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1.
Summary Carbon 13/12 isotope ratios have been determined from leaves of a hundred C3 plant species (or ecotypes) from all major mountain ranges of the globe, avoiding drought stressed areas. A general increase in 13C content was found with increasing altitude, i.e. overall discrimination against the heavy isotope is reduced at high elevation. The steepest decline of discrimination is observed in taxa typically ranging to highest elevations (e.g. the genus Ranunculus). Mean 13C for all samples collected between 2500 and 5600 m altitude is-26.15 compared to the lowland average of-28.80 (P<0.001). Forbs from highest elevations reach-24. According to theory of 13C discrimination this indicates decreasing relative limitation of carbon uptake by carboxylation. In other words, we estimate that the ratio of internal to external partial pressure of CO2 (p
i
/p
a
)in leaves of high elevation plants is lower than in leaves of low altitude. These results confirm recent gas exchange analyses in high and low elevation plants. 相似文献
2.
The production of antimicrobial phytoalexins is one of the best-known inducible defence responses following microbial infection of plants or treatment with elicitors. In the legume soybean (Glycine max L.), 1,3-1,6--glucans derived from the fungal pathogen Phytophthora sojae have been identified as potent elicitors of the synthesis of the phytoalexin, glyceollin. Recently it has been reported that during symbiotic interaction between soybean and the nitrogen-fixing bacterium Bradyrhizobium japonicum USDA 110 the bacteria synthesize cyclic 1,3-1,6--glucans. Here we demonstrate that both the fungal and the bacterial -glucans are ligands of -glucan-binding sites which are putative receptors for the elicitor signal compounds in soybean roots. Whereas the fungal -glucans stimulate phytoalexin synthesis at low concentrations, the bacterial cyclic 1,3-1,6--glucans appear to be inactive even at relatively high concentrations. Competition studies indicate that increasing concentrations of the bacterial 1,3-1,6--glucans progressively inhibit stimulation of phytoalexin synthesis in a bioassay induced by the fungal 1,3-1,6--glucans. Another type of cyclic -glucan, a 1,2--glucan from Rhizobium meliloti, that does not nodulate on soybean, seems to be inactive as elicitor and as ligand of the -glucan-binding sites. These results may indicate a novel mechanism for a successful plant-symbiont interaction by suppressing the plant's defence response.Abbreviations HG-APEA
1-[2-(4-aminophenyl)ethyl]amino-l-[hexaglucosyl]deoxyglucitol
- HG-AzPEA
l-[2-(4-azidophenyl)-ethyl]amino-l-[hexaglucosyl]deoxyglucitol
- IC50
concentration for half-maximal displacement
We thank Ines Arlt for excellent technical assistance. This work was supported by the Deutsche Forschungsgemeinschaft (SFB 369), the Bundesministerium für Bildung, Wissenschaft, Forschung und Technologie, Fonds der Chemischen Industrie (J.E.), and USDA CSRS NRI Competitive Research grant 93373059233 (A.A.B.). 相似文献
3.
Unravelling the factors that contribute to the formation and the stability of -sheet structure in peptides is a subject of great current interest. A -hairpin, the smallest -sheet motif, consists of two antiparallel hydrogen-bonded -strands linked by a loop region. We have performed a statistical analysis on protein -hairpins showing that the most abundant types of -hairpins, 2:2, 3:5 and 4:4, have characteristic patterns of 13C and 13C conformational shifts, as expected on the basis of their and angles. This fact strongly supports the potential value of 13C and 13C conformational shifts as a means to identify -hairpin motifs in peptides. Their usefulness was confirmed by analysing the patterns of 13C and 13C conformational shifts in 13 short peptides, 10–15 residues long, that adopt -hairpin structures in aqueous solution. Furthermore, we have investigated their potential as a method to quantify -hairpin populations in peptides. 相似文献
4.
