Chemoinformatic-Guided Engineering of Polyketide Synthases.

Polyketide synthase (PKS) engineering is an attractive method to generate new molecules such as commodity, fine and specialty chemicals. A significant challenge is re-engineering a partially reductive PKS module to produce a saturated β-carbon through a reductive loop (RL) exchange. In this work, we sought to establish that chemoinformatics, a field traditionally used in drug discovery, offers a viable strategy for RL exchanges. We first introduced a set of donor RLs of diverse genetic origin and chemical substrates  into the first extension module of the lipomycin PKS (LipPKS1). Product titers of these engineered unimodular PKSs correlated with chemical structure similarity between the substrate of the donor RLs and recipient LipPKS1, reaching a titer of 165 mg/L of short-chain fatty acids produced by the host Streptomyces albus J1074. Expanding this method to larger intermediates that require bimodular communication, we introduced RLs of divergent chemosimilarity into LipPKS2 and determined triketide lactone production. Collectively, we observed a statistically significant correlation between atom pair chemosimilarity and production, establishing a new chemoinformatic method that may aid in the engineering of PKSs to produce desired, unnatural products

Imparting Electrochemical Functionality into Extended Solids for Next-Generation Batteries

As global energy storage demands grow exponentially, exploitation of fossil fuels grows correspondingly leading to dangerous levels of anthropogenic climate change. These global trends have necessitated developing new forms of renewable energy storage, and lithium-ion batteries have been pioneers in making that an attainable reality. However, lithium-ion batteries are approaching their theoretical capacity, leading to an impending crisis in which energy storage demands may not be met. To meet that demand, we focus on lithium-sulfur batteries as a promising contender for next-generation batteries. Compared to lithium-ion batteries, lithium-sulfur batteries offer over 4 times the amount of charge by mass and almost twice the amount of charge by volume. Moreover, sulfur is naturally abundant, making it a highly attractive material for battery technology. Limiting their implementation, however, is the polysulfide shuttle, a phenomenon in which the intermediate polysulfides are lost to the electrolyte during battery cycling leading to eventual battery failure. Additionally, the elemental sulfur at the cathode is insulating, an inherent issue in a device reliant on the movement of electrons. To improve battery performance, we employ a materials chemistry approach to improve both charge transfer and limit the polysulfide shuttle. We begin by using metal-organic frameworks (MOFs) which are porous, tunable materials composed of metal nodes and organic linkers which come together form 1D, 2D, and 3D nets. MOFs can also be modified post-synthetically for greater functionality. However, MOFs are often insulating, so, to improve charge transfer inherent to MOFs, we design a Zr-based MOF with a molecular oligosilane to instill new charge donor abilities. To interrupt the polysulfide shuttle, we post-synthetically modify another Zr-based MOF with thiophosphates to tether polysulfides and, in turn, improve battery performance. We then apply these findings to carbon nanotubes as both a more commercially available material and to better elucidate the role of the thiophosphate group and porosity on battery performance. These works offer a fundamental approach to practical implementation of next-generation batteries. Through a deeper understanding of charge transfer and the design of better cathode materials, we observe widespread improvements in battery performance, making a fossil-free future one step closer to reality

Phosphorus-Functionalized Organic Linkers Promote Polysulfide Retention in MOF-Based Li–S Batteries

Metal–organic frameworks (MOFs) have been an area of intense research for their high porosity and synthetic tunability, which afford them controllable physical and chemical properties for various applications. In this study, we demonstrate that functionalized MOFs can be used to mitigate the so-called polysulfide shuttle effect in lithium–sulfur batteries, a promising next-generation energy storage device. UiO-66-OH, a zirconium-based MOF with 2-hydroxy­terephthalic acid, was functionalized with a phosphorus chloride species that was subsequently used to tether polysulfides. In addition, a molecular chlorophosphorane was synthesized as a model system to elucidate the chemical reactivity of the phosphorus moiety. The functionalized MOFs were then used as a cathode additive in coin cell batteries to inhibit the dissolution of polysulfides in solution. Through this work, we show that the functionalization of MOF with phosphorus enhances polysulfide redox and thereby capacity retention in Li–S batteries. While demonstrated here for polysulfide tethering in batteries, we envision this linker functionalization strategy could be more broadly utilized in separations, sensing, or catalysis applications

Chemoinformatic-Guided Engineering of Polyketide Synthases.

Polyketide synthase (PKS) engineering is an attractive method to generate new molecules such as commodity, fine and specialty chemicals. A significant challenge is re-engineering a partially reductive PKS module to produce a saturated β-carbon through a reductive loop (RL) exchange. In this work, we sought to establish that chemoinformatics, a field traditionally used in drug discovery, offers a viable strategy for RL exchanges. We first introduced a set of donor RLs of diverse genetic origin and chemical substrates  into the first extension module of the lipomycin PKS (LipPKS1). Product titers of these engineered unimodular PKSs correlated with chemical structure similarity between the substrate of the donor RLs and recipient LipPKS1, reaching a titer of 165 mg/L of short-chain fatty acids produced by the host Streptomyces albus J1074. Expanding this method to larger intermediates that require bimodular communication, we introduced RLs of divergent chemosimilarity into LipPKS2 and determined triketide lactone production. Collectively, we observed a statistically significant correlation between atom pair chemosimilarity and production, establishing a new chemoinformatic method that may aid in the engineering of PKSs to produce desired, unnatural products