Dielectric studies on pure and doped sr (NO3)2

Single crystals of pure and Na⁺-doped strontium nitrate were grown by slow evaporation of aqueous solution. Systematic measurement of dielectric constant (ϵ) and loss (tan δ) have been carried out in the frequency range of 100 Hz to 100 kHz at temperatures ranging from room temperature to 420 °C. A.C. conductivity (σ) is obtained from the data on ϵ and tan δ, ϵ, and σ were found to show anomalies around 300 °C. The results are discussed in the context of order-disorder phase transition.     

Photoswitchable multivalent sugar ligands: synthesis, isomerization, and lectin binding studies of azobenzene-glycopyranoside derivatives

Coating of azobenzene chromophore with multivalent sugar ligands has been accomplished. Such sugar coating allows the study of the isomerization properties of this chromophore in aqueous solutions. The predominantly cis-isomer-containing photostationary state (PS) mixture of these azobenzene derivatives is found to be stable for hours. The rate constants for their isomerization, as well as the Arrhenius activation energies, are determined experimentally. An assessment of the lectin binding properties of the lactoside bearing isomeric azobenzene derivatives, by isothermal calorimetric methods, reveals the existence of an unusual cooperativity in their binding to lectin peanut agglutinin. Thermodynamic parameters evaluated for the trans and the PS mixture are discussed, in detail, for the lactoside bearing bivalent azobenzene derivative.