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1.
Quantification of non-Q
B
-reducing centers in leaves using a far-red pre-illumination 总被引:1,自引:0,他引:1
An alternative approach to quantification of the contribution of non-QB-reducing centers to Chl a fluorescence induction curve is proposed. The experimental protocol consists of a far-red pre-illumination followed by a strong red pulse to determine the fluorescence rise kinetics. The far-red pre-illumination induces an increase in the initial fluorescence level (F25 μs) that saturates at low light intensities indicating that no light intensity-dependent accumulation of QA− occurs. Far-red light-dose response curves for the F25 μs-increase give no indication of superimposed period-4 oscillations. F25 μs-dark-adaptation kinetics following a far-red pre-pulse, reveal two components: a faster one with a half-time of a few seconds and a slower component with a half-time of around 100 s. The faster phase is due to the non-QB-reducing centers that re-open by recombination between QA− and the S-states on the donor side. The slower phase is due to the recombination between QB− and the donor side in active PS II reaction centers. The pre-illumination-induced increase of the F25 μs-level represents about 4–5% of the variable fluorescence for pea leaves (∼2.5% equilibrium effect and 1.8–3.0% non-QB-reducing centers). For the other plant species tested these values were very similar. The implications of these values will be discussed. 相似文献
2.
A method for quantifying differentiation between populations at multi-allelic loci and its implications for investigating identity and paternity 总被引:14,自引:0,他引:14
A method is proposed for allowing for the effects of population differentiation, and other factors, in forensic inference
based on DNA profiles. Much current forensic practice ignores, for example, the effects of coancestry and inappropriate databases
and is consequently systematically biased against defendants. Problems with the ‘product rule’ for forensic identification
have been highlighted by several authors, but important aspects of the problems are not widely appreciated. This arises in
part because the match probability has often been confused with the relative frequency of the profile. Further, the analogous
problems in paternity cases have received little attention. The proposed method is derived under general assumptions about
the underlying population genetic processes. Probabilities relevant to forensic inference are expressed in terms of a single
parameter whose values can be chosen to reflect the specific circumstances. The method is currently used in some UK courts
and has important advantages over the ‘Ceiling Principle’ method, which has been criticized on a number of grounds.
Editor's comments
The authors' work offers a sound approach to accommodating the effects of population structure, based on use of Wright'sF
ST
. Their equations 1 and 2 are very convenient, and are good approximations to the exact results given by Weir (1994). As they
point out, good estimates ofF
ST
are needed. The comments about the ‘generally mixed’ results of independence tests may be met, in part, by the paper of Maiste
and Weir in this volume. The authors cite Kraneet al. (1992) but had not seen the subsequent rebuttal by Budowleet al. (1994). The work of Wallet al. (1993) contained errors, as noted in Greenhalghet al. (1994).
An erratum to this article is available at . 相似文献
3.
The lysin content in maize endosperm protein is considered to be one of the most important traits for determining the nutritional quality of food and feed. Improving the protein quality of the maize kernel depends principally on finding a mutant with a higher lysine content. Two high-lysine mutant lines with opaque endosperm, QCL3024 and QCL3021, were isolated from a self-cross population derived from Robertsons Mutator stocks. The gene controlling this mutation is temporarily termed opaque-16 (o16). In order to illuminate the genetic locus and effect of the o16 gene, two F2:3 populations, one developed from a cross between QCL3024 and QCL3010 (a wild type line) and another from a cross between Qi205 (opaque-2 line) and QCL3021, were created, and F3 seeds from the F2 plants in the two populations were evaluated for lysine content. The distributions of lysine content and tests for their normality indicate that the lysine content in the two populations is regulated by the major gene of o16 and genes of o2 and o16, respectively. Based on two data sets of the linkage maps of the F2 plant marker genotypes and the lysine content of F3 seeds originating from the two F2:3 populations, the o16 gene was located within 5 cM, at either 3 or 2.2 cM from umc1141 in the interval between umc1121 and umc1141 on the long arm of chromosome 8, depending on the recombination rate in the two populations as determined by composite interval mapping. According to the data of the F2:3 population constructed from the o2 and o16 lines, the double recessive mutant effect was analyzed. The average lysine content of the F3 o2o2o16o16 families identified by the umc1066 and umc1141 markers was approximately 30% higher than that of the F3 o2o2 and o16o16 families, respectively. The lysine content of seven F3 families among nine F3 double recessive mutant families showed different increments, with an average increase of some 6% compared with that of the maternal o2 line. The potential application of the o16 mutant for maize high-lysine breeding may be to combine it with the o2 mutant bearing modifier genes, thus obtaining a mutant with much higher lysine content. For the purpose of pyramiding the o16 with o2 genes, the availability of closely linked markers of the o16 and o2 loci will facilitate marker-assisted selection and greatly reduce breeding time and effort. 相似文献
4.
