The mean P50 values of the respiratory pigments were determined at 0 mm Hg CO2 and 28 °C (the average environmental temperature of all the species). Comparison of these data adjusted to the individual mean physiological pH indicate an increase in P50 with terrestrialization, perhaps related to the greater abundance of oxygen in the aerial than in some the aquatic habits, and the progressive elaboration of lung breathing with terrestrialization.
The Bohr shifts (Δ log P50/ΔpH) were determined (using different PCO2 values to vary pH) and were found to decrease with terrestrialization, perhaps in adaptation to an associated rise in internal PCO2 (6–8-fold between the aquatic Callinectes sapidus Rathbun and the terrestrial Cardisoma guanhumi Latreille and probably resulting from progressive gill reduction.
The temperature shifts (ΔH cal/mol) of the haemoeyanins were found and it is suggested that they diminish with increasing evironmental temperature and temperature fluctuation accompanying terrestrialization. 相似文献
The photoinduced changes near 700 nm with Spirulina membranes are reversible and seem to be synchronous and related to the bleaching of three different pigments. This spectral diversity for photosensizable pigments is comparable with the spectral heterogeneity of the major forms of the bulk chlorophyll. It is assumed that these pigments may play the same functional role. This assumption may be related to a possible heterogeneity of Photosystem I centres recently detected by Breton using linear dichroism method (Breton, J. (1977) Biochim. Biophys. Acta 459, 66–70). 相似文献
The behaviour of the catalytic membranes has been studied in a bioreactor operating under non-isothermal conditions as a function of the applied temperature difference ΔT.
Comparison of the enzyme reaction rates under isothermal and non-isothermal conditions resulted in percentage activity increases (PAI) and reduction of the production time (τr) proportional to the size of the applied ΔT. Both these parameters increased with the increase of the spacer length.
Results have been discussed in the frame of reference of the process of thermodialysis which reduces the limitations to the diffusion of substrate and reaction products across the catalytic membrane, limitations introduced by the grafting and immobilisation process.
The advantages of employing non-isothermal bioreactors in biotechnological productive processes have been outlined. 相似文献
The b-type cytochrome in Chromatium has an -band maximum at 560 nm and a midpoint oxidation-reduction potential of −5 mV at pH 8.0. The b-type cytochrome in Chlorobium has an -band maximum at 564 nm and an apparent midpoint oxidation-reduction potential near −90 mV.
Chromatophores isolated from both Chromatium and Chlorobium cells catalyze a photoreduction of cytochrome b that is enhanced in the presence of antimycin A. Antimycin A and 2-n-heptyl-4-hydroxyquinoline-N-oxide inhibit endogenous (but not phenazine methosulfate-mediated) cyclic photophosphorylation in Chromatium chromatophores and non-cyclic electron flow from Na2S to NADP in Chlorobium chromatophores. These observations suggest that b-type cytochromes may function in electron transport reactions in photosynthetic sulfur bacteria. 相似文献
The daily ammonia production of C. crangon was 16 μmol NH3 · g −1 wet wt · day −1 in winter and 40 μmol in summer. A gross production of 12 μmol NH3 · m−2 · day −1 and 300–700 μmol μ m−2 · day−1, respectively, could be expected in the two ecosystems studied. This would account for 5% (winter) and 2–4% (summer) of the total NH+4 flux at the sediment-water interface. The contribution of the excretion of all macrofauna to the NH+4 flux from the sediment is discussed. 相似文献
The infrared spectra in the 1600–1800 cm−1 region clearly show the existence of a coordination interaction between the C-9 ketone oxygen function of one molecule and the central magnesium atom of another molecule. Infrared spectra in the OH stretching region (3200–3800 cm−1) provide a valuable test of the water content in the samples.
The analysis of the absorption and circular dichroism spectra of protochlorophyll a and vinylprotochlorophyll a in carbon tetrachloride demonstrates the existence of a monomer-dimer equilibrium in the concentration range from 10−6 to 5 · 10−4 M. The dimerization constants are (6±2) · 105 1 · M−1 for protochlorophyll a and (4.5±2) · 105 1 · M−1 for vinylprotochlorophyll a at 20 °C. The deconvolution of visible spectra in the red region has been performed in order to obtain quantitative information on the dimer structure. Two models involving a parallel or a perpendicular arrangement of the associated molecules are considered.
