Ammon Posey

Research Scientist, Washington University in St. Louis

Research Expertise

intrinsically disordered proteins
protein aggregation
phase transitions
phase separation
Cell Biology
Molecular Biology
Biochemistry
Colloid and Surface Chemistry
Catalysis
Bioengineering
Biotechnology
Condensed Matter Physics
Biomedical Engineering
Biophysics
Structural Biology
Physical and Theoretical Chemistry
Atomic and Molecular Physics, and Optics

About

Protein Biophysics, Experimental Design, Experimental Methods Development, Instrument Design, Data Analysis, Python Programming Language, Fluorescence Spectroscopy, Circular Dichroism, Static Light Scattering, Microfluidics, Capillary Electrophoresis, Electron Microscopy, Intrinsically Disordered Proteins, Phase Separation

Publications

A Lethal de Novo Mutation in the Middle Domain of the Dynamin-related GTPase Drp1 Impairs Higher Order Assembly and Mitochondrial Division

Journal of Biological Chemistry / Oct 01, 2010

Chang, C.-R., Manlandro, C. M., Arnoult, D., Stadler, J., Posey, A. E., Hill, R. B., & Blackstone, C. (2010). A Lethal de Novo Mutation in the Middle Domain of the Dynamin-related GTPase Drp1 Impairs Higher Order Assembly and Mitochondrial Division. Journal of Biological Chemistry, 285(42), 32494–32503. https://doi.org/10.1074/jbc.m110.142430

Phase Separation of Intrinsically Disordered Proteins

Methods in Enzymology / Jan 01, 2018

Posey, A. E., Holehouse, A. S., & Pappu, R. V. (2018). Phase Separation of Intrinsically Disordered Proteins. Intrinsically Disordered Proteins, 1–30. https://doi.org/10.1016/bs.mie.2018.09.035

Arginine-Enriched Mixed-Charge Domains Provide Cohesion for Nuclear Speckle Condensation

Molecular Cell / Mar 01, 2020

Greig, J. A., Nguyen, T. A., Lee, M., Holehouse, A. S., Posey, A. E., Pappu, R. V., & Jedd, G. (2020). Arginine-Enriched Mixed-Charge Domains Provide Cohesion for Nuclear Speckle Condensation. Molecular Cell, 77(6), 1237-1250.e4. https://doi.org/10.1016/j.molcel.2020.01.025

Profilin reduces aggregation and phase separation of huntingtin N-terminal fragments by preferentially binding to soluble monomers and oligomers

Journal of Biological Chemistry / Mar 01, 2018

Posey, A. E., Ruff, K. M., Harmon, T. S., Crick, S. L., Li, A., Diamond, M. I., & Pappu, R. V. (2018). Profilin reduces aggregation and phase separation of huntingtin N-terminal fragments by preferentially binding to soluble monomers and oligomers. Journal of Biological Chemistry, 293(10), 3734–3746. https://doi.org/10.1074/jbc.ra117.000357

Self-Assembly of Block Heterochiral Peptides into Helical Tapes

Journal of the American Chemical Society / Apr 27, 2020

Clover, T. M., O’Neill, C. L., Appavu, R., Lokhande, G., Gaharwar, A. K., Posey, A. E., White, M. A., & Rudra, J. S. (2020). Self-Assembly of Block Heterochiral Peptides into Helical Tapes. Journal of the American Chemical Society, 142(47), 19809–19813. https://doi.org/10.1021/jacs.9b09755

Inhibition of amyloid beta fibril formation by monomeric human transthyretin

Protein Science / Mar 14, 2018

Garai, K., Posey, A. E., Li, X., Buxbaum, J. N., & Pappu, R. V. (2018). Inhibition of amyloid beta fibril formation by monomeric human transthyretin. Protein Science, 27(7), 1252–1261. Portico. https://doi.org/10.1002/pro.3396

Molecular Motor Dnm1 Synergistically Induces Membrane Curvature To Facilitate Mitochondrial Fission

