1
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Zhao H, Sousa AA, Schuck P. Flotation Coefficient Distributions of Lipid Nanoparticles by Sedimentation Velocity Analytical Ultracentrifugation. ACS NANO 2024; 18:18663-18672. [PMID: 38967176 PMCID: PMC11256894 DOI: 10.1021/acsnano.4c05322] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2024] [Revised: 06/24/2024] [Accepted: 06/27/2024] [Indexed: 07/06/2024]
Abstract
The robust characterization of lipid nanoparticles (LNPs) encapsulating therapeutics or vaccines is an important and multifaceted translational problem. Sedimentation velocity analytical ultracentrifugation (SV-AUC) has proven to be a powerful approach in the characterization of size-distribution, interactions, and composition of various types of nanoparticles across a large size range, including metal nanoparticles (NPs), polymeric NPs, and also nucleic acid loaded viral capsids. Similar potential of SV-AUC can be expected for the characterization of LNPs, but is hindered by the flotation of LNPs being incompatible with common sedimentation analysis models. To address this gap, we developed a high-resolution, diffusion-deconvoluted sedimentation/flotation distribution analysis approach analogous to the most widely used sedimentation analysis model c(s). The approach takes advantage of independent measurements of the average particle size or diffusion coefficient, which can be conveniently determined, for example, by dynamic light scattering (DLS). We demonstrate the application to an experimental model of extruded liposomes as well as a commercial LNP product and discuss experimental potential and limitations of SV-AUC. The method is implemented analogously to the sedimentation models in the free, widely used SEDFIT software.
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Affiliation(s)
- Huaying Zhao
- Laboratory
of Dynamics of Macromolecular Assembly, National Institute of Biomedical
Imaging and Bioengineering, National Institutes
of Health, Bethesda, Maryland 20892, United States
| | - Alioscka A. Sousa
- Department
of Biochemistry, Federal University of São
Paulo, São Paulo, SP 04044, Brazil
| | - Peter Schuck
- Laboratory
of Dynamics of Macromolecular Assembly, National Institute of Biomedical
Imaging and Bioengineering, National Institutes
of Health, Bethesda, Maryland 20892, United States
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2
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Structural characterization of an L-fuculose-1-phosphate aldolase from Klebsiella pneumoniae. Biochem Biophys Res Commun 2022; 607:15-19. [PMID: 35366538 DOI: 10.1016/j.bbrc.2022.03.127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Accepted: 03/23/2022] [Indexed: 11/23/2022]
Abstract
Fuculose phosphate aldolases play an important role in glycolysis and gluconeogenesis pathways. L-fuculose 1-phosphate aldolase catalyzes the reversible cleavage of L-fuculose 1-phosphate to DHAP and L-lactaldehyde. Class II aldolases found in bacteria are linked to pathogenesis of human pathogens, and have potential applications in the biosynthesis of carbohydrates and other chiral compounds. Here we report the structure of a putative L-fuculose 1-phosphate aldolase (KpFucA) from the nosocomial pathogen Klebsiella pneumoniae to 1.85 Å resolution. The enzyme crystallizes in space group P422 with one monomer per asymmetric unit. Analytical ultracentrifugation analysis confirms that KpFucA is a tetramer in solution. A magnesium ion cofactor and sulfate ion were identified in the active pocket. Enzyme activity assays confirmed that KpFcuA has a strong preference for L-fuculose 1-phosphate as a substrate, but can also catalyze the cleavage of fructose-1,6-bisphosphate and glucose-6-phosphate. This work should provide a starting point for further investigation of the role of KpFucA in K. pneumoniae pathogenesis or in industrial applications.