Sources of organic and inorganic carbon in a headwater stream: Evidence from carbon isotope studies 总被引:7,自引:2,他引:7
Sheila M. Palmer Diane Hope Michael F. Billett Julian J.C. Dawson Charlotte L. Bryant 《Biogeochemistry》2001,52(3):321-338
A combination of stable isotope studies and 14Cdating were used to identify the main sources andprocesses controlling streamwater DOC and TIC in atemperate non-forested watershed. 13Cvalues for terrestrial (–24.9 to –29.1) and aquatic(–30.5 to –33.5) plants were similar to valuesreported in the literature for similar ecosystems.13C values for DOC in soil solution andstreamwater were consistent with soil and terrestrialvegetation, indicating that the terrestrial ecosystemis the dominant source of aquatic DOC in thiswatershed. 13C values of soil atmosphereCO2 (–17.2 to –25.2) were slightly lessnegative than would be expected for production viaaerobic soil microbial decomposition and rootrespiration. There was a close correspondence between13C values (–15.5 to –21.5) forstreamwater TIC and soil atmospheric CO2 in thecentral part of the catchment where the stream drainsCO2-rich peats. 14C dating showed thatalthough peat has been accumulating in the watershedfor at least 2700 years, DOC in soil pore water andstreamwater contains carbon of predominantly recentorigin (post-AD 1955). 相似文献
5.
The measurement of natural 15N abundance is a well-established technique for the identification and quantification of biological N2 fixation in plants. Associative N2 fixing bacteria have been isolated from sugarcane and reported to contribute potentially significant amounts of N to plant growth and development. It has not been established whether Australian commercial sugarcane receives significant input from biological N2 fixation, even though high populations of N2 fixing bacteria have been isolated from Australian commercial sugarcane fields and plants. In this study, 15N measurements were used as a primary measure to identify whether Australian commercial sugarcane was obtaining significant inputs of N via biological N2 fixation. Quantification of N input, via biological N2 fixation, was not possible since suitable non-N2 fixing reference plants were not present in commercial cane fields. The survey of Australian commercially grown sugarcane crops showed the majority had positive leaf 15N values (73% >3.00, 63% of which were >5.00), which was not indicative of biological N2 fixation being the major source of N for these crops. However, a small number of sites had low or negative leaf 15N values. These crops had received high N fertiliser applications in the weeks prior to sampling. Two possible pathways that could result in low 15N values for sugarcane leaves (other than N2 fixation) are proposed; high external N concentrations and foliar uptake of volatilised NH3. The leaf 15N value of sugarcane grown in aerated solution culture was shown to decrease by approximately 5 with increasing external N concentration (0.5–8.0 mM), with both NO3
– and NH4
+ nitrogen forms. Foliar uptake of atmospheric NH3 has been shown to result in depleted leaf 15N values in many plant species. Acid traps collected atmospheric N with negative 15N value (–24.45±0.90) from above a field recently surface fertilised with urea. The 15N of leaves of sugarcane plants either growing directly in the soil or isolated from soil in pots dropped by 3.00 in the same field after the fertiliser application. Both the high concentration of external N in the root zone (following the application of N-fertilisers) and/or subsequent foliar uptake of volatilised NH3 could have caused the depleted leaf 15N values measured in the sugarcane crops at these sites. 相似文献
6.
Our investigations of diurnal variations of the 13C/12C ratio and CO2 content in soil air were carried out in three environments during periods of high biosphere activity. It has been observed that diurnal variation of CO2 concentration is negatively correlated 13. Particularly great variations occurred at shallow soil depths (10–30 cm) when the plant cover activity was high while the soil temperature was rather low. Under such conditions the 13 variations had the magnitude of 4, while the CO2 concentration varied more than doubly. The maximum of the 13C/12C ratlo and the minimum of the CO2 concentration in a cultivated field with winter wheat took place in the afternoon, whereas in deciduous forest similar patterns were observed at dawn. In these cases soil temperatures at 10 cm depths varied less than 2°C. Hence, under wheat the variation in root respiration rate seem to be the main reason of the recorded varations. In an uncultivated grass-field during the hottest period in summer we did not measure any distinct variations of CO2 properties in spite of the fact that soil temperature varied up to 5°C. This might be due to dominant microbial respiration at the high soil temperature, which exceeded 20°C. 相似文献
7.
