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1.
B R de Costa L Band R B Rothman A E Jacobson V Bykov A Pert K C Rice 《FEBS letters》1989,249(2):178-182
The isothiocyanate analog (1S,2S-trans-2-isothiocyanato-4,5-dichloro-N- methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]benzeneacetamide, 3a) of the highly selective kappa-opioid receptor agonist, U50,488, was prepared as a potential site-directed affinity ligand for acylation of kappa-opioid receptors in vivo. The isothiocyanate (3a) which we have designated UPHIT and its enantiomer (3b) were synthesized in 3 steps starting from optically pure (1S,2S)-(+)-trans-2-pyrrolidinyl-N-methyl-cyclohexylamine (4a) and its enantiomer (4b), respectively, thus defining their absolute stereochemistry. Binding in vitro of the 1S,2S enantiomer 3a to kappa receptors labelled by [3H]U69,593 was shown to occur with an IC50 value of 25.92 +/- 0.36 nM, whereas 827.42 +/- 5.88 and 115.10 +/- 1.23 nM were obtained for the IC50 value of the 1R,2R enantiomer (3b) and (+/-)-3 respectively. Intracerebroventricular (ICV) injection of 100 micrograms of (+/-)-3 into guinea-pig brain followed by analysis of remaining kappa-binding sites 24 h later revealed that (+/-)-3 depleted 98% of the kappa receptors that bind [3H]U69,593 and 40% of those that bind [3H]bremazocine. These preliminary data suggest exciting uses for these compounds in furthering our knowledge of the kappa-opioid receptor. 相似文献
2.
P700 is rapidly, but only transiently photooxidized upon illuminating dark-adapted leaves. Initial oxidation is followed by a reductive phase even under far-red illumination which excites predominantly photosystem (PS) I. In this phase, oxidized P700 is reduced by electrons coming from PSII. Charge separation in the reaction center of PSI is prevented by the unavailability of electron acceptors on the reducing side of PSI. It is subsequently made possible by the opening of an electron gate which is situated between PSI and the electron acceptor phosphoglycerate. Electron acceptors immediately available for reduction while the gate is closed corresponded to 10 nmol · (mg chlorophyll)–1 electrons in geranium leaves, 16 nmol · (mg chlorophyll)–1 in sunflower and 22 nmol · (mg chlorophyll)–1 in oleander. Reduction of NADP during the initial phase of P700 oxidation showed that the electron gate was not represented by ferredoxin-NADP reductase. Availability of ATP indicated that electron flow was not hindered by deactivation of the thylakoid ATP synthetase. It is concluded that NADP-dependent glyceraldehydephosphate dehydrogenase is completely deactivated in the dark and activated in the light. The rate of activation depends on the length of the preceding dark period. As chloroplasts contain both NAD- and NADP-dependent glyceraldehydephosphate dehydrogenases, deactivation of the NADP-dependent enzyme disconnects chloroplast NAD and NADP systems and prevents phosphoglycerate reduction in the dark at the expense of NADPH and ATP which are generated by glucose-6-phosphate oxidation and glycolytic starch breakdown, respectively.Abbreviations Chl
chlorophyll
- P700
electron donor pigment in the reaction center of photosystem I
Cooperation of the Institute of Botany of the University of Würzburg with the Institute of Astrophysics and Atmospheric Physics of the Estonian Academy of Sciences in Tartu was supported by the Deutsche Forschungsgemeinschaft and the Estonian Academy of Sciences. This work was performed within the Sonderforschungsbereich 251 of the University of Würzburg. 相似文献
3.
