Independent fluorescence emission of the chlorophyll spectral forms in higher plant Photosystem II (original) (raw)

1992, Biochimica et Biophysica Acta (BBA) - Bioenergetics

Key word~: Fluorescence emission: Numerical decon~olutkm: (.'hh)rophql spectral lorms: l.ight-hdr~c~ting chhm~ph~ll a/h prolcm ct)mplex lk ISpinach and barley th_qakoid~,) Room-temperature steady-state emission and Q, absorption spectra of light-hancsting chlorophyll a/b protein complex 11 (LHCII) isolated from spinach have been analysed in terms of a linear combination of as.~mmctric gaussian hands. To imestigate a possible correspondence between the absorption and emission bands, the thermal emission specs um of each absorption hand has been calculated. It is demonstrated that the calculated fluorescence bands correspond closeb lo those obtained b) gaussian deconvolution. It is thus possible to associate an emission band ~ith each absorbing chlorophql spectral species: ,,a~ Cbl~5~" "". Chl~. 3, 67(I {17g l~n4 t,q5 Chl~7 z, Chl~sq~. Chl~x7, Chlt,,~7 (Chl'/,, is the spectral spccics that absorbs with maximum at ~a~clcngth n and emits u, ith maximum at wavelength m) and to interpret the emission spectrum of LHCII as a linear combination of the emission spectra of each absorbing chlorophyll spectral species. In particular, the correspondence between the 684 nm and 695 nm absorptlon bands and the emission bands with maximum at 087 nm and 697 nm lends support to the presence of long ~a~clcngth Chl u spectra forms in LHCII, the external antenna of PS !!. A close correlation between the emission and absorption gaussian bands is also fuund in the analysis of the room temperature absorption and emission spectra of ~uch membrane preparation as BBY-grana from spinach and thylakoids prepared from barley wild type and the cblorina f2 mutant (lacking LHCII). On the basis of these data, the commonly observed 5-7 nm wavelength difference between the absorption and emission spcctra maxima of chlorophyll containing biological membranes is interpreted in tcrm~ of (al the Stokc:, shifts of the single spectral forms together with (b) the increased emission contribution of the longer wavelength form~ to lhc emission spectrum caused by energy transfer.