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1.
J. M. Ellingson L. J. Fleishman E. R. Loew 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1995,177(5):559-567
The visual pigments and oil droplets in the retina of the diurnal gecko Gonatodes albogularis were examined microspectrophotometrically, and the spectral sensitivity under various adapting conditions was recorded using electrophysiological responses. Three classes of visual pigments were identified, with max at about 542, 475, and 362 nm. Spectral sensitivity functions revealed a broad range of sensitivity, with a peak at approximately 530–540 nm. The cornea and oil droplets were found to be transparent across a range from 350–700 nm, but the lens absorbed short wavelength light below 450 nm. Despite the filtering effect of the lens, a secondary peak in spectral sensitivity to ultraviolet wavelengths was found. These results suggest that G. albogularis does possess the visual mechanisms for discrimination of the color pattern of conspecifics based on either hue or brightness. These findings are discussed in terms of the variation in coloration and social behavior of Gonatodes.Abbreviations
ERG
electroretinogram
-
MSP
microspectrophotometry
-
UV
ultraviolet
- max
wavelength of maximum absorbance 相似文献
2.
G. H. Jacobs J. F. Deegan II J. Neitz B. P. Murphy K. V. Miller R. L. Marchinton 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1994,174(5):551-557
Electroretinogram (ERG) flicker photometry was used to study the spectral mechanisms in the retinas of white-tailed deer (Odocoileus virginianus) and fallow deer (Dama dama). In addition to having a rod pigment with maximum sensitivity (max) of about 497 nm, both species appear to have two classes of photopic receptors. They share in common a short-wavelength-sensitive cone mechanism having max in the region of 450–460 nm. Each also has a cone having peak sensitivity in the middle wavelengths, but these differ slightly for the two species. In white-tailed deer the max of this cone is about 537 nm; for the fallow deer the average max value for this mechanism was 542 nm. Deer resemble other ungulates and many other types of mammal in having two classes of cone pigment and, thus, the requisite retinal basis for dichromatic color vision.Abbreviations ERG
electroretinogram
- LWS
long wavelength sensitive
- MWS
middle wavelength sensitive
- SWS
short wavelength sensitive 相似文献
3.
Absorption (ABS) and circular dichroism (CD) spectra were recorded for 6 concentrations (2.0–290 M) of bacteriochlorophyll (BChl) c in each solvent. Monomer spectra were obtained by adding methanol (1:200) to each sample. The monomer showed an ABS peak and a CD trough at 664 nm in CH2Cl2 (ABS peak at 665 nm in CCl4). Dimer-plus-monomer spectra were obtained by subtracting high concentration (e.g., 290 M) spectra appropriately scaled from lower concentration (e.g., 26 M) spectra. Pure dimer spectra were then obtained by subtracting monomer spectra appropriately scaled from dimer-plus-monomer spectra. The dimer showed an ABS peak at 679 nm in both CH2Cl2 and CCl4 and a CD trough at ca. 670 nm in CH2Cl2. The optical properties of the dimer do not agree with the model for bacteriochlorophyllide d [Smith KM, Bobe FW, Goff DA and Abraham RJ (1986) J Am Chem Soc 108: 1111–1120]. Higher aggregate spectra were obtained by subtracting appropriately scaled monomer and dimer spectra from high concentration (e.g., 290 M) spectra. The aggregate showed ABS shoulders at ca. 636 and 678 nm with a peak at 702 nm in CH2Cl2 and at 708 nm in CCl4; the CD spectrum in either solvent showed peaks at 638 and 679 nm with troughs at 658 and ca. 710 nm. These spectra are consistent with an excitonic interaction between 4 chromophores in the aggregate. Each of the 12 original ABS spectra was deconvoluted in terms of the appropriate monomer, dimer and aggregate spectra, and the concentrations of each component were determined. Plots of log aggregate concentration vs. log dimer concentration lay on or near a line of slope 1.9 for CH2Cl2 and on or near a line of slope 2.1 for CCl4. The aggregate was thus shown to be a tetramer. The theoretical relationship between dimers and monomers (slope 2.0) was not observed in all cases.Abbreviations ABS
absorbance
- BChl
bacteriochlorophyll
- CD
circular dichroism
- Chl
chlorophyll
- DNS
data not shown
- PEF
4-n-propyl-5-ethyl farnesyl 相似文献
4.
