Some aspects of lamellar structure in various green leaf particles, indicated by oleic acid effects

Abstract

1. (1) The influence of oleic acid on “whole chloroplasts and large fragments”, isolated from spinach or endive leaves, was compared to that on Photosystem I (PS I) and PS I+II particles, probably stroma lamellae, isolated from the same leaves.

2. (2) Photochemical activity (Hill reaction and NADP+ photoreduction) in “whole chloroplasts and large fragments” was inhibited by oleic acid; the effect was detectable at an oleic acid/chlorophyll ratio of 1−2:1. This same ratio causes a measurable change in absorption and low temperature fluorescence spectra. Photochemical activities in PS I and to a lesser extent in PS I+II particles were much less sensitive to oleic acid. The same holds for the absorbance and fluorescence of these particles.

3. (3) Proteins were released from thoroughly washed lamellae of the various green leaf particles by a freeze—thawing procedure. The protein pattern, obtained on disk-gel electrophoresis, differed quantitatively in the various particles, the lamellae from PS I and PS I+II particles releasing a greater proportion of high-molecular weight proteins than those of “whole chloroplasts and large fragments”. Upon treatment of the lamellae with oleic acid, proteins from “whole chloroplasts and large fragments” deaggregated, whereas proteins from PS I and PS I+II lamellae were not, or much less, affected.

4. (4) It is concluded that oleic acid interacts with the proteins surrounding the chlorophyll in lamellae of “whole chloroplasts and large fragments”. In PS I and PS I+II stroma lamellae, proteins are protected in such a way that interaction with oleic acid is prevented.

Abbreviations: DPIP, 2,6-dichlorophenolindophenol; PS, photosystem