Stabilization of the structure and unctions of a photosystem i submembrane fraction by immobilization in an albumin-glutaraldehyde matrix

The effect of immobilization in an albumin-glutaraldehyde crosslinked matrix on the structure and activity of a photosystem I submembrane fraction has been studied. The photosynthetic activity recovered after immobilization was between 35 and 45% of the oxygen-uptake rates of the native material. Resulting oxygen uptake activities found in immobilized photosystem I preparations with methylviologen as acceptor were as high as 270 μmol O₂ (mg Chl h)^-1, An enhancement of photosystem I electron transfer, which is produced by incubation of thylakoid membranes at temperatures above 30 °C, was detected in native submembrane fractions, but not in the immobilized preparations. It is suggested that the increased activity at high temperature results from conformational modifications not allowed in the immobilization matrix. The insensitivity of immobilized photosystem I particles to prolonged storage at 4°C and to strong light exposure, as well as their high electron-transfer rates, demonstrates that the immobilization procedure used can be successfully applied to submembrane fractions.