PhotosensitiveChenopodiumchlorophyll protein was purified by warming the complex in a boiling water bath, followed by passing it through a Sephadex column. The shape and position of the absorption band in the absorption spectrum of purified chlorophyll protein (HCP668) were the same as those of non-treated chlorophyll protein (CP668), except for a change in the protein band in the UV region. The chlorophyll protein retained a quarter of its original photoconvertibility after heat treatment for 25 min at 100°C. Results suggested that the chlorophyll-amino acid residue binding is very stable against heat, and that chlorophyll is protected from decomposition through the rigid binding.The photoconvertibility of HCP668, as well as CP668, depended strongly upon pH, with a pronounced decrease below pH 4 and above pH 6. Optimal convertibility was at pH 5. Above pH 12, convertibility vanished completely. However, pH-inhibited convertibility of HCP668 was recovered to its original level by returning the pH to neutral.Illuminalion of CP668 in D2O with red light caused a marked increase in light scattering. This reveals the occurrence of a conformational change of apoprotein, leading to aggregation.HCP668 was degraded by mechanical treatment to give a smaller sized photosensitive chlorophyll protein without loss of photoconvertibility. This small chlorophyll protein did not precipitate in a saturated (NH4)2SO4solution. The spectral properties of this complex were identical to those of HCP668 and CP668
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