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Wang TY, Rukundo JL, Mao Z, Krylov SN. Maximizing the Accuracy of Equilibrium Dissociation Constants for Affinity Complexes: From Theory to Practical Recommendations. ACS Chem Biol 2024. [PMID: 39121869 DOI: 10.1021/acschembio.4c00259] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/12/2024]
Abstract
The equilibrium dissociation constant (Kd) is a major characteristic of affinity complexes and one of the most frequently determined physicochemical parameters. Despite its significance, the values of Kd obtained for the same complex under similar conditions often exhibit considerable discrepancies and sometimes vary by orders of magnitude. These inconsistencies highlight the susceptibility of Kd determination to large systematic errors, even when random errors are small. It is imperative to both minimize and quantitatively assess the systematic errors inherent in Kd determination. Traditionally, Kd values are determined through nonlinear regression of binding isotherms. This analysis utilizes three variables: concentrations of two reactants and a fraction R of unbound limiting reactant. The systematic errors in Kd arise directly from systematic errors in these variables. Therefore, to maximize the accuracy of Kd, this study thoroughly analyzes the sources of systematic errors within the three variables, including (i) non-additive signals to calculate R, (ii) mis-calibrated experimental instruments, (iii) inaccurate calibration parameters, (iv) insufficient incubation time, (v) unsaturated binding isotherm, (vi) impurities in the reactants, and (vii) solute adsorption onto surfaces. Through this analysis, we illustrate how each source contributes to inaccuracies in the determination of Kd and propose strategies to minimize these contributions. Additionally, we introduce a method for quantitatively assessing the confidence intervals of systematic errors in concentrations, a crucial step toward quantitatively evaluating the accuracy of Kd. While presenting original findings, this paper also reiterates the fundamentals of Kd determination, hence guiding researchers across all proficiency levels. By shedding light on the sources of systematic errors and offering strategies for their mitigation, our work will help researchers enhance the accuracy of Kd determination, thereby making binding studies more reliable and the conclusions drawn from such studies more robust.
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Affiliation(s)
- Tong Ye Wang
- Department of Chemistry, York University, Toronto, Ontario M3J 1P3, Canada
- Centre for Research on Biomolecular Interactions, York University, Toronto, Ontario M3J 1P3, Canada
| | - Jean-Luc Rukundo
- Department of Chemistry, York University, Toronto, Ontario M3J 1P3, Canada
- Centre for Research on Biomolecular Interactions, York University, Toronto, Ontario M3J 1P3, Canada
| | - Zhiyuan Mao
- Department of Chemistry, York University, Toronto, Ontario M3J 1P3, Canada
- Centre for Research on Biomolecular Interactions, York University, Toronto, Ontario M3J 1P3, Canada
| | - Sergey N Krylov
- Department of Chemistry, York University, Toronto, Ontario M3J 1P3, Canada
- Centre for Research on Biomolecular Interactions, York University, Toronto, Ontario M3J 1P3, Canada
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Farzadfard A, Kunka A, Mason TO, Larsen JA, Norrild RK, Dominguez ET, Ray S, Buell AK. Thermodynamic characterization of amyloid polymorphism by microfluidic transient incomplete separation. Chem Sci 2024; 15:2528-2544. [PMID: 38362440 PMCID: PMC10866369 DOI: 10.1039/d3sc05371g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2023] [Accepted: 01/05/2024] [Indexed: 02/17/2024] Open
Abstract
Amyloid fibrils of proteins such as α-synuclein are a hallmark of neurodegenerative diseases and much research has focused on their kinetics and mechanisms of formation. The question as to the thermodynamic stability of such structures has received much less attention. Here, we newly utilize the principle of transient incomplete separation of species in laminar flow in combination with chemical depolymerization for the quantification of amyloid fibril stability. The relative concentrations of fibrils and monomer at equilibrium are determined through an in situ separation of these species based on their different diffusivity inside a microfluidic capillary. The method is highly sample economical, using much less than a microliter of sample per data point and its only requirement is the presence of aromatic residues (W, Y) because of its label-free nature, which makes it widely applicable. Using this method, we investigate the differences in thermodynamic stability between different fibril polymorphs of α-synuclein and quantify these differences for the first time. Importantly, we show that fibril formation can be under kinetic or thermodynamic control and that a change in solution conditions can both stabilise and destabilise amyloid fibrils. Taken together, our results establish the thermodynamic stability as a well-defined and key parameter that can contribute towards a better understanding of the physiological roles of amyloid fibril polymorphism.
