Stability of etiochloroplasts isolated from pine cotyledons as studied by means of low temperature absorption and fluorescence spectroscopy.

77 K absorption and fluorescence spectra are measured during incubation of etiochloroplast isolated from pine cotyledons and suspended in buffers with or without various co-factors (GSH, ATP, CoA Abbreviations: PChl(ide) = protochlorophyll(ide); PChlideF657 = protochloro-phyllide-lipoprotein complex with fluorescence maximum at 657 nm; Chl(ide) = chlorophyll(ide); PEG = polyethylene glycol; DCIP = 2-6-dichlorophenol indophenol; ALA = \gd aminolevulinic acid; ATP = adenosine 5\t' triphosphate; CoA = coenzyme A; NADPH = nicotinamide-adenine dinucleotide phosphate, reduced. ) and NADPH. It is shown that, in the absence of co-factors, rapid spectral changes due to denaturation of the protein-pigment complexes occur. The spectral changes differ according to whether denaturation occurs in the light or in the dark. The rate of denaturation of the Ch1-protein complexes is significantly lowered when co-factors are added and a protective effect of NADPH on the PChlide-protein complexes was observed.