Oscillations in photosynthesis are initiated and supported by imbalances in the supply of ATP and NADPH to the Calvin cycle 总被引:4,自引:0,他引:4
Agu Laisk Katharina Siebke Ulvi Gerst Hillar Eichelmann Vello Oja Ulrich Heber 《Planta》1991,185(4):554-562
Oscillations in the rate of photosynthesis of sunflower (Helianthus annuus L.) leaves were induced by subjecting leaves, whose photosynthetic apparatus had been activated, to a sudden transition from darkness or low light to high-intensity illumination, or by transfering them in the light from air to an atmosphere containing saturating CO2. It was found that at the first maximum, light-and CO2-saturated photosynthesis can be much faster than steady-state photosynthesis. Both QA in the reaction center of PS II and P700 in the reaction center of PS I of the chloroplast electron-transport chain were more oxidized during the maxima of photosynthesis than during the minima. Maxima of P700 oxidation slightly preceded maxima in photosynthesis. During a transition from low to high irradiance, the assimilatory force FA, which was calculated from ratios of dihydroxyacetone phosphate to phosphoglycerate under the assumption that the reactions catalyzed by NADP-dependent glyceraldehydephosphate dehydrogenase, phosphoglycerate kinase and triosephosphate isomerase are close to equilibrium, oscillated in parallel with photosynthesis. However, only one of its components, the calculated phosphorylation potential (ATP)/(ADP)(Pi), paralleled photosynthesis, whereas calculated NADPH/NADP ratios exhibited antiparallel behaviour. When photosynthetic oscillations were initiated by a transition from low to high CO2, the assimilatory force FA declined, was very low at the first minimum of photosynthesis and increased as photosynthesis rose to its second maximum. The observations indicate that the minima in photosynthesis are caused by lack of ATP. This leads to overreduction of the electron-transport chain which is indicated by the reduction of P700. During photosynthetic oscillations the chloroplast thylakoid system is unable to adjust the supply of ATP and NADPH rapidly to demand at the stoichiometric relationship required by the carbonreduction cycle.Abbreviations PGA
3-phosphoglycerate
- DHAP
dihydroxyacetone phosphate
- P700
electron-donor pigment in the reaction enter of PS I
- QA
quinone acceptor in the reaction center of PS II
This work received support from the Estonian Academy of Sciences, the Bavarian Ministry of Science and Art and the Sonderforschungsbereich 251 of the University of Würzburg. We are grateful for criticism by D.A. Walker, Robert Hill Institute, University of Sheffield, U.K. and by Mark Stitt, Institute of Botany, University of Heidelberg, FRG. 相似文献
4.
J Patel A Fabbri C Pert L Gnessi F Fraioli R McDevitt 《Biochemical and biophysical research communications》1985,130(2):669-676
The present report examines the effect of different calcitonins and analogs on the in vitro phosphorylation of brain synaptic membrane proteins. The findings demonstrate that calcitonin is a potent inhibitor of several brain synaptic proteins and that salmon and eel calcitonins are considerably more potent than thyrocalcitonin in eliciting this effect. Deletion of leucine from position 16 in salmon calcitonin sequence resulted in a drastic loss of inhibitory activity, indicating the importance for a hydrophobic residue at position 16 in the intact calcitonin molecule. The mechanism of calcitonin inhibition of protein phosphorylation was likely due to the blockade of stimulation of protein kinases by calmodulin. 相似文献
5.
beta-FNA, the beta-fumaramate methyl ester of naltrexone, has been shown to antagonize irreversibly the actions of morphine on the guinea pig ileum and mouse vas deferens bioassays but does not affect the actions of delta-receptor ligands on the mouse vas deferens bioassay, suggesting that the compound does not irreversibly bind to the delta receptor. In this paper we examine the effect of beta-FNA on the binding of the prototypic delta agonists, Leu-enkephalin and D-Ala2-D-Leu5-enkephalin, its metabolically stable analogue, and show that treatment of membranes with beta-FNA does lead to alterations in the in vitro properties of delta receptors. 相似文献
6.
Richard B. Rothman Uwe K. Schumacher Candace B. Pert 《Journal of neurochemistry》1984,43(4):1197-1199
Abstract: (β-FNA, the β -fumaramate methyl ester of naltrexone, has been shown to antagonize irreversibly the actions of morphine on the guinea pig ileum and mouse vas deferens bioassays but does not affect the actions of δ-receptor ligands on the mouse vas deferens bioassay, suggesting that the compound does not irreversibly bind to the S receptor. In this paper we examine the effect of (β -FNA on the binding of the prototypic δ agonists, Leuenkephalin and d -Ala2 - d -Leu5 -enkephalin, its metabolically stable analogue, and show that treatment of membranes with β -FNA does lead to alterations in the in vitro properties of δ receptors. 相似文献
7.