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Affiliation(s)
- Azad Farzadfard
- Protein Biophysics Group, Department of Biotechnology and Biomedicine, Technical University of Denmark Søltofts Plads, Building 227, Kgs. Lyngby 2800 Denmark
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University Gustav Wieds Vej 14 8000 Aarhus C Denmark
| | - Antonin Kunka
- Protein Biophysics Group, Department of Biotechnology and Biomedicine, Technical University of Denmark Søltofts Plads, Building 227, Kgs. Lyngby 2800 Denmark
| | - Thomas Oliver Mason
- Protein Biophysics Group, Department of Biotechnology and Biomedicine, Technical University of Denmark Søltofts Plads, Building 227, Kgs. Lyngby 2800 Denmark
| | - Jacob Aunstrup Larsen
- Protein Biophysics Group, Department of Biotechnology and Biomedicine, Technical University of Denmark Søltofts Plads, Building 227, Kgs. Lyngby 2800 Denmark
| | - Rasmus Krogh Norrild
- Protein Biophysics Group, Department of Biotechnology and Biomedicine, Technical University of Denmark Søltofts Plads, Building 227, Kgs. Lyngby 2800 Denmark
| | - Elisa Torrescasana Dominguez
- Protein Biophysics Group, Department of Biotechnology and Biomedicine, Technical University of Denmark Søltofts Plads, Building 227, Kgs. Lyngby 2800 Denmark
| | - Soumik Ray
- Protein Biophysics Group, Department of Biotechnology and Biomedicine, Technical University of Denmark Søltofts Plads, Building 227, Kgs. Lyngby 2800 Denmark
| | - Alexander K Buell
- Protein Biophysics Group, Department of Biotechnology and Biomedicine, Technical University of Denmark Søltofts Plads, Building 227, Kgs. Lyngby 2800 Denmark
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Rukundo JL, Latimer J, Jain S, Kochmann S, Krylov SN. Streamlined Data Processing for Determination of Equilibrium Dissociation Constants with Accurate Constant via Transient Incomplete Separation (ACTIS). Anal Chem 2023; 95:3563-3568. [PMID: 36763923 DOI: 10.1021/acs.analchem.2c05607] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
The determination of accurate equilibrium dissociation constants, Kd, of protein-small molecule complexes is important but challenging as all established methods have inherent sources of inaccuracy. Accurate Constant via Transient Incomplete Separation (ACTIS) is a new method for Kd determination using transient incomplete separation of the complex from the unbound small molecule in a pressure-driven flow inside a capillary. ACTIS is accurate, and its accuracy is invariant to variations in geometries of both the fluidic system and the flow. Furthermore, ACTIS is implemented using a simple fluidic system supporting its accuracy and providing a simple-to-follow/copy template for instrumentation. Despite the simple and robust instrumentation/acquisition, the current data processing workflow is cumbersome, time consuming, and prone to hard-to-trace human errors therefore hindering ACTIS' ability to become a practical reference method for Kd determination. This technical note describes a streamlined workflow for processing ACTIS data; the workflow is implemented as a set of open-source software tools called prACTISed (https://github.com/prACTISedProgram/prACTISed). These tools allow all steps of data processing to be performed in a fast and straightforward fashion. These practical software tools complement the simple instrumentation serving both developers and users of ACTIS.
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Affiliation(s)
- Jean-Luc Rukundo
- Department of Chemistry and Centre for Research on Biomolecular Interactions, York University, Toronto, Ontario M3J 1P3, Canada
| | - Jessica Latimer
- Department of Chemistry and Centre for Research on Biomolecular Interactions, York University, Toronto, Ontario M3J 1P3, Canada
| | - Shiv Jain
- Department of Chemistry and Centre for Research on Biomolecular Interactions, York University, Toronto, Ontario M3J 1P3, Canada
| | - Sven Kochmann
- Department of Chemistry, University of Natural Resources and Life Sciences, 1190 Vienna, Austria
| | - Sergey N Krylov
- Department of Chemistry and Centre for Research on Biomolecular Interactions, York University, Toronto, Ontario M3J 1P3, Canada
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Teclemichael E, Le ATH, Krylova SM, Wang TY, Krylov SN. Bulk Affinity Assays in Aptamer Selection: Challenges, Theory, and Workflow. Anal Chem 2022; 94:15183-15188. [DOI: 10.1021/acs.analchem.2c03173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Eden Teclemichael
- Department of Chemistry and Centre for Research on Biomolecular Interactions, York University, Toronto, OntarioM3J 1P3, Canada
| | - An T. H. Le
- Department of Chemistry and Centre for Research on Biomolecular Interactions, York University, Toronto, OntarioM3J 1P3, Canada
| | - Svetlana M. Krylova
- Department of Chemistry and Centre for Research on Biomolecular Interactions, York University, Toronto, OntarioM3J 1P3, Canada
| | - Tong Ye Wang
- Department of Chemistry and Centre for Research on Biomolecular Interactions, York University, Toronto, OntarioM3J 1P3, Canada
| | - Sergey N. Krylov
- Department of Chemistry and Centre for Research on Biomolecular Interactions, York University, Toronto, OntarioM3J 1P3, Canada
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Wang TY, Rukundo JL, Le ATH, Ivanov NA, Le Blanc JCY, Gorin BI, Krylov SN. Transient Incomplete Separation of Species with Close Diffusivity to Study the Stability of Affinity Complexes. Anal Chem 2022; 94:15415-15422. [DOI: 10.1021/acs.analchem.2c03313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Tong Ye Wang
- Department of Chemistry and Centre for Research on Biomolecular Interactions, York University, Toronto, OntarioM3J 1P3, Canada
| | - Jean-Luc Rukundo
- Department of Chemistry and Centre for Research on Biomolecular Interactions, York University, Toronto, OntarioM3J 1P3, Canada
| | - An T. H. Le
- Department of Chemistry and Centre for Research on Biomolecular Interactions, York University, Toronto, OntarioM3J 1P3, Canada
| | - Nikita A. Ivanov
- Department of Chemistry and Centre for Research on Biomolecular Interactions, York University, Toronto, OntarioM3J 1P3, Canada
| | | | - Boris I. Gorin
- Eurofins CDMO Alphora, 2395 Speakman Drive #2001, Mississauga, OntarioL5K 1B3, Canada
| | - Sergey N. Krylov
- Department of Chemistry and Centre for Research on Biomolecular Interactions, York University, Toronto, OntarioM3J 1P3, Canada
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