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Enzymes provide optimal three-dimensional structures for substrate binding and the subsequent accelerated reaction. Such folding-dependent catalytic behaviors, however, are seldom mechanistically explored with reduced structural complexity. Here, we demonstrate that the α-helix, a much simpler structural motif of enzyme, can facilitate its own growth through the self-catalyzed polymerization of N -carboxyanhydride (NCA) in dichloromethane. The reversible binding between the N terminus of α-helical polypeptides and NCAs promotes rate acceleration of the subsequent ring-opening reaction. A two-stage, Michaelis–Menten-type kinetic model is proposed by considering the binding and reaction between the propagating helical chains and the monomers, and is successfully utilized to predict the molecular weights and molecular-weight distributions of the resulting polymers. This work elucidates the mechanism of helix-induced, enzyme-mimetic catalysis, emphasizes the importance of solvent choice in the discovery of new reaction type, and provides a route for rapid production of well-defined synthetic polypeptides by taking advantage of self-accelerated ring-opening polymerizations. The folding-dependent catalytic behavior of enzymes is of fundamental biological importance, yet mechanistically underexplored. Here, the authors show that an α-helix, commonly found in proteins, can facilitate its own growth through the self-catalyzed polymerization of N-carboxyanhydride in solvents with low polarity.

Synthetic polypeptides have received increasing attention due to their ability to form higher ordered structures similar to proteins. The control over their secondary structures, which enables dynamic conformational changes, is primarily accomplished by tuning the side-chain hydrophobic or ionic interactions. Herein we report a strategy to modulate the conformation of polypeptides utilizing donor–acceptor interactions emanating from side-chain H-bonding ligands. Specifically, 1,2,3-triazole groups, when incorporated onto polypeptide side-chains, serve as both H-bond donors and acceptors at neutral pH and disrupt the α-helical conformation. When protonated, the resulting 1,2,3-triazolium ions lose the ability to act as H-bond acceptors, and the polypeptides regain their α-helical structure. The conformational change of triazole polypeptides in response to the donor-acceptor pattern was conclusively demonstrated using both experimental-based and simulation-based methods. We further showed the utility of this transition by designing smart, cell-penetrating polymers that undergo acid-activated endosomal escape in living cells. Hydrogen bonding plays a major role in determining the tridimensional structure of biopolymers. Here, the authors show that control over a polypeptide conformation can be achieved by altering the donor-acceptor properties of side-chain triazole units via protonation-deprotonation.

Catalysis observed in enzymatic processes and protein polymerizations often relies on the use of supramolecular interactions and the organization of functional elements in order to gain control over the spatial and temporal elements of fundamental cellular processes. Harnessing these cooperative interactions to catalyse reactions in synthetic systems, however, remains challenging due to the difficulty in creating structurally controlled macromolecules. Here, we report a polypeptide-based macromolecule with spatially organized α-helices that can catalyse its own formation. The system consists of a linear polymeric scaffold containing a high density of initiating groups from which polypeptides are grown, forming a brush polymer. The folding of polypeptide side chains into α-helices dramatically enhances the polymerization rate due to cooperative interactions of macrodipoles between neighbouring α-helices. The parameters that affect the rate are elucidated by a two-stage kinetic model using principles from nucleation-controlled protein polymerizations; the key difference being the irreversible nature of this polymerization. The secondary and tertiary structure of a protein has profound implications on function and catalysis. Now, both the secondary and tertiary structures of a synthetic polymer have been utilized to catalyse the polymerization of N-carboxyanhydrides. Both the folding of the resulting polypeptides into α-helices and their macromolecular organization dramatically enhance the polymerization rate.

Ribozymes synthesize proteins in a highly regulated local environment to minimize side reactions caused by various competing species. In contrast, it is challenging to prepare synthetic polypeptides from the polymerization of N-carboxyanhydrides (NCAs) in the presence of water and impurities, which induce monomer degradations and chain terminations, respectively. Inspired by natural protein synthesis, we herein report the preparation of well-defined polypeptides in the presence of competing species, by using a water/dichloromethane biphasic system with macroinitiators anchored at the interface. The impurities are extracted into the aqueous phase in situ, and the localized macroinitiators allow for NCA polymerization at a rate which outpaces water-induced side reactions. Our polymerization strategy streamlines the process from amino acids toward high molecular weight polypeptides with low dispersity by circumventing the tedious NCA purification and the demands for air-free conditions, enabling low-cost, large-scale production of polypeptides that has potential to change the paradigm of polypeptide-based biomaterials.

