Ionel Popa

Associate Professor
 KEN 3180



Proteins are the work-horse of our cells, and, at molecular level, take part in essentially every aspect of life: are the building blocks of cells, catalyze biochemical reactions or store and release energy. My lab combines protein engineering, surface functionalization and computer programming with instrument development to pursue two main and inter-connected areas of research: how the mechanical response of proteins is related to their function (related to molecular biophysics) and how to design protein hydrogels as smart materials (related to soft condensed matter).

  1. Single molecule protein mechanics
    Force is a natural perturbation which proteins in our body experience all the time. My laboratory uses a technique based on single molecule magnetic tweezers and covalent attachment to study the unfolding kinetics of proteins under force and their relation to cancer, muscle dystrophy or inflammatory diseases. This technique, has the unique advantage of being able to tether single molecules at physiologically relevant forces (1-120 pN) for extreme periods of time (up to 15 days for a single molecule). Most biological processes happen on the seconds-to-minutes time scale and the magnetic tweezers approach used in my laboratory can capture these ‘long’ time scales as it tethers single proteins under a broad range of mechanical perturbations.
  2. Smart materials based on protein-hydrogels
    Biomimetic materials hold the promise of revolutionizing medicine by allowing for artificial organs and targeted drug release. We use engineered proteins to obtain protein-hydrogels, which are a new type of material with unique properties. We currently make protein hydrogels by chemically crosslinking pure proteins. These amorphous materials can harvest from the biodiversity of proteins, while retaining large amounts of water (>90%), have a unique response to mechanical stress through the unfolding of the constituent protein domains and can respond to various stimuli. With these materials, we aim to advance the fields of smart materials and soft biorobotics.

Biographical Sketch

Ionel Popa received his B.Sc. degree in Chemical Engineering from Gh. Asachi Technical University in 2005 and his Ph.D. in Physical and Analytical Chemistry from University of Geneva in 2010, under the direction of Prof. Michal Borkovec. He then joined the group of Julio M. Fernandez at Columbia University to study protein biophysics, where he held the positions of Postdoctoral Fellow and Associate Research Scientist. Since fall 2015, he joined the University of Wisconsin-Milwaukee, where he currently holds the rank of Assistant Professor.

Selected Publications

Sharma, Sabita, Subramani, Smrithika, and Popa, Ionel. “Does protein unfolding play a functional role in vivo?.” FEBS Journal 288.6 (2021): 1742 – 1758.
Khoury, Luai, Slawinski, Marina, Collison, Daniel R., and Popa, Ionel. “Cation-induced shape programming and morphing in protein-based hydrogels.” Science Advances 6.18 (2020): eaba6112.
Dahal, Narayan, Nowitzke, Joel, Eis, Annie, and Popa, Ionel. “Binding Induced Stabilization Measured on the Same Molecular Protein Substrate using Single Molecule Magnetic Tweezers and Hetero-Covalent Attachments.” The Journal of Physical Chemistry B 124.16 Ed. ACS. (2020): 3283-3290.
Khoury, Luai R., and Popa, Ionel. “Chemical unfolding of protein domains induces shape change in programmed protein hydrogels.” Nature Communications 10.1 (2019): 5439.
Stoneman, M R., Biener, G, Ward, R J., Pediani, J D., Badu, D, Eis, A, Popa, Ionel, Milligan, G, and Raicu, Valerica. “A general method to quantify ligand-driven oligomerization from fluorescence-based images.” Nature methods 16.6 (2019): 493-496.
Khoury, Luai R., Nowitzke, Joel, Shmilovich, Kirill, and Popa, Ionel. “Study of Biomechanical Properties of Protein-Based Hydrogels Using Force-Clamp Rheometry.” Macromolecules 51.4 (2018): 1441 – 1452.
Shmilovich, Kirill, and Popa, Ionel. “Modeling protein-based hydrogels under force.” Physical Review Letters 121. (2018): 168101.
Valle-Orero, Jessica, Rivas-Pardo, Jaime A., and Popa, Ionel. “Multidomain proteins under force.” Nanotechnology 28.17 (2017): 174003.
Popa, Ionel, Rivas-Pardo, J A., Eckels, E C., Echelman, D J., Badilla, C L., Valle-Orero, J, and Fernández, J M. “A HaloTag Anchored Ruler for Week-Long Studies of Protein Dynamics.” Journal of the American Chemical Society 138.33 (2016): 10546-53.
Rivas-Pardo, J A., Eckels, E C., Popa, Ionel, Kosuri, P, Linke, W A., and Fernández, J M. “Work Done by Titin Protein Folding Assists Muscle Contraction.” Cell Reports 14.6 (2016): 1339-47.
Popa, Ionel, Berkovich, R, Alegre-Cebollada, J, Badilla, C L., Rivas-Pardo, J A., Taniguchi, Y, Kawakami, M, and Fernandez, J M. “Nanomechanics of HaloTag tethers.” Journal of the American Chemical Society 135.34 (2013): 12762-71.
Popa, Ionel, Kosuri, P, Alegre-Cebollada, J, Garcia-Manyes, S, and Fernandez, J M. “Force dependency of biochemical reactions measured by single-molecule force-clamp spectroscopy.” Nature Protocols 8.7 (2013): 1261-76.
Berkovich, R, Hermans, R I., Popa, Ionel, Stirnemann, G, Garcia-Manyes, S, Berne, B J., and Fernandez, J M. “Rate limit of protein elastic response is tether dependent.” Proceedings of the National Academy of Sciences of the United States of America 109.36 (2012): 14416-21.
Popa, Ionel, Sinha, P, Finessi, M, Maroni, P, Papastavrou, G, and Borkovec, M. “Importance of charge regulation in attractive double-layer forces between dissimilar surfaces.” Physical Review Letters 104.22 (2010): 228301.
Popa, Ionel, Gillies, G, Papastavrou, G, and Borkovec, M. “Attractive and repulsive electrostatic forces between positively charged latex particles in the presence of anionic linear polyelectrolytes.” The Journal of Physical Chemistry. B 114.9 (2010): 3170-7.