1,720,974 research outputs found
Dynamic and modular formation of a synergistic transphosphorylation catalyst
Get PDFEnzymes accelerate chemical reactions by forming cooperative interactions using precisely positioned functional groups. This has inspired the construction of artificial catalysts by the attachment of functional groups onto molecular scaffolds or solid supports to induce synergistic interactions. Herein, the transphosphorylation reaction is used as a model to demonstrate that cooperativity can also occur intermolecularly between multiple functional groups within self-assembled vesicular structures. We demonstrate that the modular and dynamic nature of such systems allow for triggered reorganization and the up- or down-regulation of catalytic activity. Such concepts have the potential to be used in the design of synergistic catalysts and their incorporation into responsive catalytic systems in water
Adsorption mechanisms of short-chain and ultrashort-chain PFAS on anion exchange resins and activated carbon
No full textShort-chain and ultrashort-chain per-/polyfluoroalkyl substances (PFAS) have become ubiquitous in aquatic environments worldwide, and their concentrations are rising. Studies have shown adsorption on activated carbon (AC) and anion exchange resins (AERs) as efficient removal techniques for long-chain PFAS (C >= 8). However, limited data are available on the adsorption of short-chain PFAS (C <= 4), especially ultrashort-chain PFAS. In this study, isotherm experiments were conducted to elucidate the possible adsorption mechanisms of widely detected short-chain perfluorobutanesulfonic acid (PFBS) and perfluorobutanoic acid (PFBA), and ultrashort-chain perfluoropropionic acid (PFPrA) on AC and AERs. Various factors, such as adsorbate concentration and characteristics, adsorbent properties, and the water matrix, influenced the adsorption of the target compounds. At concentrations > 1 mg L-1, strong base AER (A900) displayed the highest adsorption affinity among the four adsorbents investigated. An average 20 times decrease in the adsorption of three PFAS in the presence of competing CaCl2 salt affirmed the importance of ionic interactions. In contrast, both ionic interactions and hydrophobic interactions were equally important at concentrations < 1 mg L-1 for adsorption on AER and AC. The higher dipole moment of PFBS could be responsible for its higher adsorption on AERs compared to PFPrA and PFBA, while PFBS's greater adsorption on AC could be attributed to hydrophobic partitioning, which was supported by the calculated Langmuir and Freundlich model parameters. The isotherm data also suggested adsorption through additional mechanisms(s), which could include negative charge-assisted hydrogen bonds between PFBA and AC functional groups. Among the three short-chain PFAS, PFPrA exhibited the least adsorption and maximum desorption irrespective of the adsorbent type and adsorbate concentrations. Overall, our results suggest that AERs and ACs can be used to remove short-chain PFBA and PFBS through electrostatic and non-electrostatic interactions. This implies that an adsorption treatment train consisting of a series of stages, each targeting different interaction mechanisms, is needed to remove a wide range of PFAS
Modular Assembly and Optimization of an Artificial Esterase from Functionalised Surfactants
Get PDFA strategy for the screening and optimization of an artificial esterase is presented that utilizes the self‐assembly of amphiphilic molecules. Unlike conventional approaches that rely on the attachment of key functional groups onto molecular scaffolds or surfaces, the modular assembly of amphiphiles allows a large number of catalytic combinations to be investigated with minimal synthetic effort. In this study, iterative combinatorial screens led to an optimized esterase comprising amphiphiles that act as a nucleophilic catalyst, an oxyanion hole and a metal ion chelator. Cooperativity is observed between the functional headgroups of the amphiphiles, an effect that is diminished when co‐assembled with non‐functionalized surfactants. Assessment of the catalytic efficiency (kcat/KM) of our optimized catalysts against recently reported artificial esterases shows comparable efficiency, indicating that efficient catalysis is possible with dynamic self‐assembled systems despite the absence of pre‐defined rigid binding pockets
Dynamic self-assembled supramolecular catalysts
No full textSummary Supramolecular enzyme mimics have traditionally targeted substrate binding or transition state stabilization by utilizing highly rigid structures. Enzymes, however, are not static structures and must adopt numerous conformations to bind the substrate, perform catalysis, and release the product. In this chapter, we explore how combining the concepts of dynamic self-assembly and cooperativity allows the generation of catalysts that respond to changes in the supramolecular structure. In such systems, catalytic activity is an emergent property of the supramolecular assembly, which permits modulation of catalytic activity by control over the self-assembly process. This allows the introduction of negative feedback loops, stimuli-responsive properties, and the design of systems that operate out-of-equilibrium. The dynamic nature of these systems lends itself to potential applications in catalyst discovery and optimization, the construction of artificial transmembrane receptors, and smart materials with responsive and life-like properties
Manipulation of Optical Force-Induced Micro-Assemblies at the Air-Liquid Interface