Lucy H. Senter Dale R. Sanson David G. Corley Michael S. Tempesta Audrey A. Rottinghaus George E. Rottinghaus 《Mycopathologia》1991,113(2):127-131
Twenty-six trichothecene mycotoxins produced by Fusarium sporotrichioides (MC-72083) and Fusarium sambucinum were screened for relative cytotoxicity in cultured baby hamster kidney (BHK-21) cells. The relative cytotoxicity was measured as LC100. The most cytotoxic trichothecenes were T-2 toxin (5 ng/ml) and the recently isolated 4-propanoyl HT-2 (5 ng/ml) and 3-hydroxy T-2 toxin (5 ng/ml). T-2 tetraol (1 × 104 ng/ml), 8--hydroxytrichothecene (1 × 104 ng/ml), sporotrichiol (2 × 104 ng/ml), 8-oxodiacetoxyscirpenol (6 × 104 ng/ml) and 8-acetyl T-2 tetraol (1 × 105 ng/ml) were the least toxic of the regular trichothecenes. None of the modified trichothecenes or the apotrichothecene were very cytotoxic: 8--hydroxysambucoin (2 × 103 ng/ml), FS-1 (5 × 103 ng/ml), 8--hydroxysambucoin (8 × 104 ng/ml) and trichotriol (1 × 105 ng/ml). The modified trichothecenes, FS-2 and FS-3, were not toxic even at 1 × 105 ng/ml. The baby hamster kidney cell bioassay proved to be a very sensitive and reproducible means of screening new trichothecene mycotoxins for relative cytotoxicity. 相似文献
5.
Flash-induced optical kinetics at room temperature of cytochrome (Cyt) c
551 and an Fe-S center (CFA/CFB) bound to a purified reaction center (RC) complex from the green sulfur photosynthetic bacterium Chlorobium tepidum were studied. At 551 nm, the flash-induced absorbance change decayed with a t
1/2 of several hundred ms, and the decay was accelerated by 1-methoxy-5-methylphenazinium methyl sulfate (mPMS). In the blue region, the absorbance change was composed of mPMS-dependent (Cyt) and mPMS-independent component (CFA/CFB) which decayed with a t
1/2 of 400–650 ms. Decay of the latter was effectively accelerated by benzyl viologen (Em –360 mV) and methyl viologen (–440 mV), and less effectively by triquat (–540 mV). The difference spectrum of Cyt c had negative peaks at 551, 520 and 420 nm, with a positive rise at 440 to 500 nm. The difference spectrum of CFA/CFB resembled P430 of PSI, and had a broad negative peak at 430435 nm.Abbreviations (B)Chl
(bacterio)chlorophyll
- Cyt
cytochrome
- FA, FB and FX
iron-sulfur center A, B and X of Photosystem I
- CFA, CFB and CFX
FA-,FB- and FX-like Fe-S center of Chlorobium
- mPMS
1-methoxy-5-methylphenazinium methyl sulfate
- PSI
Photosystem I
- RC
reaction center 相似文献
6.
The combined effects of water activity (aw) and temperature on mycotoxin production by Penicilium commune (cyclopiazonic acid — CPA) and Aspergillus flavus (CPA and aflatoxins — AF) were studied on maize over a 14-day period using a statistical experimental design. Analysis of variance showed a highly significant interaction (P 0.001) between these factors and mycotoxin production. The minimum aw/temperature for CPA production (2264 ng g–1
P. commune, 709 ng g–1
A. flavus) was 0.90 aw/30 °C while greatest production (7678 ng g–1
P. commune, 1876 ng g–1
A. flavus) was produced at 0.98 aw/20 °C. Least AF (411 ng g–1) was produced at 0.90 aw/20 °C and most (3096 ng g–1) at 0.98 aw/30 °C. 相似文献
7.
