Particles iron/sulfur-containing

High temperature combustion at a nearly stoichiometric fuel-air ratio produced substantially different trends. While the behavior of sulfur and zinc did not change significantly, the fine particles contained large amounts of aluminum, silicon, and calcium. Iron made up a relatively small amount of the fine particles in this case. The difference between the two experiments is probably due to increased vaporization of the refractory species at higher combustion temperatures. The relative decrease in fine particle iron may result from dilution with silicon and, to a lesser extent, aluminum and calcium. 

Interesting results have been obtained for mitochondrial particles prepared from the yeast Candida utilis grown in a medium containing 57Fe. This allowed hyperfine interactions for 57Fe atoms in the ESR spectrum to be characterized. Certain of the iron-sulfur proteins are also proton pumps. 

Any particle, unique or consistent, may also contain one or several of the following and only the following elements silicon, calcium, aluminum, copper, iron, sulfur, phosphorus (rare), zinc (only if copper > zinc), nickel (rare, only with copper, zinc), potassium, chlorine. The presence of some tin is a possibility in obsolete ammunition. 

B Ke, K Sugahara and ER Shaw (1975) Further purification of Triton Subchloroplast fraction I (TSF-I particles). Isolation of a cytochrome-free high-P700 particle and a complex containing cytochromes f and b, plastocyanin and iron-sulfur protein s). Biochim Biophys Acta 408 12-25... 

R Cammack and MCW Evans (1975) EPR spectra of iron-sulfur proteins in dimethylsulfoxide solutions e vi-dence of chloroplast photosystem I particles contain 4Fe-4S centers. Biochem Biophys Res Commun 38 1114-11188... 

Fig. 10. (A) Flash-induced absorbance changes at 387,430 and 455 nm in a sample of PS-I particles from Synechococcus sp. under a mild reducing condition (ascorbate+ DCIP) or containing ferricyanide (FeCy) (B) difference spectra constructed from the aA amplitudes at the beginning and end ofthe 200-ns phase, i.e., at 5 ns and 1.6 /iS, respectively. The spectrum in the inset of (B) represents AA [P700 A,-] - [P700 A,] measured at 10 K (taken from Fig. 4 above). The dotted-line difference spectrum in (B) is that for [P700 -P700]. Figure source Brettel (1988) Electron transfer fifom Ay to an iron-sulfur center with tw=2O0 ns at room temperature in photosystem I. Characterization by flash absorption spectroscopy. FEBS Lett239 95,96.

Photochemical activity of FeS-X in PS-1 particles with all the phylloquinone removed was also demonstrated in a sample of P700-enriched particles (Chl/P700=13) in a pH=10 buffer containing 8204 to pre-reduce FeS-A/FeS-B. Continuous illumination ofthe sample at 9 K induced the formation ofan EPR line at g 1.78 that decayed in the dark. This result appears to suggest that FeS-X can undergo reversible photoreduction in PS-I particles without any phylloquinone and with its terminal acceptors FeS-A/B prereduced chemically, just as in untreated particles containing phylloquinone. The authors explained these results by proposing that Aq may be in close proximity to the iron-sulfur centers and can thus transfer electrons directly to them even in the absence of A,. 

The hexane-extracted particles that still retained one Q per P700 retained 81 % of the NADP -reduction activity ofthe unextracted control. In contrast, particles extracted with hexane-0.3% methanol had all the OQ removed and the NADP -reduction activity was completely lost. The NADP -reduction activity of the hexane/methanol-extracted particles could be reactivated by readdition of exogenous but only when the hexane extract was also added back. Exogenous OQ alone, even at a rather high concentration, could not reactivate NADP photoreduction and the hexane extract alone was also not effective, presumably because of its low Q content. The nature ofthe component in the hexane extract that contributes to reconstitution is as yet unknown. As the hexane extract contains OQ,chlorophylls,carotenoids,lipidsand other nonpolar molecules, some critical component is probably needed to ensure the correct membrane structure for binding ferredoxin and/or Fd-NADP -reductase. This conclusion is supported by the fact that activity of prior terminal acceptors such as the iron-sulfur centers do not require the hexane extract. 

Fillers must be free of sulfur-containing impurities, iron, and zinc. In order to minimize reduction in clarity, fillers should have a fine particle size and an index of refraction close to that of the PVC resin. If opacity is desired, however, high refractive index fillers such as talc or calcium carbonate can be used to minimize the amounts of the more expensive titanium dioxide opacifying pigment required. 

The reducing side of photosystem I (PS I) reaction center of oxygenic photosynthetic organisms is known to consist of five different acceptors (1,2). The primary electron acceptor, called AO, is assumed to be a monomeric chlorophyll molecule. An electron is passed from AO to a secondary acceptor A1 which is believed to be phylloquinone. The electron transfer involves three different iron-sulfur centers, called FX, FB and FA. PS I high-molecular-mass subunits (about 82 kDa) are known to contain AO, Al, and FX as well as P700 (1,2). FA and FB are believed to be located in a small polypeptide of about 9 kDa (3,4). As we demonstrated elsewhere (5), heat treatment of spinach PS I particles in the presence of ethylene glycol (EG) caused the selective destruction of the iron-sulfur centers and led to the dissociation of polypeptides from the particles. A small subunit of about 5 kDa was closely associated with large subunits under this treatment. In this paper, we present the N-terminal amino acid sequence of the 5 kDa polypeptide. 

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