https://hal-univ-rennes1.archives-ouvertes.fr/hal-00879623/document

Luminescent materials incorporating pyrazine or quinoxaline moieties

A key issue for the application of π-conjugated organic molecules as thin film solid-state materials is the packing structure, which drastically affects optical and electronic properties due to intermolecular coupling. In this regard, merocyanine dyes usually pack in H-coupled antiparallel arrangements while structures with more interesting J-type coupling have been rarely reported. Here we show that for three highly dipolar merocyanine dyes, which exhibit the same π-scaffold and accordingly equal properties as monomers in solution, the solid-state packing can be changed by a simple variation of aliphatic substituents to afford narrow and intense absorption bands with huge hypsochromic (H) or bathochromic (J) shifts for their thin films and nanocrystals. Time-dependent density functional theory calculations show that the energetic offset of almost 1 eV magnitude results from distinct packing motifs within the crystal structures that comply with the archetype H- or J-aggregate structures as described by Ka...

Exciton Coupling of Merocyanine Dyes from H- to J-type in the Solid State by Crystal Engineering

A new eco-friendly, selective and sensitive method was developed for preconcentration and determination of trace levels of sulfite by ultrasonic-assisted cloud point extraction (UA-CPE). The method is based on the selective ion-association of the anionic complex, Cu(SO3)22−, produced depending on sulfite concentration in the presence of excess Cu(II) ions with toluidine blue (TB+) at pH 7.5, and then extraction of the formed ion-associate complex into the surfactant rich phase of Triton X-45 micelles. Under the optimized reagent conditions, the calibration curve is linear in range of 2.5–350 μg L−1, and the limits of detection and quantification of the method (LOD and LOQ) (3σblank/m and 10σblank/m) are 1.15 and 3.82 μg L−1 with a sensitivity enhancement factor of 95. The results demonstrated that the method achieved acceptable quantitative recoveries of 95.7–102.9% with relative standard deviations (RSDs) of 2.1–4.8%. The method showed good selectivity, and was successfully applied to the quantification of sulfite species in vegetable and dried fruit samples with satisfactory results. The results were compared with those of the standard 5,5′-dithio-bis(2-nitrobenzoic acid) (DTNB) method, and the two paired t-test was used to determine whether the results obtained by the two methods differ significantly.

A new simple UV-Vis spectrophotometric method for determination of sulfite species in vegetables and dried fruits using a preconcentration process

In the context of gene delivery, chitosan has been widely used as a safe and effective polycation to complex DNA, RNA and more recently, siRNA. However, much less attention has been paid to chitosan oligosaccharides (COS) despite their biological properties. This study proposed to carry out a physicochemical study of COS varying in degree of polymerization (DP) from 5 to 50, both from the point of view of the solution properties and the complexing behavior with siRNA. The main parameters studied as a function of DP were the apparent pKa, the solubility versus pH, the binding affinity with siRNA and the colloidal properties of complexes. Some parameters, like the pKa or the binding enthalpy with siRNA, showed a marked transition from DP 5 to DP 13, suggesting that electrostatic properties of COS vary considerably in this range of DP. The colloidal properties of siRNA/COS complexes were affected in a different way by the COS chain length. In particular, COS of relatively high DP (≥50) were required to form small complex particles with good stability.

https://hal.archives-ouvertes.fr/hal-02194615/document

Effects of Chain Length of Chitosan Oligosaccharides on Solution Properties and Complexation with siRNA.

The chromatin observed by conventional electron microscopy under the nuclear envelope constitutes a single layer of dense 30–35 nm granules, while ∼30 nm fibrils laterally attached to them, form large patches of lamin-associated domains (LADs). This particular surface “epichromatin” can be discerned by specific (H2A+H2B+DNA) conformational antibody at the inner nuclear envelope and around mitotic chromosomes. In order to differentiate the DNA conformation of the peripheral chromatin we applied an Acridine orange (AO) DNA structural test involving RNAse treatment and the addition of AO after acid pre-treatment. MCF-7 cells treated in this way revealed yellow/red patches of LADs attached to a thin green nuclear rim and with mitotic chromosomes outlined in green, topologically corresponding to epichromatin epitope staining by immunofluorescence. Differentially from LADs, the epichromatin was unable to provide metachromatic staining by AO, unless thermally denatured at 94oC. DNA enrichment in GC stret...

https://www.tandfonline.com/doi/pdf/10.1080/19491034.2018.1431081

Differential staining of peripheral nuclear chromatin with Acridine orange implies an A-form epichromatin conformation of the DNA.

J-aggregate structure in a chloroform solvate of a 2,3-dicyanopyrazine dye – Separation of two-dimensional stacking dye layers by solvate formation

Metachromatic staining with toluidine blue (TB) has been used as a cytological too lf or tissue recognition and cancer diagnosis. Recently, its strong potentia lf or infertility diagnosis was also reported. Metachromatic staining is important i nb iological applications, but the origi no f spectral changes has not been fully understood, although dye aggregation on biological materials is thought to be the cause. In this study, we investigated the dimer structure of TB formed on DNA oligomers by using a computational method, particularly focusing on the spectral changes caused by TB dimer formation. The structure of the TB­DNA complexes was constructed on the basi so f the calculated molecular structure of TB and crystal data of A- and B-form DNA oligomers, assuming that there was an electrostatic interaction between them. The resulting spectral shift was then evaluated using the extended-dipole model. The examination of B-DNA revealed that possibl eT B dimers result in a hypsochromic spectral shif to f absorption. On the other hand, the dimerization of TB on A-DNA was found to be quite difficult, because the helical geometry of A-DNA restricted the binding sites of TB. These results suggest that the metachromati cc olor observed during biological staining i ss ignificantly affected by the helical geometry of DNA.

/pdf/consideration-on-the-metachromatic-spectra-of-toluidine-blue-51ooxpde9n.pdf

Saori Sato

Papers

J-aggregate structure in a chloroform solvate of a 2,3-dicyanopyrazine dye – Separation of two-dimensional stacking dye layers by solvate formation

Consideration on the Metachromatic Spectra of Toluidine Blue Dimers Formed on DNA Oligomers