Ethylene treatment (approx. 20 l ·1-1 in air for 2 d) of tobacco (Nicotiana tabacum L. cv. Havana 425) plants markedly increases the endo--1,3-glucanase (EC 3.2.1.39) content of leaves. The antigenic form of the enzyme induced is the same one whose production is blocked by treating cultured cells with combinations of auxin (1.1 · 10-5 M -naphthaleneacetic acid) and cytokinin (1.4 · 10-6 M kinetin). Evidence is presented that cultured tobacco cells require ethylene for -1,3-glucanase accumulation: i) ethylene treatment increased the accumulation of \-1,3-glucanase in callus tissues >10 d after subculturing and in cell-suspension cultures; ii) callus tissues can produce ethylene; iii) conditions known to inhibit ethylene production (1 mM CoCl2; 33° C treatment) or ethylene action (approx. 1.6 mmol · 1-1 norbornadiene in air) inhibited -1,3-glucanase accumulation by callus tissues treated for 4 d following subculturing; and, these inhibitory effects were prevented by exogenous ethylene. Combinations of auxin and cytokinin blocked ethylene-induced accumulation of -1,3-glucanase by cell-suspension cultures. The results favor a model in which ethylene induces results favor a model in which ethylene induces 1,3-glucanase accumulation, and auxin and cytokinin inhibit this induction process.Abbreviations NAA
-naphthaleneacetic acid
- NDE
norbornadiene 相似文献
8.
Yazdi Mojtaba Tabatabaei Khosravi Amir Abbas Nemati Mahboob Motlagh Niloofar Davoodi Vijeh 《World journal of microbiology & biotechnology》2003,19(1):79-84
Two intracellular -glucosidases (E.C. 3.2.1.21) were purified from the filamentous fungus Neurospora crassa, mutant cell-1 (FGSC no. 4335) and characterized. The extent of purification were 2.55- and 28.89-fold for -glucosidase A and -glucosidase B, respectively. -Glucosidase A was a dimeric protein, and B a monomeric protein, with molecular masses of 178 and 106 kDa, respectively. Both isoenzymes were glycoproteins with relatively high carbohydrate contents (-glucosidase A, 29.2%; -glucosidase B, 34.2%). The isoelectric points determined by IEF were 6.27 and 4.72, respectively. pH optima for activity were determined to be 5.0 and 5.5, and temperature optima to be 55 and 60 °C, for -glucosidases A and B, respectively. Both purified -glucosidases. especially -glucosidase B, showed relatively high stability against pH and temperature. Both enzymes were stable in the pH range of 5.0–9.0. The activities were completely retained up to 48 h at temperatures below 40 °C. At higher temperatures, enzymes were relatively unstable and lost their activities at 60 °C after 24 h. Both -glucosidases were highly activated by CuCl2, and inhibited by SnCl2 and KMnO4. Hg2+ and Ag+ also inhibited severely -glucosidase B. The K
m and V
max values of the isoenzymes against cellobiose as substrate were 1.50 mM and 12.2mol min–1 mg–1 for -glucosidase A and 2.76 mM and 143.5 mol min–1 mg–1 for -glucosidase B. 相似文献
9.
Eric Mossel Fernando Formaggio Giovanni Valle Marco Crisma Claudio Toniolo Mitsunobu Doi Toshimasa Ishida Quirinus B. Broxterman Johan Kamphuis 《Letters in Peptide Science》1998,5(2-3):223-225
In order to obtain further information on the role played by phenyl ring position in the C-methylated -amino acid side chain on peptide preferred conformation, the crystal-state structural preferences of C-methyl, C-phenylglycine peptides have been determined by X-ray diffraction. This study shows that either the fully extended conformation or the -bend/310-helical structures are adopted by peptides characterized by this C-methylated, -branched, aromatic -amino acid. 相似文献
10.
