On the nature and possible functions of the 673- and 684-mμ forms in vivo of chlorophyll

The two major forms in vivo of chlorophyll, C 672 and C 683, are considered in the literature as corresponding to distinct arrangements or orientations of a single chlorophyll a molecule on the lipoprotein carrier. We used the spectral shift of Shibata (obtained in the dark after illumination of an etiolated material) as a method of separating the two forms. It was found, by means of difference spectrophometry, that the acetone extract of C 683 was not identical with that of C 672. Chromatographic analysis of the extracts showed further 3hat C 683 corresponded to the non-phytylated chlorophyllide a, while C 672 corresponded to the phytylated chlorophyll a. The time course of the transformation of chlorophyllide a to chlorophyll a was found to be parallel to that of the transformation of C 683 to C 672 (in the dark). We also found that the peak in vivo at 650 mμ of the young etiolated material corresponded to the non-esterified protochlorophyllide, while the peak at 635 mμ of the old etiolated material corresponded to the esterified protochlorophyll. The results prove that esterification determines the position of the principal red peaks in vivo of chlorophyll, probably because it changes the nature of the relations between the pigment and the lipoprotein complex. © 1965.