Jörg-Christian Greie Gabriele Deckers-Hebestreit Karlheinz Altendorf 《Journal of bioenergetics and biomembranes》2000,32(4):357-364
Membrane-bound ATP synthases (F1F0) catalyze the synthesis of ATP via a rotary catalyticmechanism utilizing the energy of an electrochemical ion gradient. The transmembrane potentialis supposed to propel rotation of a subunit c ring of F0 together with subunits and of F1,hereby forming the rotor part of the enzyme, whereas the remainder of the F1F0 complexfunctions as a stator for compensation of the torque generated during rotation. This reviewfocuses on our recent work on the stator part of the F0 complex, e.g., subunits a and b. Usingepitope insertion and antibody binding, subunit a was shown to comprise six transmembranehelixes with both the N- and C-terminus oriented toward the cytoplasm. By use of circulardichroism (CD) spectroscopy, the secondary structure of subunit b incorporated intoproteoliposomes was determined to be 80% -helical together with 14% turn conformation, providingflexibility to the second stalk. Reconstituted subunit b together with isolated ac subcomplexwas shown to be active in proton translocation and functional F1 binding revealing the nativeconformation of the polypeptide chain. Chemical crosslinking in everted membrane vesiclesled to the formation of subunit b homodimers around residues bQ37 to bL65, whereas bA32Ccould be crosslinked to subunit a, indicating a close proximity of subunits a and b near themembrane. Further evidence for the proposed direct interaction between subunits a and b wasobtained by purification of a stable ab
2 subcomplex via affinity chromatography using Histags fused to subunit a or b. This ab
2 subcomplex was shown to be active in proton translocationand F1 binding, when coreconstituted with subunit c. Consequences of crosslink formationand subunit interaction within the F1F0 complex are discussed. 相似文献
5.
Hitoshi Onouchi Ryuichi Nishihama Mitsuko Kudo Yasunori Machida Chiyoko Machida 《Molecular & general genetics : MGG》1995,247(6):653-660
Excision of a DNA segment can occur in Arabidopsis thaliana by reciprocal recombination between two specific recombination sites (RSs) when the recombinase gene (R) from Zygosaccharomyces rouxii is expressed in the plant. To monitor recombination events, we generated several lines of transgenic Arabidopsis plants that carried a cryptic -glucuronidase (GUS) reporter gene which was designed in such a way that expression of the reporter gene could be induced by R gene-mediated recombination. We also made several transgenic lines with an R gene linked to the 35S promoter of cauliflower mosaic virus. Each transgenic line carrying the cryptic reporter gene was crossed with each line carrying the R gene. Activity of GUS in F1 and F2 progeny was examined histochemically and recombination between two RSs was analyzed by Southern blotting and the polymerase chain reaction. In seedlings and plantlets of F1 progeny and most of the F2 progeny, a variety of patterns of activity of GUS, including sectorial chimerism in leaves, was observed. A small percentage of F2 individuals exhibited GUS activity in the entire plant. This pattern of expression was ascribed to germinal recombination in the F1 generation on the basis of an analysis of DNA structure by Southern blotting. These results indicate that R gene-mediated recombination can be induced in both somatic and germ cells of A. thaliana by cross-pollination of parental transgenic lines. 相似文献
6.