The hemodynamic and metabolic response of the cortex depends spatially and temporally on the activity of multiple cell types. Optogenetics enables specific cell types to be modulated with high temporal precision and is therefore an emerging method for studying neurovascular and neurometabolic coupling. Going beyond temporal investigations, we developed a microprojection system to apply spatial photostimulus patterns in vivo. We monitored vascular and metabolic fluorescence signals after photostimulation in Thy1-channelrhodopsin-2 mice. Cerebral arteries increased in diameter rapidly after photostimulation, while nearby veins showed a slower smaller response. The amplitude of the arterial response was depended on the area of cortex stimulated. The fluorescence signal emitted at 450/100 nm and excited with ultraviolet is indicative of reduced nicotinamide adenine dinucleotide, an endogenous fluorescent enzyme involved in glycolysis and the citric acid cycle. This fluorescence signal decreased quickly and transiently after optogenetic stimulation, suggesting that glucose metabolism is tightly locked to optogenetic stimulation. To verify optogenetic stimulation of the cortex, we used a transparent substrate microelectrode array to map cortical potentials resulting from optogenetic stimulation. Spatial optogenetic stimulation is a new tool for studying neurovascular and neurometabolic coupling.

Catalysis observed in enzymatic processes and protein polymerizations often relies on the use of supramolecular interactions and the organization of functional elements in order to gain control over the spatial and temporal elements of fundamental cellular processes. Harnessing these cooperative interactions to catalyse reactions in synthetic systems, however, remains challenging due to the difficulty in creating structurally controlled macromolecules. Here, we report a polypeptide-based macromolecule with spatially organized α-helices that can catalyse its own formation. The system consists of a linear polymeric scaffold containing a high density of initiating groups from which polypeptides are grown, forming a brush polymer. The folding of polypeptide side chains into α-helices dramatically enhances the polymerization rate due to cooperative interactions of macrodipoles between neighbouring α-helices. The parameters that affect the rate are elucidated by a two-stage kinetic model using principles from nucleation-controlled protein polymerizations; the key difference being the irreversible nature of this polymerization.

Direct neural stimulation has recently become a standard therapy for neurological disorders such as Parkinson's Disease, Essential Tremors, and Dystonia. Currently, deep brain electro-stimulation and neuro-pharmaceutical treatments are the dominant therapeutic options available to the public. As our understanding of brain function and neurological diseases improves, we are able to develop more advanced neuromodulation techniques. These methods could become viable treatment solutions for treating brain dysfunction. Optogenetics, first introduced by a research team led by Karl Deisseroth at Stanford University, has proved to be a versatile technique with remarkable potential to be used in treatments for brain disorders, dysfunction, and injuries. Optogenetics makes use of light-gated ion channels and pumps, originally derived from certain types of algae or bacteria, to bi-directionally modulate the activity of neurons in mammals. By adopting new advances in the field of optics and photonics, including high-speed high-resolution spatial light modulators, solid-state lasers, and ultra-low noise photodetectors, we can build sophisticated devices which allow precise and resolute optical patterning in both the spatial and temporal domains. In this thesis, I present an optogenetic brain-machine interface that offers high spatiotemporal neuromodulation functionality. The incorporation of imaging and sensing devices of neural activity into the system allowed us to run multiple independent experiments. These optogenetic experiments include closed-loop modulation of multiple areas of tissue, investigating the causal relationship between neural activity and blood flow, and quantifying the relationship between neural activity and cell metabolism. To understand light to brain tissue interaction in a rat brain, a device has been developed which allows one to extract the optical properties throughout the tissue. Utilizing this data, Monte Carlo software was used to predict light distribution within the brain. This has far reaching effects for the future use of optogenetics. Our approach will allow the investigator the ability to precisely understand how introduced light will be distributed within the rat brain where light-gated ion channels have been genetically expressed. This becomes noticeably important when attempting to determine which areas of the brain tissue will and won't be modulated by the introduced light. Due to the many advantages optogenetics inherently provides, it is a rising prospect for novel neuromodulation therapies. With continued research and development of devices, we could create new therapies for disabilities that arise from dysfunction of the human brain.