ACS Central Science / Nov 08, 2017

Lee, M. W., Lee, E. Y., Lai, G. H., Kennedy, N. W., Posey, A. E., Xian, W., Ferguson, A. L., Hill, R. B., & Wong, G. C. L. (2017). Molecular Motor Dnm1 Synergistically Induces Membrane Curvature To Facilitate Mitochondrial Fission. ACS Central Science, 3(11), 1156–1167. https://doi.org/10.1021/acscentsci.7b00338

GADIS: Algorithm for designing sequences to achieve target secondary structure profiles of intrinsically disordered proteins

Protein Engineering Design and Selection / Aug 08, 2016

Harmon, T. S., Crabtree, M. D., Shammas, S. L., Posey, A. E., Clarke, J., & Pappu, R. V. (2016). GADIS: Algorithm for designing sequences to achieve target secondary structure profiles of intrinsically disordered proteins. Protein Engineering Design and Selection, 29(9), 339–346. https://doi.org/10.1093/protein/gzw034

Dilute phase oligomerization can oppose phase separation and modulate material properties of a ribonucleoprotein condensate

Apr 20, 2021

Seim, I., Posey, A. E., Snead, W. T., Stormo, B. M., Klotsa, D., Pappu, R. V., & Gladfelter, A. S. (2021). Dilute phase oligomerization can oppose phase separation and modulate material properties of a ribonucleoprotein condensate. https://doi.org/10.1101/2021.04.19.440511

A Targeted Mutation Identified through pK Measurements Indicates a Postrecruitment Role for Fis1 in Yeast Mitochondrial Fission

Journal of Biological Chemistry / Sep 01, 2016

Koppenol-Raab, M., Harwig, M. C., Posey, A. E., Egner, J. M., MacKenzie, K. R., & Hill, R. B. (2016). A Targeted Mutation Identified through pK Measurements Indicates a Postrecruitment Role for Fis1 in Yeast Mitochondrial Fission. Journal of Biological Chemistry, 291(39), 20329–20344. https://doi.org/10.1074/jbc.m116.724005

Gold Nanoshell Assembly on a Ferritin Protein Employed as a Bio-Template

Journal of Nanoscience and Nanotechnology / Mar 01, 2010

Kim, J.-W., Posey, AmmonE., Watt, GeraldD., Choi, SangH., & Lillehei, PeterT. (2010). Gold Nanoshell Assembly on a Ferritin Protein Employed as a Bio-Template. Journal of Nanoscience and Nanotechnology, 10(3), 1771–1777. https://doi.org/10.1166/jnn.2010.2078

Mechanistic Inferences From Analysis of Measurements of Protein Phase Transitions in Live Cells

Journal of Molecular Biology / Jun 01, 2021

Posey, A. E., Ruff, K. M., Lalmansingh, J. M., Kandola, T. S., Lange, J. J., Halfmann, R., & Pappu, R. V. (2021). Mechanistic Inferences From Analysis of Measurements of Protein Phase Transitions in Live Cells. Journal of Molecular Biology, 433(12), 166848. https://doi.org/10.1016/j.jmb.2021.166848

A First Glimpse of Nucleation of Phase Transitions in Living Cells

Molecular Cell / Jul 01, 2018

Posey, A. E., & Pappu, R. V. (2018). A First Glimpse of Nucleation of Phase Transitions in Living Cells. Molecular Cell, 71(1), 1–3. https://doi.org/10.1016/j.molcel.2018.06.028

Basin Mapping Method for Extracting Comparative Assessments of Protein Phase Behavior from In Vivo Measurements

Biophysical Journal / Feb 01, 2020

Lalmansingh, J. M., Posey, A. E., Kandola, T., Halfmann, R., & Pappu, R. V. (2020). Basin Mapping Method for Extracting Comparative Assessments of Protein Phase Behavior from In Vivo Measurements. Biophysical Journal, 118(3), 538a. https://doi.org/10.1016/j.bpj.2019.11.2949

Increasing the Accuracy in All-Atom Simulations of Intrinsically Disordered Proteins based on the Absinth Model