Joseph E. Neigel 《Conservation Genetics》2002,3(2):167-173
Since the introduction of allozyme methods inthe mid 1960s it has been a standard practiceto report Wright's measure of populationsubdivision, F
ST, for surveys ofgenetic variation. Its widespread use hasprovided us with a sense of what values can beexpected in particular situations and how theycan be interpreted. With some theoreticaljustification, F
ST has also beenused to estimate rates of gene flow. Howeverthere are conditions under which F
STis inappropriate for gene flow estimation andcan lead to incorrect or even absurdconclusions. These pitfalls have promptedcritics to suggest that F
ST hasfailed to deliver what its proponents havepromised and should be abandoned. A furtherchallenge has been the development of newmethods that offer even greater promise. Thusit is reasonable to ask if perhaps it is timeto retire F
ST and turn to new andmore powerful methods for the inference of geneflow from genetic markers. Here I will arguethat although gene flow should be estimated bymore powerful approaches whenever practical,F
ST remains a useful measure of theaverage effects of gene flow and will continueto be used for comparative purposes. 相似文献
7.
Methanobacterium thermoautotrophicum, growing on medium supplemented with 2 mol 63NiCl2/l, was found to take up 1.2 mol 63Ni per g cells (dry weight). More than 70% of the radioisotope was incorporated into a compound, which dissociated from the protein fraction after heat treatment, was soluble in 70% acetone, and could be purified by chromatography on QAE-Sephadex A-25, Sephadex G-25, and DEAE cellulose. The purified 63Ni labelled compound had an absorption spectrum and properties identical to those of factor F
430 and is therefore considered to be identical with factor F
430.Factor F
430, a compound of molecular weight higher than 1000 with an absorbance maximum at 430 nm, has recently been purified from Methanobacterium thermoautotrophicum (Gunsalus and Wolfe, 1978). The structure and function of this compound are not yet known. 相似文献
8.
F0 fluorescence and thermoluminescence (TL) were recorded simultaneously on various dark-adapted leaf samples. Above 40 °C,
a sharp peak of TL coincided with the onset of the heat-induced F0 rise. It results from a back-transfer of an electron from the secondary QB
-to the primary acceptor QA of photosystem 2, followed by a luminescence-emitting recombination with Tyr-D1. This demonstrates that the critical temperature at which the F0 starts rising also corresponds to a shift towards the left of the QA↔QB
- equilibrium.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
9.
J. T. Keltjens J. M. H. Hermans G. J. F. A. Rijsdijk C. Van der Drift G. D. Vogels 《Antonie van Leeuwenhoek》1988,54(3):207-220
F430 is the prosthetic group of the methylcoenzyme M reductase of methanogenic bacteria. The compound isolated from Methanosarcina barkeri appears to be identical to the one obtained from the only distinctly related Methanobacterium thermoautotrophicum. F430 is thermolabile and in the presence of acetonitrile or C10
in4
sup-
two epimerization products are obtained upon heating; in the absence of these compounds F430 is oxidized to 12, 13-didehydro-F430. The latter is stereoselectively reduced under H2 atmosphere to F430 by cell-free extracts of M. barkeri or M. thermoautotrophicum. H2 may be replaced by the reduced methanogenic electron carrier coenzyme F420.Abbreviations CH3S-CoM
methylcoenzyme M, 2-methylthioethanesulfonic acid
- HS-CoM
coenzyme M, 2-mercaptoethanesulfonic acid
- F430
Ni(II) tetrahydro-(12, 13)-corphin with a uroporphinoid (III) ligand skeleton
- 13-epi-F430 and 12,13-di-epi-F430
the 12, 13- and 12, 13-derivatives of F430
- 12, 13-didehydro-F430
F430 oxidized at C-12 and C-13
- coenzyme F420
7,8-didemethyl-8-hydroxy-5-deazaflavin derivative
- coenzyme F420H2
reduced coenzyme F420
- MV+
methylviologen semiquinone
- HPLC
high-performance liquid chromatography 相似文献
10.
