Background: A NAD(P)H-dependent enoate reductase (OYE2p) from Saccharomyces cerevisiae YJM1341 was discovered by genome data mining for asymmetric reduction of (E/Z)-citral to (R)-citronellal with high enantioselectivity. Methods:This enzyme was heterologously expressed in E. coli and characterized for its biocatalytic properties. OYE2p was identified with reduction activities toward a diverse range of ɑ,β-unsaturated compounds bearing conjugated aldehyde, ketone, imide, carboxylic acid and ester.Results: OYE2p showed the highest specific activity at 40 °C and a pH optimum at 7.0-8.0. The stability of OYE2p was rather pH-independent, and the half-life time values of the enzyme at pH 6.0-8.0 were more than 257 h. With regard to the reduction of (E)-citral and (Z)-citral, OYE2p exhibited different selectivity patterns. (E)-citral was exclusively reduced to (R)-citronellal by OYE2p in ≥ 99% ee, which was independent on pH. OYE2p produced both enantiomers of citronellal from (Z)-citral, but showed (R)-citronellal formation tendency, and the ee value of (R)-citronellal was affected by pH in the reaction system. Accordingly, the ee values for (R)-citronellal formation increased with the increasing levels of E-isomer in the (E/Z)-citral mixture as well as the increase of pH. Under the reaction conditions (30 °C and pH 8.6), using purified OYE2p as catalyst, 200 mM (E/Z)-citral (an approximately 10:9 mixture of geometric E-isomer and Z-isomer) was efficiently converted to (R)-citronellal with 88.8% ee and 87.2% yield. Conclusion:All these positive features demonstrate high potential of OYE2p for practical synthesis of (R)-citronellal and in asymmetric reduction of activated alkenes.

Oil spills have huge and immediate economically, socially, and environmentally adverse impacts. Current methods to remediate oil spills do not provide a sustainable solution, in terms of cost, ease of deployment, and further impact on the environment. Here we report an oil spill remediation solution in form of an oleophilic, hydrophobic, and magnetic (OHM) sponge that is economical, efficient, and ecofriendly; thereby promising a potentially industry-adaptable approach. The OHM sponge can not only selectively remove the oil from oil/water interface but also recover the oil by a simple squeezing process. Furthermore, the OHM sponge can be reused for many cycles. The OHM sponge works effectively in diverse and extreme aquatic conditions (pH, salinity) and can absorb a variety of oils and oil-based compounds. The selective absorption/desorption, recovery, high absorption capacity, and reusability under one platform open new prospects for potentially sustainable water and environmental remediation applications.

Supramolecular materials, which rely on dynamic non-covalent interactions, present a promising approach to advance the capabilities of currently available biosensors. The weak interactions between supramolecular monomers allow for adaptivity and responsiveness of supramolecular or self-assembling systems to external stimuli. In many cases, these characteristics improve the performance of recognition units, reporters, or signal transducers of biosensors. The facile methods for preparing supramolecular materials also allow for straightforward ways to combine them with other functional materials and create multicomponent sensors. To date, biosensors with supramolecular components are capable of not only detecting target analytes based on known ligand affinity or specific host-guest interactions, but can also be used for more complex structural detection such as chiral sensing. In this Review, we discuss the advancements in the area of biosensors, with a particular highlight on the designs of supramolecular materials employed in analytical applications over the years. We will first describe how different types of supramolecular components are currently used as recognition or reporter units for biosensors. The working mechanisms of detection and signal transduction by supramolecular systems will be presented, as well as the important hierarchical characteristics from the monomers to assemblies that contribute to selectivity and sensitivity. We will then examine how supramolecular materials are currently integrated in different types of biosensing platforms. Emerging trends and perspectives will be outlined, specifically for exploring new design and platforms that may bring supramolecular sensors a step closer towards practical use for multiplexed or differential sensing, higher throughput operations, real-time monitoring, reporting of biological function, as well as for environmental studies.

Multi-scale organization of molecular and living components is one of the most critical parameters that regulate charge transport in electroactive systems-whether abiotic, biotic, or hybrid interfaces. In this article, an overview of the current state-of-the-art for controlling molecular order, nanoscale assembly, microstructure domains, and macroscale architectures of electroactive organic interfaces used for biomedical applications is provided. Discussed herein are the leading strategies and challenges to date for engineering the multi-scale organization of electroactive organic materials, including biomolecule-based materials, synthetic conjugated molecules, polymers, and their biohybrid analogs. Importantly, this review provides a unique discussion on how the dependence of conduction phenomena on structural organization is observed for electroactive organic materials, as well as for their living counterparts in electrogenic tissues and biotic-abiotic interfaces. Expansion of fabrication capabilities that enable higher resolution and throughput for the engineering of ordered, patterned, and architecture electroactive systems will significantly impact the future of bioelectronic technologies for medical devices, bioinspired harvesting platforms, and in vitro models of electroactive tissues. In summary, this article presents how ordering at multiple scales is important for modulating transport in both the electroactive organic, abiotic, and living components of bioelectronic systems.