Seung R. Paik Ken Yokoyama Masasuke Yoshida Toshiko Ohta Yasuo Kagawa William S. Allison 《Journal of bioenergetics and biomembranes》1993,25(6):679-684
The ATPase activity of the F1-ATPase from the thermophilic bacterium PS3 is stimulated at concentrations of rhodamine 6G up to about 10 µM where 70% stimulation is observed at 36°C. Half maximal stimulation is observed at about 3 µM dye. At rhodamine 6G concentrations greater than 10 µM, ATPase activity declines with 50% inhibition observed at about 75 µM dye. The ATPase activities of the 33 and 33 complexes assembled from isolated subunits of TF1 expressed inE. coli deleted of theunc operon respond to increasing concentrations of rhodamine 6G nearly identically to the response of TF1. In contrast, the ATPase activities of the 33 and 33 complexes are only inhibited by rhodamine 6G with 50% inhibition observed, respectively, at 35 and 75 µM dye at 36°C. The ATPase activity of TF1 is stimulated up to 4-fold by the neutral detergent, LDAO. In the presence of stimulating concentrations of LDAO, the ATPase activity of TF1 is no longer stimulated by rhodamine 6G, but rather, it is inhibited with 50% inhibition observed at about 30 µM dye at 30°C. One interpretation of these results is that binding of rhodamine 6G to a high-affinity site on TF1 stimulates ATPase activity and unmasks a low-affinity, inhibitory site for the dye which is also exposed by LDAO. 相似文献
11.
J. Desmet E. Tieghem H. Van Dael E. Van Cauwelaert 《European biophysics journal : EBJ》1991,20(5):263-268
By means of reaction calorimetry we measured the apparent enthalpy change, Happ, of the binding of Mn2+-ions to goat -lactalbumin as a function of temperature. The observed Happ can be written as the sum of contributions resulting from a conformational and a binding process. In combination with the thermal unfolding curve of goat -lactalbumin, we succeeded in separating the complete set of thermodynamic parameters (H, G, S, Cp) into the binding and conformational contributions. By circular dichroism we showed that NH
4
+
-ions, upon binding to bovine a-lactalbumin, induce the same conformational change as do Na+ and K+: the binding constant
equals 98 ± 9 M–1.Abbreviations BLA
bovine -lactalbumin
- GLA
goat -lactalbumin
- HLA
human -lactalbumin
- CD
circular dichroism
Offprint requests to: H. Van DaelDeceased 相似文献
12.
Carbon and nitrogen isotope ratios in different compartments of a healthy and a declining Picea abies forest in the Fichtelgebirge,NE Bavaria 总被引:4,自引:0,他引:4
Summary Natural carbon and nitrogen isotope ratios were measured in different compartments (needles and twigs of different ages and crown positions, litter, understorey vegetation, roots and soils of different horizons) on 5 plots of a healthy and on 8 plots of a declining Norway spruce (Picea abies (L.) Karst.) forest in the Fichtelgebirge (NE Bavaria, Germany), which has recently been described in detail (Oren et al. 1988a; Schulze et al. 1989). The 13C values of needles did not differ between sites or change consistently with needle age, but did decrease from the sun-to the shade-crown. This result confirms earlier conclusions from gas exchange measurements that gaseous air pollutants did no long-lasting damage in an area where such damage was expected. Twigs (13C between-25.3 and-27.8) were significantly less depleted in 13C than needles (13C between-27.3 and-29.1), and 13C in twigs increased consistently with age. The 15N values of needles ranged between-2.5 and-4.1 and varied according to stand and age. In young needles 15N decreased with needle age, but remained constant or increased in needles that were 2 or 3 years old. Needles from the healthy site were more depleted in 15N than those from the declining site. The difference between sites was greater in old needles than in young ones. This differentiation presumably reflects an earlier onset of nitrogen reallocation in needles of the declining stand. 15N values in twigs were more negative than in needles (-3.5 to-5.2) and showed age- and stand-dependent trends that were similar to the needles. 15N values of roots and soil samples increased at both stands with soil depth from-3.5 in the organic layer to +4 in the mineral soil. The 15N values of roots from the mineral soil were different from those of twigs and needles. Roots from the shallower organic layer had values similar to twigs and needles. Thus, the bulk of the assimilated nitrogen was presumably taken up by the roots from the organic layer. The problem of separation of ammonium or nitrate use by roots from different soil horizons is discussed. 相似文献
13.
