Search

The CoA thioester of 2‐(carboxymethyl)cyclohexane‐1‐carboxylic acid has been identified as a metabolite in anaerobic naphthalene degradation by the sulfate‐reducing culture N47. This study identified and characterised two acyl‐CoA dehydrogenases (ThnO/ThnT) and an intramolecular CoA‐transferase (ThnP) encoded within the substrate‐induced thn operon, which contains genes for anaerobic degradation of naphthalene. ThnP is a CoA transferase belonging to the family I (Cat 1 subgroup) that catalyses the intramolecular CoA transfer from the carboxyl group of 2‐(carboxymethyl)cyclohexane‐1‐carboxyl‐CoA to its carboxymethyl moiety, forming 2‐carboxycyclohexylacetyl‐CoA. Neither acetyl‐CoA nor succinyl‐CoA functions as an exogenous CoA donor for this reaction. The flavin‐dependent homotetrameric dehydrogenase ThnO is specific for (1R,2R)‐2‐carboxycyclohexylacetyl‐CoA with an apparent Km value of 61.5 μM, whereas ThnT is a promiscuous enzyme catalysing the same reaction at lower rates. Identifying these three enzymes confirmed the involvement of the thn gene cluster in the anaerobic naphthalene degradation pathway. This study establishes a modified metabolic pathway for anaerobic naphthalene degradation upstream of 2‐(carboxymethyl)cyclohexane‐1‐carboxyl‐CoA and provides further insight into the subsequent second‐ring cleavage reaction. [ABSTRACT FROM AUTHOR]

Rotaxanes are mechanically interlocked molecules where a ring (macrocycle) is threaded onto a linear molecule (thread). The position of the macrocycle on different stations on the thread can be controlled in response to external stimuli, making rotaxanes applicable as molecular switches. Here we show that bistable rotaxanes based on the combination of a Zn(II) tetraphenylporphyrin photosensitizer, attached to the macrocycle, and a black-hole-quencher, attached to the thread, are capable of singlet oxygen production which can be switched on/off by the addition of base/acid. However, we found that only a sufficiently long linker between both stations on the thread enabled switchability, and that the direction of switching was inversed with regard to the original design. This unexpected behavior was attributed to intramolecular folding of the rotaxanes, as indicated by extensive theoretical calculations. This evidences the importance to take into account the conformational flexibility of large molecular structures when designing functional switchable systems. Singlet oxygen is a highly useful reagent for organic synthesis, disinfection and photodynamic therapy, but its high reactivity calls for systems where its photochemical generation can be switched on and off on demand. Here, the authors report porphyrin-decorated pH-switchable [2]rotaxanes for singlet oxygen photoproduction, finding that molecular folding of the rotaxanes influences the on/off switching in an unforeseen way. [ABSTRACT FROM AUTHOR]

Rotaxanes can serve as scaffolds for the generation of bifunctional catalysts. We have now generated acid–base functionalized rotaxanes featuring two chiral subunits. The mechanical bond leads to increased reaction rates and also to strongly altered enantioselectivites in comparison to the non-interlocked control catalysts. [ABSTRACT FROM AUTHOR]

Mechanically interlocked molecules (MIMs) carry great potential in different fields of chemistry, based on their specific structures, their internal dynamics, their stimuli‐responsive behavior, and other unique features of the mechanical bond. This minireview presents some of the most recent developments in their use for medical and biological applications. For example, they have been used to influence, enhance or block the action of therapeutic agents to enable targeted drug delivery. The dynamic structural properties have been used to generate switches and transporters, as well as sensors for various medically relevant species. Building MIMs by incorporating biomolecules like DNA and proteins has served as a novel way to control their properties. [ABSTRACT FROM AUTHOR]

Keywords: Antitumor agents; Rotaxanes; Sensors; Supramolecular chemistry; Theranostics EN Antitumor agents Rotaxanes Sensors Supramolecular chemistry Theranostics 5104 5104 1 10/19/21 20211007 NES 211007 B The Front Cover b shows an artistic rendition of a cell culture incorporating mechanically interlocked molecules (MIMs), illustrating different strategies in which they have been applied for biological and medical functions. Front Cover: Mechanically Interlocked Molecules for Biomedical Applications (Eur. J. Org. Antitumor agents, Rotaxanes, Sensors, Supramolecular chemistry, Theranostics. [Extracted from the article]