We measured F420-dependent N5,N10-methylenetetrahydro-methanopterin dehydrogenase, N5, N10-methenyltetrahydro-methanopterin cyclohydrolase, and F420-reducing hydrogenase levels in Methanosarcina barkeri grown on various substrates. Variation in dehydrogenase levels during growth on a specific substrate was usually <3-fold, and much less for cyclohydrolase. H2–CO2-, methanol-, and H2–CO2+ methanol-grown cells had roughly equivalent levels of dehydrogenase and cyclohydrolase. In acetate-grown cells cyclohydrolase level was lowered 2 to 3-fold and dehydrogenase 10 to 80-fold; this was not due to repression by acetate, since, if cultures growing on acetate were supplemented with methanol or H2–CO2, dehydrogenase levels increased 14 to 19-fold, and cyclohydrolase levels by 3 to 4-fold. Compared to H2–CO2- or methanol-grown cells, acetate-or H2–CO2 + methanol-grown cells had lower levels of and less growth phase-dependent variation in hydrogenase activity. Our data are consistent with the following hypotheses: 1. M. barkeri oxidizes methanol via a portion of the CO2-reduction pathway operated in the reverse direction. 2. When steps from CO2 to CH3-S-CoM in the CO2-reduction pathway (in either direction) are not used for methanogenesis, hydrogenase activity is lowered.Abbreviations MF
methanofuran
- H4MPT
5,6,7,8-tetrahydromethanopterin
- HS-HTP
7-mercaptoheptanoylthreonine phosphate
- CoM-S-S-HTP
heterodisulfide of HS-CoM and HS-HTP
- F420
coenzyme F420 (a 7,8-didemethyl-8-hydroxy-5-deaza-riboflavin derivative)
- H2F420
reduced coenzyme F420
- HC+=H4MPT
N5,N10-methenyl-H4MPT
- H2C=H4MPT
N5,N10-methylene-H4MPT
- H3C=H4MPT
N5-methyl-H4MPT
- BES
2-bromoethanesulfonic acid 相似文献
11.
S. Rospert J. Breitung K. Ma B. Schwörer C. Zirngibl R. K. Thauer D. Linder R. Huber K. O. Stetter 《Archives of microbiology》1991,156(1):49-55
Methanopyrus kandleri belongs to a novel group of abyssal methanogenic archaebacteria that can grow at 110°C on H2 and CO2 and that shows no close phylogenetic relationship to any methanogen known so far. Methyl-coenzyme M reductase, the enzyme catalyzing the methane forming step in the energy metabolism of methanogens, was purified from this hyperthermophile. The yellow protein with an absorption maximum at 425 nm was found to be similar to the methyl-coenzyme M reductase from other methanogenic bacteria in that it was composed each of two -, - and -subunits and that it contained the nickel porphinoid coenzyme F430 as prosthetic group. The purified reductase was inactive. The N-terminal amino acid sequence of the -subunit was determined. A comparison with the N-terminal sequences of the -subunit of methyl-coenzyme M reductases from other methanogenic bacteria revealed a high degree of similarity.Besides methyl-coenzyme M reductase cell extracts of M. kandleri were shown to contain the following enzyme activities involved in methanogenesis from CO2 (apparent Vmax at 65°C): formylmethanofuran dehydrogenase, 0.3 U/mg protein; formyl-methanofuran: tetrahydromethanopterin formyltransferase, 13 U/mg; N
5,N10-methenyltetrahydromethanopterin cyclohydrolase, 14 U/mg; N
5,N10-methylenetetrahydromethanopterin dehydrogenase (H2-forming), 33 U/mg; N
5,N10-methylenetetrahydromethanopterin reductase (coenzyme F420 dependent), 4 U/mg; heterodisulfide reductase, 2 U/mg; coenzyme F420-reducing hydrogenase, 0.01 U/mg; and methylviologen-reducing hydrogenase, 2.5 U/mg. Apparent Km values for these enzymes and the effect of salts on their activities were determined.The coenzyme F420 present in M. kandleri was identified as coenzyme F420-2 with 2 -glutamyl residues.Abbreviations H–S-CoM
coenzyme M
- CH3–S-CoM
methylcoenzyme M
- H–S-HTP
7-mercaptoheptanoylthreonine phosphate
- MFR
methanofuran
- CHO-MFR
formyl-MFR
- H4MPT
tetrahydromethanopterin
- CHO–H4MPT
N
5-formyl-H4MPT
- CH=H4MPT+
N
5,N10-methenyl-H4MPT
- CH2=H4MPT
N
5,N10-methylene-H4MPT
- CH3–H4MPT
N
5-methyl-H4MPT
- F420
coenzyme F420
- 1 U=
1 mol/min 相似文献
12.