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3
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Cho YI, Armstrong CL, Sulpizio A, Acheampong KK, Banks KN, Bardhan O, Churchill SJ, Connolly-Sporing AE, Crawford CE, Cruz Parrilla PL, Curtis SM, De La Ossa LM, Epstein SC, Farrehi CJ, Hamrick GS, Hillegas WJ, Kang A, Laxton OC, Ling J, Matsumura SM, Merino VM, Mukhtar SH, Shah NJ, Londergan CH, Daly CA, Kokona B, Charkoudian LK. Engineered Chimeras Unveil Swappable Modular Features of Fatty Acid and Polyketide Synthase Acyl Carrier Proteins. Biochemistry 2022; 61:217-227. [PMID: 35073057 PMCID: PMC9357449 DOI: 10.1021/acs.biochem.1c00798] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The strategic redesign of microbial biosynthetic pathways is a compelling route to access molecules of diverse structure and function in a potentially environmentally sustainable fashion. The promise of this approach hinges on an improved understanding of acyl carrier proteins (ACPs), which serve as central hubs in biosynthetic pathways. These small, flexible proteins mediate the transport of molecular building blocks and intermediates to enzymatic partners that extend and tailor the growing natural products. Past combinatorial biosynthesis efforts have failed due to incompatible ACP-enzyme pairings. Herein, we report the design of chimeric ACPs with features of the actinorhodin polyketide synthase ACP (ACT) and of the Escherichia coli fatty acid synthase (FAS) ACP (AcpP). We evaluate the ability of the chimeric ACPs to interact with the E. coli FAS ketosynthase FabF, which represents an interaction essential to building the carbon backbone of the synthase molecular output. Given that AcpP interacts with FabF but ACT does not, we sought to exchange modular features of ACT with AcpP to confer functionality with FabF. The interactions of chimeric ACPs with FabF were interrogated using sedimentation velocity experiments, surface plasmon resonance analyses, mechanism-based cross-linking assays, and molecular dynamics simulations. Results suggest that the residues guiding AcpP-FabF compatibility and ACT-FabF incompatibility may reside in the loop I, α-helix II region. These findings can inform the development of strategic secondary element swaps that expand the enzyme compatibility of ACPs across systems and therefore represent a critical step toward the strategic engineering of "un-natural" natural products.
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Affiliation(s)
- Yae In Cho
- Department of Chemistry, Haverford College, Haverford, PA 19041
| | | | - Ariana Sulpizio
- Department of Chemistry, Haverford College, Haverford, PA 19041
| | | | | | - Oishi Bardhan
- Department of Chemistry, Haverford College, Haverford, PA 19041
| | | | | | | | | | - Sarah M. Curtis
- Department of Chemistry, Haverford College, Haverford, PA 19041
| | | | | | | | | | | | - Austin Kang
- Department of Chemistry, Haverford College, Haverford, PA 19041
| | | | - Joie Ling
- Department of Chemistry, Haverford College, Haverford, PA 19041
| | | | | | | | - Neel J. Shah
- Department of Chemistry, Haverford College, Haverford, PA 19041
| | | | - Clyde A. Daly
- Department of Chemistry, Haverford College, Haverford, PA 19041
| | - Bashkim Kokona
- Department of Chemistry, Haverford College, Haverford, PA 19041
- Spark Therapeutics, Philadelphia PA 19041
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4
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Bou-Assaf GM, Budyak IL, Brenowitz M, Day ES, Hayes D, Hill J, Majumdar R, Ringhieri P, Schuck P, Lin JC. Best Practices for Aggregate Quantitation of Antibody Therapeutics by Sedimentation Velocity Analytical Ultracentrifugation. J Pharm Sci 2022; 111:2121-2133. [PMID: 34986360 DOI: 10.1016/j.xphs.2021.12.023] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 12/24/2021] [Accepted: 12/24/2021] [Indexed: 11/18/2022]
Abstract
Analytical ultracentrifugation (AUC) is a critical analytical tool supporting the development and manufacture of protein therapeutics. AUC is routinely used as an assay orthogonal to size exclusion chromatography for aggregate quantitation. This article distills the experimental and analysis procedures used by the authors for sedimentation velocity AUC into a series of best-practices considerations. The goal of this distillation is to help harmonize aggregate quantitation approaches across the biopharmaceutical industry. We review key considerations for sample and instrument suitability, experimental design, and data analysis best practices and conversely, highlight potential pitfalls to accurate aggregate analysis. Our goal is to provide experienced users benchmarks against which they can standardize their analyses and to provide guidance for new AUC analysts that will aid them to become proficient in this fundamental technique.
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Affiliation(s)
| | - Ivan L Budyak
- Bioproduct Research and Development, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN 46285, USA
| | - Michael Brenowitz
- Departments of Biochemistry and Molecular Pharmacology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461
| | - Eric S Day
- Pharmaceutical Development, Genentech a Member of the Roche Group, 1 DNA Way, South San Francisco, CA 94080
| | - David Hayes
- IntlSoSci, 23 Washington St., Gorham, NH 03581
| | - John Hill
- Department of Bioengineering, University of Washington, Seattle, WA 98105
| | - Ranajoy Majumdar
- Bioproduct Research and Development, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN 46285, USA
| | - Paola Ringhieri
- Analytical Development Biotech Department, Merck Serono S.p.a, Guidonia, RM, Italy; an affiliate of Merck KGaA
| | - Peter Schuck
- Laboratory of Dynamics of Macromolecular Assembly, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, 13 South Drive, Bethesda, MD 20892
| | - Jasper C Lin
- Pharmaceutical Development, Genentech a Member of the Roche Group, 1 DNA Way, South San Francisco, CA 94080.