Biophysical Journal / Feb 01, 2018

Fossat, M. J., Harmon, T. S., Posey, A. E., Choi, J.-M., & Pappu, R. V. (2018). Increasing the Accuracy in All-Atom Simulations of Intrinsically Disordered Proteins based on the Absinth Model. Biophysical Journal, 114(3), 432a. https://doi.org/10.1016/j.bpj.2017.11.2392

The Variable Domain from the Mitochondrial Fission Mechanoenzyme Drp1 Promotes Liquid-Liquid Phase Separation

Biophysical Journal / Feb 01, 2020

Hill, B., Posey, A. E., Bagheri, M., Harwig, M. C., Kennedy, N. W., Hilser, V. J., & Harden, J. L. (2020). The Variable Domain from the Mitochondrial Fission Mechanoenzyme Drp1 Promotes Liquid-Liquid Phase Separation. Biophysical Journal, 118(3), 193a. https://doi.org/10.1016/j.bpj.2019.11.1170

Quantitative analysis of intracellular protein phase transitions

Biophysical Journal / Feb 01, 2023

Posey, A. E., & Pappu, R. V. (2023). Quantitative analysis of intracellular protein phase transitions. Biophysical Journal, 122(3), 206a. https://doi.org/10.1016/j.bpj.2022.11.1239

How does sequence influence charge regulation of disordered proteins?

Biophysical Journal / Feb 01, 2023

Fossat, M. J., Posey, A. E., Gupta, N., & Pappu, R. V. (2023). How does sequence influence charge regulation of disordered proteins? Biophysical Journal, 122(3), 200a. https://doi.org/10.1016/j.bpj.2022.11.1211

Demixing of distinct ribonucleoprotein condensates is under dynamical control

Biophysical Journal / Feb 01, 2023

Pappu, R. V., Lin, A. Z., Ruff, K. M., Jalihal, A. P., Dar, F., Posey, A. E., King, M. R., Lalmansingh, J. M., & Gladfelter, A. S. (2023). Demixing of distinct ribonucleoprotein condensates is under dynamical control. Biophysical Journal, 122(3), 443a. https://doi.org/10.1016/j.bpj.2022.11.2390

Dynamical control enables the formation of demixed biomolecular condensates

Feb 08, 2023

Pappu, R., Lin, A., Ruff, K., Jalihal, A., Dar, F., King, M., Lalmansingh, J., Posey, A., Seim, I., & Gladfelter, A. (2023). Dynamical control enables the formation of demixed biomolecular condensates. https://doi.org/10.21203/rs.3.rs-2440278/v1

Quantifying Coexistence Concentrations in Multi-Component Phase-Separating Systems Using Analytical HPLC

Biomolecules / Oct 14, 2022

Bremer, A., Posey, A. E., Borgia, M. B., Borcherds, W. M., Farag, M., Pappu, R. V., & Mittag, T. (2022). Quantifying Coexistence Concentrations in Multi-Component Phase-Separating Systems Using Analytical HPLC. Biomolecules, 12(10), 1480. https://doi.org/10.3390/biom12101480

Heterogeneous distributions of charge states determine the apparent net charge of intrinsically disordered proteins

Biophysical Journal / Feb 01, 2022

Posey, A. E., Fossat, M. J., & Pappu, R. V. (2022). Heterogeneous distributions of charge states determine the apparent net charge of intrinsically disordered proteins. Biophysical Journal, 121(3), 197a. https://doi.org/10.1016/j.bpj.2021.11.1732

The variable domain from the mitochondrial fission mechanoenzyme Drp1 promotes liquid-liquid phase separation

Biophysical Journal / Feb 01, 2022

Hill, B., Posey, A. E., BAGHERI, M., Harwig, M. C., Kennedy, N. W., Hilser, V. J., & Harden, J. L. (2022). The variable domain from the mitochondrial fission mechanoenzyme Drp1 promotes liquid-liquid phase separation. Biophysical Journal, 121(3), 40a. https://doi.org/10.1016/j.bpj.2021.11.2507

Charge state heterogeneity in single alpha helices helps maintain helicity over a large range of pH values