Two soluble c-type cytochromes (c-553 and c-555) and the nonheme iron-containing protein rubredoxin of the non-thiosulfate-utilizing green sulfur bacterium Pelodictyon luteolum were highly purified by ion exchange column chromatography, gel filtration and ammonium sulfate fractionation. Both cytochrome are small and basic hemoproteins, while rubredoxin is an acidic small nonheme iron protein. Cytochrome c-553 has a molecular weight of 13,000 determined by Sephacryl S-200 chromatography and of 10,700 by electrophoresis on SDS acrylamide gel, an isoelectric point at pH 10.2, a redox-potential of +220 mV. It shows maxima at 413 nm in the oxidized form, and the characteristic three maxima in the reduced state (-band at 553 nm, -band at 523 nm, -band at 417 nm). The best purity index (A
280/A
417) obtained was 0.18. Cytochrome c-555 (best purity index obtained: A
280/A
418=0.17) has an isoelectric point at pH 10.5, a molecular weight of 9,500 (by electrophoresis on SDS acrylamide gel) and a redox-potential of +160mV. The reduced form of this cytochrome shows the typical bands of c-type cytochromes at 555 (551) nm (-band), 523 nm (-band) and 418 nm (-band), while the oxidized form has the -band at 413 nm.Rubredoxin (best purity index obtained: A
280/A
490=3.5) is an acidic small protein. Its molecular weight estimated by gel filtration and SDS acrylamide gel electrophoresis is 27,000 and 6,300 respectively. The monomer of this protein contains one iron atom per molecule. Rubredoxin has an isoelectric point at pH 2.8 and shows maxima at 570 nm, 490 nm and 370 nm in the oxidized form.During anaerobic sulfide oxidation of a growing culture of Pelodictyon luteolum elemental sulfur is the first main product, which appears in the medium. Elemental sulfur is further oxidized to sulfate, after the available sulfide is completely consumed by the cells.Non-common abbreviations C
Chlorobium
- P
Pelodictyon
- SDS
sodium dodecylsulfate
- HIPIP
high-potential-iron-sulfur-protein Offprint requests to: U. Fischer 相似文献
8.
Paul A. Lemke Norman D. Davis Sriram K. Iyer Gregory W. Creech Urban L. Diener 《Journal of industrial microbiology & biotechnology》1988,3(2):119-125
Summary A convenient miniassay for aflatoxin has been developed for cultures ofAspergillus flavus andA. parasiticus grown for 3–10 days in 10 ml of a coconut extract medium. The sensitivity of the assay, as measured by photofluorometry (365 nm maximum excitation; 445 nm maximum emission), is of the order of 0.01 M (3.12 ng/ml) for aflatoxin B1 dissolved in aqueous iodine (0.26 mM). High performance liquid chromatography, monitored by fluorometric analysis of both an aflatoxin B1 standard and selected culture filtrates, confirmed the sensitivity of the assay and indicated specificity for iodine-enhanced fluorescence of aflatoxin in the coconut extract medium. Thin layer chromatography further confirmed the aflatoxin titers and the specificity for enhancement of aflatoxins B1 and G1 in culture filtrates.Alabama Agricultural Experiment Station Journal No. 6-871297. 相似文献
9.
