SOME SPECTRAL CHARACTERISTICS OF CHLOROPHYLL c FROM TRIDACNA CROCEA ZOOXANTHELLAE

¹ CSIRO Marine Laboratory, Cronulla, N.S.W., Australia
² Tokugawa Institute for Biological Research, Mejiromachi, Tokyo, Japan

Absorption spectra of chlorophyll c prepared from Tridacna zooxanthellae (and now known to be the component chlorophyll c₂) were scrutinized with special attention to the ratio of the Soret to the red band in methanol and acetone and the spectral changes resulting from the addition of water, acid and alkali. The band ratios of the chlorophyll c preparation determined with methanol and with acetone as the solvent were 9.4, but the ratios determined in aqueous mixtures of these organic solvents were appreciably lower than this value, which was interpreted as due to polymerization of chlorophyll c molecules. When chlorophyll c in aqueous acetone was acidified with HC1, the spectrum was changed to a spectrum with a sharp Soret band which is regarded as the spectrum of pheophytin c. When acidified in aqueous methanol, however, the Soret band dropped remarkably, being accompanied first by a slight shift of band to longer wavelengths and next by a greater shift to shorter wavelengths. These two steps of band shifts were interpreted as due to dimerization and further polymerization of dimeric chlorophyll c, respectively. The alkaline hydrolysis with NaOH and that with ammonia gave different spectra. These spectral characteristics of chlorophyll c, isolated from Tridacna crocea zooxanthellae, will help to resolve controversies over the spectral properties of this pigment, especially those caused by unrecognized polymerization.