| | 22 | Author
| Michael Bender, Ulrich Heber, K. Arl-, Josef Dietz | Requires cookie* | | | Title
| Saline Growth Conditions Favour Supercooling and Increase the Freezing Tolerance of Leaves of Barley and Wheat  | | | | Abstract
| When young plants o f barley and wheat grown in hydroponic culture were subjected to salt stress, their freezing tolerance increased with increasing severity o f salt stress. Detached leaves from salt-stressed plants also exhibited an increased ability to supercool. A voidance o f ice for mation permitted leaf survival at subzero temperatures which were no longer tolerated when ice nucleation resulted in extracellular freezing. The increased freezing tolerance under salt stress is attributed to osm otic adjustment o f the plants. Increased cellular solute concentra tions decrease the extent o f cellular dehydration at freezing temperatures, thereby decreasing mechanical and chemical stresses on biomembranes during freezing and thawing. | | | |
Reference
| Z. Naturforsch. 47c, 695—7 (1992); received M ay 14/July 9 1992 | | | |
Published
| 1992 | | | |
Keywords
| Barley, Chlorophyll a, Fluorescence, Freezing Tolerance (Leaves), Salt Stress, Supercooling | | | |
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| default:Reihe_C/47/ZNC-1992-47c-0695.pdf | | | | Identifier
| ZNC-1992-47c-0695 | | | | Volume
| 47 | |
| 23 | Author
| G. Renger, H. M. Gleiter, E. Haag, F. Reifarth | Requires cookie* | | | Title
| Photosystem II: Thermodynamics and Kinetics of Electron Transport from Qa" to Q b(Q b' ) and Deleterious Effects of Copper(II) | | | | Abstract
| Studies on thermodynamics and kinetics o f electron transfer from QA~ to QB(QB") were per formed by m onitoring laser flash induced changes o f the relative fluorescence emission as a function o f temperature (220 K < T < 310 K) in isolated thylakoids and PS II membrane frag ments. In addition, effects o f bivalent metal ions on PS II were investigated by measuring conven tional fluorescence induction curves, oxygen evolution, manganese content and atrazine bind ing mostly in PS II membrane fragments. It was found: a) the normalized level o f the fluores cence remaining 10 s after the actinic flash (FJF0) steeply increases at temperatures below -1 0 to -2 0 °C, b) the fast phase o f the transient fluorescence change becomes markedly retard ed with decreasing temperatures, c) am ong different cations (Cu2+, Zn2+, Cd2+, N i2+, Co2+) only Cu2+ exhibits marked effects in the concentration range below 100 jim and d) Cu2+ decreases the normalized variable fluorescence, inhibits oxygen evolution and diminishes the affinity to atrazine binding without affecting the number o f binding sites. The content o f about four manganeses per functionally competent oxygen evolving complex is not changed by [Cu2+] < 70 |iM. Based on these findings it is concluded: i) a temperature dependent equilibrium between an inactive (I) and active (A) state o f QA~ reoxidation by Q b(Qb) is characterized by standard | | | |
Reference
| Z. Naturforsch. 48c, 234 (1993); received November 23 1992 | | | |
Published
| 1993 | | | |
Keywords
| Photosystem II, Q B-Site, Copper(II) Effects, Fluorescence, Oxygen Evolution | | | |
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| default:Reihe_C/48/ZNC-1993-48c-0234.pdf | | | | Identifier
| ZNC-1993-48c-0234 | | | | Volume
| 48 | |
| 24 | Author
| ShigetohM. Iyachi11, JoachimB. Ürger, K. Iriakos, K. Otzabasisb, JensT. Hielm Annc, H. O. Rst Senger | Requires cookie* | | | Title
| Photosynthetic Characteristics of Three Strains of Cyanobacteria Grown under Low-or High-C02 Conditions | | | | Abstract
| Quantum requirements of photosynthetic oxygen evolution at 679 nm, fluorescence em is sion spectra at liquid nitrogen temperature (77 K) and fluorescence induction kinetics in the presence of DCM U, were measured in the cyanobacteria Anabaena variabilis M3, Anabaena variabilis ATCC 29413 and A nacystis nidulans R2, each grown under low-or high-C02 condi tions. L o w -C 0 2 grown cells o f the cyanobacteria showed a higher quantum requirement of photosynthetic oxygen evolution and a higher ratio o f F7U)_740 to F680_700 fluorescence and a lower variable fluorescence in the presence of D CM U than high-C02 grown cells. These findings indicate a change in excitation energy distribution in favour of photosystem I. The result might be an enhancement in ATP formation caused by cyclic electron flow which in turn provokes dissolved inorganic carbon (D IC) accumulation in these low-C02 grown cells. | | | |
