About

Charles M. Schroeder is a Professor and the Ray and Beverly Mentzer Faculty Scholar in Chemical and Biomolecular Engineering at the University of Illinois Urbana-Champaign. He is also an Affiliate in the Departments of Chemistry, Materials Science and Engineering, and Bioengineering, and a member of the Center for Biophysics and Computational Biology and the Institute for Genomic Biology in Biosystems Design. His research focuses on single molecule studies of polymer dynamics and biological systems, extending the field of single polymer dynamics to new materials. Professor Schroeder's work involves designing and implementing integrated microdevices for high-throughput screening of biomolecules for medical analysis, studying the action of natural and evolved enzymes at the molecular level, and investigating the non-equilibrium dynamics of soft materials. His research is highly interdisciplinary, bridging biology, engineering, and biotechnology, with applications in disease diagnosis, prediction of drug response, personalized medicine, and understanding biological mechanisms such as enzymatic reactions and viral infection pathways. He has been recognized with several awards, including the Camille Dreyfus Teacher-Scholar Award, NSF CAREER Award, Arthur B. Metzner Award from the Society of Rheology, and a Packard Fellowship in Science and Engineering. Since joining the department in 2008, Professor Schroeder has contributed extensively to research, education, and service in the field of bioengineering and molecular biophysics.

Research topics

• Neuroscience
• Biology
• Computer Science
• Genetics
• Cognitive psychology
• Computational biology
• Psychology
• Evolutionary biology

Selected publications

• Single-Molecule Electron Transport in Peptoids

  The Journal of Physical Chemistry B · 2026-03-04

  articleOpen accessSenior authorCorresponding

  Peptoids are structural analogs of peptides in which side chains are appended to the backbone nitrogen rather than the α-carbon. The sequence-defined modularity of peptoids enables precise control over structure–function relationships, enabling applications in energy storage and biomedical materials. Despite recent progress, the role of sequence and conformation on electron transport in peptoid molecules is not fully understood. Here, we synthesize a library of peptoid oligomers and characterize their molecular electronic properties using the scanning tunneling microscope-break junction (STM-BJ) technique. Our results show well-defined electron transport behavior for peptoid sequences containing aromatic side groups lacking hydrogen bonds (H-bonds) and without chemical substitutions at the N–Cα position. This behavior fundamentally differs from electron transport in peptides, where H-bond interactions give rise to higher conductance states. All-atom molecular dynamics (MD) simulations are used to understand the conformational heterogeneity of peptoids, and molecular conformations obtained from MD simulations are used in quantum mechanical calculations based on the nonequilibrium Green’s function–density functional theory (NEGF-DFT) formalism. In all cases, computational results are in reasonable qualitative agreement with experiments. Our work demonstrates that the conductance behavior of peptoids depends on monomer identity, including side-chain aromaticity and substitution at the N–Cα position. Overall, this work provides new insights into the structure–function relationships governing electron transport in peptoid-based materials and establishes design rules for peptoid-based molecular junctions.

  PublisherDOI

• Generative Multi-Property Refinement of Polymer Chemistries

  ChemRxiv · 2026-02-22

  articleOpen access

  We present a generative, multi-objective optimization method for polymer chemistry. By leveraging monomer-level properties that are directly correlated with polymer properties, we design targeted step-growth polymers with desired glass transition temperatures (T g), band gaps (E g), and Flory-Huggins interaction parameters with water (χ water) across a broad chemical space. Generative design is accomplished using a variational autoencoder integrated with linear property prediction heads. Linear organization of the latent space enables the identification of a single latent vector to steer 1 the simultaneous optimization of multiple polymer property objectives. Subsequent Bayesian optimization within the latent space allows further enhancement of T g , E g , and χ water relative to a reference polymer chemistry. We subsequently applied the generative model to design per-and polyfluoroalkyl substances (PFAS)-based polymers with reduced fluorine content but comparable physical properties. Overall, this work establishes a generative, multi-objective approach for navigating early-stage polymer design, prior to experimental validation or computationally expensive simulations.