Polypeptides provide form and function to every form of life we know on earth. They have the ability to accelerate reactions that would otherwise not occur on a timescale reasonable for life, they can assemble to form extremely complex and hierarchical structures that translate nanoscale movement into macroscopic movement as exemplified in muscle tissue, and they have a unique ability to construct themselves via ribosomes. The first part of my research has concentrated on asking the question, “How can synthetic materials behave like those found in nature?”. While it is a broad question, my research has demonstrated that polymer systems can utilize cues given by their architecture to alter their behavior. In more specific terms, I have shown that polymer kinetics can be governed by not only secondary structure, but also tertiary structure. Utilizing N-carboxyanhydride monomers that polymerize to form polypeptides, the folding of the polymers into α-helices was shown to drastically increase the rate of propagation. Furthermore, when the α-helices were organized in a close, parallel array along a separate polymer scaffold, the polymerization was found to increase in rate even more substantially. The second part of my thesis focuses on a separate project altogether, sponsored by The Dow Chemical Company. This project focuses on the utilization of ring-opening metathesis polymerization (ROMP) to fabricate new useful materials. ROMP has been a widely utilized and powerful polymerization method to create extremely smart and tunable materials. While a few monomers capable of being polymerized with ROMP have found commercial success, there is substantial room for development. In the second part of my thesis I demonstrated that functional monomers capable of undergoing ROMP can be incorporated into polyesters via the alternating polymerization of epoxides and anhydrides. The utilization of these polymers as multi-functional crosslinkers for thermosets was also demonstrated, incorporating the small molecules 4-dimethylaminopyridine as an agent to limit the curing at room temperature.

Risk stratification for hospitalized adults with COVID-19 is essential to inform decisions about individual patients and allocation of resources. So far, risk models for severe COVID outcomes have included age but have not been optimized to best serve the needs of either older or younger adults. Models also need to be updated to reflect improvements in COVID-19 treatments. This retrospective study analyzed data from 6906 hospitalized adults with COVID-19 from a community health system across five states in the western United States. Risk models were developed to predict mechanical ventilation illness or death across one to 56 days of hospitalization, using clinical data available within the first hour after either admission with COVID-19 or a first positive SARS-CoV-2 test. For the seven-day interval, models for age ≥ 18 and < 50 years reached AUROC 0.81 (95% CI 0.71–0.91) and models for age ≥ 50 years reached AUROC 0.82 (95% CI 0.77–0.86). Models revealed differences in the statistical significance and relative predictive value of risk factors between older and younger patients including age, BMI, vital signs, and laboratory results. In addition, for hospitalized patients, sex and chronic comorbidities had lower predictive value than vital signs and laboratory results.

Monitoring COVID-19 infection risk among health care workers (HCWs) is a public health priority. We examined the seroprevalence of SARS-CoV-2 among HCWs following the fall infection surge in Minnesota, and before and after COVID-19 vaccination. Additionally, we assessed demographic and occupational risk factors for SARS-CoV-2 infection. We conducted two rounds of seroprevalence testing among a cohort of HCWs: samples in round 1 were collected from 11/22/20-02/21/21 and in round 2 from 12/18/20-02/15/21. Demographic and occupational exposures assessed with logistic regression were age, sex, healthcare role and setting, and number of children in the household. The primary outcome was SARS-CoV-2 IgG seropositivity. A secondary outcome, SARS-CoV-2 infection, included both seropositivity and self-reported SARS-CoV-2 test positivity. In total, 459 HCWs were tested. 43/454 (9.47%) had a seropositive sample 1 and 75/423 (17.7%) had a seropositive sample 2. By time of sample 2 collection, 54% of participants had received at least one vaccine dose and seroprevalence was 13% among unvaccinated individuals. Relative to physicians, the odds of SARS-CoV-2 infection in other roles were increased (Nurse Practitioner: OR[95%CI] 1.93[0.57,6.53], Physician's Assistant: 1.69[0.38,7.52], Nurse: 2.33[0.94,5.78], Paramedic/EMTs: 3.86[0.78,19.0], other: 1.68[0.58,4.85]). The workplace setting was associated with SARS-CoV-2 infection (p = 0.04). SARS-CoV-2 seroprevalence among HCWs reporting duties in the ICU vs. those working in an ambulatory clinic was elevated: OR[95%CI] 2.17[1.01,4.68]. SARS-CoV-2 seroprevalence in HCW increased during our study period which was consistent with community infection rates. HCW role and setting-particularly working in the ICU-is associated with higher risk for SARS-CoV-2 infection.