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81.
Effects of Controlled Atmospheres on Production of Sesquiterpenoid Stress Metabolites by White Potato Tuber: Possible Involvement of Cyanide-resistant Respiration
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Levels of katahdinone (solavetivone), lubimin, rishitin, and phytuberin, sesquiterpenoid stress metabolites of white potato (Solanum tuberosum), were monitored in tuber slices which were challenged with an extract of Phytophthora infestans and incubated under controlled atmospheres. A mixture of ethylene in air enhanced stress metabolite production. This enhancement was amplified by higher partial pressures of oxygen. Stress metabolite production was inhibited by salicylhydroxamic acid. These results suggest the involvement of cyanide-resistant respiration in the production of potato stress metabolites, compounds which may serve as phytoalexins. 相似文献
82.
We have observed that preincubation of 48 hour-fasted or alloxan diabetic rat liver slices, with no exogenous energy supply, for 3 hours resulted in an increased rate of incorporation of [1-14C] acetate into fatty acids and cholesterol during the following 2 hours. This preincubation effect was enhanced by the presence of glucose (25mM) in or prevented by the addition of dibutyryl cyclic adenosine 3′,5′ monophosphate (10?4M) to the preincubation medium. Preincubation of normal rat liver slices did not change their rate of incorporation of [1-14C] acetate into fatty acids or cholesterol. The rate of 14CO2 synthesized by normal, fasted or diabetic liver slices was little affected by preincubation. The preincubation effect, i.e. enhanced fatty acid synthesis was also observed in suspensions of hepatocytes from fasted and diabetic rats, preincubated for 2 hours, followed by a 1 hour incubation with either [1-14C] acetate or [3H] H2O as precursor. We conclude from these data that there is concurrent and coordinated short- and long-term regulation of fatty acid biosynthesis in fasted and diabetic rat livers. Further, we suggest that the release of inhibition by preincubation of these tissues provides a useful tool for studying the coordinated control 相似文献
83.
Sabine Voigt Salah El Kousy Nicola Schwelle Lutz Nover Martin Luckner 《Phytochemistry》1978,17(10):1705-1709
In the hyphae of Penicillium cyclopium the in vitro measurable activities of 3 enzymes of alkaloid biosynthesis are induced endogenously during 相似文献
84.
Kazu Kurosawa W.David Ollis Brian T. Redman Ian O. Sutherland Herbert M. Alves Otto R. Gottlieb 《Phytochemistry》1978,17(8):1423-1426
The absolute configurations of isoflavans and isoflavanquinones isolated from Cyclolobium, Dalbergia and Machaerium species were established by comparison of their ORD curves with that of (3S)-5,7,3′,4′-tetra-methoxyisoflavan and (3S)-7,4′-dimethoxyisoflavan-2′,5′-quinone, respectively. The assignments were checked by the ozonolysis of the isoflavan (?)-duartin to (R)-paraconic acid and the oxidation of isoflavans to isoflavanquinones. The PMR spectra of the dihydropyran ring of the isoflavans are discussed in terms of the preferred conformation of this ring. 相似文献
85.
The potentiometric acid-base titration curve of fully protonated lysozyme at ionic strengths of 0.10 and 1.0 m has been performed. The stoichiometry and the pKa values of each titratable group have been determined through the linearization of titration curves. Two types of carboxylic groups with pKa values of 3.76 and 5.02, the imidazole group with pKa 7.37 and the amine group with pKa 9.63, have been identified at an ionic strength of 0.10 m at 25.0°C. The number of titratable groups found per mole of protein has been 5.12 and 5.60 for the two types of carboxylic groups, 1.13 for the imidazole group, and 3.19 for the amino groups. The endpoint of the titration of the protein obtained by this method accords quite well with the endpoint obtained by the use of Gran function applied to the excess of strong base. 相似文献
86.
Expression and characterization of the N-terminal half of antistasin, an anticoagulant protein derived from the leech Haementeria officinalis 总被引:1,自引:0,他引:1
L O Palladino J S Tung C Dunwiddie K Alves A B Lenny C Przysiecki D Lehman E Nutt G C Cuca S W Law 《Protein expression and purification》1991,2(1):37-42
Antistasin, a 15-kDa anticoagulant protein isolated from the salivary glands of the Mexican leech Haementeria officinalis, has been shown to be a potent inhibitor of factor Xa in the blood coagulation cascade. Antistasin possesses a twofold internal homology between the N- and C-terminal halves of the molecule, suggesting a gene duplication event in the evolution of the antistasin gene. This structural feature also suggests that either or both halves of the protein may possess biological activity if expressed as separate domains. Because the N-terminal domain contains a factor Xa P1-reactive site, we chose to express this domain in an insect cell baculovirus expression system. Characterization of this recombinant half antistasin molecule reveals that the N-terminal domain inhibits factor Xa in vitro, with a K(i) of 1.7 nM. 相似文献
87.
Winfrid Liebrich Sabine Gonser Silke Brüderlein Peter Schlag 《In vitro cellular & developmental biology. Animal》1991,27(5):345-346
Supported by the “Tumorzentrum Heidelberg-Mannheim”. 相似文献
88.
The effect of mutual shading on the root/shoot ratio and on the number of nodal roots of maize was studied. Plants of two varieties (Dea and LG2281) were grown in individual pots of 9 L, at three plant densities: 7.5, 11 and 15 plants m–2. A control experiment was carried out in order to study if root growth was affected by the small size of the pots. Maize plants (cv Dea) were grown at a low plant density (7.5 plants m–2) in pots of two different volumes (9 and 25 L respectively). In both experiments plants were watered every two hours with a nutrient solution. Some plants were sampled at five dates in the main experiment and the following data were recorded: foliar stage; root, stem and leaf dry weight; number of root primordia and number of emerged roots per phytomer. The final sampling date occurred at silking.Results of the control experiment showed that the root biomass was lower in small pots but the number of nodal roots per phytomer was not affected.Results of the main experiment showed that the total plant biomass and the root/shoot ratio were lower at high plant density. The number of emerged roots was strongly reduced on the upper phytomer (P8). This reduction was mainly due to a lower percentage of root primordia which elongated. A proposed interpretation is that the number of roots which emerge on upper phytomers is controlled by carbohydrate availability. 相似文献
89.
In-situ gelation of semidilute xanthan solutions with trivalent chromium, aluminum or iron ions was studied by rheology and UV-spectroscopy. Measurements of the elastic modulus of xanthan gel cylinders prepared by dialysis against the complexing ion at pH values from 2 to 6 indicate that monomeric species of the ion are ineffective, whereas dimeric or higher oligomeric species are effective in crosslinking the polysaccharide. When chromium was used as the crosslinking species, the dependence of the gelation rate on the ionic concentration followed a power law with a coefficient of 1·7. The gelation time and the gelation rate were found to extrapolate to zero at 1 m
Cr for 2·5 mg/ml xanthan. The limiting concentration of xanthan needed for gelation with 5 m
Cr(III) at 20°C was estimated as 0·35 mg/ml. This critical xanthan concentration is close to the overlap concentration c* estimated from the experimentally determined intrinsic viscosity [η] using c* = 1·4/[η]. An apparent activation energy for crosslinking of xanthan was calculated as Ea = 42 kJ/mol and Ea = 108 kJ/mol for Cr and Al ions, respectively. The fractal dimensionality of xanthan-Cr at the sol-gel transition was estimated as 1·3 applying the Chambon-Winter criterion for gelation, thus indicating that this gelation criterion is applicable also to stiff-chain polysaccharides such as xanthan. 相似文献
90.