Solution-Induced Intercalation

Several techniques such as intercalation of polymer from solution, in-situ intercalative polymerization, melt intercalation, direct mixture of polymer and particulates, template synthesis, in-situ polymerization and solgel process, are being employed for the preparation of polmer-layered silicate nanocomposites. Among them the most common and important approaches are in-situ polymerization, solution-induced intercalation method, and melt processing method, which are briefly discussed below. 

This solution-induced intercalation process has the novelty to swell and disperse clays into a polymer solution. This process is difficult to carry out commercially because of the high cost factor of the solvents. In addition, phase separation in this process is quite tedious for solvent separation from the phase. There are also health and safety concerns associated with the application of this technology. However, this technology is exclusively applicable to water soluble polymers. As the solvent used in this process is water, which is a low-cost as well as an eco-friendly solvent with minimum... 

The dye 4, 6-Diamidino-2-PhenyIindole (DAPI) in 0.001%W/V aqueous solution can be used directly on smears, ciyosections and embedded specimens to locate and count culture bacteria, without regard to their viability, in cheese and other cultured products. The dye reacts with nucleic acids by intercalation. Excitation at 360nm is best for this dye. It is worth noting two other facts about its use. DAPI cross reacts with dairy proteins, but the color of the protein-dye complex is different from that of the nucleic acid-dye complex (the latter is a steely blue/white) and so the two reactions may be discriminated. The dye also may take up to 15 minutes to enter bacterial cells, particularly spores, before fluorescence is observed. An alternative nucleic acid dye, Ethidium Bromide, has less contrast between the fluorescence induced in cells and the fluorescence of cross-reacting dairy proteins. It should be tried in other products such as meats if DAPI is not successful. 

In aqueous solution, intercalated Hoechst 3342 protects DNA against strand breakage beyond OH-scavenging (quenching diameter by Hoechst 3-4 bp Adhikary et al. 1997a). Besides, intercalated Hoechst reacts with OH-induced DNA on the ms time scale. The Hoechst-reactive damaged DNA sites are likely the oxidizing radicals A and G and pyrimidine peroxyl radicals (Table 12.17 for further pulse radiolysis studies on Hoechst in aqueous solution see Adhikary et al. 2000). 

A second major area in which the CD observed in a solute-polymer system has proven to be very useful in studies of the interactions has been for the particular instance where the polymer was an oligonucleotide. This area is also characterized by an extremely large literature, so in the present work we will restrict our focus on the CD induced in planar aromatic molecules which may or may not intercalate in the oligonucleotide structure. Perrin and Hart have reviewed the work performed prior to 1970 [67], and the focus of the current review will be on later works. 

The induced CD of an electric dipole transition of a solute intercalated in DNA has been calculated using a matrix method and wavefunctions proposed for the transitions of... 

The CD induced in the visible absorption bands of proflavine cation intercalated to DMA was characterized in terms of the dye-DNA base pair exciton interactions [84]. In this work, the data were obtained at very low amounts of intercalated solute relative to the amount of oligonucleotide, with the goal of observing the CD spectra of isolated and monomeric dye systems. Substantial ionic strength effects were noted, indicating the electrostatic nature of the interaction. Comparison of the data with the results obtained after theoretical modeling indicated that the proflavine molecules insert in the DNA helix with the molecular plane parallel to the stacking plane of the DNA base pairs. 

It has been shown that methylene blue binds to DNA in a manner similar to that of acridine orange, with the intercalated solute being coplanar with the base pairs at low dye/polymer ratios and low ionic strengths [89]. The induced CD data indicated the existence of two origins for the observed chirality. At low ratios of dye/polymer, the CD is... 

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