Flavocytochrome c-553 of the non-thiosulfateutilizing green sulfur bacterium Chlorobium limicola strain 6330 was partially purified by ion exchange column chromatography and ammonium sulfate fractionation (highest purity index obtained: A
280/A
417 red=0.96). It is autoxidizable and located in the soluble fraction. This hemoprotein contains a flavin component and one heme per molecule. The dithionite reduced spectrum reveals the typical maxima of a c-type cytochrome: =553,5 nm; =523 nm; =417 nm, while the oxidized form shows a -band at 410 nm and two shoulders at 440 nm and 480 nm indicating the flavin component. The flavocytochrome is a basic protein with an isoelectric point at pH 9.0 (± 0.5), a redox potential of 65 mV, a molecular weight of 56,000. It participates in sulfide oxidation and shows neither adenylylsulfate reductase nor sulfite reductase activity.
C. limicola further contains a soluble cytochrome c-555 (highest purity index obtained: A
280/A
412 ox=0.13; isoelectric point between pH 9.5 and 10) and the non-heme iron-containing proteins rubredoxin and ferredoxin, but lacks cytochrome c-551. Besides these soluble electron transfer proteins a membrane-bound c-type cytochrome (=554,5 nm) can be detected spectrophotometrically.Non-common abbreviations HIPIP
high-potential iron sulfur protein
- APS
adenylylsulfate 相似文献
10.
Lyngberg OK Solheid C Charaniya S Ma Y Thiagarajan V Scriven LE Flickinger MC 《Extremophiles : life under extreme conditions》2005,9(3):197-207
Thermostable polymers cast as thin, porous coatings or membranes may be useful for concentrating and stabilizing hyperthermophilic microorganisms as biocatalysts. Hydrogel matricies can be unstable above 65°C. Therefore a 55-m thick, two layer (cell coat + polymer top coat) bimodal, adhesive latex coating of partially coalesced polystyrene particles was investigated at 80°C using Thermotoga maritima as a model hyperthermophile. Coating permeability (pore structure) was critical for maintaining T. maritima viability. The permeability of bimodal coatings generated from 0.8 v/v of a suspension of non-film-forming 800 nm polystyrene particles with high glass transition temperature (Tg= 94°C, 26.9% total solids) blended with 0.2 v/v of a suspension of film-forming 158 nm polyacrylate/styrene particles (Tg –5°C, 40.9% total solids) with 0.3 g sucrose/g latex was measured in a KNO3 diffusion cell. Diffusivity ratio remained above 0.04 (Deff/D) when incubated at 80°C in artificial seawater (ASW) for 5 days. KNO3 permeability was corroborated by cryogenic-SEM images of the pore structure. In contrast, the permeability of a mono-dispersed acrylate/vinyl acetate latex Rovace SF091 (Tg~10°C) rapidly decreased and became impermeable after 2 days incubation in ASW at 80°C. Thermotoga maritima were entrapped in these coatings at a cell density of 49 g cell wet weight/liter of coating volume, 25-fold higher than the density in liquid culture. Viable T. maritima were released from single-layer coatings at 80°C but accurate measurement of the percentage of viable entrapped cells by plate counting was not successful. Metabolic activity could be measured in bilayer coatings by utilization of glucose and maltose, which was identical for latex-entrapped and suspended cells. Starch was hydrolyzed for 200 h by latex-entrapped cells due to the slow diffusion of starch through the polymer top coat compared to only 24 h by suspended T. maritima. The observed reactivity and stability of these coatings was surprising since cryo-SEM images suggested that the smaller low Tg polyacrylate/styrene particles preferentially bound to the T. maritima toga-sheath during coat formation. This model system may be useful for concentrating, entrapment and stabilization of metabolically active hyperthermophiles at 80°C. 相似文献
11.
