Interaction between a photoisomerizable azobenzene compound and alpha-lactalbumin: Spectroscopic and computational simulation studies

The combination of light and photoresponsive compounds provides a peculiar way of regulating biological systems. Azobenzene is a classical organic compound with photoisomerization properties. Exploring the interactions between azobenzene and proteins can deepen the biochemical applications of the azobenzene compounds. In this paper, the interaction of 4-[(2,6-dimethylphenyl)diazenyl]-3,5-dimethylphenol with alpha-lactalbumin was investigated by UV-Vis absorption spectra, multiple fluorescence spectra, computer simulations, and circular dichroism spectra. Most critically, the interaction differences between proteins and the trans- and cis-isomer of ligands have been analyzed and compared. Results showed that both isomers of ligands were bound to alpha-lactalbumin to form ground state complexes and statically quenched the steady-state fluorescence of alpha-lactalbumin. The van der Waals forces and hydrogen bonding dominated the binding; the difference is that the binding of the cis-isomer to alpha-lactalbumin is more rapidly stabilized, and the binding strength is greater than the trans-isomer. These binding differences were modeled and analyzed by molecular docking and kinetic simulations, and we found that both isomers bind through the hydrophobic aromatic cluster 2 of alpha-lactalbumin. However, the bent structure of the cis-isomer is more closely aligned with the construction of the aromatic cluster and may have contributed to the above differences.

A tactical nanomissile mobilizing antitumor immunity enables neoadjuvant chemo-immunotherapy to minimize postsurgical tumor metastasis and recurrence

Neoadjuvant chemotherapy has become an indispensable weapon against high-risk resectable cancers, which benefits from tumor downstaging. However, the utility of chemotherapeutics alone as a neoadjuvant agent is incapable of generating durable therapeutic benefits to prevent postsurgical tumor metastasis and recurrence. Herein, a tactical nanomissile (TALE), equipped with a guidance system (PD-L1 monoclonal antibody), ammunition (mitoxantrone, Mit), and projectile bodies (tertiary amines modified azobenzene derivatives), is designed as a neoadjuvant chemo-immunotherapy setting, which aims at targeting tumor cells, and fast-releasing Mit owing to the intracellular azoreductase, thereby inducing immunogenic tumor cells death, and forming an in situ tumor vaccine containing damage-associated molecular patterns and multiple tumor antigen epitopes to mobilize the immune system. The formed in situ tumor vaccine can recruit and activate antigen-presenting cells, and ultimately increase the infiltration of CD8⁺ T cells while reversing the immunosuppression microenvironment. Moreover, this approach provokes a robust systemic immune response and immunological memory, as evidenced by preventing 83.3% of mice from postsurgical metastasis or recurrence in the B16-F10 tumor mouse model. Collectively, our results highlight the potential of TALE as a neoadjuvant chemo-immunotherapy paradigm that can not only debulk tumors but generate a long-term immunosurveillance to maximize the durable benefits of neoadjuvant chemotherapy.

Photochromic holo-cellulose wood-based aerogel grafted azobenzene derivative by SI-ATRP

Wood is actually a natural polymers composite that is easy to process, mainly constituted of cellulose, hemicellulose and lignin. However, most wood-based functional materials are prepared by physical methods, which undoubtedly limit the application of wood-based materials. Herein, the wood aerogel (WA) was obtained from wood by delignification and freezing dried. The WA then was fabricated into an unexpected photochromic wood aerogel (PWA) via surface-initiated atom transfer radical polymerization (SI-ATRP) covalently grafting poly{6-[4-(4-methoxyphenyl-azo)phenoxy]hexyl methacrylate} (PMAZOM). Both WA and PWA showed good compression resilience. The hydrophobicity of PWA was obviously enhanced because of the surface modification. The color of PWA can change from yellow to orange-red after being irradiated by UV light for 30 s. The color of sample can be reversibly changed to yellow under sunlight for 200 s. The lightweight and photosensitive wood aerogel is potential to apply for optical information storage materials and photosensitive devices.

Molecular characteristics of a fluorescent chemosensor for the recognition of ferric ion based on photoresponsive azobenzene derivative

Metal ion recognition is of great significance in biological and environmental detection. So far, there is very few research related to the ferric ion sensing based on photoresponsive azobenzene derivatives. In this work, we report a highly selective fluorescent "turn-off" sensor for Fe³⁺ ions and the molecular sensing characteristics based on an azobenzene derivative, N-(3,4,5-octanoxyphenyl)-N'-4-[(4-hydroxyphenyl)azophenyl]1,3,4-oxadiazole (AOB-t8). The binding association constant was determined to be 6.07×10³M^-1 in ethanol and the stoichiometry ratio of 2:2 was obtained from Job's plot and MS spectra. The AOB-t8 might be likely to form the dimer structure through the chelation of ferric ion with the azobenzene moiety. Meanwhile, it was found that the photoisomerization property of AOB-t8 was regulated by the binding with Fe³⁺. With the chelation of Fe³⁺, the regulated molecular rigidity and the perturbed of electronic state and molecular geometry was suggested to be responsible for the accelerated isomerization of AOB-t8 to UV irradiation and the increased fluorescence lifetime of both trans- and cis-AOB-t8-Fe(III). Moreover, the reversible sensing of AOB-t8 was successfully observed by releasing the iron ion from AOB-t8-Fe(III) with the addition of citric acid.

Molecular structure and modeling studies of azobenzene derivatives containing maleimide groups

The molecular orbital calculations have been carried out to investigate the structure and stability of (E) / (Z) isomers of some azobenzene derivatives containing maleimide groups. A special attention has been devoted to the compound (E)-1, (E)-1-(4-(phenyldiazenyl)phenyl)-1H-pyrrole-2,5-dione, for which the available crystallographic experimental data have been used to validate the modeling structures computed at the theoretical levels AM1, PM3, RHF/6-31+G(d,p) and B3LYP/6-31+G(d,p). To this end, the discrepancy between experimental and calculated structural parameters has been ascertained in terms of root-mean-square deviation (RMSD). The quantum calculations at the level RHF/6-31+G(d,p) yield the most accurate results on (E)-1 structure giving a deviation error from crystallographic data of about 5.00% for bond lengths and 0.97% for interatomic angles. The theoretical electronic absorption spectra of azobenzene derivatives of concern have been computed by means of configuration-interaction method (CI) at the level of semi-empirical Hamiltonians (AM1 and PM3). Likewise, the molecular energy spectra, electrostatic potential and some quantitative structure activity relationship (QSAR) properties of studied molecules have been computed and discussed in the paper.