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5
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Lu Y, Joosten L, Donkers J, Andriulo F, Slaghek TM, Phillips-Jones MK, Gosselink RJA, Harding SE. Characterisation of mass distributions of solvent-fractionated lignins using analytical ultracentrifugation and size exclusion chromatography methods. Sci Rep 2021; 11:13937. [PMID: 34230572 PMCID: PMC8260654 DOI: 10.1038/s41598-021-93424-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Accepted: 06/18/2021] [Indexed: 11/13/2022] Open
Abstract
Lignins are valuable renewable resources for the potential production of a large array of biofuels, aromatic chemicals and biopolymers. Yet native and industrial lignins are complex, highly branched and heterogenous macromolecules, properties that have to date often undermined their use as starting materials in lignin valorisation strategies. Reliable knowledge of weight average molar mass, conformation and polydispersity of lignin starting materials can be proven to be crucial to and improve the prospects for the success of such strategies. Here we evaluated the use of commonly-used size exclusion chromatography (SEC)-calibrated with polystyrene sulphonate standards-and under-used analytical ultracentrifugation-which does not require calibration-to characterise a series of lignin fractions sequentially extracted from soda and Kraft alkaline lignins using ethyl acetate, methyl ethyl ketone (MEK), methanol and acetone:water (fractions F01-F04, respectively). Absolute values of weight average molar mass (Mw) determined using sedimentation equilibrium in the analytical ultracentrifuge of (3.0 ± 0.1) kDa and (4.2 ± 0.2) kDa for soda and Kraft lignins respectively, agreed closely with previous SEC-determined Mws and reasonably with the size exclusion chromatography measurements employed here, confirming the appropriateness of the standards (with the possible exceptions of fraction F05 for soda P1000 and F03 for Indulin). Both methods revealed the presence of low (~ 1 kDa) Mw material in F01 and F02 fractions followed by progressively higher Mw in subsequent fractions. Compositional analysis confirmed > 90% (by weight) total lignins successively extracted from both lignins using MEK, methanol and acetone:water (F02 to F04). Considerable heterogeneity of both unfractionated and fractionated lignins was revealed through determinations of both sedimentation coefficient distributions and polydispersity indices. The study also demonstrates the advantages of using analytical ultracentrifugation, both alongside SEC as well as in its own right, for determining absolute Mw, heterogeneity and conformation information for characterising industrial lignins.
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Affiliation(s)
- Yudong Lu
- National Centre for Macromolecular Hydrodynamics, School of Biosciences, University of Nottingham, Sutton Bonington, Leicestershire, LE12 5RD, UK
| | - Lionard Joosten
- Wageningen Food and Biobased Research, 6708 WG, Wageningen, The Netherlands
| | - Jacqueline Donkers
- Wageningen Food and Biobased Research, 6708 WG, Wageningen, The Netherlands
| | - Fabrizio Andriulo
- SciCult Laboratory, Department of Collection Management, Museum of Cultural History, University of Oslo, St. Olavs Plass, 0130, Oslo, Norway
| | - Ted M Slaghek
- Wageningen Food and Biobased Research, 6708 WG, Wageningen, The Netherlands
| | - Mary K Phillips-Jones
- National Centre for Macromolecular Hydrodynamics, School of Biosciences, University of Nottingham, Sutton Bonington, Leicestershire, LE12 5RD, UK.
| | | | - Stephen E Harding
- National Centre for Macromolecular Hydrodynamics, School of Biosciences, University of Nottingham, Sutton Bonington, Leicestershire, LE12 5RD, UK.
- SciCult Laboratory, Department of Collection Management, Museum of Cultural History, University of Oslo, St. Olavs Plass, 0130, Oslo, Norway.
