THE PIGMENT-PROTEIN COMPOUND IN PHOTOSYNTHETIC BACTERIA I. THE EXTRACTION AND PROPERTIES OF PHOTOSYNTHIN Bx

It has been known since Herlitzka's work in 1912 that it is possible to prepare colloidal solutions of chlorophyll by grinding plant tissue. Lubimenko (1927) found that some leaves (Funkia and Aspidistra genuses) gave on extraction with water clear stable green solutions which contained all the chlorophyll of the original leaf in combination with a protein. Other leaves gave extracts which contained water soluble protein-combined chlorophyll but which were not stable, while still a third group of plants had the chlorophyll attached to an insoluble protein. He showed that the protein-chlorophyll solutions had the same absorption bands as the living leaf. Mestre presented additional evidence that indicated the occurrence of chlorophyll-protein compounds in green plants. Wald has measured the absorption curves and studied the protein properties of such solutions. Stoll and Wiedermann have made a careful study of the methods of preparation and the properties of these compounds, and Smith has published an absorption curve and preliminary centrifugal studies of the protein-chlorophyll solution extracted with digitalin from spinach indicating a molecular weight of over 70,000 in solution with digitalin. Incidental to the study of plant virus proteins Price and Wyckoff and Loring, Osborn, and Wyckoff have prepared pure solutions showing sharp sedimentation boundaries of the chlorophyll-protein compounds from peas and beans. Sedimentation constants of 77 X 10 -13, 117 X 10 -13, and 54 X 10 -13 were found. These studies all tend to show that in the living leaf chlorophyll occurs in combination with a protein much in the same way that heroin is attached to a protein forming hemoglobin. The protein apparently varies from species to species perhaps even more than does giobin from different species of animals. As Stoll and Wiedermanr~ as well as Smith have pointed out, 469