Uranous ion oxidation and carbon dioxide fixation byThiobacillus ferrooxidans

The stoichiometric oxidation of uranous-to uranyl-uranium byThiobacllus ferrooxidans is demonstrated. Fixation of¹⁴CO₂ and the effect of inhibitors demonstrate that energy is conserved during the oxidation and used for energy-dependent reverse electron flow and carbon dioxide fixation.Abbreviations HOQNO 2-heptyl-4-hydroxyquinoline-N-oxide - 8-HQ 8-hydroxyquinoline - TTFA thenoyltrifluoroacetone     

Photosynthetic apparatus of chilling-sensitive plants IX. The involvement of α-tocopherol in the electron transport chain and the anti-oxidizing system in chloroplasts of tomato leaves

1. The role of tocopherols in tomato chloroplasts from fresh, cold and dark-stored as well as stored and illuminated leaves was studied.2. The cold and dark storage of leaves results in a loss of chloroplast α- and γ-tocopherols of about 30–40% accompanied by an increase in chloroplast δ-tocopherol of about 40%. On illumination of stored leaves, an elevation of α- and γ-tocopherol level to about 110 and 95% of the control, respectively, occurs, whilst δ-tocopherol content is not affected.3. Experiments performed with 2,2-diphenyl-1-picrylhydrazyl-treated chloroplasts show that only about 70% of total α-tocopherol is functionally active in the electron transport of Photosystem II between the diphenyl-carbazide (DPC) donation site and the inhibition site of DBMIB.4. A small amount of α-tocopherol quinone (about 10% of α-tocopherol content) is found in chloroplasts from fresh, fresh and illuminated as well as cold and dark-stored tomato leaves, whereas the illumination of the latter increases the chloroplast α-tocopherol quinone content 3-fold. Moreover, following the illumination of chloroplasts from cold and dark-stored as well as stored and illuminated leaves, the oxidation of exogenous α-tocopherol to α-tocopherol quinone is 2-fold faster then in chloroplasts from fresh leaves.5. The primary product (‘α-tocopheroxide’) formed during the α-tocopherol oxidation by illuminated chloroplasts was identified as 8a-hydroxy-α-tocopheron.6. Exogenous α-tocopherol inhibits the lipid photoperoxidation by about 40–50% in chloroplasts from all three kinds of tomato leaf.7. The results seem to suggest that chloroplast α-tocopherol is involved in both electron transport of PS II and antioxidizing system of chloroplasts.     

Leishmania mexicana: Energy metabolism of amastigotes and promastigotes

The utilisation of substrates by Leishmania mexicana amastigotes and promastigotes differed significantly. The rates of uptake and catabolism of nonesterified fatty acids were up to 10-fold higher with amastigotes. Almost all the available exogenous fatty acids were consumed during amastigote transformation and by stationary phase of promastigote growth. The results suggest that fatty acids are important energy substrates for amastigotes, whereas promastigote utilisation may reflect the requirement for these substrates in anabolism. Glucose was utilised by amastigotes and promastigotes but the rate of catabolism was up to 10-fold higher in promastigotes. Uptake of glucose occurred throughout amastigote transformation and growth in vitro of promastigotes. High-subpassage promastigotes exhibited markedly lower glucose but higher amino acid utilisation than low-subpassage promastigotes. Asparagine, glutamine, glutamate, leucine, lysine, methionine, and threonine were consumed in large quantities by amastigotes and promastigotes, whereas alanine and glycine were excreted. Proline was catabolised to CO₂ by amastigotes and promastigotes but only at a low rate, and it was excreted in large amounts throughout promastigote growth. The major end products of energy metabolism were found to be CO₂ and succinate with both forms of the parasite and there was a secretion of up to 12 and 16% of the total protein synthesised by transforming amastigotes and growing promastigotes, respectively. Catabolism in amastigotes and promastigotes was found to be sensitive to cyanide and amytal, whereas 2-mercaptoacetate and 4-pentenoate primarily affected β-oxidation in the amastigote.     

Flux of reduced chemical constituents (Fe2+, Mn2+, NH inf4 sup+ and CH4) and sediment oxygen demand in Lake Erie

Sediment pore water concentrations of Fe²⁺, Mn²⁺, NH _inf4 ^sup+ and CH₄ were analyzed from both diver-collected cores and anin situ equilibration device (peeper) in Lake Erie's central basin. Sediment oxygen demand (SOD) was measured at the same station with a hemispheric chamber (including DO probe and recorder) subtending a known area of sediments. The average SOD was 9.4 mM m⁻² day⁻¹ (0.3 g m⁻² day⁻¹). From pore water gradients within the near-surface zone, the chemical flux across the interface was calculated indirectly using Fick's first law modified for sediments. These calculations, using core and peeper gradients, always showed sediment loss to overlying waters, and variations between the two techniques differed by less than an order of magnitude for Fe²⁺ and CH₄. The transport of these reduced constituents can represent a sizeable oxygen demand, ranging from less than 1% for Fe²⁺ and Mn²⁺ to as high as 26% for NH _inf4 ^sup+ , and 30% for CH₄. The average flux of these constituents could account for about a third of the SOD at the sediment-water interface of this station.     

