Synthesis of High-Performance Aqueous Fluorescent Nanodispersions for Textile Printing-A Study of Influence of Moles Ratio on Fastness Properties.

Aqueous fluorescent dispersions containing dyed acrylic-based copolymer nanoparticles possess significant credentials concerning green technology as compared to those prepared with the conventional vinyl-based monomers in textile and garment sectors; however, their essential textile fastness properties are yet to achieve. In the present work, a series of acrylic nanodispersions were synthesized by varying the moles ratio of benzyl methacrylate (BZMA), methyl methacrylate (MMA), and 2-hydroxypropyl methacrylate (HPMA) monomers. This was done to study their effect on dye aggregation and dyed polymer particles agglomeration. FT-IR spectral analysis showed the formation of polymer structures, while Malvern Analyzer, Transmission Electron Microscopy, and Scanning Electron Microscopy analysis suggested that the particles are spherical in shape and their size is less than 200 nm. The obtained nanodispersions were later applied on cotton fabrics for the evaluation of wash fastness and colour migration. Premier color scan spectrophotometer and zeta potential measurement studies suggested that colour migration of printed cotton fabrics increased with an increasing agglomeration of particles and it was also observed to increase with the moles ratio of MMA and zeta potentials.

Effect of dC → d(m5C) substitutions on the folding of intramolecular triplexes with mixed TAT and C+GC base triplets.

Oligonucleotide-directed triple helix formation has been recognized as a potential tool for targeting genes with high specificity. Cystosine methylation in the 5' position is both ubiquitous and a stable regulatory modification, which could potentially stabilize triple helix formation. In this work, we have used a combination of calorimetric and spectroscopic techniques to study the intramolecular unfolding of four triplexes and two duplexes. We used the following triplex control sequence, named Control Tri, d(AGAGAC5TCTCTC5TCTCT), where C5 are loops of five cytosines. From this sequence, we studied three other sequences with dC → d(m5C) substitutions on the Hoogsteen strand (2MeH), Crick strand (2MeC) and both strands (4MeHC). Calorimetric studies determined that methylation does increase the thermal and enthalpic stability, leading to an overall favorable free energy, and that this increased stability is cumulative, i.e. methylation on both the Hoogsteen and Crick strands yields the largest favorable free energy. The differential uptake of protons, counterions and water was determined. It was found that methylation increases cytosine protonation by shifting the apparent pKa value to a higher pH; this increase in proton uptake coincides with a release of counterions during folding of the triplex, likely due to repulsion from the increased positive charge from the protonated cytosines. The immobilization of water was not affected for triplexes with methylated cytosines on their Hoogsteen or Crick strands, but was seen for the triplex where both strands are methylated. This may be due to the alignment in the major groove of the methyl groups on the cytosines with the methyl groups on the thymines which causes an increase in structural water along the spine of the triplex.

Application of differential scanning calorimetry to measure the differential binding of ions, water and protons in the unfolding of DNA molecules.

BACKGROUND: The overall stability of DNA molecules globally depends on base-pair stacking, base-pairing, polyelectrolyte effect and hydration contributions. In order to understand how they carry out their biological roles, it is essential to have a complete physical description of how the folding of nucleic acids takes place, including their ion and water binding. SCOPE OF REVIEW: To investigate the role of ions, water and protons in the stability and melting behavior of DNA structures, we report here an experimental approach i.e., mainly differential scanning calorimetry (DSC), to determine linking numbers: the differential binding of ions (Δnion), water (ΔnW) and protons (ΔnH(+)) in the helix-coil transition of DNA molecules. GENERAL SIGNIFICANCE: We use DSC and temperature-dependent UV spectroscopic techniques to measure the differential binding of ions, water, and protons for the unfolding of a variety of DNA molecules: salmon testes DNA (ST-DNA), one dodecamer, one undecamer and one decamer duplexes, nine hairpin loops, and two triplexes. These methods can be applied to any conformational transition of a biomolecule. MAJOR CONCLUSIONS: We determined complete thermodynamic profiles, including all three linking numbers, for the unfolding of each molecule. The favorable folding of a DNA helix results from a favorable enthalpy-unfavorable entropy compensation. DSC thermograms and UV melts as a function of salt, osmolyte and proton concentrations yielded releases of ions and water. Therefore, the favorable folding of each DNA molecule results from the formation of base-pair stacks and uptake of both counterions and water molecules. In addition, the triplex with C(+)GC base triplets yielded an uptake of protons. Furthermore, the folding of a DNA duplex is accompanied by a lower uptake of ions and a similar uptake of four water molecules as the DNA helix gets shorter. In addition, the oligomer duplexes and hairpin thermodynamic data suggest ion and water binding depends on the DNA sequence rather than DNA composition.