NMR evidences of the chlorophyll a-WATER interaction

The nuclear magnetic resonance spectra of chlorophyll a in nonpolar solvents (carbon tetrachloride, chloroform) are presented and interpreted in terms of dimer interaction. In order to obtain information on the arrangement of chlorophyll a in vivo, the spectral properties of chlorophyll a aggregates - prepared either in the presence or in the absence of water - were compared. The aggregation maps were pictured from methanol-d4 titration data of dehydrated and nondehydrated chlorophyll a. The titration of chlorophyll a with water was done by using samples with different degrees of dryness. From the water and methanol-d4 titration data, similar changes of the nmr spectra were obtained. On the account of these results, an evaluation was made of the maximum amount of water lost by the chlorophyll a during the dehydration process. (author)