates against a variety of cell lysates and serum, allows specific recruitment of proteins from complex mixtures and mass-specific detection and affinity measurement at sub-nM concentrations. Our approach preserves the mass resolution and accuracy of mass photometry, thereby enabling visualisation and quantification of oligomeric states, interactions and complexes directly from cell lysates.

biophysics↗

bioRxiv2026

Modular DNA nanosensors enable state-aware multiplexed single-molecule mass photometry in complex media

Proteins exist in diverse biochemical states, including oligomers, complexes, heterogeneous proteoforms and shed fragments that encode functional and regulatory information. Yet, these molecular states remain difficult to resolve with existing analytical techniques, which typically require labelling, immobilisation or amplification and collapse this information into a single readout. Here, we introduce a modular platform that integrates programmable DNA nanostructures with single-molecule mass photometry for rapid, label-free and multiplexed protein analysis in native and complex media, without washing, enrichment or immobilisation, making native biochemical states observable directly in serum and plasma. DNA nanostructures act as nanosensors whose mass and mobility on supported lipid bilayers provide orthogonal identifiers for target identity and biochemical state, thereby decoupling recognition from readout. We define the analytical specificity and response window, demonstrate quantitative affinity determination, and resolve oligomeric and proteoform differences under native conditions. The nanosensors are rapidly reprogrammable to new targets, support multiplexed detection with internal controls for non-specific interactions, and enable selective resetting via strand displacement. Together, these capabilities establish nanoscale programmability as a route to state-resolved single-molecule protein profiling adaptable to both diagnostic and mechanistic applications.

biophysics↗

bioRxiv2024

Best practice mass photometry: A guide to optimal single molecule mass measurement

Mass photometry (MP) has emerged as a powerful approach to study biomolecular structure, dynamics and interactions. The capabilities of the method ultimately hinge on the ability to accurately measure the tiny optical contrast generated by individual molecules landing at a glass-water interface, which enables mass-resolved quantification of biomolecular mixtures. Ideally, this capability is only limited by shot noise inherent to photon detection, but in practice depends on additional parameters and details of the assay. Here, we focus on the key parameters affecting MP performance, and present simple steps that can be taken to achieve optimal MP performance in terms of mass resolution, quantitative detection limit and analyte concentration range without compromising the ease and simplicity of the technique.

biophysics↗

bioRxiv2024

NIPBL and STAG1 enable loop extrusion by providing differential DNA-cohesin affinity

DNA loop extrusion by cohesin has emerged as a critical pathway for chromosome organization. In vitro single-molecule experiments indicate that loop extrusion requires the assembly of an heteropentameric complex consisting of the SMC1/SMC3 heterodimer, STAG1, NIPBL and the kleisin SCC1. The multimeric nature of this complex and regulatoin of its dynamic DNA interactions that are modulated by ATP binding-hydrolysis cycles make it challenging to reveal the molecular mechanism of loop extrusion. Here, we use mass photometry to quantify the key interactions responsible for cohesin assembly, DNA binding, and their modulation by ATP binding and hydrolysis. We find that STAG1 binds tightly to the trimeric complex formed by the SMC1/SMC3 heterodimer and SCC1, creating a DNA binding site whose strength is modulated by the presence of ATP. NIPBL binds strongly to both DNA and the STAG1-tetramer, enabling assembly of the holoenzyme in the absence of DNA or ATP. Taken together, these results suggest that NIPBL acts as a DNA anchor, while a dynamic STAG1-Trimer binding site drives DNA loop formation.

biophysics↗

bioRxiv2023

Full-Length Single-Molecule Protein Fingerprinting

Proteins are the primary functional actors of the cell. Hence, their identification is pivotal to advance our understanding of cell biology and disease. Current protein analysis methods are of limited use for distinguishing proteoforms. In particular, mass spectrometric methods often provide only ambiguous information on post-translational modification sites, and sequences of co-existing modifications may not be resolved. Here we demonstrate FRET-based single-molecule protein fingerprinting to map the location of individual amino acids and a post-translational modification within single full-length protein molecules. Using an approach that relies on transient binding of fluorescently labeled DNA strands to probe the amino acids on a protein one by one we show that we can fingerprint intrinsically disordered proteins as well as folded globular proteins with sub-nanometer resolution. We anticipate that this technology will be used for proteoform identification in biological and translational research with ultimate sensitivity.

biophysics↗

bioRxiv2022

MukBEF-dependent chromosomal organization in widened Escherichia coli

The bacterial chromosome is spatially organized through protein-mediated compaction, supercoiling, and cell-boundary confinement. Structural Maintenance of Chromosomes (SMC) complexes are a major class of chromosome-organizing proteins present throughout all domains of life. Here, we study the role of the Escherichia coli SMC complex MukBEF in chromosome architecture and segregation. Using quantitative live-cell imaging of shape-manipulated cells, we show that MukBEF is crucial to preserve the toroidal topology of the E. coli chromosome and that it is non-uniformly distributed along the chromosome: it prefers locations towards the origin and away from the terminus of replication, and it is unevenly distributed over the origin of replication along the two chromosome arms. Using an ATP hydrolysis-deficient MukB mutant, we find that MukBEF translocation along the chromosome is ATP-dependent, in contrast to its loading onto DNA. MukBEF and MatP are furthermore found to be essential for sister chromosome decatenation. We propose a model that explains how MukBEF, MatP, and their interacting partners organize the chromosome and contribute to sister segregation and recombination. The combination of bacterial cell-shape modification and quantitative fluorescence microscopy paves way to investigating chromosome-organization factors in vivo.

microbiology↗

bioRxiv2021

Evaluation of FRET X for Single-Molecule Protein Fingerprinting

Single-molecule protein identification is a novel, as of yet unrealized concept with potentially groundbreaking applications in biological research. We propose a method called FRET X (Forster Resonance Energy Transfer via DNA eXchange) fingerprinting, in which the FRET efficiency is read out between exchangeable dyes on protein-bound DNA docking strands, and accumulated FRET efficiency values constitute the fingerprint for a protein. To evaluate the feasibility of this approach, we simulated fingerprints for hundreds of proteins using a coarse-grained lattice model and experimentally demonstrated FRET X fingerprinting on a system of model peptides. Measured fingerprints are in agreement with our simulations, corroborating the validity of our modeling approach. In a simulated complex mixture of >300 human proteins of which only cysteines, lysines and arginines were labeled, a support vector machine was able to identify constituents with 95% accuracy. We anticipate that our FRET X fingerprinting approach will form the basis of an analysis tool for targeted proteomics.

biophysics↗