Reference
| Z. Naturforsch. 51c, 40—4 (1996); received August 4/October 6 1995 | | | |
Published
| 1996 | | | |
Keywords
| Quantum Requirement, Fluorescence, Dissolved Inorganic Carbon, Anabaena variabilis, Anacystis nidulans | | | |
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| default:Reihe_C/51/ZNC-1996-51c-0040.pdf | | | | Identifier
| ZNC-1996-51c-0040 | | | | Volume
| 51 | |
| 25 | Author
| SujataR M Ishra, SurendraChandra Sabat | Requires cookie* | | | Title
| Effect of Magnesium and Calcium Ions on the Photoelectron Transport Activity of Low-Salt Suspended Hydrilla verticillata Thylakoids: Possible Sites of Cation Interaction | | | | Abstract
| Stimulatory effect o f divalent cations like calcium (Ca2+) and magnesium (M g2+) was inves tigated on electron transport activity of divalent cation deficient low-salt suspended (LS) thylakoid preparation from a submerged aquatic angiosperm, Hydrilla verticillata. Both the cations stimulated electron transport activity of LS-suspended thylakoids having an intact water oxidation complex. But in hydroxylamine (N H 2OH) -or alkaline Tris -washed thyla koid preparations (with the water oxidation enzyme impaired), only Ca2+ dependent stimula tion of electron transport activity was found. The apparent K m of Ca2+ dependent stimulation of electron flow from H 20 (endogenous) or from artificial electron donor (exogenous) to dichlorophenol indophenol (acceptor) was found to be identical. Calcium supported stimula tion of electron transport activity in N H 2OH -or Tris -washed thylakoids was electron donor selective, i.e., Ca2+ ion was only effective in electron flow with diphenylcarbazide but not with N H 2OH as electron donor to photosystem II. A magnesium effect was observed in thylakoids having an intact water oxidation complex and the ion became unacceptable in N H 2OH -or Tris -washed thylakoids. Indirect experimental evidences have been presented to suggest that Mg2+ interacts with the water oxidation complex, while the Ca2+ interaction is localized betw een Y z and reaction center of photosystem II. | | | |
Reference
| Z. Naturforsch. 53c, 849—8 (1998); received March 16/May 12 1998 | | | |
Published
| 1998 | | | |
Keywords
| Aquatic Angiosperm, Divalent Cation, Electron Transport, Fluorescence, Hydrilla verticillata | | | |
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| default:Reihe_C/53/ZNC-1998-53c-0849.pdf | | | | Identifier
| ZNC-1998-53c-0849 | | | | Volume
| 53 | |
| 26 | Author
| Wanda Wagner, Maria Zaborowska, Wlodzimierz Puzyna, David Shugar | Requires cookie* | | | Title
| Studies on Purine-Pyrimidine Hydrogen Bonded Base Pairing by Means of Absorption and Emission Spectroscopy | | | | Abstract
| Procedures are described for measurement of association constants between potentially com plementary purine and pyrimidine bases by hydrogen bonding in non-aqueous medium by means of absorption and emission spectroscopy. The methods require that one of the two constituents be fluorescent and exhibit a long wavelength absorption band not, or only partially, overlapped by the second constituent. The foregoing has been applied to measurements of the association constants, and other parameters, of hydrogen-bonded complexes of 2-aminopurine with 1-substituted uracil, thymine and barbital in chloroform solution, both in the ground and excited states. It was estab lished that the 1:1 hydrogen-bonded base pairs 2-aminopurine : 1-cyclohexyluracil and 2-amino purine: 1-octylthymine maintain the ground-state equilibrium during the life time of the excited state, whereas for the corresponding pair 2-aminopurine: 1-methylbarbital this equilibrium is per turbed on excitation. The influence of N-alkylation of the 2-aminopurine residue on base-pairing with the pyrimidines has also been examined. The results are compared with those obtained by other methods. The specific advantages of the procedures employed, and their possible applications to studies on the behaviour of fluorescent residues in polynucleotides, are discussed. | | | |
Reference
| (Z. Naturforsch. 29c, 672 [1974]; received August 1 1974) | | | |
Published
| 1974 | | | |