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6
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Zhao H, Li W, Chu W, Bollard M, Adão R, Schuck P. Quantitative Analysis of Protein Self-Association by Sedimentation Velocity. ACTA ACUST UNITED AC 2021; 101:e109. [PMID: 32614509 DOI: 10.1002/cpps.109] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Sedimentation velocity analytical ultracentrifugation is a powerful classical method to study protein self-association processes in solution based on the size-dependent macromolecular migration in the centrifugal field. This technique can elucidate the assembly scheme, measure affinities ranging from picomolar to millimolar Kd , and in favorable cases provide information on oligomer lifetimes and hydrodynamic shape. The present step-by-step protocols detail the essential steps of instrument calibration, experimental setup, and data analysis. Using a widely available commercial protein as a model system, the protocols invite replication and comparison with our results. A commentary discusses principles for modifications in the protocols that may be necessary to optimize application of sedimentation velocity analysis to other self-associating proteins. ©2020 Wiley Periodicals LLC. Basic Protocol 1: Measurement of external calibration factors Basic Protocol 2: Sedimentation velocity experiment for protein self-association Basic Protocol 3: Sedimentation coefficient distribution analysis in SEDFIT and isotherm analysis in SEDPHAT.
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Affiliation(s)
- Huaying Zhao
- Dynamics of Macromolecular Assembly Section, Laboratory of Cellular Imaging and Macromolecular Biophysics, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland
| | - Wenqi Li
- National Protein Science Facility, School of Life Science, Tsinghua University, Beijing, China
| | - Wendan Chu
- National Protein Science Facility, School of Life Science, Tsinghua University, Beijing, China
| | - Mary Bollard
- Dynamics of Macromolecular Assembly Section, Laboratory of Cellular Imaging and Macromolecular Biophysics, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland
| | - Regina Adão
- Dynamics of Macromolecular Assembly Section, Laboratory of Cellular Imaging and Macromolecular Biophysics, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland
| | - Peter Schuck
- Dynamics of Macromolecular Assembly Section, Laboratory of Cellular Imaging and Macromolecular Biophysics, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland
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7
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Klein JG, Wu Y, Kokona B, Charkoudian LK. Widening the bottleneck: Heterologous expression, purification, and characterization of the Ktedonobacter racemifer minimal type II polyketide synthase in Escherichia coli. Bioorg Med Chem 2020; 28:115686. [PMID: 33069071 DOI: 10.1016/j.bmc.2020.115686] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 07/16/2020] [Accepted: 07/22/2020] [Indexed: 10/23/2022]
Abstract
Enzyme assemblies such as type II polyketide synthases (PKSs) produce a wide array of bioactive secondary metabolites. While the molecules produced by type II PKSs have found remarkable clinical success, the biosynthetic prowess of these enzymes has been stymied by 1) the inability to reconstitute the bioactivity of the minimal PKS enzymes in vitro and 2) limited exploration of type II PKSs from diverse phyla. To begin filling this unmet need, we expressed, purified, and characterized the ketosynthase chain length factor (KS-CLF) and acyl carrier protein (ACP) from Ktedonobacter racemifer (Kr). Using E. coli as a heterologous host, we obtained soluble proteins in titers signifying improvements over previous KS-CLF heterologous expression efforts. Characterization of these enzymes reveals that KrACP has self-malonylating activity. Sedimentation velocity analytical ultracentrifugation (SV-AUC) analysis of holo-KrACP and KrKS-CLF indicates that these enzymes do not interact in vitro, suggesting that the acylated state of these proteins might play an important role in facilitating biosynthetically relevant interactions. These results lay important groundwork for optimizing the interaction between KrKS-CLF and KrACP and exploring the biosynthetic potential of other non-actinomycete type II PKSs.
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Affiliation(s)
- Joshua G Klein
- Haverford College, Department of Chemistry, Haverford, PA 19041, United States
| | - Yang Wu
- Haverford College, Department of Chemistry, Haverford, PA 19041, United States
| | - Bashkim Kokona
- Haverford College, Department of Chemistry, Haverford, PA 19041, United States.
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8
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Acheampong KK, Kokona B, Braun GA, Jacobsen DR, Johnson KA, Charkoudian LK. Colorimetric Assay Reports on Acyl Carrier Protein Interactions. Sci Rep 2019; 9:15589. [PMID: 31666546 PMCID: PMC6821831 DOI: 10.1038/s41598-019-51554-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2019] [Accepted: 09/25/2019] [Indexed: 01/15/2023] Open
Abstract
The ability to produce new molecules of potential pharmaceutical relevance via combinatorial biosynthesis hinges on improving our understanding of acyl-carrier protein (ACP)-protein interactions. However, the weak and transient nature of these interactions makes them difficult to study using traditional spectroscopic approaches. Herein we report that converting the terminal thiol of the E. coli ACP 4'-phosphopantetheine arm into a mixed disulfide with 2-nitro-5-thiobenzoate ion (TNB-) activates this site to form a selective covalent cross-link with the active site cysteine of a cognate ketoacyl synthase (KS). The concomitant release of TNB2-, which absorbs at 412 nm, provides a visual and quantitative measure of mechanistically relevant ACP-KS interactions. The colorimetric assay can propel the engineering of biosynthetic routes to novel chemical diversity by providing a high-throughput screen for functional hybrid ACP-KS partnerships as well as the discovery of novel antimicrobial agents by enabling the rapid identification of small molecule inhibitors of ACP-KS interactions.
