Experiments on the extraction and photoconversion of chenopodium chlorophyll protein CP 668

Abstract

1. 1. The amount of extractable, photoconvertible, protein-chlorophyll complex CP 668 from Chenopodium album leaves was found to be very variable, depending on site and day of leaf collection.

2. 2. Photoconversion of CP 668 into a 740-nm absorbing form probably does not occur in intact leaves; CP 668 in its extracted form is concluded to be an artifact.

3. 3. CP 668 may be separated from other “soluble”, non-photoconvertible material absorbing at about 668 nm by precipitation with polyethyleneglycol

4. 4. CP 740, the phototransformed form of CP 668, does not show any clear absorption band in ethanol. It is suggested that the 740-nm band arises from interaction of photo-oxidized chlorophyll with protein.

5. 5. Photoconversion of CP 668 into CP 740 is promoted by lowering the pH from about 8 to 6.

6. 6. Photoconversion of CP 668 is inhibited by β-mercaptoethanol and KCN; it is slightly inhibited in Tris buffer as compared with phosphate buffer.

7. 7. In discussing the experiments it is suggested that CP 668 is a denatured form of a native chlorophyll-protein complex containing essential SH groups.