  PublisherOA PDFDOI

• Single-MoleculeElectron Transport in Peptoids

  Figshare · 2026-03-04

  articleSenior author

  Peptoids are structural analogs of peptides in which side chains are appended to the backbone nitrogen rather than the α-carbon. The sequence-defined modularity of peptoids enables precise control over structure–function relationships, enabling applications in energy storage and biomedical materials. Despite recent progress, the role of sequence and conformation on electron transport in peptoid molecules is not fully understood. Here, we synthesize a library of peptoid oligomers and characterize their molecular electronic properties using the scanning tunneling microscope-break junction (STM-BJ) technique. Our results show well-defined electron transport behavior for peptoid sequences containing aromatic side groups lacking hydrogen bonds (H-bonds) and without chemical substitutions at the N–C_α position. This behavior fundamentally differs from electron transport in peptides, where H-bond interactions give rise to higher conductance states. All-atom molecular dynamics (MD) simulations are used to understand the conformational heterogeneity of peptoids, and molecular conformations obtained from MD simulations are used in quantum mechanical calculations based on the nonequilibrium Green’s function–density functional theory (NEGF-DFT) formalism. In all cases, computational results are in reasonable qualitative agreement with experiments. Our work demonstrates that the conductance behavior of peptoids depends on monomer identity, including side-chain aromaticity and substitution at the N–C_α position. Overall, this work provides new insights into the structure–function relationships governing electron transport in peptoid-based materials and establishes design rules for peptoid-based molecular junctions.

  DOI

• Solvent Environment Influences Molecular Conformation and Electron Transport in Peptides

  The Journal of Physical Chemistry Letters · 2026-05-17

  articleSenior authorCorresponding

  Hierarchical structures play a key role in governing the electronic properties of peptides. Despite recent advances, establishing clear structure–property relationships that connect the solvent environment, molecular conformation, and electron transport at the single-molecule level remains challenging. Here, we use a combination of single-molecule experiments, molecular dynamics (MD) simulations, and machine learning (ML) analysis to understand how electron transport in peptides depends on solvent conditions for several different environments including water, 2,2,2-trifluoroethanol, acetonitrile, and glycerol. Our results reveal two distinct conductance populations for peptides in water or 2,2,2-trifluoroethanol: a high-conductance state associated with defined secondary structures (β turns or 310 helices) and a low-conductance state corresponding to extended primary structures. Peptides show a diminished high-conductance state in acetonitrile, which is known to weakly stabilize secondary structures and denature peptides. Interestingly, the high-conductance state is diminished in glycerol for tetrapeptides but not for pentapeptides. Unsupervised ML analysis using silhouette clustering and Gaussian mixture modeling suggests that solvent-dependent conductance behavior is mediated by peptide conformation. Complementary MD simulations, time-lagged independent component analysis of intramolecular hydrogen-bonding (H-bonding) distances, and Pearson correlation coefficients further reveal how solvent-peptide interactions and secondary structures govern electron transport pathways. Overall, our results show that the solvent environment significantly influences electron transport in peptides mediated by secondary structure and H-bonding interactions.

  PublisherDOI

• Cell-Free Expression of Soluble Leafhopper Proteins from Brochosomes

  ACS Synthetic Biology · 2025-03-07 · 1 citations

  article

  Brochosomes are proteinaceous nanostructures produced by leafhopper insects with superhydrophobic and antireflective properties. Unfortunately, the production and study of brochosome-based materials has been limited by poor understanding of their major constituent subunit proteins, known as brochosomins, as well as their sensitivity to redox conditions due to essential disulfide bonds. Here, we used cell-free gene expression (CFE) to achieve recombinant production and analysis of brochosomin proteins. Through the optimization of redox environment, reaction temperature, and disulfide bond isomerase concentration, we achieved soluble brochosomin yields of up to 341 ± 30 μg/mL. Analysis using dynamic light scattering and transmission electron microscopy revealed distinct aggregation patterns among cell-free mixtures with different expressed brochosomins. We anticipate that the CFE methods developed here will accelerate the ability to change the geometries and properties of natural and modified brochosomes, as well as facilitate the expression and structural analysis of other poorly understood protein complexes.

