Remote-control of the enantiomeric supramolecular recognition mediated by chiral azobenzenes bound to human serum albumin.

Three novel tyrosine-conjugated azobenzene molecules were designed and their ability to target a natural chiral host matrix (human serum albumin, HSA) was investigated. We found that the interplay between the spatial configuration of the chiral substituents and the change in local symmetry resulting from the photoisomerization process strongly affects the optical activity of the bound photochromes. In particular, the different signal amplification obtained upon binding of the photoswitches to the biopolymer enables obtaining a chirooptical system tunable over a wide range of wavelengths.

Effective control of the intrinsic DNA morphology by photosensitive polyamines.

Non-viral vectors for gene therapy such as DNA-cationic probe complexes offer important bio-safety advantages over viral approaches, due to their reduced pathogenicity, immunogenicity and cytotoxicity. In the present study we examine two polycationic water-soluble azobenzene derivatives (bis-Azo-2N and bis-Azo-3N) containing different linear unsubstituted polyamine moieties and we demonstrate the ability of such photochromes to destabilize the intrinsic B-DNA secondary structure in a concentration-dependent manner. Furthermore, through a detailed series of biophysical experiments, varying the photochrome conformation, temperature, salt and DNA concentration, we provide a detailed insight into the azobenzene-DNA binding pathway (Ka: bis-Azo-2N(trans)-DNA = 5.3 ± 0.3 × 104 M-1, Ka: bis-Azo-2N(cis)-DNA = 2.6 ± 0.2 × 104 M-1, Ka: bis-Azo-3N(trans)-DNA = 7.1 ± 0.4 × 104 M-1 and Ka: bis-Azo-3N(cis)-DNA = 5.1 ± 0.4 × 104 M-1) establishing the versatility of such materials as promising candidates for use in non-viral gene delivery systems.