Electron transport of normal and photobleachedAnabaena cylindrica was studied using spectral and kinetic analyses of absorbance transients induced by single turnover flashes. Between 500 and 600 nm two positive bands (540 and 566 nm) and two negative bands (515 and 554 nm) were found. Absorbance changes at 515 and 540 nm were partly characterized. None of these absorbance changes represent an electrochromic shift. Absorbance changes at 554 and 566 nm correspond to the oxidation of cytochromef and the reduction of cytochromeb
563, respectively. We found a very slight 3-(3,4-dichlorophenyl)-1, 1-dimethylurea (DCMU) sensitivity of cytochromef in normal cells, while DCMU was completely ineffective for cytochromef reduction in photobleached cells. The absorbance change of cytochromeb
563 increased, while the absorbance change of cytochromef was smaller than in normal cells. The increased O2 evolution in photobleached cells and the negligible electron transport via cytochromef suggest the participation of other electron acceptor(s) in the electron-transport chain of photobleachedAnabaena cylindrica. 相似文献
12.
The fluorescence of the voltage sensitive dye, diS-C3-(5), has been analyzed by means of synchronous excitation spectroscopy. Using this rather rare fluorescence technique we have been able to distinguish between the slightly shifted spectra of diS-C3-(5) fluorescence from cells and from the supernatant. It has been found that diS-C3-(5) fluorescence in the supernatant can be selectively monitored at exc = 630 nm and em= 650 nm, while the cell associated fluorescence can be observed at exc= 690 nm and em = 710 nm. A modified theory for the diSC3-(5) fluorescence response to the membrane potential is presented, according to which a linear relationship exists between the logarithmic increment of the dye fluorescence intensity in the supernatant, In I/I°, and the underlying change in the plasma membrane potential, p=p-°p. The theory has been tested on human myeloid leukemia cells (line ML-1) in which membrane potential changes were induced by valinomycin clamping in various K+ gradients. It has been demonstrated that the membrane potential change, p,can be measured on an absolute scale.
Offprint requests to: J. Plasek 相似文献
13.
Changes in phosphorus concentrations and pH in the rhizosphere of some agroforestry and crop species 总被引:2,自引:0,他引:2
The aim of this work was to assess whether agroforestry species have the ability to acquire P from pools unavailable to maize. Tithonia diversifolia(Hemsley) A. Gray, Tephrosia vogelii Hook f., Zea mays and Lupinus albusL. were grown in rhizopots and pH change and depletion of inorganic and organic P pools measured in the rhizosphere. Plants were harvested at the same growth stage, after 56 days for maize and white lupin and 70 days for tithonia and tephrosia, and the rhizosphere sampled. The rhizosphere was acidified by tithonia (pH change –0.3 units to pH 4.8) and lupins (–0.2 units to 4.9), alkalinised by tephrosia (+0.4 units to pH 5.4), and remained unchanged with maize growth. Concurrent with acidification in the rhizosphere of tithonia there was a decline in resin-P (0.8 g P g–1). However, there was also a decline in NaOH extractable inorganic P (NaOH-Pi) (5.6 g P g–1 at the root surface) and organic P pools (NaOH-Po) (15.4 g P g–1 at 1.5 mm from the root), which would not be expected without specific P acquisition mechanisms. Alkalinisation of tephrosia rhizosphere was accompanied by changes in all measured pools, although the large depletion of organic P (21.6 g P g–1 at 5 mm from the root) suggests that mineralisation, as well as desorption of organic P, was stimulated. The size of changes of both pH and P pools varied with distance away from the rhizoplane. Decline of more recalcitrant P pools with the growth of the agroforestry species contrasted with the effect of maize growth, which was negligible on resin-P and NaOH-Pi, but led to an accumulation of P as NaOH-Po (14.2 g P g–1 at 5 mm from the root). Overall the depletion of recalcitrant P pools, particularly Po, suggests that the growth of tithonia and tephrosia enhance desorption and dissolution of P, while also enhancing organic P mineralisation. Both species appear to have potential for agroforestry technologies designed to enhance the availability of P to crops, at least in the short term. 相似文献
14.
