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

• 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.