  PublisherDOI

• Ligand-dependent G protein dynamics underlying opioid signaling efficacy

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-07-01 · 2 citations

  preprintOpen access

  Activation of heterotrimeric G proteins by G protein-coupled receptors (GPCRs) requires large-scale opening of the Gα α-helical domain (AHD) to expose the nucleotide-binding site and facilitate GDP-GTP exchange. While orthosteric ligands are known to modulate GPCR conformation and signaling efficacy, how these effects propagate to the G protein itself remains unclear. Using single-molecule fluorescence resonance energy transfer (smFRET) imaging, we monitored AHD motions in Gi proteins coupled to the μ-opioid receptor (μOR) across a spectrum of ligand- and nucleotide-bound states. We find that receptor ligands differentially modulate these dynamics from over 70 angstrom away, with higher-efficacy agonists more effectively promoting transitions to an open, low-nucleotide-affinity conformation. These data also capture transient μOR-Gi intermediates during nucleotide binding and suggest that μ-opioid ligand efficacy arises in part from allosteric control over G protein conformational equilibria that kinetically gate activation.

  PublisherOA PDFDOI

• Electrochemically Mediated Au–C(sp²) Anchors for Molecular Electronics

  The Journal of Physical Chemistry C · 2025-09-19 · 3 citations

  articleSenior authorCorresponding

  Terminal anchor groups play a key role in the stability and electronic properties of molecular junctions. Single molecule junctions typically consist of two preinstalled terminal anchors linking organic molecules to metal electrodes. Here, we show that p-terphenyl derivatives containing only a single terminal anchor show conductance features similar to junctions with two preinstalled terminal anchors. A set of p-terphenyl derivatives with one terminal anchor was prepared using automated chemical synthesis and characterized using single molecule electronics experiments, molecular dynamics (MD) simulations, bulk electrochemistry and spectroscopy, and nonequilibrium Green’s function-density functional theory (NEGF-DFT) calculations. Our results show that 4-amino-p-terphenyl (PPP) and related analogs exhibit a well-defined high conductance state that is diminished or absent in other p-terphenyl derivatives lacking a preinstalled amine terminal anchor or fluorine or methyl substitutions at the terminal para position. However, a low conductance state is observed in all amino-p-terphenyl derivatives with one preinstalled anchor due to molecular junctions formed by noncovalent dimeric π–π stacking interactions. The observed high conductance state diminishes upon the addition of reducing agents and is restored upon the addition of an oxidizing agent. Our results suggest that the high conductance state arises due to Au–C(sp2) bond formation facilitated by a single electron oxidation event at the electrode surface. A series of control experiments with different anchor groups shows that primary amines play a key role in forming Au–C bonds for molecular junctions. Overall, these results suggest that Au–C bond formation gives rise to high conductance pathways in organic molecules containing only one preinstalled terminal anchor. Insights from this work can be leveraged in the design of molecular electronic devices, particularly in understanding the mechanisms of molecular binding and junction formation.

  PublisherDOI

• Ring polymer physics and rheology: Challenges and opportunities

  Journal of Rheology · 2025-12-31 · 5 citations

  article1st authorCorresponding

  Understanding the structure and dynamics of ring or cyclic polymers is a long-standing challenge in polymer science, with important implications for emerging biological phenomena such as chromosome territories. This Perspective article provides a comprehensive overview of the current state of ring polymer physics and rheology, highlighting emerging challenges and opportunities for future research. Key scientific questions are considered regarding the properties of synthetic and biological ring polymer systems using theory, simulations, and experiments. This article was inspired by stimulating discussions at a CECAM Flagship workshop on Ring Polymer Dynamics in Prato, Italy, in June 2023. Several of the concepts and results discussed here are also presented in the Journal of Rheology virtual issue on ring polymers (https://pubs.aip.org/jor/collection/1392/Ring-Polymers). Broadly, this article aims to spark conceptual advances in polymer physics and rheology by exploring new phenomena and open scientific questions that are unique to ring polymer systems.

