Formation of Supramolecular Nanostructures through in Situ Self-Assembly and Post-Assembly Modification of a Biocatalytically Constructed Dipeptide Hydrazide**

Aqueous self-assembly of short peptides has attracted growing attention for the construction of supramolecular materials for various bioapplications. Herein, we describe how the thermolysin-assisted biocatalytic construction of a dipeptide hydrazide from an N-protected amino acid and an amino acid hydrazide leads to the formation of thermally stable supramolecular hydrogels. In addition, we demonstrate the post-assembly modification of the supramolecular architectures constructed in situ tethering hydrazide groups as a chemical handle by means of fluorescence imaging.     

Gas Hydrate Formation in Reversed Micelles

We describe a technique to modify protein solubility and optimize enzyme activity in reversed micellar solutions. The technique is based on the ability of hydrates of natural gas to form in the micro-aqueous phase. Clathrate hydrates are crystalline inclusions of water and gas, and their formation in bulk water has traditionally been studied with relevance to natural gas recovery. We have found that hydrates can form in the environment of the microaqueous pools of reversed micelles, and that their extent of formation can be well controlled through the thermodynamic variables of temperature and pressure. Additionally, formation of hydrates affects the size and aggregation number of the micelles, and thus influences the solubility and conformation of encapsulated proteins. We demonstrate how the concept can be used in two applications: (i) protein extraction into reversed micelles and subsequent recovery, and (ii) optimization of enzyme activity in reversed micelles.     

生物催化用于C—C键的立体选择性合成

C—C键的立体选择性形成是有机合成化学的重要方面. 生物催化剂的立体选择性是它们的主要优势之一, 用酶催化C—C键形成已引起了广泛关注. 总结了生物转化中C—C键形成的最新应用, 着重讨论了醛缩酶和转酮醇酶生物催化剂的应用.     

离子液体中的生物催化反应

本文综述了近年来离子液体中生物催化反应的研究进展。离子液体作为新的绿色溶剂,用于生物催化反应具有以下特点:在离子液体中酶有良好的稳定性、选择性和反应活性。离子液体可溶解极性大的反应物, 产物易分离,酶和离子液体可重复使用。对离子液体中的生物催化进行了展望。     

Hydrolysis of new phthalimide-derived esters catalyzed by immobilized lipase

The last step of the production of four phthalimide-derived acids, designed to act as antiasthma drugs, was performed by enzymatic hydrolysis of the respective methyl or ethyl esters. The esters 4-ethyl-[2-(1,3-dioxo-1,3-dihydro-2-isoindoylyl)]-phenoxyacetic methyl ester (PHT-MET), 4-ethyl-[2-(1,3-dioxo-1,3-dihydro-2-isoindoylyl)]-phenoxyacetic ethyl ester, 4-(1,3-dioxo-1,3-dihydro-2-isoindoylyl)-phenoxyacetic ethyl ester, and 2-(1,3-dioxo-1, 3-dihydro-2-isoindoylyl)-phenoxyacetic ethyl ester were hydrolyzed by immobilized lipase. The enzymatic reaction could be used only to produce the desired 4-substituted compounds. The best result that was found to hydrolysis of PHT-MET, and, therefore, that ester was selected for optimization experiments in a three-phase system. Reactions were performed with solid biocatalyst (Lipozyme® RM IM), organic solvent phase (ethyl acetate), and aqueous phase (saturated Na₂CO₃ solution). To optimize the reaction conditions, an experimental design optimization procedure was used. The variables studied were the amount of enzyme, the temperature, and the volume of the aqueous solution. Time course experiments were then performed for different initial enzyme concentrations (0.5, 0.9, and 1.4 U_H/mL of solvent). The optimized reaction conditions found were 20 mg of Lipozyme (0.9 U_H/mL_solvent) and 5.0 mL of Na₂CO_3(sat) at 40°C for 6 h.     

Fibrous Networks with Incorporated Macrocycles: A Chiral Stimuli‐Responsive Supramolecular Supergelator and Its Application to Biocatalysis in Organic Media

A new and versatile, crown ether appended, chiral supergelator has been designed and synthesized based on the bis‐urea motif. The introduction of a stereogenic center improved its gelation ability significantly relative to its achiral analogue. This low‐molecular‐weight gelator forms supramolecular gels in a variety of organic solvents. It is sensitive to multiple chemical stimuli and the sol–gel phase transitions can be reversibly triggered by host–guest interactions. The gel can be used to trap enzymes and release them on demand by chemical stimuli. It stabilizes the microparticles in Pickering emulsions so that enzyme‐catalyzed organic reactions can take place in the polar phase inside the microparticles, the organic reactants diffusing through the biphasic interface from the surrounding organic phase. Because of the higher interface area between the organic and polar phases, enzyme activity is enhanced in comparison with simple biphasic systems.     

Enantioconvergent Biocatalytic Redox Isomerization

Alcohol dehydrogenases can act as powerful catalysts in the preparation of optically pure γ‐hydroxy‐δ‐lactones by means of an enantioconvergent dynamic redox isomerization of readily available Achmatowicz‐type pyranones. Imitating the traditionally metal‐mediated “borrowing hydrogen” approach to shuffle hydrides across molecular architectures and interconvert functional groups, this chemoinspired and purely biocatalytic interpretation effectively expands the enzymatic toolbox and provides new opportunities in the assembly of multienzyme cascades and tailor‐made cellular factories.     

Transition Metal-Promoted Reactions in Aqueous Media and Biological Settings

During the last decade, there has been a tremendous interest for developing non-natural biocompatible transformations in biologically relevant media. Among the different encountered strategies, the use of transition metal complexes offers unique possibilities due to their high transformative power. However, translating the potential of metal catalysts to biological settings, including living cells or small-animal models such as mice or zebrafish, poses numerous challenges associated to their biocompatibility, and their stability and reactivity in crowded aqueous environments. Herein, we describe the most relevant advances in this direction, with a particular emphasis on the systems’ structure, their mode of action and the mechanistic bases of each transformation. Thus, the key challenges from an organometallic perspective might be more easily identified.