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Affiliation(s)
- Kofi K Acheampong
- Department of Chemistry, Haverford College, Haverford, PA, 19041-1391, USA
| | - Bashkim Kokona
- Department of Chemistry, Haverford College, Haverford, PA, 19041-1391, USA
| | - Gabriel A Braun
- Department of Chemistry, Haverford College, Haverford, PA, 19041-1391, USA
| | | | - Karl A Johnson
- Department of Biology, Haverford College, Haverford, PA, 19041-1391, USA.
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9
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Rivas MA, Courouble VC, Baker MC, Cookmeyer DL, Fiore KE, Frost AJ, Godbe KN, Jordan MR, Krasnow EN, Mollo A, Ridings ST, Sawada K, Shroff KD, Studnitzer B, Thiele GAR, Sisto AC, Nawal S, Huff AR, Fairman R, Johnson KA, Beld J, Kokona B, Charkoudian LK. The Effect of Divalent Cations on the Thermostability of Type II Polyketide Synthase Acyl Carrier Proteins. AIChE J 2018; 64:4308-4318. [PMID: 31527922 DOI: 10.1002/aic.16402] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The successful engineering of biosynthetic pathways hinges on understanding the factors that influence acyl carrier protein (ACP) stability and function. The stability and structure of ACPs can be influenced by the presence of divalent cations, but how this relates to primary sequence remains poorly understood. As part of a course-based undergraduate research experience, we investigated the thermostability of type II polyketide synthase (PKS) ACPs. We observed an approximate 40 °C range in the thermostability amongst the 14 ACPs studied, as well as an increase in stability (5 - 26 °C) of the ACPs in the presence of divalent cations. Distribution of charges in the helix II-loop-helix III region was found to impact the enthalpy of denaturation. Taken together, our results reveal clues as to how the sequence of type II PKS ACPs relates to their structural stability, information that can be used to study how ACP sequence relates to function.
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Affiliation(s)
| | - Valentine C. Courouble
- Dept. of Chemistry Haverford College Haverford PA 19041
- Biochemistry 390 (“Biochemistry Superlab”) Haverford College Haverford PA
| | - Miranda C. Baker
- Dept. of Chemistry Haverford College Haverford PA 19041
- Biochemistry 390 (“Biochemistry Superlab”) Haverford College Haverford PA
| | | | - Kristen E. Fiore
- Dept. of Chemistry Haverford College Haverford PA 19041
- Biochemistry 390 (“Biochemistry Superlab”) Haverford College Haverford PA
| | - Alexander J. Frost
- Dept. of Biology Haverford College Haverford PA 19041
- Biochemistry 390 (“Biochemistry Superlab”) Haverford College Haverford PA
| | | | - Michael R. Jordan
- Dept. of Physics Haverford College Haverford PA 19041
- Biochemistry 390 (“Biochemistry Superlab”) Haverford College Haverford PA
| | - Emily N. Krasnow
- Dept. of Biology Haverford College Haverford PA 19041
- Biochemistry 390 (“Biochemistry Superlab”) Haverford College Haverford PA
| | - Aurelio Mollo
- Dept. of Chemistry Haverford College Haverford PA 19041
- Biochemistry 390 (“Biochemistry Superlab”) Haverford College Haverford PA
| | - Stephen T. Ridings
- Dept. of Chemistry Haverford College Haverford PA 19041
- Biochemistry 390 (“Biochemistry Superlab”) Haverford College Haverford PA
| | - Keisuke Sawada
- Dept. of Chemistry Haverford College Haverford PA 19041
- Biochemistry 390 (“Biochemistry Superlab”) Haverford College Haverford PA
| | - Kavita D. Shroff
- Dept. of Biology Haverford College Haverford PA 19041
- Biochemistry 390 (“Biochemistry Superlab”) Haverford College Haverford PA
| | - Bradley Studnitzer
- Dept. of Chemistry Haverford College Haverford PA 19041
- Biochemistry 390 (“Biochemistry Superlab”) Haverford College Haverford PA
| | - Grace A. R. Thiele
- Dept. of Chemistry Haverford College Haverford PA 19041
- Biochemistry 390 (“Biochemistry Superlab”) Haverford College Haverford PA
| | | | - Saadia Nawal
- Dept. of Chemistry Haverford College Haverford PA 19041
| | - Adam R. Huff
- Dept. of Chemistry Haverford College Haverford PA 19041
| | | | | | - Joris Beld
- Dept. of Microbiology and Immunology Drexel University College of Medicine Philadelphia PA 19102
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10
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Measuring macromolecular size distributions and interactions at high concentrations by sedimentation velocity. Nat Commun 2018; 9:4415. [PMID: 30356043 PMCID: PMC6200768 DOI: 10.1038/s41467-018-06902-x] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Accepted: 09/14/2018] [Indexed: 12/17/2022] Open