L. Ding K. J. Wang G. M. Jiang Y. G. Li C. D. Jiang M. Z. Liu S. L. Niu Y. Peng 《Photosynthetica》2006,44(1):26-31
Diurnal variation of gas exchange, chlorophyll (Chl) fluorescence, and xanthophyll cycle components of three maize (Zea mays L.) hybrids released in different years, i.e. Baimaya (1950s), Zhongdan2 (1970s), and Nongda108 (1990s), were compared. On cloudless days, the newer hybrids always had
higher net photosynthetic rate (P
N), especially at noon, than the older ones. At noon, all the hybrids decreased their maximal yield of photosystem 2 (PS2)
photochemistry (Fv/Fm) and actual quantum yield of PS2 (ΦPS2), the newer ones always showing higher values. Generally, the newer hybrids displayed higher photochemical quenching of Chl
(qP) and lower non-photochemical quenching (NPQ). The interhybrid differences in P
N may be owing to their differential photochemical efficiency. A midday depression in P
N occurred in all hybrids, which might be caused by serious photoinhibition or by decreased stomatal conductance. However,
midday depression in P
N was more obvious in the older hybrids, especially when leaves were senescent. The higher de-epoxidation state of the xanthophylls
was noted in older hybrids, which was confirmed by their larger NPQ. The newer maize hybrids did not need a strong de-epoxidation
state since they had a better photosynthetic quantum conversion rate and a lower NPQ. 相似文献
13.
One of the major effects of fluoride on oral bacteria is a reduction in acid tolerance, and presumably also in cariogenicity. The reduction appears to involve transport of protons across the cell membrane by the weak acid HF to dissipate the pH gradient, and also direct inhibition of the F1F0, proton-translocating ATPases of the organisms, especially for Streptococcus mutans. This direct inhibition by fluoride was found to be dependent on aluminum. The dependence on aluminum was indicated by the protection against fluoride inhibition afforded by the Al-chelator deferoxamine and by loss of protection after addition of umolar levels of Al3+, which were not inhibitory for the enzyme in the absence of fluoride. The F1 form of the enzyme dissociated from the cell membrane previously had been found to be resistant to fluoride in comparison with the F1F0 membrane-associated form. However, this difference appeared to depend on less aluminum in the F1 preparation in that the sensitivity of the F1 enzyme to fluoride could be increased by addition of umolar levels of Al3+. The effects of Al on fluoride inhibition were apparent when enzyme activity was assayed in terms of phosphate release from ATP or with an ATP-regenerating system containing phosphoenolpyruvate, pyruvate kinase, NADH and lactic dehydrogenase. Also, Be2+ but not other metal cations, e.g. Co2+, Fe2+, Fe3+, Mn2, Sn2+, and Zn2+, served to sensitize the enzyme to fluoride inhibition. The differences in sensitivities of enzymes isolated from various oral bacteria found previously appeared also to be related to differences in levels of Al. Even the fluoride-resistant enzyme of isolated membranes of Lactobacillus casei ATCC 4646 could be rendered fluoride-sensitive through addition of Al3+. Thus, the F1F0 ATPases of oral bacteria were similar to E1E2 ATPases of eukaryotes in being inhibited by Al-F complexes, and the inhibition presumably involved formation of ADP-Al-F
inf3
sup-
complexes during catalysis at the active sites of the enzymes. 相似文献
14.
Pulse amplitude modulated (PAM) fluorometry has been suggested as a tool for estimating environmental stresses on corals.
However, information regarding natural changes in maximal quantum yields (F
v/F
m) of corals during “normal” (i.e. non-bleaching) years has been limited. In this study, seasonal variations in F
v/F
m for Stylophora pistillata and Favia favus, measured in situ, correlated with seasonal changes in solar irradiance but not in sea temperature. Interactions between
sea temperature and irradiance were further studied by growing these corals and Pocillopora damicornis under controlled conditions. Exposure to high light with normal or high temperatures resulted in lower F
v/F
m values than exposure to low light at both temperatures. Thus, high irradiances may cause decreased F
v/F
m values in corals at least as much as, if not more than, high temperatures. Such seasonal variations should be taken into
account when using PAM fluorometry as a diagnostic tool for predicting coral bleaching. 相似文献
15.
