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pubmed:abstractText |
A Fourier transform infrared (FTIR) difference spectrum upon photooxidation of the accessory chlorophyll (Chlz) of photosystem II (PS II) was obtained at 210 K with Mn-depleted PS II membranes in the presence of fericyanide and silicomolybdate. The observed Chlz+/Chlz spectrum showed two differential bands at 1747/1736 and 1714/1684 cm-1. The former was assigned to the free carbomethoxy C = 0 and the latter to the keto C = 0 that is hydrogen-bonded or in a highly polar environment. Also, the negative 1614 cm-1 band assignable to the macrocycle mode indicated 5-coordination of the central Mg. The negative 1660 cm-1 band, possibly due to the strongly hydrogen-bonded keto C = 0, may suggest oxidation of one more Chlz, although an alternative assignment, the amide I mode of proteins perturbed by Chlz oxidation, is also possible.
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