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Yang B, Gomes DEB, Liu Z, Santos MS, Li J, Bernardi RC, Nash MA. Engineering the Mechanical Stability of a Therapeutic Affibody/PD-L1 Complex by Anchor Point Selection. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.21.595133. [PMID: 38826272 PMCID: PMC11142103 DOI: 10.1101/2024.05.21.595133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2024]
Abstract
Protein-protein complexes can vary in mechanical stability depending on the direction from which force is applied. Here we investigated the anisotropic mechanical stability of a molecular complex between a therapeutic non-immunoglobulin scaffold called Affibody and the extracellular domain of the immune checkpoint protein PD-L1. We used a combination of single-molecule AFM force spectroscopy (AFM-SMFS) with bioorthogonal clickable peptide handles, shear stress bead adhesion assays, molecular modeling, and steered molecular dynamics (SMD) simulations to understand the pulling point dependency of mechanostability of the Affibody:(PD-L1) complex. We observed diverse mechanical responses depending on the anchor point. For example, pulling from residue #22 on Affibody generated an intermediate unfolding event attributed to partial unfolding of PD-L1, while pulling from Affibody's N-terminus generated force-activated catch bond behavior. We found that pulling from residue #22 or #47 on Affibody generated the highest rupture forces, with the complex breaking at up to ~ 190 pN under loading rates of ~104-105 pN/sec, representing a ~4-fold increase in mechanostability as compared with low force N-terminal pulling. SMD simulations provided consistent tendencies in rupture forces, and through visualization of force propagation networks provided mechanistic insights. These results demonstrate how mechanostability of therapeutic protein-protein interfaces can be controlled by informed selection of anchor points within molecules, with implications for optimal bioconjugation strategies in drug delivery vehicles.
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Affiliation(s)
- Byeongseon Yang
- Institute for Physical Chemistry, Department of Chemistry, University of Basel, 4058 Basel, Switzerland
- Department of Biosystems Science and Engineering, ETH Zurich, 4056 Basel, Switzerland
| | - Diego E. B. Gomes
- Department of Physics, Auburn University, Auburn, Alabama 36849, United States
| | - Zhaowei Liu
- Institute for Physical Chemistry, Department of Chemistry, University of Basel, 4058 Basel, Switzerland
- Department of Biosystems Science and Engineering, ETH Zurich, 4056 Basel, Switzerland
- Present address: Department of Bionanoscience, Delft University of Technology, 2629HZ Delft, the Netherlands
| | - Mariana Sá Santos
- Institute for Physical Chemistry, Department of Chemistry, University of Basel, 4058 Basel, Switzerland
- Department of Biosystems Science and Engineering, ETH Zurich, 4056 Basel, Switzerland
| | - Jiajun Li
- Institute for Physical Chemistry, Department of Chemistry, University of Basel, 4058 Basel, Switzerland
- Department of Biosystems Science and Engineering, ETH Zurich, 4056 Basel, Switzerland
| | - Rafael C. Bernardi
- Department of Physics, Auburn University, Auburn, Alabama 36849, United States
| | - Michael A. Nash
- Institute for Physical Chemistry, Department of Chemistry, University of Basel, 4058 Basel, Switzerland
- Department of Biosystems Science and Engineering, ETH Zurich, 4056 Basel, Switzerland
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Sedlacek O, Egghe T, Khashayar P, Purino M, Lopes P, Vanfleteren J, De Geyter N, Hoogenboom R. Multifunctional Poly(2-ethyl-2-oxazoline) Copolymers Containing Dithiolane and Pentafluorophenyl Esters as Effective Reactive Linkers for Gold Surface Coatings. Bioconjug Chem 2023; 34:2311-2318. [PMID: 38055023 DOI: 10.1021/acs.bioconjchem.3c00444] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/07/2023]
Abstract
Surface functionalization with biological macromolecules is an important task for the development of sensor materials, whereby the interaction with other biological materials should be suppressed. In this work, we developed a novel multifunctional poly(2-ethyl-2-oxazoline)-dithiolane conjugate as a versatile linker for gold surface immobilization of amine-containing biomolecules, containing poly(2-ethyl-2-oxazoline) as antifouling polymer, dithiolane for surface immobilization, and activated esters for protein conjugation. First, a well-defined carboxylic acid containing copoly(2-ethyl-2-oxazoline) was synthesized by cationic ring-opening copolymerization of 2-ethyl-2-oxazoline with a methyl ester-containing 2-oxazoline monomer, followed by postpolymerization modifications. The side-chain carboxylic groups were then converted to amine-reactive pentafluorophenyl (PFP) ester groups. Part of the PFP groups was used for the attachment of the dithiolane moiety, which can efficiently bind to gold surfaces. The final copolymer contained 1.4 mol% of dithiolane groups and 4.5 mol% of PFP groups. The copolymer structure was confirmed by several analytical techniques, including NMR spectroscopy and size-exclusion chromatography. The kinetics of the PFP ester aminolysis and hydrolysis demonstrated significantly faster amidation compared to hydrolysis, which is essential for subsequent protein conjugation. Successful coating of gold surfaces with the polymer was confirmed by spectroscopic ellipsometry, showing a polymer brush thickness of 4.77 nm. Subsequent modification of the coated surfaces was achieved using bovine serum albumin as a model protein. This study introduces a novel reactive polymer linker for gold surface functionalization and offers a versatile polymer platform for various applications including biosensing and surface functionalization.