No full textColloidal particles trapped by a focused laser at the air-liquid interface provide an interesting assembly dynamic. In this study, we demonstrated manipulating optical force-induced swarms via dynamic locomotion of assemblies built with holographic optical tweezers. This manipulation approach builds the foundation for autonomous control of building assemblies at the air-liquid interface, which is the first time optical micro-robots have performed this feat. Our proposed semi-autonomous control allows users to produce small dynamic secondary assemblies at the interface, which are transported to and merged with a main static assembly. This static-dynamic approach grows assemblies up to similar to 2.1 times larger than conventional methods. Manipulation and control of large-scale optical force-induced assemblies in real-time to create re-configurable swarms has the potential to lead the development of new technology and approaches for complex tasks, such as the development of new material, transportation of biological matter, studying biofilm formation created by bacteria colonies at the air-liquid interface, and more
Nanoprecipitation to produce hydrophobic cellulose nanospheres for water-in-oil Pickering emulsions
Get PDFIn recent years, there has been growing interest in replacing petroleum-based water-in-oil (W/O) emulsifiers with sustainable and less toxic natural materials. Pickering emulsifiers are considered well-suited candidates due to their high interfacial activity and the ability to form emulsions with long-term stability. However, only sporadic examples of natural materials have been considered as inverse Pickering emulsifiers. This study describes the synthesis of a series of hydrophobic cellulose nanospheres by bulk modification with acyl groups of different chain lengths followed by nanoprecipitation, and their application as inverse emulsifiers. Modification with acyl groups of longer chain length (C16, C18) afforded lower degrees of substitution, but resulted in greater thermal stability than groups with shorter acyl chains (C12, C14). Formation of nanospheres with low aspect ratios and narrow size distributions required low initial cellulose concentrations (< 1% w/v), high volumetric ratios of antisolvent to solvent (> 10:1), and slow addition rates (< 20 mL/h). The modified cellulose nanospheres were able to reduce the interfacial tension between water and hexane from 45.8 mN/m to 31.1 mN/m, with an effect that increased with the number of carbons in the added acyl chains. The stearate-modified nanospheres exhibited superhydrophobic behavior, showing a contact angle of 156 degrees +/- 4 degrees with water, and demonstrated emulsification performance comparable to the commonly used molecular surfactant sorbitan stearate. Our findings suggest that hydrophobically modified cellulose nanospheres have the potential to be a bio-derived alternative to traditional molecular W/O emulsifiers
Addressing the Persistence of Per- and Poly-Fluoroalkyl Substances (PFAS): Current Challenges and Potential Solutions
Get PDFThe combined stability, mobility, and bioaccumulation of per- and poly-fluoroalkyl substances (PFAS) has prompted a global environmental crisis. PFAS have unique properties owing to their strong, hydrophobic C–F bonds, which result in their resistance to water, oil, chemicals, and heat. Applications of PFAS include their use as water-, grease-, and fire-proof coatings, emulsifiers, and surfactants, spanning most manufacturing sectors. The continued regulation of specific PFAS provides significant research opportunities for chemists and their collaborators across environmental, social, engineering, and materials sciences. Solutions in the areas of detection and analysis, immobilisation and destruction, and the creation of viable and safe alternatives are urgently needed. In this tutorial review, PFAS and their associated challenges are described, followed by a summary of existing solutions and future research opportunities
Harnessing light and synthetic cells: a bridge to novel frontiers in water pollution remediation
No full textIn this recent period of escalating environmental challenges, water pollution stands out as a critical issue. The reliance on microbial processes represents the pillar of wastewater treatments, while accompanied by several drawbacks. The present Ph.D. work addresses pressing environmental through the development of innovative engineered liposomal carriers, known as "Smart Cells". These systems display selective permeability of the membrane upon external stimuli, standing as prototype models that lay the groundwork for the controlled release of active reagents for pollution remediation and encapsulation of contaminants in wastewaters. These features were tackled by leveraging tailored artificial amphiphiles that combine stimuli-responsive, fluorescence, and catalytic features. Azobenzene photoswitches were incorporated as light-responsive unit, enabling reversible control over membrane permeability. The incorporation of these amphiphiles in vesicles resulted in cell-like behaviors in response to light irradiation, alongside the formation of transient pores. The efforts addressed in this topic also extend to photo-pharmacological applications, focusing on combating tuberculosis. In this respect, the synthesis of crucial building blocks in the development of novel trehalose-decorated amphiphiles was aimed at modulating the membrane permeability in Mycobacteria to promote drug permeation. On the whole, these developments underscored the versatility and potential of "Smart Cells" systems for tackling complex environmental and pharmacological challenges, providing a promising platform for future applications in pollution remediation, advanced membrane dynamics studies, vesicular catalysis, and controllable drug delivery
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