A new enzyme modification has been devised where various vinyl monomers were graftpolymerized using enzyme‐containing aliphatic azo groups as initiators. Thus, an enzyme, lipase, which is not soluble in organic solvents, was made soluble in organic solvents. The modified enzyme catalyzed the esterification reaction in chloroform. Catalytic activity in chloroform was obtained by modification with amphiphilic polymers, such as poly(N‐vinylpyrrolidone), as well as hydrophobic polymers, such as polystyrene and poly (methyl methacrylate). The catalytic activities of the hybrid enzymes increased linearly with increased solubility in chloroform. The hybrid enzymes were thermally stable and used repeatedly.
Trypsin was modified with a hydrophobic synthetic polymer, polystyrene. The attachment was achieved by first coupling free amines in the trypsin with azo-bis(4-cyano-valeric acid) and then irradiating the product in the presence of styrene. Decomposition of the azo structure provided free radical initiation of styrene polymerization, with the trypsin thus becoming part of the end group for the polymer chain initiated. That the modified trypsin retained catalytic activity when dissolved in chloroform was demonstrated by using it to catalyze the formation of a peptide linkage between amino acids. The catalytic reaction was stereoselective.
Thin films of amorphous silicon-germanium alloy (a-Si 1Ϫx Ge x ) were prepared by sputtering silicon and germanium targets with argon in a radio-frequency (rf) magnetron sputtering system. For the film prepared at an rf power of 200 W, the energy gap and the refractive index showed monotonous changes between those for silicon and germanium with a deviation from linearity in the correlating line of the energy gap. The deviation was attributable to the decrease in structural disorder in the film as shown in Tauc coefficient B. For the film prepared at an rf power of 50 W, some deviations of the energy gap and the refractive index from the monotonous changes increased with decreasing x, because of an excess amount of dangling silicon bonds. Fourier transform infrared spectra indicated absorption due to the modes derived from the dangling bonds. The absorption coefficient showed that the deviations of the energy gap and the refractive index at x ϭ 0 were proportional to the excess amount of dangling bonds of silicon. The excess amount of dangling bonds of silicon retarded crystallization in the solid state.
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