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Chiral poly(acrylamide) macromonomers (PMB-1, PMB-2, PPAE-1, and PPAE-2) were synthesized from 2-methacryloyloxyethyl isocyanate and prepolymers, that is, poly[(S)-methylbenzyl acrylamide] or poly(L-phenylalanine ethylester acrylamide with a terminal carboxylic acid or hydroxy group. Radical homopolymerizations of poly(acrylamide) macromonomers were carried out under several conditions to obtain the corresponding optically active polymers. A strong temperature dependence on the specific optical rotation was observed for poly(PPAE-2) in comparison with that for the corresponding prepolymer. This might have resulted from a change in the conformation caused by hydrogen bonds between polymer-graft branches in the polymacromonomer. Radical copolymerizations of poly(acrylamide) macromonomers with styrene and methyl methacrylate were performed with azobisisobutyronitrile in tetrahydrofuran at 60°C. Chiroptical properties of the copolymers were slightly influenced by comonomer units. Chiral stationary phases were prepared by the radical polymerization of poly-(acrylamide) macromonomers in the presence of silica gel containing vinyl groups on the surface. Some racemic compounds such as menthol and mandelic acid were resolved on the chiral stationary phases for high-performance liquid chromatography. The conformation based on hydrogen bonds between polymer-graft branches in the polymacromonomers may play an important role in chiral discrimination.

We studied the effect of stretch on the membrane potentials and ultrastructure of isolated ventricular papillary muscles of guinea pigs. The muscles were stimulated at 0.5 Hz and stretched stepwise from slack length (90% of Lmax) to 100% (mild stretch), 110-120% (moderate stretch), and 130-140% of Lmax (severe stretch), under microscopic control. In control Tyrode solution (K + = 5.4 mM, Ca2 + =1.8 mM, Mg2 + = 0.5 mM), the mild to moderate stretch significantly depolarized the resting potential (RP) by about 6 mV as compared to that in slack length, whereas the severe stretch hyperpolarized the membrane by about 5 mV. The latter finding was new and was focused on in later experiments. Both the hyperpolarization and depolarization became more marked when [K+]0 was decreased to 1.35-2.7 mM, and became less with elevated [K+]o to 10.8--21.6 mM, thereby suggesting the participation of altered K+ conductance (gK) with these changes in the RP. Perfusion with low [Ca2 +]o (0.45 mM) enhanced the depolarization but eliminated the hyperpolarization; high [Ca2 +]o (7.2 mM) inhibited the depolarization without effect on the hyperpolarization. D-600 (1 /IM), caffeine (10 mM), and ryanodine (1 µM), all of which may produce decreases in [Ca2 +]i, abolished the hyperpolarization with inconsistent effects on the depolarization. Moderate to severe stretches decreased the maximum rate of rise of action potential (Vmax)' by shifting the Vmax'M relationship toward hyperpolarizing direction. The shift could be reversed partially after increasing [Mg2 +]o to 8.0 mM. Electron microscopic examination revealed that the sarcoplasmic reticulum (SR) remained intact with mild to moderate stretches with significant lengthening of sarcomere length, while with a severe stretch, the SR showed a structural disarrangement with a non-uniform lengthening of sarcomere length. Our observations suggest that stretch-induced hyperpolarization is probably mediated by the increase in gK, presumably secondary to the increase in

A novel esterase was found in Pseudomonas fluorescens cells and purified to homogeneity as determined by polyacrylamide gel electrophoresis. The esterase was extracted from the cells by freeze-thawing and hypotonic treatment. Purification was achieved by ammonium sulfate precipitation, followed by successive chromatographies on DEAE-cellulose and benzylamine-agarose and then electrophoresis. The enzyme catalyzed the hydrolysis of methyl esters, such as methyl butyrate, but its hydrolyzing activity decreased with increase in the chain length of the alcohol moiety, and it did not catalyze the hydrolysis of triacylglycerols, such as triacetin. In contrast, the enzyme acted on various acyl residues in a series of methyl esters, such as dimethyl succinate, methyl methacrylate, and dimethyl malate. The optimum pH for activity of this enzyme with methyl butyrate was 7.0-8.5. The enzyme was inhibited by phenylmethylsulfonylfluoride. Its molecular weight was estimated as 48,000 by molecular sieve electrophoresis and gel filtration on Sephadex G-150.