Cells of the phototrophic bacterium Chromatium vinosum strain D were shown to contain a siroheme sulfite reductase after autotrophic growth in a sulfide/bicarbonate medium. The enzyme could not be detected in cells grown heterotrophically in a malate/sulfate medium. Siroheme sulfite reductase was isolated from autotrophic cells and obtained in an about 80% pure preparation which was used to investigate some molecular and catalytic properties of the enzyme. It was shown to consist of two different types of subunits with molecular weights of 37,000 and 42,000, most probably arranged in an 44-structure. The molecular weight of the native enzyme was determined to 280,000, 51 atoms of iron and 47 atoms of acid-labile sulfur were found per enzyme molecule. The absorption spectrum indicated siroheme as prosthetic group; it had maxima at 280 nm, 392 nm, 595 nm, and 724 nm. The molar extinction coefficients were determined as 302×103 cm2xmmol-1 at 392 nm, 98×103 cm2 xmmol-1 at 595 nm and 22×103 cm2x-mmol-1 at 724 nm. With reduced viologen dyes as electron donor the enzyme reduced sulfite to sulfide, thiosulfate, and trithionate. The turnover number with 59 (2 e-/enzyme moleculexmin) was low. The pH-optimum was at 6.0. C. vinosum sulfite reductase closely resembled the corresponding enzyme from Thiobacillus denitrificans and also desulfoviridin, the dismilatory sulfite reductase from Desulfovibrio species. It is proposed that C. vinosum catalyses anaerobic oxidation of sulfide and/or elemental sulfur to sulfite in the course of dissimilatory oxidation of reduced sulfur compounds to sulfate.Non-common abbreviations APS
adenylyl sulfate
- SDS
sodium dodecyl sulfate 相似文献
15.
When treated with blue light, intact cells of Euglena gracilis Klebs var. bacillaris Cori, bleached strain W3BUL, show a series of positive peaks at 384, 411, and 440 nm in the blue-light-minus-dark difference spectrum; bleached strain 1224-5/24 shows a series of positive peaks at 386, 417, and 448 nm under the same conditions. The same changes are observed in a 27,000xg supernatant from darkgrown W3. The absorption change appears to be a consequence of shifts in the absorption of carotenoids; it is not seen in cells of W3BUL grown on SAN 9789 (4-chloro-5-(methylamino)-2-(,, -trifluoro-m-tolyl)-3(2H)pyridazinone) to deplete the carotenoids or in cells of W10BSmL, a mutant lacking carotenoids. Inhibitors of flavin-mediated reactions, reductants and valinomycin had no effect on the activity of the system. The activity in the 27,000xg supernatant was associated with material of a molecular weight more than 2.5×106 and was insensitive to heating for 2 min at 100° C but was reduced or eliminated on longer heat treatment or addition of Triton X-100, indicating a possible association with membrane material. Photoactivity is enriched in the lower density fractions of a flotation gradient, and correlates with the -carotene content in all fractions. Similar spectral changes can be obtained by comparing the iodine catalyzed cis-to-trans isomerization of -carotene in a CS2-CHCl3 solvent. The action spectrum for the absorbance change shows effectiveness peaks in the 370–390 and 420–448-nm regions, with no marked effectiveness past 500 nm. Thus the photosensitizer may not be a carotenoid (at least not a normally-occurring C40 carotenoid). These blue-lightinduced absorption changes and their action spectra are discussed in relation to such blue-light-mediated responses as carotenogenesis, chloroplast development and phototaxis.Abraham and Etta Goodman Professor of Biology, to whom reprint requests should be directed 相似文献
16.