  PublisherDOI

• Functional monomer design for synthetically accessible polymers

  Chemical Science · 2025-01-01 · 9 citations

  articleOpen access

  Machine learning (ML) has emerged as a powerful tool to navigate polymer structure-property relationships. Despite recent progress, data sparsity is a major obstacle hindering the practical application of ML in polymer science. In this work, we explore functional monomer design by developing the first comprehensive database of monomer-level chemical and physical properties for approximately 12M synthetically accessible polymers. We generated diverse monomer-level properties by integrating quantum chemistry calculations with active learning to efficiently probe a vast chemical space of synthetically feasible polymers. Monomer-level property descriptors are benchmarked against both higher level computational predictions and experimental data to the extent possible, demonstrating their relevance to polymer design. Our results show that many monomer-level properties are weakly correlated, implying a strong freedom for functional design such that multiple physical properties can be simultaneously optimized by monomer selection. Moreover, the synthetically accessible nature of this chemical space allows targeted monomers to be considered by common polymerization mechanisms to facilitate their synthetic realization. Overall, this work opens new avenues for creating synthetically accessible polymers and provides new insights for designing next generation polymeric materials.

  PublisherOA PDFDOI

• Anion and Cation Size Effects on Viscoelasticity and Ion Transport of Imine Vitrimer Electrolytes

  Chemistry of Materials · 2025-09-03 · 3 citations

  article

  Vitrimers are a subclass of covalent adaptable networks where bond exchange occurs without breaking, thereby offering polymer materials with enhanced mechanical strength, thermal stability, and reprocessability compared to conventional electrolytes. Despite recent progress, we lack a complete understanding of the role of ions in controlling the physical and chemical properties of vitrimers. In this work, we study how different salts affect the viscoelasticity, morphology, and ionic conductivity of imine vitrimers. Our results show that addition of salt decreases relaxation times at elevated temperatures due to the catalytic effect of the cations, with smaller cations leading to faster relaxation. However, the activation energy for terminal relaxation increases with smaller cation size. This apparent discrepancy is attributed to the complex interplay among bond exchange kinetics, chain diffusion, and salt dissociation. Anions act as plasticizers by reducing the shear modulus, except lithium bromide. Ionic conductivity increases with larger anions due to smaller salt dissociation energies, whereas the cation type has a minor impact as polymer segmental dynamics dominate ionic transport. Imine-based vitrimers are reprocessable and recyclable, maintaining original mechanical properties and ionic conductivity after recovery. Mixed salt vitrimers exhibited tunable viscoelasticity and ionic conductivity intermediate to the analogous pure salt systems. Overall, this work highlights the role of salt in the dynamic and conductive properties of imine vitrimers.

  PublisherDOI

Recent grants

• NIH Grant R21MH103814

  NIH · $440k · 2017

• Collaborative Research: Dynamics of Circular Macromolecules (DNA): From Single Molecules to Highly Entangled States

  NSF · $175k · 2016–2020

• NIH Grant R01MH111439

  NIH · $5.1M · 2022

• NIH Grant R03TW005674

  NIH · $96k · 2005

• CAREER: Molecular Rheology of Architecturally Complex Polymers

  NSF · $400k · 2013–2018

Frequent coauthors

• Péter Lakatos

  Nathan Kline Institute for Psychiatric Research

  139 shared

• Ashesh D. Mehta

  54 shared

• Stephan Bickel

  Feinstein Institute for Medical Research

  38 shared

• Nienke van Atteveldt

  Vrije Universiteit Amsterdam

  36 shared

• Manuel Mercier

  Inserm

  36 shared

• Songsong Li

  University of Chicago

  36 shared

• Daniel C. Javitt

  Columbia University Irving Medical Center

  35 shared

• Brian E. Russ

  Icahn School of Medicine at Mount Sinai

  34 shared

Awards & honors

• Camille Dreyfus Teacher-Scholar Award
• NSF CAREER Award
• Arthur B. Metzner Award from the Society of Rheology
• Packard Fellowship in Science and Engineering