The mode of binding of 2-(4-(dimethylamino)styryl)-1-methylpyridinium iodide (DASPMI) with calf thymus DNA as revealed from different steady state and time-resolved emission spectroscopic measurements has been reported in this paper. Fluorescence enhancement of DASPMI and its quenching by potassium iodide (KI) points to groove binding of dye with ct-DNA, rather than intercalation in the ct-DNA helix. An increase in steady state anisotropy and fluorescence lifetime hints at binding with ct-DNA. The value of binding constant from emission and association constant from circular dichroic spectrum also indicates weak binding. The strong dependence on ionic strength or salt in controlling the binding of DASPMI with ct-DNA by electrostatic interaction confirms groove binding. The high semicone angle of DASPMI in ct-DNA certainly rules out the possibility of intercalated bonding. A theoretical modeling shows that the probe is bound to ct-DNA as a crescent with a curvature of 11.35 A, which is the previously known curvature of probe in the minor groove.

The synthesis and binding properties of new macrocyclic polyethers are described. These systems incorporate 2,2'bipyridyl functions in such a fashion that binding of metal nuclei can occur at either the macrocycle or the bipyridyl function. Evidence is presented that binding of alkali metals occurs at the crown ether cavity while binding of transition metals occurs at the bipyridyl function. Binding of two different metals is interpreted in terms of a simple model for allosteric effects.

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Analysis of Polarization-Depolarization Current, recorded from high voltage oilpaper insulation using insulation model is common among researchers. It is reported that paper insulation of power transformers undergoes non-uniform aging. Unlike Conventional Debye Model (CDM), Modified Debye Model (MDM) is capable of modeling such non-uniform aging. However, factors like insulation geometry affect the values of the MDM branch parameters. Therefore, model parameterized using data obtained from one insulation system finds limited use in assessing the condition of a different transformer, even with similar loading history and power rating. The present paper shows that a performance parameter, which is less sensitive to insulation geometry, can be evaluated from Transfer Function, TF M (s) of MDM. The parameter is the zero Z 1 of TF M (s) which is located farthest away from the origin in the Left Half Plane of s-plane. The capability of Z 1 as an insulation condition sensitive parameter is first tested on laboratory samples and then on data recorded from several real life power transformers. Results obtained for these transformers show that there is a good correlation between magnitude of Z 1 and paper moisture content obtained from Frequency Domain Spectroscopy (FDS) using IDAX 300.

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