Nabil A. Bayakly Lewis E. Deaton 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1992,162(5):463-468
Summary The ventricle of the mussel Geukensia demissa is inhibited by 5-hydroxytryptamine and excited by the molluscan neuropeptide FMRFamide. Supra-threshold doses of amide result in marked positive chronotropy and inotropy within 5–15 s. 5-Hydroxytryptamine at 10-8
M produces diastolic arrest within 10 s. A 1-min exposure to FMRFamide (5 · 10-8
M) results in a small increase in the cytoplasmic levels of adenosine 3,5-cyclic monophosphate; shorter or longer exposures have no effect. The cAMP content of ventricles incubated in 5 · 10-8
M 5-hydroxytryptamine for 1 min decreases by 2.3 pmol/mg protein; longer or shorter incubations have no effect. Treatment with forskolin results in 3-or 4-fold increases in adenosine 3,5-cyclic monophosphate, but forskolin has no effect on the mechanical activity of the ventricle. The levels of inositol monophosphate, inositol 1,4-diphosphate, and inositol 1,4,5-triphosphate in tissues exposed to 5-hydroxytryptamine are not different from levels in control tissues. FMRFamide decreases the levels of these phosphoinositides by 50% or more. Lower concentrations of phorbol 12,13-diacetate (10-8 to 10-7
M) and phorbol 12-myristate, 13-acetate (10-6
M) cause positive chronotropy in the isolated ventricle; higher concentrations induce systolic arrest. These results suggest that the effects of 5HT on the ventricle are not mediated by adenosine 3,5-cyclic monophosphate or inositol 1,4,5-triphosphate. The effects of FMRFamide may involve a decrease in inositol 1,4,5-triphosphate. The effects of amide may involve a decrease in inositol 1,4,5-triphosphate. The response of the ventricles to phorbol esters suggest that protein kinase C may be involved in the regulation of cardiac contractility.Abbreviations cAMP
adenosine 3,5-cyclic monophosphate
- DMA
dimethylformamide
- DMSO
dimethylsulfoxide
- FMRFamide
Phenylalanyl-methionyl-arginyl-phenylalanylamide
- 5HT
5-hydroxytryptamine
- IP
inositol monophosphate
- IP2
inositol 1,4-diphosphate
- IP3
inositol 1,4,5-triphosphate
- PDA
phorbol 12,13-diacetate
- PMA
phorbol 12-myristate, 13-acetate
- SW
sea water
Present address: MSU; E.M. Center, Memphis, TN 38152, USA 相似文献
17.
The substrate specificity factor, V
cKo/VoKc, of spinach (Spinacia oleracea L.) ribulose 1,5-bisphosphate carboxylase/oxygenase was determined at ribulosebisphosphate concentrations between 0.63 and 200 M, at pH values between 7.4 and 8.9, and at temperatures in the range of 5° C to 40° C. The CO2/O2 specificity was the same at all ribulosebisphosphate concentrations and largely independent of pH. With increasing temperature, the specificity decreased from values of about 160 at 5° C to about 50 at 40° C. The primary effects of temperature were on K
c [Km(CO2)] and V
c [Vmax (CO2)], which increased by factors of about 10 and 20, respectively, over the temperature range examined. In contrast, K
o [Ki (O2)] was unchanged and V
o [Vmax (O2)] increased by a factor of 5 over these temperatures. The CO2 compensation concentrations () were calculated from specificity values obtained at temperatures between 5° C and 40° C, and were compared with literature values of . Quantitative agreement was found for the calculated and measured values. The observations reported here indicate that the temperature response of ribulose 1,5-bisphosphate carboxylase/oxygenase kinetic parameters accounts for two-thirds of the temperature dependence of the photorespiration/photosynthesis ratio in C3 plants, with the remaining one-third the consequence of differential temperature effects on the solubilities of CO2 and O2.Abbreviations RuBPC/O(ase)
ribulose 1,5-bisphosphate carboxylase/oxygenase
- RuBP
ribulose 1,5-bisphosphate
-
CO2 compensation concentration 相似文献
18.