Chimeric G proteins, obtained by exchanging their C-terminal portion for that of a G protein from an unrelated class, drive the receptor selectivity to that corresponding to the introduced G protein domain. The 2A-adrenoceptor (2AAR), which yielded an efficacious and weak [35S]GTPS binding response by respectively G o and G i3 protein, was investigated in CHO-K1 cells co-expressing chimeric G proteins for which the six last C-terminal amino acids between G o and G i3 proteins, and reciprocally, were permuted. Activation of the chimeric G o / i3 protein was highly efficient whereas the G i3 / o protein yielded a weak stimulation. These [35S]GTPS binding responses were not different from their parental wild-type G o and G i3 proteins. Similar results were obtained with an 2AAR carrying a facilitating Thr373Lys mutation in a putative G protein interaction domain. These data indicate that the six terminal G o protein amino acids do not constitute a major 2AAR interaction domain for G protein activation. 相似文献
14.
R. Lohrmann 《Journal of molecular evolution》1976,8(3):197-210
Summary Aqueous solutions of linear inorganic polyphosphates incubated in presence of Mg ions depolymerize to give trimetaphosphate. The presence of a nucleoside 5-phosphate has little influence upon the reaction. Drying the products obtained by incubating a linear polyphosphate with Mg ions in the presence of a nucleoside 5-phosphate yields nucleoside 5-polyphos-phates. The prebiological relevance of the reactions is discussed.Abbreviations Pn(n=1,2,3,)
linear polyphosphate containing n phosphate residues
- P3!
trimetaphosphate
- A
adenosine
- pnN
nucleoside 5-polyphosphate containing n phosphate residues, e.g. with N = A, n = 4
- p4N
adenosine 5-tetraphosphate
-
P
*
lpmA
pnA, (n = 1 + m); adenosine 5-polyphosphate containing n phosphate units with33p-label on terminal 1 phosphate groups 相似文献
15.
In this study, we investigate the effects of endothelin-1 (ET-1) and insulin on the cellular activity of protein kinase FA/glycogen synthase kinase-3 (kinase FA/GSK-3) in rat adipocytes. The cellular activity of kinase FA/GSK-3 is inhibited to 50% of control within 30 min when cells are treated with 1 nM ET-1 at 37°C; in addition, significant inhibition to 60% of control is observed at as low as 1 pM ET-1. Conversely, ET-1 at concentrations up to 1 nM has no direct effect on purified kinase FA/GSK-3 in vitro. Immunoblotting analysis further reveals that the protein level of this kinase is not significantly changed when treated with 1 nM ET-1 for 30 min. Similar to ET-1, insulin as low as 10 nM can also induce inactivation of kinase FA/GSK-3 to 50% of control in adipocytes when processed under identical conditions. Most importantly, when treated with both insulin and ET-1, the activity of kinase FA/GSK-3 can be decreased only to 50% of control. Taken together, the results provide initial evidence that ET-1 and insulin may regulate this important multisubstrate/multifunctional protein kinase in a common signaling pathway in cells. 相似文献
16.
Hydrogen consumption by various thermophilic, mesophilic and/or psychrotrophic homoacetogens and methanogens was measured at temperatures between 4 and 80°C. Within the tolerated temperature range H2 was consumed until a final H2 threshold partial pressure was reached. H2 thresholds generally decreased with temperature, parallel to the values calculated from the thermodynamics prevailing under culture conditions, i.e. the Gibbs free energy (G) of H2 oxidation corrected for temperature by both the free-energy form of the Nernst equation and the Van't Hoff equation. The difference between the observed and the calculated H2 partial pressures gives the minimum energy required for H2 utilization being about-5 to-6 kJ/mol H2 for the homoacetogenes and-9 to-12 kJ/mol H2 for methanogens. The temperature dependence of the standard Gibbs free energy (G0) as described by the Van't Hoff equation apparently became the more important for thermodynamics as well as H2 thresholds the more the temperature deviated from standard conditions (i.e. 25°C). Correction factors for calculation of temperature-corrected G
infT
sup0
are presented for various H2-producing and H2-consuming reactions. 相似文献
17.