Succinate oxidation by coupled potato tuber mitochondria followed by rapid scan spectrometry

Oxidation of succinate by potato tuber mitochondria has been investigated from aerobiosis to complete anuerobiosis. Difference spectra of the various steps were recorded by a rapid scan spectrometer delivering averaged spectra every 3 s in the range 380 to 630 mm. The transitions between state 3 and 4 resulted in large redox changes, essentially for the b cytochromes, and in significant changes in the spectral baseline (light scattering). At anaerobiosis the cytochromes c, c₁ and a were reduced while cytochrome a, remained oxidized. – Addition of uncouplers in aerobiosis induced oxidation of the b cytochromes, and when anaerobiosis occurred cytochromes c, c₁a and a₃ were reduced simultaneously. When uncouplers were added in anaerobiosis a partial oxidation of the b cytochromes and the reduction of cytochrome a₃ were observed. These results are interpreted as the building up of a membrane potential, maximal in state 4 and stable after anaerobiosis. The cytochromes buried in the membrane equilibrate with the membrane potential, and their redox states are sensitive to the changes. Variations of membrane potential also induce changes in the light scattering by the mitochondrial membrane.     

Oxygen consumption by Campylobacter sputorum subspecies Bubulus with formate as substrate

The kinetics of oxygen utilization by the microaerophile Campylobacter sputorum subspecies bubulus was studied. With formate as substrate two enzyme systems were found to be responsible for electron transfer between formate and oxygen. In the case of lactate oxidation one enzyme system could account for the activity measured. One of the formateoxidizing systems possessed a high affinity for oxygen [K _m(O₂)=approx. 4M O₂]. From inhibitor studies it was concluded that a respiratory chain was involved in its activity. Respiration by this system must be responsible for proton translocation and electron transport-linked phosphorylation at formate oxidation. The other enzyme system had an extremely low affinity for oxygen [K _m (O₂)=approx. 1 mM O₂]. It was tentatively identified as the H₂O₂-producing formate oxidase previously found in C. sputorum. The H₂O₂ production by this enzyme is implicated in an explanation of the microaerophilic nature of C. sputorum. Sensitivity of formate dehydrogenase to H₂O₂ was demonstrated. The influence of the formate concentration on aerobic formate oxidation was determined. The pH- and temperature dependencies of oxygen uptake with formate as substrate were examined at airsaturation and at a low dissolved oxygen tension.Abbreviations TL medium tryptose-lactate medium - TF medium tryptose-formate medium - HQNO 2-n-heptyl-4-hydroxyquinoline N-oxide - SHAM salicylhydroxamic acid - DCPIP 2,6-dichlorophenolindophenol     

Studies on the origin of the near-infrared (800–900 nm) absorption of cytochrome c oxidase

Data are presented which were collected in the course of the past ten years and bear on the correlation of absorbance at 800 nm and the EPR signal at g = 2 (‘copper signal’) of cytochrome c oxidase in various states of oxidation and ligation. Both EPR and optical reflectance spectra were obtained at low temperature (?170 to ?190°C). For some sets of samples spectra were recorded in the range 500–1100 nm. A particular effort was made to study this correlation with what are called ‘mixed valence’ states (Greenwood, C., Wilson, M.T. and Brunori, M. (1974) Biochem. J. 137, 205–215), when cytochrome a and the EPR-detectable copper are thought to be oxidized and the other components reduced and vice versa. These data show no evidence that the copper component of cytochrome oxidase which has so far not been detected by EPR makes a contribution to the absorption between 800 and 900 nm exceeding 10–15% of the total, which is close to or within the error of the respective measurements. For the various states of the oxidase examined in this work the 700–800 nm region did not appear to be more useful than the 800–900 nm region for determining the state of the EPR-undetectable copper in a reliable way. These conclusions are in agreement with results presented previously from other laboratories concerning the relationship of optical (approx. 800 nm) and EPR spectroscopic (g = 2) data obtained with the enzyme.     

Dynamics of energy substrates in the haemolymph of Locusta migratoria during flight

In the two-fuel system for flight of the migratory locust, the haemolymph carbohydrate concentration falls during flight periods of up to 1 hr, the decrease being greater in case the pre-flight carbohydrate level is higher. The increase in the lipid concentration from the onset of flight is virtually independent of the initial lipid concentration. Flight intensity affects these changes in substrate concentrations: the carbohydrate level decreases more rapidly if flight speed is higher, whereas the increase in lipid concentration is delayed at higher flight speeds. Respiratory carbon dioxide production is elevated rapidly during flight and reaches over eight times the resting level. From the rate of ¹⁴CO₂ production after labelling of the haemolymph diglyceride pool it is concluded that diglycerides contribute to providing the energy for flight from the earliest stage of flying activity; diglyceride oxidation increases until maximum utilization is attained after some 45 min of flight. The decline in haemolymph carbohydrate concentration due to flying activity results in a decrease of haemolymph osmolarity. Free amino acids, particularly taurine, increase markedly in the haemolymph during flight; yet their concentration only partially counterbalances the fall in haemolymph osmolarity.     

A new amine,stizolamine, from Stizolobium hassjoo

A new pyrazine derivative, stizolamine (1-methyl-3-guanidino-6-hydroxymethylpyrazin-2-one), has been isolated from seeds of Stizolobium hassjoo. This amine, which has a blue fluorescence, gives guanidine, N-methyl-alanine, oxalic acid, alanine and glycine on treatment with 6 N HCl. The permanganate oxidation product of stizolamine is 4-amino-6-methylcarbamoyl-1,3,5-triazine-2-carboxylic acid.