Biophysical Journal / Feb 01, 2022

Fossat, M. J., Posey, A. E., & Pappu, R. V. (2022). Charge state heterogeneity in single alpha helices helps maintain helicity over a large range of pH values. Biophysical Journal, 121(3), 300a. https://doi.org/10.1016/j.bpj.2021.11.1254

The soluble N-termini of mechanosensitive ion channels MSL8, MSL9, and MSL10 are environmentally sensitive intrinsically disordered regions with distinct biophysical characteristics

Oct 14, 2022

Flynn, A. J., Miller, K., Codjoe, J. M., King, M. R., Posey, A. E., & Haswell, E. S. (2022). The soluble N-termini of mechanosensitive ion channels MSL8, MSL9, and MSL10 are environmentally sensitive intrinsically disordered regions with distinct biophysical characteristics. https://doi.org/10.1101/2022.10.14.512244

Uncovering the Physical Basis for Selective Mixing Versus Unmixing of Protein-RNA Condensates

Biophysical Journal / Feb 01, 2021

Lin, A. Z., Posey, A. E., Dar, F., Gladfelter, A. S., & Pappu, R. V. (2021). Uncovering the Physical Basis for Selective Mixing Versus Unmixing of Protein-RNA Condensates. Biophysical Journal, 120(3), 93a. https://doi.org/10.1016/j.bpj.2020.11.774

Phase Separation of the Variable Domain of Dynamin Related Protein 1 in TMAO Suggests a Role in Assembly

Biophysical Journal / Feb 01, 2018

Hill, B., Posey, A., Bagheri, M., Kennedy, N., & Harden, J. (2018). Phase Separation of the Variable Domain of Dynamin Related Protein 1 in TMAO Suggests a Role in Assembly. Biophysical Journal, 114(3), 589a. https://doi.org/10.1016/j.bpj.2017.11.3223

Heuristics for the Effects of Sequence and Conformational Contexts on pKA Values of Ionizable Residues Inferred from Q-Canonical Monte Carlo Simulations

Biophysical Journal / Feb 01, 2020

Fossat, M. J., Posey, A. E., & Pappu, R. V. (2020). Heuristics for the Effects of Sequence and Conformational Contexts on pKA Values of Ionizable Residues Inferred from Q-Canonical Monte Carlo Simulations. Biophysical Journal, 118(3), 539a–540a. https://doi.org/10.1016/j.bpj.2019.11.2956

Principles of Ligand Modulation of Phase Behavior in Multicomponent Systems

Biophysical Journal / Feb 01, 2020

Ruff, K. M., Dar, F., Posey, A. E., & Pappu, R. V. (2020). Principles of Ligand Modulation of Phase Behavior in Multicomponent Systems. Biophysical Journal, 118(3), 371a. https://doi.org/10.1016/j.bpj.2019.11.2126

Quantifying the Effects of Charge Regulation on Disorder-Order Transitions of Highly Charged Protein Sequences

Biophysical Journal / Feb 01, 2020

Posey, A. E., Fossat, M. J., & Pappu, R. V. (2020). Quantifying the Effects of Charge Regulation on Disorder-Order Transitions of Highly Charged Protein Sequences. Biophysical Journal, 118(3), 540a–541a. https://doi.org/10.1016/j.bpj.2019.11.2960

Introducing a Novel Multi-Level Method for Simulating the pH Dependence of Charge State Fluctuations and Conformational Ensembles of Intrinsically Disordered Proteins

Biophysical Journal / Feb 01, 2019

Fossat, M. J., Posey, A. E., & Pappu, R. V. (2019). Introducing a Novel Multi-Level Method for Simulating the pH Dependence of Charge State Fluctuations and Conformational Ensembles of Intrinsically Disordered Proteins. Biophysical Journal, 116(3), 287a. https://doi.org/10.1016/j.bpj.2018.11.1549

Modeling the Effects of Ligand Binding on the Phase Behavior of Aggregation-Prone Proteins

