A new class of photo-cross-linkable main-chain liquid crystalline polymers (PMCLCPs) containing bis(benzylidene)cycloalkanone groups have been synthesized and studied for their liquid crystalline and photochemical properties. The bis(benzylidene)cycloalkanone group in the chain functions both as a mesogen and as a photoreactive center. All of the polymers exhibit a nematic mesophase. Two kinds of photoreactions, namely, photoisomerization and photo-cross-linking, operate in these polymers. Above T" at the initial stages of irradiation, photoisomerization predominates the cross-linking, which results in the disruption of the chromophore aggregates. Below Tg, because of the restricted mobility of the chains, only cross-linking takes place. Studies on the model compound, bis(benzylidene)cyclopentanone, confirm the above observations and demonstrate further that the cross-linking proceeds by the 2v + 2v cycloaddition reaction of the bis(benzylidene)cycloalkanone moieties. The cross-linking rate decreases with increase in the size of the cycloalkanone ring. Heating the solution cast polymer film results in the ordered aggregation of the chromophores just above T, and also at the crystal to crystal transition temperature, which facilitates the photo-croes-linMng reactions. In the isotropic phase, the random orientation of the chromophores drastically curtails the cross-linking rate.

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Invertase (beta-D -fructofuranoside fructohydrolase-E.C. 3.2.1.26) is a sucrose hydrolyzing enzyme found in microbial, plant and animal sources. Invertase from Candida utilis is a dimeric glycoprotein composed of two identical monomer subunits with an apparent molecular mass of 150 kDa. We investigated the mechanism of stabilization of invertase with polyols (glycerol, xylitol, and sorbitol). Activity, thermodynamic and kinetic measurements of invertase were performed as a function of polyol concentration and showed that polyols act as very effective stabilizing agents. The result from the solvent-invertase interaction shows preferential exclusion of the polyols from the protein domain leading to preferential hydration of protein. Apparent thermal denaturation temperature of the protein (T ( m )) rose from 75 degrees C to a maximum of 85 degrees C in 30% glycerol. The stabilization has been attributed to the preferential hydration of the enzyme.

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