E. halochloris thylakoids and spheroplasts were treated with trypsin, thermolysin or proteinase K to determine which proteins are exposed at the different membrane surfaces. Based on SDS polyacrylamide analysis, all 9 polypeptides are exposed on the cytoplasmic side. Only one (28 kDa) is accessible from the periplasmic side. This polypeptide is generally isolated as the H-subunit of the reaction centers of photosynthetic bacteria, but is in the case of E. halochloris rather isolated with the antenna (B 800/1020) (Steiner and Scheer, Biochim . Biophys. Acta 807, 278, 1983).
Proteolysis is accompanied by a shift of the absorption band at longest wavelengths from 1020 to 960 nm (B 800/960), which upon standing is shifted further to 680 nm (“B” 800/680). The spectral changes are similar to the ones reported earlier for treatment with acid, and are also inducible with urea. The correlation of SDS-PAGE and absorption spectroscopy shows, that the chroophores absorbing at 1020 nm are transformed sim ultaneously with the degradation of the 6.5 kDa (=α) polypeptide.
Fluorescence detected ODMR measurements in zero field on the triplet states of light harvesting (LH) pigments in chromatophores from Rhodopseudomonas sphaeroides R 26.1 and Rhodopseudom onas capsulata A1a+ are reported. In both cases at least two distinct triplet states in the antenna system with zfs values of D between 209 and 217 and E between 56 and 67 x 10-4 cm-1 are observed.
Fluorescence detected ODMR measurements in zero field on the triplet state of the reaction center in whole cells of Rhodopseudomonas viridis, in reaction center solution and in reaction center crystals are reported. In solution and in the crystal a sign reversal of the F-ODMR signals is observed by variation of the wavelength of detection. The signs of the signals are interpreted with the Vredenberg-Duysens relation.