Biophysical Journal / Feb 01, 2019

Ruff, K. M., Posey, A. E., & Pappu, R. V. (2019). Modeling the Effects of Ligand Binding on the Phase Behavior of Aggregation-Prone Proteins. Biophysical Journal, 116(3), 199a. https://doi.org/10.1016/j.bpj.2018.11.1100

Experimental and Theoretical Methods for Mapping Coexistence Curves of Phase-Separating Biological Macromolecules

Biophysical Journal / Feb 01, 2019

Posey, A. E., Holehouse, A. S., Ruff, K. M., & Pappu, R. V. (2019). Experimental and Theoretical Methods for Mapping Coexistence Curves of Phase-Separating Biological Macromolecules. Biophysical Journal, 116(3), 349a. https://doi.org/10.1016/j.bpj.2018.11.1901

Advances in Quantitative Analysis of Intracellular Protein Phase Separation Kinetics and its Modulation by Cellular Interactions

Biophysical Journal / Feb 01, 2018

Posey, A. E., Kandola, T., Pappu, R. V., & Halfmann, R. (2018). Advances in Quantitative Analysis of Intracellular Protein Phase Separation Kinetics and its Modulation by Cellular Interactions. Biophysical Journal, 114(3), 588a. https://doi.org/10.1016/j.bpj.2017.11.3219

Sequence-Encoded Charge Patterning of the Intrinsically Disordered Tail of FtsZ Impacts Polymerization and Bacterial Cell Division

Biophysical Journal / Feb 01, 2018

Cohan, M., Posey, A., Mittal, A., Grigsby, S., Holehouse, A., Buske, P. J., Levin, P. A., & Pappu, R. V. (2018). Sequence-Encoded Charge Patterning of the Intrinsically Disordered Tail of FtsZ Impacts Polymerization and Bacterial Cell Division. Biophysical Journal, 114(3), 590a. https://doi.org/10.1016/j.bpj.2017.11.3226

The Intrinsically Disordered Tail of FtsZ Impacts Polymerization and Bacterial Cell Division Through Sequence-Encoded Charge Patterning

Biophysical Journal / Feb 01, 2017

Cohan, M. C., Posey, A., Grigsby, S., Holehouse, A. S., Mittal, A., Buske, P. J., Levin, P., & Pappu, R. V. (2017). The Intrinsically Disordered Tail of FtsZ Impacts Polymerization and Bacterial Cell Division Through Sequence-Encoded Charge Patterning. Biophysical Journal, 112(3), 510a–511a. https://doi.org/10.1016/j.bpj.2016.11.2760

Polyglutamine Length Dependent Structural Properties and Phase Behavior of Huntingtin Exon 1

Biophysical Journal / Feb 01, 2017

Ruff, K. M., Warner, J. B., Posey, A. E., Siong Tan, P., Lemke, E. A., Pappu, R. V., & Lashuel, H. A. (2017). Polyglutamine Length Dependent Structural Properties and Phase Behavior of Huntingtin Exon 1. Biophysical Journal, 112(3), 511a. https://doi.org/10.1016/j.bpj.2016.11.2762

Charge Neutralization, Not Salt Bridges, Stabilizes Alpha Helices in Repeating Blocks of Acidic and Basic Residues

Biophysical Journal / Feb 01, 2017

Posey, A. E., Harmon, T. S., & Pappu, R. V. (2017). Charge Neutralization, Not Salt Bridges, Stabilizes Alpha Helices in Repeating Blocks of Acidic and Basic Residues. Biophysical Journal, 112(3), 345a–346a. https://doi.org/10.1016/j.bpj.2016.11.1874

Profilin Binding Modulates the Aggregation and Phase Separation of Huntingtin N-Terminal Fragments via Polyphasic Linkage

Biophysical Journal / Feb 01, 2016

Posey, A. E., Ruff, K. M., Harmon, T. S., Holehouse, A. S., & Pappu, R. V. (2016). Profilin Binding Modulates the Aggregation and Phase Separation of Huntingtin N-Terminal Fragments via Polyphasic Linkage. Biophysical Journal, 110(3), 399a. https://doi.org/10.1016/j.bpj.2015.11.2156