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Affiliation(s)
- Ondrej Sedlacek
- Department of Organic and Macromolecular Chemistry, Supramolecular Chemistry Group, Faculty of Sciences, Ghent University, Krijgslaan 281 S4, Ghent 9000, Belgium
- Department of Physical and Macromolecular Chemistry, Faculty of Science, Charles University, Prague 2 128 40, Czech Republic
| | - Tim Egghe
- Research Unit Plasma Technology (RUPT), Department of Applied Physics, Faculty of Engineering and Architecture, Ghent University, Sint-Pietersnieuwstraat 41 B4, Ghent 9000, Belgium
| | - Patricia Khashayar
- Centre for Microsystems Technology (CMST), IMEC and Ghent University, Technologiepark 216, Zwijnaarde, Ghent 9052, Belgium
| | - Martin Purino
- Department of Organic and Macromolecular Chemistry, Supramolecular Chemistry Group, Faculty of Sciences, Ghent University, Krijgslaan 281 S4, Ghent 9000, Belgium
| | - Paula Lopes
- Centre for Microsystems Technology (CMST), IMEC and Ghent University, Technologiepark 216, Zwijnaarde, Ghent 9052, Belgium
| | - Jan Vanfleteren
- Centre for Microsystems Technology (CMST), IMEC and Ghent University, Technologiepark 216, Zwijnaarde, Ghent 9052, Belgium
| | - Nathalie De Geyter
- Research Unit Plasma Technology (RUPT), Department of Applied Physics, Faculty of Engineering and Architecture, Ghent University, Sint-Pietersnieuwstraat 41 B4, Ghent 9000, Belgium
| | - Richard Hoogenboom
- Department of Organic and Macromolecular Chemistry, Supramolecular Chemistry Group, Faculty of Sciences, Ghent University, Krijgslaan 281 S4, Ghent 9000, Belgium
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Doffini V, Liu H, Liu Z, Nash MA. Iterative Machine Learning for Classification and Discovery of Single-Molecule Unfolding Trajectories from Force Spectroscopy Data. NANO LETTERS 2023; 23:10406-10413. [PMID: 37933959 DOI: 10.1021/acs.nanolett.3c03026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2023]
Abstract
We report the application of machine learning techniques to expedite classification and analysis of protein unfolding trajectories from force spectroscopy data. Using kernel methods, logistic regression, and triplet loss, we developed a workflow called Forced Unfolding and Supervised Iterative Online (FUSION) learning where a user classifies a small number of repeatable unfolding patterns encoded as images, and a machine is tasked with identifying similar images to classify the remaining data. We tested the workflow using two case studies on a multidomain XMod-Dockerin/Cohesin complex, validating the approach first using synthetic data generated with a Monte Carlo algorithm and then deploying the method on experimental atomic force spectroscopy data. FUSION efficiently separated traces that passed quality filters from unusable ones, classified curves with high accuracy, and identified unfolding pathways that were undetected by the user. This study demonstrates the potential of machine learning to accelerate data analysis and generate new insights in protein biophysics.
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Affiliation(s)
- Vanni Doffini
- Institute of Physical Chemistry, Department of Chemistry, University of Basel, 4058 Basel, Switzerland
- Department of Biosystems Science and Engineering, ETH Zurich, 4058 Basel, Switzerland
- Swiss Nanoscience Institute, 4056 Basel, Switzerland
| | - Haipei Liu
- Institute of Physical Chemistry, Department of Chemistry, University of Basel, 4058 Basel, Switzerland
- Department of Biosystems Science and Engineering, ETH Zurich, 4058 Basel, Switzerland
| | - Zhaowei Liu
- Institute of Physical Chemistry, Department of Chemistry, University of Basel, 4058 Basel, Switzerland
- Department of Biosystems Science and Engineering, ETH Zurich, 4058 Basel, Switzerland
| | - Michael A Nash
- Institute of Physical Chemistry, Department of Chemistry, University of Basel, 4058 Basel, Switzerland
- Department of Biosystems Science and Engineering, ETH Zurich, 4058 Basel, Switzerland
- Swiss Nanoscience Institute, 4056 Basel, Switzerland
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