Esch E 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2005,111(1):100-109
The gametes produced in meiosis provide information on the frequency of recombination and also on the interdependence of recombination events, i.e. interference. Using F2 individuals, it is not possible in all cases to derive the gametes, which have fused, and which provide the information about interference unequivocally when three or more segregating markers are considered simultaneously. Therefore, a method was developed to estimate the gametic frequencies using a maximum likelihood approach together with the expectation maximisation algorithm. This estimation procedure was applied to F2 mapping data from rice (Oryza sativa L.) to carry out a genome-wide analysis of crossover interference. The distribution of the coefficient of coincidence in dependence on the recombination fraction revealed for all chromosomes increasing positive interference with decreasing interval size. For some chromosomes this mutual inhibition of recombination was not so strong in small intervals. The centromere had a significant effect on interference. The positive interference found in the chromosome arms were reduced significantly when the intervals considered spanned the centromere. Two chromosomes even demonstrated independent recombination and slightly negative interference for small intervals including the centromere. Different marker densities had no effect on the results. In general, interference depended on the frequency of recombination events in relation to the physical length. The strength of the centromere effect on interference seemed to depend on the strength of recombination suppression around the centromere.Electronic Supplementary Material Supplementary material is available for this article at 相似文献
16.
Developing desorption isotherms for inorganic phosphorus (P) is a time-consuming and non-standardized procedure. Anion exchange
membranes (AEMs) have been successfully used in studies of P desorption kinetics and total membrane-desorbable P, but rarely
have they been used for developing P desorption isotherms. Our study had two objectives: (1) to evaluate the suitability of
using multiple strips of AEMs (termed the Multiple AEM Method) to develop P desorption isotherms; and (2) to compare the Multiple
AEM Method with a sequential-extraction approach using AEMs (termed the Sequential AEM Method) to determine if the manner
in which AEMs were used would influence the slope of the desorption isotherm, i.e. the partition coefficient. Both methods
yielded well-defined, but numerically different desorption isotherms for all levels of sorbed P. However, estimated K
d
values among methods were equivalent in the low and medium levels of P sorbed. The Multiple AEM method was quicker than the
Sequential AEM method, but both gave similar K
d
values in an agriculturally significant range of soil solution concentrations. These methods should be tested on a range
of soil type to determine their suitability in developing P desorption isotherms and to move toward method standardization
for desorption isotherms. 相似文献
17.
S. Kauffer R. Schmid K. Steffens G. Deckers-Hebestreit K. Altendorf 《Archives of microbiology》1987,148(3):187-192
The ATP synthase complex of Klebsiella pneumoniae (KF1F0) has been purified and characterized. SDS-gel electrophoresis of the purified F1F0 complexes revealed an identical subunit pattern for E. coli (EF1F0) and K. pneumoniae. Antibodies raised against EF1 complex and purified EF0 subunits recognized the corresponding polypeptides of EF1F0 and KF1F0 in immunoblot analysis. Protease digestion of the individual subunits generated an identical cleavage pattern for subunits , , , , a, and c of both enzymes. Only for subunit different cleavage products were obtained. The isolated subunit c of both organisms showed only a slight deviation in the amino acid composition. These data suggest that extensive homologies exist in primary and secondary structure of both ATP synthase complexes reflecting a close phylogenetic relationship between the two enterobacteric tribes.Abbreviations ACMA
9-amino-6-chloro-2-methoxyacridine
- DCCD
N,N-dicyclohexylcarbodiimide
- FITC
fluorescein isothiocyanate
- SDS
sodium dodecyl sulfate
- TTFB
4,5,6,7-tetrachloro-2-trifluoromethylbenzimidazole 相似文献
18.
Lars-Göran Sundblad Göran Samuelsson Bosse Wigge Per Gardeström 《Photosynthesis research》1990,23(3):269-282
Two green algal species, Chlamydomonas reinhardtii and Scenedesmus obliquus, exhibited a relative maximum during the decay of luminescence, when adapted to low CO2 conditions that was not observed in high CO2 adapted cells.From the kinetics of transient changes in the level of dark fluorescence, after illumination and parallel to the luminescence maxima, it was concluded that the maximum in Scenedesmus was mainly related to a decrease in nonphotochemical quenching, whereas in Chlamydomonas the maximum was mainly related to a dark reduction of the primary PS II acceptor QA.ATP/ADP ratios from low CO2 adapted Scenedesmus showed transient high levels after a dark/light transition that was not observed in high CO2 adapted cells. After 30 s of illumination the ATP/ADP ratios however stabilized at the same steady state level as in high CO2 adapted cells.Dark addition of HCO3
- to low CO2 adapted cells of Chlamydomonas resulted in a rapid transient quenching of luminescence that was not observed in low CO2 adapted cells of neither species.It is concluded that the luminescence maxima present in both low CO2 adapted Scenedesmus and Chlamydomonas reflect adaptation of the cells to low CO2 conditions. It is further suggested that the difference in mechanistic origin of luminescence maxima in the two species reflects differences in adaptation.Abbreviations ADP
adenosine-diphosphate
- ATP
adenosine-triphosphate
- Ci
inorganic carbon
- FD
dark fluorescence recorded under dark adapted conditions
- F0
fluorescence with all reaction centers open
- FV
variable fluorescence
- PS I
photosystem I
- PS II
photosystem II
- QA
the first quinone acceptor of PS II 相似文献
19.