Keywords
| Purines and Pyrimidines, Hydrogen Bonding, Base-pairing, Excited States, Fluorescence | | | |
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| default:Reihe_C/29/ZNC-1974-29c-0672.pdf | | | | Identifier
| ZNC-1974-29c-0672 | | | | Volume
| 29 | |
| 28 | Author
| Jacek Wierzchowski, M. Arian Szczęśniak, D. Avid Shugar | Requires cookie* | | | Title
| Fluorescence Emission Properties of the Cation of 4-Aminopyrazole(3,4-d) pyrimidine, an Adenine Analogue: Evidence for Phototautomerism | | | | Abstract
| A study has been made of the emission spectra at room temperature, in aqueous and alcoholic media, of 4-aminopyrazolo(3,4-d)pyrimidine (APP) and some o f its methylated derivatives. The cationic forms APPH+, N 2-methyl-APPH+ and N 7-methyl-APPH+ exhibit intense fluorescence un der these conditions, the first two exhibiting excitation spectra which differ from the absorption spectra, pointing to the existence o f a tautomeric equilibrium in the ground state. From the shape o f the excitation spectra, and comparisons with methylated analogues in fixed tautomeric forms, it follows that the emission of APPH+ originates exclusively from the species N (2)-H ,N (7)-H +, the other forms being non-fluorescent. The proportion o f the emitting species, calculated from the ex citation wavelength dependence o f the quantum yield, is in good agreement with data for the ground state. The emission spectrum of APPH+ in aqueous medium consists o f two bands with /lmax 360 nm and 430 nm, which exhibit identical excitation spectra, but are quenched to different extents by H30 +. The 430 nm emission band is absent in alcoholic media. A similar behaviour is exhibited by N 7-methyl-APPH+, whereas the neutral form o f this analogue exhibits only the 430 nm band. These results indicate that the long wavelength emission band o f APPH+ originates from the rare tautomeric species N(7)-H formed in the excited state by photodissociation o f the N(2)-H proton from the species N(2)-H ,N(7)-H+. This is further confirmed by results obtained with the aid o f the basicity method, as well as by salt efects in non-aqueous media. Consideration is given to the possibility of such processes occurring in other analogues o f nucleic acid derivatives. | | | |
Reference
| Z. Naturforsch. 35c, 878—8 (1980); received July 28 1980 | | | |
Published
| 1980 | | | |
Keywords
| Fluorescence, Phototautomerism, Pyrazolo(3, 4-d)pyrimidines, Adenine Analogues, Protonation Sites | | | |
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| default:Reihe_C/35/ZNC-1980-35c-0878.pdf | | | | Identifier
| ZNC-1980-35c-0878 | | | | Volume
| 35 | |
| 29 | Author
| IouriE. Borissevitcha+, ChristianeP F Borgesa++, GalinaP. Borissevitcha+++, VictorE. Yushmanova+, SoniaR W Louroh, Marcel Tabaka | Requires cookie* | | | Title
| Binding and Location of Dipyridamole Derivatives in Micelles: the Role of Drug Molecular Structure and Charge | | | | Abstract
| Binding and localization of the vasodilator and antitumor drug coactivator dipyridamole (D IP) and of its three derivatives, RA14. RA47 and RA25 (D IP D), to cationic (cetyltrimeth-ylammonium chloride), anionic (sodium dodecylsulfate), zwitterionic (N-hexadecyl-N.N-di-methyl-3-ammonio-l-propanesulfonate). and neutral (r-octylphenoxypolyethoxyethanol) m i celles was studied using fluorescence, optical absorption and 'H N M R spectroscopy. The analysis of N M R . optical absorption and fluorescence data indicates that the depth of local ization of the drugs in the micelles from the surface decreased in the order D IP > RA 14 > RA47 > RA25. The binding constants for the neutral drug forms change in the same order in the range of 1400-3100 m _1 for D IP to 80-300 m _1 for RA25. This order is identical with the reported biological activity of D IP D . For the protonated drugs in zwitterionic or neutral micelles the binding constants are reduced by a factor of 20-75. | | | |
Reference
| Z. Naturforsch. 51c, 578—590 (1996); received March 28/May 31 1996 | | | |
Published
| 1996 | | | |
Keywords
| Dipyridamole and Derivatives, Micelle, Drug Location, Absorption, Fluorescence, N M R | | | |
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| default:Reihe_C/51/ZNC-1996-51c-0578.pdf | | | | Identifier
| ZNC-1996-51c-0578 | | | | Volume
| 51 | |
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