In modern malting barley breeding it is important to increase the level of -amylase activity level in barley. The aim of this study was to investigate if a PCR method for screening -amy1 alleles can be used as an indicator for -amylase activity level in barley. Activity was assayed from 24 cultivars, 7 lines, and a Hordeum spontaneum PI 296897 strain grown in the same field. The -amy1 alleles were identified by amplifying the intron III-specific region of the gene using PCR. No new alleles were detected in addition to the three alleles found earlier: cv Adorra-like, cv Haruna Nijo-like and PI 296897-like -amy1 allele. Samples were grouped according to the nature of their -amy1 locus and enzyme activities were compared between the groups. Cultivars carrying a cv Haruna Nijo-like -amy1 allele had 1.3 times and lines carrying a PI 296897-like -amy1 allele had 2.1 times higher -amylase activity than cultivars carrying a cv Adorra-like -amy1 allele. The mean activities are significantly different in the allele groups (Kruskal–Wallis: for protein H= 11.54, P< 0.01; for meal H= 12.74, P< 0.01). PCR fragments can be used as allele specific markers to predict the level of -amylase activity in breeding when such variation of the intron III is concerned. 相似文献
18.
Masayuki Gotoh Jun-ichi Kitanaka Yoshimi Hirasawa Kaoru Kondo Akemichi Baba 《Neurochemical research》1994,19(6):679-685
Desensitization of prostaglandin (PG) F2 receptor-mediated phosphoinositide (PI) hydrolysis was investigated in cultured rat astrocytes. Prolonged exposure of astrocytes differentiated by dibutyryl cyclic AMP-treatment to PGF2 caused the desensitization of subsequent PGF2-induced PI hydrolysis. The desensitization was time- and PGF2 dose-dependent; maximal decrease in the PI hydrolysis was observed after exposure to 10 M PGF2 for 4 h and the degree of the desensitization was 31.7±2.7% of control. Pretreatment with either PGD2 or PGE2 also induced the desensitization of subsequent PGF2-stimulated PI hydrolysis and conversely pretreatment of PGF2 decreased the PI responses to PGD2 and PGE2. The desensitization prevented by phloretin and was reversible upon removal of the agonist. Protein synthesis inhibitors blocked the recovery of the desensitization. Treatment of the cells with phorbol 12-myristate 13-acetate had no effect on the desensitization. These results suggest that prolonged exposure of the astrocytes to PGF2 caused the desensitization of the receptors. 相似文献
19.
Summary Organic pyrophosphates such as UppA and NAD are formed when a solution containing a nucleotide, a nucleoside 5-polyphosphate, Mg2+ and imidazole are allowed to dry out. We suggest that this synthesis may have occured concurrently with oligonucleotide formation.Abbreviations Im
Imidazole
- CDI
1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride
- EDTA
ethylenediaminetetraacetic acid
- A
adenosine
- U
uridine
- pnA
adenosine 5-poly-phosphate containing n phosphate residues
- pU
uridine 5-phosphate
- AppA
P1,P2-diadenosine 5-pyrophosphate
- UppA
P1-(uridine 5)-P2-(adenosine 5)-pyrophosphate
- ImpA
adenosine 5-phosphorimidazolide
- NMN
nicotinamide mononucleotide
- NAD
nicotinamide-adenine dinucleotide 相似文献
20.
Summary The angular dependence of1JC,H in model compounds related to -linked oligosaccharides has been established by FPT INDO quantum chemical calculations. Values calculated for models of (1 1)-, (1 2)-, (1 3)- and (1 4)-linked disaccharides were compared, and the effect of the orientation of HO-2 elucidated. The angular dependence of1JC,H on the torsional angles H and H and the solvent dielectric constant (s) was characterized in the form:1JC,H = A cos2+B cos + C sin2 + D since + E + Fe. The1JC,H values, measured by DEPT methods for C-1-H-1 and C-X-H-X in cellobiose, cyclic trisaccharide and hexopyranoses were used to adjust the calculated angular dependences. Based on the occurrence of the conformers for agarobiose, neoagarobiose, mannobiose and methyl -xylobioside, the thermodynamically averaged <1JC,H > values were calculated. The results obtained (<1JC-1,H-1 > 162.4, <1JC-4, H-4 > 147.6 Hz for methyl -xylobioside; <1JC-1,H-1 > 162.4 and <1JC-4,H-4] > 147.6 Hz for mannobiose; <1JC-1,H-1 > 162.8 Hz for neo agarobiose and <1JC-1,H-1 > 163.2 Hz for agarobiose) agree well with the experimental values of 162.7, 147.5, 160.4, 147.2, 160.9 and 165.7 Hz, respectively. 相似文献