J. H. Becking 《Plant and Soil》1983,75(3):343-360
Summary Isotopic15N2 experiments confirmed nitrogen fixation inParasponia parviflora. The conversion ratio C2H4/N2 was 6.7 under the experimental conditions employed. Measurements of the δ15N in leaves of Parasponia and Trema showed on the basis of these determinations thatParasponia parviflora possesses N2-fixing capacity and can be distinguished in this respect from the non-nitrogen-fixingTrema cannabina tested by the same method. Therefore, δ15N can be used to monitor N2 fixation in natural ecosystems. Hydrogen evolution and the relative efficiency of N2 fixation in this relation have been determined. DetachedParasponia parviflora root nodules grown in soil and tested in an argon/oxygen atmosphere produced appr. 4 μmol H2.h−1.g−1 fresh weight root nodules. The relative efficiency of hydrogen utilization as measured in argon, air, and in the presence
of C2H2 10% (v/v) was for both equations
used for to express this efficiency 0.96 and 0.97, respectively. This indicates that Parasponia like the root nodules of
some actinorhizal symbioses (Alnus, Myrica, Elaeagnus) and some tropical legumes (Vigna sinensis) has evolved mechanisms of minimizing net hydrogen production in air, thus increasing the efficiency of electron transfer
to nitrogen. The oxygen relation of nitrogen fixation (C2H2) inParasponia parviflora root nodules was determined. The nitrogenase activity of Parasponia root nodules increased at increasing oxygen concentrations
up till c. 40% O2. At oxygen levels above 40% O2, the nitrogenase activity of the root nodules was nil or very erratic suggesting that at these oxygen levels the nitrogenase
is not longer protected against the harmful effect of oxygen. In this respect Parasponia root nodules differ from actinorhizal
root nodules in other nonlegumes, where optimal nitrogenase activity was observed in the range of 12–25% oxygen. Respiration
experiments with Parasponia root nodules showed that in the range 10, 20, and 40% oxygen, the respiration rate (CO2 evolution) increased concomitantly with an increase of the acetylene reduction rate. The CO2/C2H4 values obtained varied between 8.1 and 19.2, being therefore 2–3 times higher than similar estimations in some actinorhizal
and legume root nodules. The respiratory quotient (RQ) of detachedParasponia parviflora root nodules was in air initially approximately 2.0, but this value dropped to about 1.0 in a 3-hours period. 相似文献
20.
Bhatt D Cole SP Grabar TB Claggett SB Cain BD 《Journal of bioenergetics and biomembranes》2005,37(2):67-74
The peripheral stalk of F1F0 ATP synthase is composed of a parallel homodimer of b subunits that extends across the cytoplasmic membrane in F0 to the top of the F1 sector. The stalk serves as the stator necessary for holding F1 against movement of the rotor. A series of insertions and deletions have been engineered into the hydrophilic domain that interacts with F1. Only the hydrophobic segment from {val-121} to {ala-132} and the extreme carboxyl terminus proved to be highly sensitive to mutation. Deletions in either site apparently abolished enzyme function as a result of defects is assembly of the F1F0 complex. Other mutations manipulating the length of the sequence between these two areas had only limited effects on enzyme function. Expression of a b subunit with insertions with as few as two amino acids into the hydrophobic segment also resulted in loss of F1F0 ATP synthase. However, a fully defective b subunit with seven additional amino acids could be stabilized in a heterodimeric peripheral stalk within a functional F1F0 complex by a normal b subunit. 相似文献