Chromatophores properties

It has become clear in the recent years that electron transfer chains of mitochondria, chloroplasts and some bacteria all contain a cytochrome be complex with very similar structural and functional properties (see Refs. 87, 176-180). Although we focus here on the mitochondrial Complex III, much information has, in particular, come from studies on the bacterial chromatophore system [8,87,176,178]. 

Paul, F. and Vignais, P. M. "Photophosphorylation in bacterial chromatophores entrapped in alginate gel improvement of the physical and biochemical properties of gel beads with barium chloride as gel-inducing agent" Enzyme Microb. Technol. 1980. 2 281-287. 

Fig. 7. Redox-titration ourves of the reaction centers in (A) Rb. sphaeroides, (B) Cf. aurantiacus, (C) Rp. viridis and (D) Chromatium. See text for other details. Figure sources (A) Dutton and Jackson (1972) Thermodynamic and kinetic characterization of electron-transfer components in situ in Rhodopseudomonas spheroides and Rhodospiriiium rubrum. Eur J Biochem. 39 500 (B) Bruce, Fuiler and Biankenship (1982) Primary photochemistry in the facultatively aerobic green photosynthetic bacterium Chloroflexus aurantiacus. Proc Nat Acad, USA. 79 6533 (C) Prince, Leigh and Dutton (1976) Thermodynamic properties ofthe reaction center of Rhodopseudomonas viridis. Biochim Blophys Acta. 440 625 (D) Cusanovich, Bartsch and Kamen (1968) Light-induced electron transport In Chromatium. II. Light-induced absorbance changes in Chromatium chromatophores. Biochim Biophys Acta 153 408.

Fig. 4. Difference absorption spectrum of photoreduced bacleriopheophytin (B

Alegria and Dutton used the Langmuir-Blodgett (LB) technique to deposit multiple (mono) layers of either the Rp. viridis reaction-center complex or of the corresponding chromatophores, in either case dispersed in a phospholipid matrix. The absorption spectmm of the LB-film was almost identical to that of the reaction center complex in solution, as shown in Fig. 10 (A), indicating that the in vitro properties of the photosynthetic apparatus are stable and essentially retained in the LB-films. The authors used a combination of redox potentiometry and absorption spectroscopy to identify the four Rp. viridis hemes and their redox potentials, and also determined their orientations by linear-dichroism measurements. 

An attempt to produce films of chromatophores was made by Clayton by drying aqueous suspensions onto solid supports. Dehydration of RC from Rhodopseudomonas sphaeroides alters their adsorption spectra, photochemical efficiency, fluorescence yield and reaction kinetics of electrons that return from reduced ubiquinone to oxidized bacteriochlorophyll. The properties of the air-dried films were restored by exposure to water vapour. It suggests that water helps to preserve an optimal configuration for photochemical efficiency. 

The development of photochemical active films of chromatophores has also involved the dialysis method. The photoactive sheet derived from Rhodopseudomonas viridis had characteristic properties of a three-dimensional thin crystal, showing linear dichroism in the absorption spectrum. That indicates a correct orientation in the arrangement of the chromatophores. 

Hamlin and Valencia washed orange pulp from several crop years were dried and analyzed. The range in values of total pectin, neutral detergent fiber and crude fiber were 26.0-45.6%, 15.8-31.0% and 9.9-20.6% respectively. In addition, detailed nutrient and dietary fiber analyses were obtained for selected samples. Functional properties such as flavor muting, chromatophore formation and oil holding properties were noted. Food processing modification yields a novel form of the hydrated pulp with extended functional properties. 

Since 1970 (1), the fluorescence properties of the acridine derivatives have been utilized to detect the energization state of biological membranes. On the other hand, these compounds have been pointed out as uncoupling agents in chromatophores membranes (2,3), spinach thylakoids (4,5) and submitochondrial particles (6). However, their mechanism of action remains to be fully clarified. The results reported here are the initial part of the study of this action on thylakoid membranes of Anabaena sp. 7119. 

A comparison between some of the properties of the ATP hydrolytic activity of the F.-ATPase purified from the two organisms and between the properties of the ATPase activity of the chromatophores from the same organisms is shown in Table 2. It is evident that th preparations of F show the highest activity with Ca as the divalent cation. HCOl is an activator in both cases, and or both preparations, diethylstilbestrol inhibits the Ca -promoted activity but... 

Among the enniatin antibiotics, beauvericin is the one characterized in greater detail. This carrier is most interesting with respect to an anion-dependence of its transport properties Moreover, in contrast to valinomycin, it is capable of com-plexing alkaline earth as well as alkali metal ions . A study of the effects of beauvericin on the conductivity of artificial lipid membranes in the presence of both mono- and divalent cations revealed a second-order relationship between conductance and antibiotic concentration Finally, Prince, Crofts, and Steinrauf detected an apparent charge of plus one for calcium in the beauvericin-mediated transport across bacterial chromatophore membranes... 

The aim of derivatization is to introduce into the molecule a suitable chromatophore or fluorophore. Precolumn and postcolumn derivatization are used in HPLC. Some of the reagents, their properties, separation conditions, and reactions are summarized below. 

Table 1. Composition and energy transfer properties of phospholipid-enriched chromatophores.

F. Parak, E. N. Frolov, A. A. Kononenko, R. L. Mssbauer, V. I. Goldanskii, A. B. Rubin, Evidence for a correlation between the photoinduced electron transfer and dynamic properties of the chromatophore membranes from Rhodospirillum rubrum, FEBS Lett. 117 (1980) 368-372. 

The low temperature spectroscopic properties of the reaction centers RC s) of Rps, V lV idis in crystalline form have been compared with those of reaction centers in suspension and chromatophores. At. 4.2 K and 1.5 K the fluorescence spectrum of the dithionite reduced chromatophores exhibits a band at 1065 + nm. This emission was used to obtain FDMR spectra of the RC pR - state, yielding 1d = (160 + 2)x 10" cm-l,[E = (38 + 1)... 

Resonance Raman (RR) spectroscopy can be used to yield information about ground state interactions assumed by bacteriochlorophyll a (BChl) in antenna structures of RhodospzvvttaZes, This technique permits investigations of the local environment of BChl molecules within the intracytoplasmic membrane and within antenna complexes, and, in particular, of their bonding with their host polypeptides (Lutz, 1981). Using this method, we studied chromatophores and antenna complexes of several species of Rhodospiritlaceae and Chromatiaoeae in order to compare, on a structural basis, complexes defined by their biochemical and electronic properties. 

Energy-transducing processes in the cytoplasmic membrane of Rps. sphaeroides such as electron-transfer-linked proton translocation, and solute transport can be studied in whole cells or in isolated membrane vesicles wnich have retained their functional properties. In these latter systems the membrane-bound activities can be separated from activities in the cytoplasm. Two procedures have been described for the isolation of membrane vesicles. Mechanical disruption of the cells by sonication. French-press treatment or grinding with aluminium yields so-called chromatophores which are mainly derived from the intracytoplasmic membranes (Oelze, Drews, 1972). 

Michels PAM and Konings WN (1978) Structural and functional properties of chromatophores and membrane vesicles from Rhodopseudomonas sphaeroides, Biochim.Biophys.Acta 507, 353-368. 

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