Peptides naturally have stimuli-adaptive structural conformations that are advantageous for endowing synthetic materials with dynamic functionalities. Here, we investigate a carbodiimide-based approach, combined with electrostatic modulation, to instruct π-conjugated peptides to self-assemble and be responsive to thermal disassembly cues upon consumption of the assembly trigger. Quaterthiophenefunctionalized peptides are utilized as a model system herein to study the formation of kinetically trapped structures at non-equilibrium states. Peptides were designed to have aspartic acid at the termini to allow intramolecular anhydride formation upon adding carbodiimide, which consequentially reduces the electrostatic repulsion and facilitates assembly. We show that the carbodiimide-fueled assembly and subsequent thermally assisted disassembly can be modulated by the net charge of the peptidic monomers, suggesting an assembly mechanism that can be encoded by sequence design. This carbodiimide-based approach for the assembly of designer π-conjugated systems offers a unique opportunity to develop bioelectronic supramolecular materials with controllable formation of transient structures.

Ethyl (R)-2-hydroxy-4-phenylbutanoate ((R)-HPBE) is an important versatile intermediate for the synthesis of angiotensin-converting enzyme inhibitors. Herein, a structure-guided rational design was adopted to improve the catalytic performance of carbonyl reductase...

What prompted you to investigate this topic?Conjugated polymers and oligomers with unique optoelectronic properties are commonly processed using organic solvents, which can limit their utility for biological applications. As a result, side chain engineering with water-soluble biomolecules has been employed as an approach in the past years to achieve stimuli-triggered formation of functional assemblies of πconjugated systems under aqueous environments. However, several strategies to trigger H-bonding-mediated assembly of biomolecules in water often involve environmental changes that are far from physiological conditions, such as extreme changes in pH and ionic strength. Moreover, these biomolecular H-bonding interactions have been traditionally driven by external stimuli that most often reflect binary "on-off" states, despite peptides and proteins dynamically assembling and reassembling in response to chemical fuels under native biological environments. With these considerations in mind, we sought to recapitulate the natural fuel-driven processes for biomolecules in a synthetic material system designed for a targeted function. Specifically, we studied a carbodiimide-fueled pathway for instructing the monomers of semiconducting πconjugated peptides to assemble under aqueous conditions without relying on extreme changes in pH or ionic strength. This supramolecular system was also used as a model to demonstrate that we can use the peptide sequence to encode how the assembly-disassembly process can be tuned in water. What is the most significant result of this study?This study demonstrates the first example of a carbodiimidefueled assembly of peptidic monomers bearing a semiconducting unit. Importantly, our results show the molecular design-dependent conditions by which assembly and disassembly processes start to occur. We also show that the morphologies that can be accessed through this fuel-driven approach are distinct from the structures afforded by pH-driven assemblies.

Precision control over molecular structure-function correlations in adaptive conjugated polymers such as polydiacetylene (PDA) is rarely demonstrated in completely aqueous environments due to solvent incompatibility, yet critical for realizing their biomedical applications. For PDAs, the chromogenic transitions that are key to their stimuli-responsiveness depend on the conformation and electronic structure of the π-conjugated backbone, which can be influenced by the nature of flanking, solubilizing groups that guide the topochemical polymerization of PDAs. Here, we investigate the dependence of amphiphilic polydiacetylene properties based on the characteristic contributions of amino acids that comprise the peptide segments serving as a biomimetic template for diacetylene polymerization in water. While sequence engineering has long been used as an effective approach to tune the function of peptide- or protein-based materials, it remains elusive how the interplay between steric effects and hydrophobicity at the residue level can impact the assembly behavior and the bulk properties of the resulting materials from hierarchically ordered 1-D nanostructures. We leverage the strict geometric requirements needed to topochemically polymerize diacetylenes bearing hexameric peptide moieties to systematically probe the impact of molecular volume and polarity changes brought by dipeptide substitution domains to the assembly behavior, photophysics, electrical properties, and biocompatibility of peptide-PDA assemblies. From a series of peptide-diacetylene monomers with systematically varied sequence, we show that steric contributions predominate the resulting photophysical properties, but the trends in the formation of higher order assemblies comprising the film bioscaffolds are distinct from the trends in PDA electronic structure changes driven by the peptide templates due to the combined impact of sterics and hydrophobicity. This work demonstrates how sequence-tunable, biomimetic interactions can be used as a synthetic handle to rationally tune PDA properties across length scales.