From 1H NMR spectra, it appears that the region of overlap occurs near ring V, in agreement with the interpretation of the infrared spectra. 相似文献
The internal cytochrome c participates in redox reactions with both soluble and insolubilized cytochrome c present externally, and with external cytochrome b5. No reaction was observed with plastocyanin, cytochrome c oxidase or NADPH-cytochrome c reductase.
A study has been made of the reaction of the internal cytochrome c with the low molecular weight reductants, ascorbate and glutathione. Complex kinetics are observed with both reagents: with ascorbate the results are best explained by assuming the existence, in the membrane, of a redox-active species able to undergo dedimerization. A protein bound disulfide bond would satisfy the requirement. 相似文献
The time course of fluorescence in chromatophores was separated into two phases, i.e. an initial rapid rise (ƒi) and a subsequent slow increase towards a steady level of emission (ƒv). The ƒi and the ƒv components showed different emission spectra having different peak position. The ƒv component was emitted from the longest wavelength-absorbing form of bulk bacteriochlorophyll (B890), the ƒi component from both B890 and B850.
The magnitude of the ƒv component depended on experimental conditions controlling the states of the cyclic electron transport in chromatophores, including changes in levels of redox potential of the medium, additions of electron donors and inhibitors. The magnitude of the ƒi component was not affected by these experimental conditions. It was, therefore, concluded that only the ƒv component is related to the cyclic electron transport, and that the magnitude of ƒv is controlled by the oxidation-reduction state of the primary electron acceptor for the photochemical reaction center in chromatophores. 相似文献
The soils varied from moderately rich sandy soils to rich sandy or loamy soils. On the two sandy soils S. canadensis developed poorly. Tree species dominated (>50% of total cover) on these plots after 14–18 years. On the soils rich in nutrients, S. canadensis developed strongly. Tree species did not dominate there before 21–25 years. The diversity of woody species increased over time and reached 33 species altogether. Indigenous Acer, Quercus and Betula species prevailed. Alien species, typical for urban ruderal sites, were rare.
The results support the idea of establishing urban woodlands by spontaneous succession as a cheap way to develop near-natural plant communities rich in species. 相似文献
The new species Bowmanites cupulatus is introduced to accommodate fructufications most probably belonging to Sphenophyllum miravallis.
S. crenulatum Knight ex Wagner is considered to be a heterotypic synonym of S. miravallis, the latter name having priority. 相似文献
The possibility of “spill-over” of light absorbed by System II to System I was studied. There is no probability that this spill-over, if any, exceeds 25% in Chlorella.
The apparent equilibrium constant is decreased by 3(3,4-dichlorophenyl)-1,1-dimethylurea. This is not in favor of the hypothesis of fully independent electron-transfer chains in photosynthesis; it is therefore likely that some communication between those chains exists. 相似文献
The membrane fragments prepared from Anabaena cells grown in the presence of diphenylamine have the activities of both Photosystem 1 (NADP+ reduction with DCIP-ascorbate as electron donor) and Photosystem 2 (DCIP reduction with 1,5-diphenylcarbazide as electron donor).
The fluroescence spectra of these cells at 77°K show peaks at 696 and 731 nm and a shoulder around 687 nm. The fluorescence intensity at 687 and 696 nm is higher in these cells than in normal-Anabaena cells. 相似文献
Similar measurements made with azurin instead of plastocyanin gave k = 6 · 106 and approx. 2 · 107 M−1 · s−1 for reaction of reduced azurin with cytochrome ƒ and algal cytochrome respectively.
Rate constants of 115 and 80 M−1 · s−1 were found for reduction of plastocyanin by ascorbate and hydroquinone at 298 °K and pH 7.0. The rate constants for the oxidation of plastocyanin, cytochrome ƒ, Pseudomonas cytochrome c-551 and red algal cytochrome c-553 by ferricyanide were found to be between 3 · 104 and 8 · 104 M−1 · s−1.
The results are discussed in relation to photosynthetic electron transport. 相似文献
The results indicate that the strong increase in the yield of bacteriochlorophyll emission that occurred upon generating reducing conditions is, at least mainly, due to a direct effect on the light-harvesting systems, and does not involve the reaction center as had been earlier postulated. 相似文献
The kinetic data have been analyzed in terms of the thermodynamics of the interactions. This analysis indicates that the copper protein has a ΔE of about 0.038 V more positive than the heme c component, a value that compares favorably with that of 0.040 V obtained by equilibrium methods. The value of ΔE obtained by the kinetic method for the internal reaction is less precise but is reasonably close to that of 0.070 V determined by an equilibrium technique. 相似文献