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Chirality plays a fundamental role in natural phenomena, yet its manifestation on solid surfaces remains relatively unexplored. In this study, we investigate the formation of chiroptical melanin-based self-assembled films on quartz substrates, leveraging mussel-inspired surface chemistry. Water-soluble porphyrins serve as molecular synthons, facilitating the spontaneous formation of hetero-aggregates in phosphate-buffered saline containing L- or D-DOPA. Spectroscopic analysis reveals chiral transfer from DOPA enantiomers to porphyrin hetero-aggregates, followed by the disruption of these latter and subsequent generation of chiral melanin structures in solution. Quartz substrates inserted into these solutions spontaneously accumulate homogeneous melanin-like films over days, demonstrating the feasibility of self-assembly. The resulting films exhibit characteristic UV/Vis and CD spectra, with distinct signals indicating successful chiral induction. Interestingly, the AFM characterizations reveal a distinct surface morphology, and in addition, some thermal and mechanical properties have been taken into account. Overall, this study sheds light on the formation, stability, and chiroptical properties of melanin-based films, paving the way for their application in various fields., (© 2024 Wiley Periodicals LLC.)

In this work, we have characterized the interactions of monospermine porphyrin derivative with calf thymus DNA (ct-DNA) and poly (dG-dC) 2 in both B and Z conformation. By several spectroscopic techniques (UV-vis, electronic circular dichroism and resonance light scattering), the binding modes of monospermine porphyrin derivative with different DNA sequences have been elucidated. In the presence of ct-DNA, the porphyrin binds along the external double helix as well as in the presence of B conformation of poly (dG-dC) 2 . Whilst when the Z form of the poly (dG-dC) 2 is induced, a slight intercalation of the porphyrin between the basis has been detected., (© 2020 Wiley Periodicals LLC.)

In this study we show the outstanding agreement between simulation and experimental data concerning the efficient stabilization effect by NaCl of Z conformation. We demonstrate by circular dichroism (CD) experiments that Na(+) not only is able to induce a B to Z form transition in a short (GC)3 alternated portion of a sequence having 17 basis, but also is the best stabilizer in comparison with other Z inducers used (spermine and NiCl2). This result was confirmed by free energy calculations., (© 2015 Wiley Periodicals, Inc.)

Traces of biological contaminants that cannot be detected, but are expected to be present, in ultra-pure water suffice to select the emerging chiral sign in the spontaneous mirror symmetry breaking that takes place during the formation of the J-aggregates of the amphiphilic diprotonated tetrakis-(4-sulfonatophenyl)porphyrin (H(4)TPPS(4)(2-)). This is demonstrated by competition experiments with a chiral cationic surfactant. The sensitivity of the detection depends on the hierarchical control of the H(4)TPPS(4)(2-) self-aggregation.

The interactions between Lambda and Delta enantiomers of ruthenium(II)-phenanthroline cationic complex ([Ru(phen)(3)](2+)) and three anionic porphyrins have been characterized by absorption, circular dichroism (CD), fluorescence, and resonance light scattering (RLS). The three porphyrins used in this study have been chosen for the different number (two or four) and reciprocal (symmetrical, cis or trans) disposition of the anionic (4-sulphonatophenyl) peripheral groups in the meso positions. All the techniques evidence the formation of inorganic-organic hybrids. In particular, CD and fluorescence measurements show that the inorganic moiety is able to transfer to porphyrins not only chirality (as shown from the appearance of an induced CD signal (ICD) in the absorption region of porphyrins) but, most likely, also energy., ((c) 2008 Wiley-Liss, Inc.)

The interaction between the tetra-anionic porphyrin H2TPPS and its copper derivative, CuTPPS, with the tetra-cationic porphyrin H2T4 and its copper derivative, CuT4, leads, in aqueous solution, to the formation of remarkably stable and kinetically inert heteroaggregates. The aggregation process is under hierarchic control and, in the presence of a suitable chiral mold, leads to the formation of chiral porphyrin heteroassemblies as stable and inert as the achiral ones. Because of these properties, the chirality of the porphyrin "imprinted" heteroaggregates not only survives the disruption of the template, but also to its complete removal from the solution. Notably, the template-free chiral porphyrin system is an excellent mold for its own self-replication. The relevant characteristics of these chiral heteroaggregates together with the knowledge of the forces that guide the aggregation processes permitted us to design a new but similar system. This system not only is able to store chiral information, but also is capable to release and restore it reversibly, in a cyclic manner. This has been achieved by modulating the charges carried by one of the two coupled porphyrins through protonation under various pH conditions. The role of the central metal ion and the template-free chiral structure of the CuT4-H2TPPS heteroaggregate, determined through EDXD analysis, are also presented., ((c) 2007 Wiley-Liss, Inc.)

To extend the model that explains why and how much absorption flattening (AF) influences circular dichroism (CD) signals, we have investigated the interesting case of exciton CD in the Soret region of a noncovalent complex formed by (Delta-RuPhen(3))(2+) and the tetraanionic porphyrin H(2)TPPS. Different concentrations have been studied by using an AF emulator and spectra simulation. The CD spectra of this compound occasionally show distortions in the solution sampling mode with the increase of concentration; the inhomogeneous distribution in the cell volume is due to aggregation and is the source of the AF effect. On the basis of these results, we conclude that AF is an important cause of distortions in CD spectra for Delta-RuPhen(3) . H(2)TPPS complexes and might affect the CD bands of other aggregated systems as well.

CD and uv-visible absorption studies with several tetracationic water-soluble porphyrin derivatives show that some of these species can serve as probes to discriminate between A- and B-conformational forms of single-stranded polynucleotides. It is also observed that these porphyrins can participate in the formation of double helices by forming transient intermediate complexes en-route to duplex formation.