Yuichi Takeuchi Reiko Fukumoto Hirokazu Kasahara Takeshi Sakaki Mitsutoshi Kitao 《Plant cell reports》1995,14(9):566-570
Cotyledons excised from dark-grown seedlings of cucumber (Cucumis sativus L.) were cultured in vitro under UV radiation at different wavelengths, obtained by passage of light through cut-off filters with different transmittance properties. Growth and the synthesis of chlorophyll (Chl) in cotyledons were inhibited and malondialdehyde was accumulated upon irradiation at wavelengths below 320 nm. Exogenous application of scavengers of free radicals reversed the growth inhibition induced by UV-B. Measurement of the fluorescence of Chl a suggested that electron transfer in photosystems was affected by UV-B irradiation. On the basis of these results, the involvement is postulated of active species of oxygen in damages to thylakoid membranes and the growth inhibition that are induced by UV-B irradiation.Abbreviations Chl
chlorophyll
- Fm
maximal fluorescence (dark)
- Fm
maximal fluorescence (light)
- Fv
variable fluorescence (dark)
- Fv
variable fluorescence (light)
- MDA
malondialdehyde
- O2
Superoxide radical
- PS
photosystem
- qN
non-photochemical quenching of fluorescence
- qP
photochemical quenching of fluorescence
- UV-BBE
biologically effective UV-B radiation
- WL(T = 0.5)
wavelength at which 50% transmittance occurs 相似文献
19.
Rhodopseudomonas palustris cells, characterized by a lamellar type intracytoplasmic chromatophore membrane system after phototrophic growth, yielded a crude supernatant cell-free fraction (S-144) after ultracentrifugation which retained the contents of both the cell compartments. After thiosulfate-dependent growth, a protein system was isolated from S-144 which catalyzed the thiosulfate-linked reduction of an endogenous c-type cytochrome. — The colorless oxidoreductase protein, after purification to homogeneity, revealed a molecular weight of 93,000 and, after SDS treatment, a particle weight of 48,000. It was focused at an average pI of 5.45. Apparent K
m values for several substrates were in the M range. The electron acceptor for thiosulfate oxidation was found to be a cytochrome c from S-144. The homogeneous acceptor protein, at liquid nitrogen temperature, exhibited absorption maxima at 549.0, 518.5 and 418.0 nm, and shoulders at 525.5, 512.0 and 508.0 nm. Its molecular weight was found to be 17,000 (gel filtration) and 16,000 (SDS gel electrophoresis). It was characterized by a pI of 10.0. Its midpoint redox potential of E
m,7.0=+228 mV was determined by redox titrations and the value of +205 mV by spectrophotometric calculations.Abbreviations BSA
bovine serum albumin
- HiPIP
high potential nonheme iron protein
- IEF
isoclectric focusing
- SDS
dodecylsulfate, sodium salt
- Temed
N,N,N,N-tetramethylethylenediamine 相似文献
20.
The dissociation products of isolated phycobilisomes of Mastigocladus laminosus were separated and analyzed by ultracentrifugation and, in part, by isoelectric focusing. With the exception of the allophycocyanin core, the sedimentation constants of peripheral phycocyanin- and phycoerythrocyanin-phycocyanin complexes lay in the range of 6 to 17S. The latter was represented by a 17S aggregate of two hexameric phycocyanins (dodecamer, dipartite unit). A complex with an absorption maximum at 610 nm (phycocyanin) and a shoulder at 580 nm (phycoerythrocyanin), a fluorescence emission maximum at 645 nm and a sedimentation constant of 11 S is described as a heterogeneously composed hexamer of ()3-phycoerythrocyanin-()3-phycocyanin. It was stable under extended dissociation in the cold and under isoelectric focusing. An aggregate of 14 S with an absorption maximum at 576 nm and a shoulder in the fluorescence emission spectrum at 625 nm (phycoerythrocyanin) in addition to the maximum at 645 nm (phycocyanin) is interpreted as a polar phycoerythrocyanin/ phycoerythrocyanin-phycocyanin complex. Combining these complexes with phycocyanin dodecamers creates peripheral rods of the phycobilisome. A proposal of the phycobiliprotein distribution within the phycobilisome of M. laminosus is presented.Abbreviations APC
allophycocyanin
- PC
phycocyanin
- PE
phycoerythrin
- PEC
phycoerythrocyanin 相似文献