The kinetics of the postillumination reduction of P700+ which reflects the rate constant for plastoquinol (PQH2) oxidation was recorded in sunflower leaves at different photon absorption densities (PAD), CO2 and O2 concentrations. The P700 oxidation state was calculated from the leaf transmittance at 830 nm logged at 50 s intervals. The P700+ dark reduction kinetics were fitted with two exponents with time constants of 6.5 and about 45 ms at atmospheric CO2 and O2 concentrations. The time constant of the fast component, which is the major contributor to the linear electron transport rate (ETR), did not change over the range of PADs of 14.5 to 134 nmol cm-2 s-1 in 21% O2, but it increased up to 40 ms under severe limitation of ETR at low O2 and CO2. The acceptor side of Photosystem I (PS I) became reduced in correlation with the downregulation of the PQH2 oxidation rate constant. It is concluded that thylakoid pH-related downregulation of the PQH2 oxidation rate constant (photosynthetic control) is not present under normal atmospheric conditions but appears under severe limitation of the availability of electron acceptors. The measured range of photosynthetic control fits with the maximum variation of ETR under natural stress in C3 plants. Increasing the carboxylase/oxygenase specificity would lead to higher reduction of the PS I acceptor side under stress.Abbreviations Cyt b
6
f
cytochrome b
6
f complex
- Cw
cell-wall CO2 concentration, M
- ETR
electron transport rate
- Fd
ferredoxin
- FNR
ferredoxin-NADP reductase
- FRL
far-red light
- PC
plastocyanin
- PAD
photon absorption density nmol cm-2 s-1
- PFD
photon flux density nmol cm-2 s-1
- PS I
Photosystem I complex
- PQ
plastoquinon
- PQH2
plastoquinol
- PS II
Photosystem II complex
- P700
Photosystem I donor pigment, reduced
- S830
830 nm signal (D830, difference of S830 from the dark level)
- WL
white light
- Yl
maximum quantum yield of PS I electron transport, rel. un 相似文献
8.
R. C. Agu T. U. Anyanwu A. H. Onwumelu 《World journal of microbiology & biotechnology》1993,9(6):660-661
High-ethanol-resistant yeasts, characterized as Saccharomyces sp., were isolated from Nigerian palm wine with added sucrose for high gravity brewing. The yeast isolates that survived the highest ethanol production were used to ferment brewery wort and produced 8.2 to 8.5% (v/v) ethanol; values almost double that of the control yeast from a local brewery. 相似文献
9.
Terry W. Moody Duncan P. Taylor Candace B. Pert 《Journal of cellular biochemistry》1981,15(2):153-159
The effect of nucleotides on central nervous system neuropeptide receptor binding was investigated. The guanine nucleotides, guanosine-5′-triphosphate and guanylyl-5′-imidodiphosphate, significantly inhibited the binding of radiolabeled vasoactive intestinal polypeptide but not that of [Tyr4]bombesin to rat brain membranes. Vasoactive intestinal polypeptide binding was inhibited by guanine nucleotides in a dose-dependent manner. Using a 20 μM dose, 60% of the specific vasoactive intestinal polypeptide binding was inhibited by guanylyl-5′-imidodiphosphate, which was more potent than guanosine-5′-triphosphate, whereas other nucleotides were not effective. This reduction in binding was a consequence of lower affinity of the receptor for vasoactive intestinal polypeptide, which in turn resulted from an increased rate of dissociation. 相似文献
10.
Naltrexone, an opiate antagonist, was administered to young obese (ob/ob) and lean mice for five weeks. Animals had continuous access to food and received 10 mg/kg SC twice daily with equivalent volumes of saline given to controls. The effects on body weight, and pituitary and plasma levels of β-endorphin-like material were measured. Naltrexone-injected obese animals gained weight more slowly over the first three weeks while the weight gain of lean animals was not affected by naltrexone. Plasma levels of β-endorphin were shown to be significantly higher in untreated ob/ob mice and this difference increased with age (4–20 weeks). With naltrexone treatment, plasma levels in +/? mice rose and exceeded those in ob/ob. Saline treatment appeared to be a stress, and pituitary β-endorphins rose 4–6 fold in ob/ob compared with +/?. While naltrexone reduced the levels in ob/ob pituitary towards normal, no effect on β-endorphin levels in pituitary of lean mice was obtained. In vitro studies of effects of the opiate antagonists, naloxone, on insulin secretion by isolated islets provided additional evidence of resistance of lean mice to naloxone relative to ob/ob. (IRI secretion fell only in naloxone treated ob/ob islets.) These observations support the contention that this form of genetic obesity is characterized by elevated endogenous opiate levels and an increased sensitivity to opiate antagonists such as naltrexone or naloxone. 相似文献