Synthesis of new acyclic chelators H4aPyta and H6aPyha and their complexes with Cu2+, Ga3+, Y3+, and Bi3.

In this article, we present the synthesis and characterization of new acyclic pyridine-containing polyaminocarboxylate ligands H4aPyta and H6aPyha, which differ in structural rigidity and the number of chelating groups. Their abilities to form complexes with Cu2+, Ga3+, Y3+, and Bi3+ cations, as well as the stability of the complexes, were evaluated by potentiometric titration method, radiolabeling with the corresponding radionuclides, in vitro studies, mass spectrometry, and HPLC. The structures of the resulting complexes were determined using NMR spectroscopy and DFT calculations. The results obtained made it possible to evaluate the influence of the structural features of the complexes on their stability. The developed chelators H4aPyta and H6aPyha were proved to be promising for further research in the field of radiopharmaceuticals.

DNA-based assemblies with bischromophoric styryl dye-chromene conjugates and cucurbit[7]uril.

Novel conjugates consist of 4-styrylpyridinium dye and 2,2-diphenyl-2H-chromene moiety were obtained, and their affinity to double stranded DNA and cucurbit[7]uril was investigated. With a combination of absorption, fluorescence and circular dichroism spectroscopies as well as MALDI-TOF mass spectrometry, we demonstrate that these compounds can interact with macromolecules to form of the supramolecular assemblies due to two suitable binding sites. The ternary complex is formed as a result of the intercalation of a positively charged styryl part between DNA base pairs, while cucurbit[7]uril is located on the alkyl chain between two moieties of conjugate. All these findings provide valuable information into controlling the interaction between organic molecules, DNA and cucurbit[7]uril.

Cucurbiturils in nucleic acids research.

During the past ten years, the importance of cucurbiturils (CB[n]) as macrocyclic hosts in supramolecular assemblies with various types of natural and synthetic nucleic acids (NAs) has increased explosively. As a component of such systems, CB[n] macrocycles can play a wide spectrum of roles from drug and gene delivery vehicles to catalysts/inhibitors of biochemical reactions and even building blocks for NA-based materials. The aim of this highlight article is to describe the development of the CB[n] applications in nucleic acids research and to outline the current situation and perspectives of this fascinating synergistic combination of supramolecular chemistry of CB[n] and NAs.

Cucurbit[7]uril-driven modulation of ligand-DNA interactions by ternary assembly.

The design of small organic molecules with a predictable and desirable DNA-binding mechanism is a topical research task for biomedicine application. Herein, we demonstrate an attractive supramolecular strategy for controlling the non-covalent ligand-DNA interaction by binding with cucurbituril as a synthetic receptor. With a combination of UV/vis, CD and NMR experiments, we demonstrate that the bis-styryl dye with two suitable binding sites can involve double stranded DNA and cucurbituril in the formation of the supramolecular triad. The ternary assembly is formed as a result of the interaction of macrocyclic cucurbituril with one pyridinium fragment of the bis-styryl dye, while the second pyridinium fragment of the dye is effectively associated with DNA backbones, which leads to a change in the ligand-DNA binding mode from aggregation to a minor groove. This exciting outcome was supported by molecular docking studies that help to understand the molecular orientation of the supramolecular triad and elucidate the destruction of dye aggregates caused by cucurbituril. These studies provide valuable information on the mechanisms of DNA binding to small molecules and recognition processes in bioorganic supramolecular assemblies constructed from multiple non-covalent interactions.

Encapsulation-Controlled Photoisomerization of a Styryl Derivative: Stereoselective Formation of the Anti Z-Isomer in the Cucurbit[7]uril Cavity.

The photochemical isomerization of a styrylpyridinium dye (SP) bearing an unsymmetrically attached benzo-15-crown-5 ether has been studied in aqueous solution in the absence and presence of cucurbit[7]uril (CB[7]). The detailed analysis of the UV/Vis and NMR spectra showes that the isomeric composition of the photostationary mixtures of SP can be modulated by the host-guest complexation with CB[7]. It was found that steric hindrance caused by encapsulation of SP in the host cavity induces the exclusive formation of the anti conformer of Z-SP in contrast with the mixture of both anti and syn conformers obtained during photoisomerization of the dye without CB[7]. Remarkably, the displacement of anti Z-SP from CB[7] does not lead to the transformation of the anti Z-isomer into the syn Z-isomer pointing out the conformational memory of the system. The results provide an interesting example of the supramolecular stereorecognition by the achiral CB[7] host.

Light-induced piston nanoengines: ultrafast shuttling of a styryl dye inside cucurbit[7]uril.

The combination of photoactive styryl(pyridinium) dyes and cucurbit[7]uril (CB[7]) in an integrated supramolecular system allowed us to design a novel high speed molecular machine based on the fully reversible shuttling motion of the dye inside the CB[7] host cavity. The driving force of this movement is the electrostatic potential change after the occurrence of intramolecular charge transfer in the excited state of the dye molecule that can be externally controlled by light. Steady-state and time-resolved optical spectroscopy as well as DFT calculations provided an unambiguous evidence for the ultrafast piston-like movement of the system between two states. The shuttling process occurs in the picosecond timescale and its bistability depends on the strength of the dye donor fragment.