The light-induced signals visualized by the dashed lines originate from the [4-13C]-ALA-labelled Chl a and Phe a cofactors. Table 1 shows the chemical shifts of the observed signals and of literature values of light-induced signals from Chl a aggregates and isolated PS1 and D1D2 particles (Boender et al. 1995; Alia et al. 2004; Diller et al. 2005). With the possible exception of the

absorptive feature at 153.4 ppm (see below), all light-induced signals are of emissive nature. Fig. 5 13C MAS NMR spectra of fresh [4-13C]-ALA-labelled Synechocystis cells (a), and from isolated PS1 (b) and PS2 (c) particles from spinach at natural abundance. Spectrum A depicts a zoom of the aromatic selleck compound region of Spectrum 4A. Assigned centerbands

are visualized by dashed lines. In Spectrum B the absorptive signal from the sucrose buffer is marked by an asterisk. All three spectra have been obtained under continuous illumination by white light at a temperature of 235 K, magnetic field of 4.7 Tesla and MAS frequency of 8 kHz Aurora Kinase inhibitor Table 1 13C chemical shifts of the photo-CIDNP signals obtained at 4.7 T in comparison to literature Chemical shifts Chl a Assignment atom PS1 PS2 PS1 + PS2 σ ss a σb σc σd 170.0 19 167.1 E 166.8 A 166.9 E 162.0 14 160.4 E 162.2 A   155.9 1 154.8 E 156.0 A 154.8 E 154.4 6 154.3 A 149.8 E 154.0 16 152.6 E 151.6 A   150.7 4 149.9 E 149.2 A   147.2 11 147.2 E 147.7 A 147.6 E 147.2 9     146.2 8 144.2 E 146.0 A 144.2 E 138.0 3 138.6 E 137.4 A 138.6 E 136.1 2 ~136 E 136.0 A   134.0 12   133.9 A   133.4 7 ~132 E ~132.0 A   126.2 check 13   128.3 E 108.2 10 105.4 E 106.9 E ~104.5 E 102.8 15 104.7 E 98.1 5   97.9 E   93.3 20   92.2 E   51.4 17     53.9 aBoender (1995), data obtained from solid aggregates of Chl a. b Alia et al. (2004), data obtained from isolated PS1 particles from spinach. c Diller et al. (2005), data obtained from D1D2 particles of spinach. d This work, data

obtained from living Synechocystis whole cells containing both PS1 and PS2. Abbreviations: σ = chemical shift, A absorptive signal, E emissive signal As suggested by Table 1, most of the light-induced signals observed in Synechocystis cells appear at frequencies matching very well with those observed in isolated photosystems of spinach. For example, the signals at 166.9, 154.8, 147.6, 144.2, and 138.6 ppm are observed in isolated PS1 at very similar frequencies. This similarity suggests that photosystems are highly conserved even between different families. We also conclude that the isolation of the photosystems from plants did not significantly affect the electronic properties of the photochemical machinery. Spectra B and C in Fig. 5 show 13C photo-CIDNP MAS NMR data obtained from isolated PS1 and PS2, respectively, from spinach at natural abundance.