Analysis of the optical absorbance spectra of D1-D2-cytochrome b-559 complexes by absorbance-detected magnetic resonance: Structural properties of P680

摘要: Abstract Absorbance-detected magnetic resonance (ADMR) spectroscopy was applied to D1-D2-cyt b-559 complexes isolated by different isolation methods. The triplet of the primary donor (3P680) does not show a homogeneous response microwaves; maximum triplet-induced long-wavelength bleaching varied from 678 685.5 nm, whereas |D|-value changed 0.0293 0.0281 cm−1 with increasing monitoring wavelength within band. |E|-value 0.0043 for all detection wavelengths. Triplet-minus-singlet (T — S) difference spectra monitored ADMR did any indication dimeric structure P680. Linear dichroic (LD) P680 yielded angles between optical Qy transition moments and x-, y- z- axes 49° ± 2°, 32° 4° 65° 3°, respectively. From LD-ADMR chlorophyll (Chl a) in vitro corresponding 55° 6° 43° 7° x- y-axes, respectively, were obtained. With value 30° 3° angle plane spanned y-axes membrane obtained Van Mieghem et al. (Van Mieghem, F.J.E., Satoh, K. Rutherford, A.W. (1991) Biochim. Biophys. Acta 1058, 379–385), it follows that optical-transition moment makes an 36° 8°. This is quite calculated crystal or monomeric bacteriochlorophyll bacterial reaction centers (RCs). close correspondence relative orientation both 3P680 3Chl as determined shape T S spectra, which reflect Chl state, concluded has little, no interaction other pigments complex. Our observations contrast strikingly our previous experiments on RCs purple bacteria (Lous E.J. Hoff, A.J. (1988) Proc. Natl. Acad. Sci. USA 84, 6147–6151) strongly suggest analogy complex RC observed biochemical components extend conformation pigments. An additional ascribed pheophytin (Pheo) observed, having |D| = 0.0338 cm− |E| 0.0021 cm−1. due Pheo-triplet maximal at 680.0 0.2 nm; least one Pheo present its absorption this wavelength. Double-resonance showed formation 3Pheo depends population 3P680. Simulation Gaussian bands revealed three types P680, two could be freezing slightly variations basically similar conformation. One type differs considerably respect width bleaching, spectrum influence a-triplet likely have two. degraded samples, composed mixture intact characterised below 674 differ fresh which, room temperature, 676 nm. Together observation yield samples much lower, indicates completely inhibited.