Abstract
In concentrated macromolecular solutions, weak physical interactions control the solution behavior including particle size distribution, aggregation, liquid-liquid phase separation, or crystallization. This is central to many fields ranging from colloid chemistry to cell biology and pharmaceutical protein engineering. Unfortunately, it is very difficult to determine macromolecular assembly states and polydispersity at high concentrations in solution, since all motion is coupled through long-range hydrodynamic, electrostatic, steric, and other interactions, and scattering techniques report on the solution structure when average interparticle distances are comparable to macromolecular dimensions. Here we present a sedimentation velocity technique that, for the first time, can resolve macromolecular size distributions at high concentrations, by simultaneously accounting for average mutual hydrodynamic and thermodynamic interactions. It offers high resolution and sensitivity of protein solutions up to 50 mg/ml, extending studies of macromolecular solution state closer to the concentration range of therapeutic formulations, serum, or intracellular conditions. Many aspects of concentrated macromolecular solutions, such as encountered in cytosol or in pharmaceutical formulations, are dependent on particle size distributions and weak intermolecular interactions. Here, the authors exploit hydrodynamic separation in the centrifugal field to measure both.
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11
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Chaturvedi SK, Zhao H, Schuck P. Sedimentation of Reversibly Interacting Macromolecules with Changes in Fluorescence Quantum Yield. Biophys J 2017; 112:1374-1382. [PMID: 28402880 DOI: 10.1016/j.bpj.2017.02.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Revised: 02/10/2017] [Accepted: 02/21/2017] [Indexed: 11/29/2022] Open
Abstract
Sedimentation velocity analytical ultracentrifugation with fluorescence detection has emerged as a powerful method for the study of interacting systems of macromolecules. It combines picomolar sensitivity with high hydrodynamic resolution, and can be carried out with photoswitchable fluorophores for multicomponent discrimination, to determine the stoichiometry, affinity, and shape of macromolecular complexes with dissociation equilibrium constants from picomolar to micromolar. A popular approach for data interpretation is the determination of the binding affinity by isotherms of weight-average sedimentation coefficients sw. A prevailing dogma in sedimentation analysis is that the weight-average sedimentation coefficient from the transport method corresponds to the signal- and population-weighted average of all species. We show that this does not always hold true for systems that exhibit significant signal changes with complex formation-properties that may be readily encountered in practice, e.g., from a change in fluorescence quantum yield. Coupled transport in the reaction boundary of rapidly reversible systems can make significant contributions to the observed migration in a way that cannot be accounted for in the standard population-based average. Effective particle theory provides a simple physical picture for the reaction-coupled migration process. On this basis, we develop a more general binding model that converges to the well-known form of sw with constant signals, but can account simultaneously for hydrodynamic cotransport in the presence of changes in fluorescence quantum yield. We believe this will be useful when studying interacting systems exhibiting fluorescence quenching, enhancement, or Förster resonance energy transfer with transport methods.
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Affiliation(s)
- Sumit K Chaturvedi
- Dynamics of Macromolecular Assembly Section, Laboratory of Cellular Imaging and Macromolecular Biophysics, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland
| | - Huaying Zhao
- Dynamics of Macromolecular Assembly Section, Laboratory of Cellular Imaging and Macromolecular Biophysics, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland
| | - Peter Schuck
- Dynamics of Macromolecular Assembly Section, Laboratory of Cellular Imaging and Macromolecular Biophysics, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland.
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