Molecular Mechanisms Behind Mitochondrial Fission

Biophysical Journal / Jan 01, 2012

Hill, B., Koppenol-Raab, M., Lees, J. P. B., Marie Manlandro, C., Picton, L. K., Posey, A., & Wells, R. C. (2012). Molecular Mechanisms Behind Mitochondrial Fission. Biophysical Journal, 102(3), 26a. https://doi.org/10.1016/j.bpj.2011.11.167

Dynamical control enables the formation of demixed biomolecular condensates

Jan 04, 2023

Lin, A. Z., Ruff, K. M., Jalihal, A., Dar, F., King, M. R., Lalmansingh, J. M., Posey, A. E., Seim, I., Gladfelter, A. S., & Pappu, R. V. (2023). Dynamical control enables the formation of demixed biomolecular condensates. https://doi.org/10.1101/2023.01.04.522702

Uncovering the Contributions of Charge Regulation to the Stability of Single Alpha Helices**

ChemPhysChem / Jan 04, 2023

Fossat, M. J., Posey, A. E., & Pappu, R. V. (2023). Uncovering the Contributions of Charge Regulation to the Stability of Single Alpha Helices**. ChemPhysChem. Portico. https://doi.org/10.1002/cphc.202200746

Uncovering the contributions of charge regulation to the stability of single alpha helices

Sep 28, 2022

Fossat, M. J., Posey, A. E., & Pappu, R. V. (2022). Uncovering the contributions of charge regulation to the stability of single alpha helices. https://doi.org/10.1101/2022.09.28.509894

Quantifying charge state heterogeneity for proteins with multiple ionizable residues

Biophysical Journal / Dec 01, 2021

Fossat, M. J., Posey, A. E., & Pappu, R. V. (2021). Quantifying charge state heterogeneity for proteins with multiple ionizable residues. Biophysical Journal, 120(24), 5438–5453. https://doi.org/10.1016/j.bpj.2021.11.2886

Glycine-Rich Peptides from FUS Have an Intrinsic Ability to Self-Assemble into Fibers and Networked Fibrils

Biochemistry / Oct 14, 2021

Kar, M., Posey, A. E., Dar, F., Hyman, A. A., & Pappu, R. V. (2021). Glycine-Rich Peptides from FUS Have an Intrinsic Ability to Self-Assemble into Fibers and Networked Fibrils. Biochemistry, 60(43), 3213–3222. https://doi.org/10.1021/acs.biochem.1c00501

Quantifying charge state heterogeneity for proteins with multiple ionizable residues

Sep 01, 2021

Fossat, M. J., Posey, A. E., & Pappu, R. V. (2021). Quantifying charge state heterogeneity for proteins with multiple ionizable residues. https://doi.org/10.1101/2021.08.31.458420

Mechanistic inferences from analysis of measurements of protein phase transitions in live cells

Nov 05, 2020

Posey, A. E., Ruff, K. M., Lalmansingh, J. M., Kandola, T. S., Lange, J. J., Halfmann, R., & Pappu, R. V. (2020). Mechanistic inferences from analysis of measurements of protein phase transitions in live cells. https://doi.org/10.1101/2020.11.04.369017

Evolved sequence features within the intrinsically disordered tail influence FtsZ assembly and bacterial cell division

Apr 14, 2018

Cohan, M. C., Posey, A. E., Grigsby, S. J., Mittal, A., Holehouse, A. S., Buske, P. J., Levin, P. A., & Pappu, R. V. (2018). Evolved sequence features within the intrinsically disordered tail influence FtsZ assembly and bacterial cell division. https://doi.org/10.1101/301622

Education

Johns Hopkins University

PhD, Molecular Biophysics / 2014

Baltimore, Maryland, United States of America

Brigham Young University

BS, Biophysics / 2006

Provo, Utah, United States of America

Experience

Washington University in St. Louis

Senior Research Scientist / 2014Present

Johns Hopkins University

Doctoral Researcher / 20082014

Dissertation: Intrinsic disorder and amphitropism in the mitochondrial fission mechanoenzyme Drp1

NASA Langley Research Center

Research Scholar / 20042005

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