Studies on the Hill reaction of membrane fragments of blue-green algae I. Stabilizing effect of various media on the 2,6-dichlorophenol indophenol-Hill activity of membrane fragments obtained from Anabaena cylindrica and Anabaena variabilis

The stability of DPIP-Hill activity of membrane fragments fromblue-green algae was investigated in various suspension media.Two blue-green algae, Anabaena cylindrica and A. variabiliswere used. Activities for the DPIP-Hill reaction were stable in the twoalgal preparations only when preparations were suspended ina medium containing high concentrations of carbohydrates orPEG. Required concentrations of carbohydrates or PEG differedgready in die two preparations; 1.5 M sucrose or 20% PEG forA. cylindrica and 0.3 M sucrose or 6% PEG for A. variabiliswere minimal for maintaining full activity in 2 hr incubationat 0°C, respectively. Below these concentrations, activitiesdecreased rapidly. In both preparations, stabilizing effects,on a molar basis, varied in different kinds of solutes. However,a simple relation was found between the effects and water concentrationsof media. In A. cylindrica, a 50% decay in activity occurredin 2 hr incubation at 0°G in a medium with 43.8 M water,and, in A. variabilis, the water concentration was 53.4 M. In media free of carbohydrate or PEG, Mg++ ion had a moderatestabilizing ability. EDTA acted antagonistically to Mg++. Effectiveconcentrations were the same in two preparations. However, inthe medium containing carbohydrate or PEG, their actions wereinsignificant. Results suggest that the molecular organization in membranesnecessary for Hill reaction is easily destroyed under high waterconcentrations, and that added solutes stabilize the activityby reducing water concentrations. (Received February 13, 1971; )