| | 2 | Author
| JonathanM. Keske, J.Malcolm Bruce, P. Leslie, D. Utton | Requires cookie* | | | Title
| A New Method of Solvation Analysis: Applications to Quinones  | | | | Abstract
| A new method o f analysis o f the factor contributing to solvation o f small molecules is de scribed. A pproxim ations o f the energetic contributions to the entry o f a molecule into water have been derived from partition coefficient data o f solutes and selected derivatives from a multiplicity o f solvents. These include taking separate account energy o f the cost o f introduction o f a molecular cavity in water, the strength o f solute-water dipolar interactions, and the strengths o f hydrogen bond formation with water o f the lone pairs and hydroxylic hydrogens associated with the molecule. In this report the solvation-free energies o f benzoquinone and hydroquinone in water are described. We also consider the solvation o f the sem iquinone anion and show it to be fundamentally different from that o f either the quinone or hydroquinone; this is discussed as a potentiality for selective binding ("solvation") o f quinone, sem iquinone and hydroquinone in sites o f redox catalysis such as those found in the photosynthetic reaction center. | | | |
Reference
| Z. Naturforsch. 45c, 430 (1990); received December 18 1989 | | | |
Published
| 1990 | | | |
Keywords
| Quinone, Ligand Binding, Reaction Centers, Solvation | | | |
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| default:Reihe_C/45/ZNC-1990-45c-0430.pdf | | | | Identifier
| ZNC-1990-45c-0430 | | | | Volume
| 45 | |
| 3 | Author
| I. Agalidis, E. Rivasb, F. Reiss-Hussona | Requires cookie* | | | Title
| Characterization of Reaction Center-B875 Complex of Rhodocyclus gelatinosus: Q B Site Properties Derived from Reconstitution Experiments | | | | Abstract
| Purified reaction center-B875 pigment-protein complex isolated from Rc. gelatinosus (I. Agalidis, E. Rivas, and F. Reiss-Husson, Photosynth. Res. 23, 2 4 9 -2 5 5 (1990)) was further characterized. In the chromatophores, the quinone content was shown to be 6 menaquinones 8 and 16 ubiquinones 8 per reaction center, indicating that the pool contained both quinone types. Besides the primary (M K S) and secondary (U Q X) electron acceptors o f the reaction cen ter, the com plex contains residual quinones from the membrane pool (about 3 M K X and 5 U Q 8) probably associated with the phospholipids. Apparent particle weight o f the complex including bound detergent was 520 ± 46 kDa. The secondary quinone Q B was partially removed from the RC by treatment with 2 -3 % octaethyleneglycol dodecyl ether and 3 —4 m M orthophenanthroline. Reconstitution experi ments showed that U Q 6, U Q 9 and U Q ,0 could replace Q B but that M K S and M K , could not. It was concluded that Q B site has a clear specificity towards ubiquinone binding. | | | |
Reference
| Z. Naturforsch. 46c, 99—105 (1991); received October 10/November 26 1990 | | | |
Published
| 1991 | | | |
Keywords
| Purple Bacteria, Reaction Center, Secondary Electron Acceptor, Quinones | | | |
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| default:Reihe_C/46/ZNC-1991-46c-0099.pdf | | | | Identifier
| ZNC-1991-46c-0099 | | | | Volume
| 46 | |
| 4 | Author
| SeymourSteven Brody, Karel Heremans | Requires cookie* | | | Title
| Pressure Induced Shifts in Spectral Properties of Pigment-Protein Complexes and Photosynthetic Organisms | | | | Abstract
| Application o f elevated pressure (up to 1200 bars) results in a bathochrom ic shift o f the absorption bands o f photosynthetic pigments. The photosynthetic system s studied include: photosystem I particles, chloroplasts, acetone extracts o f chloroplasts, A U T particles and light harvesting particles o f Rh. sphaeroides, light harvesting particles o f R26. Sim ilar spectral changes are observed in all systems. The spectral shifts appear to be associated w ith pressure-induced changes in the local electric fields o f the pigm ents, rather than changes in the index o f refraction o f the solvent. | | | |
Reference
| Z. Naturforsch. 39c, 1104 (1984); received June 18 1984 | | | |
Published
| 1984 | | | |
Keywords
| Photosynthesis, Chlorophyll, High Pressure, Reaction Centers, C hlorophyll-Protein C om plexes | | | |
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| default:Reihe_C/39/ZNC-1984-39c-1104.pdf | | | | Identifier
| ZNC-1984-39c-1104 | | | | Volume
| 39 | |
| 5 | Author
| R. Steiner, B. Kalumenos, H. Scheer | Requires cookie* | | | Title
| The Photosynthetic Apparatus of Ectothiorhodospira halochloris 3. Effect of Proteolytic Digestion on the Photoactivity | | | | Abstract
| of Rhodopseudomonas viridis and Ectothiorhodospira halochloris were treated with proteinase K. The photochemical activity (light minus dark difference spectra) were compared to the polypeptide composition (SDS-polyacrylamide gel analysis). In E. halo chloris, difference bands appear at 806 (+), 838 (+) and 854 nm (-) . All three decrease in intensity upon incubation with proteinase K., but this decrease is much slower than the proteolysis of both the reaction center and antenna related polypeptides. Photochemical activity remains high as long as a small part of the RC and two lower molecular weight polypeptides M* (22.0 kDa) and B* (15.3 kDa) are present. The M subunit is the most stable polypeptide in the RC of Rp. viridis too, and the photochemical activity is related to the remainder of this and to the one newly formed polypeptide (15.3 kDa), but doesn't show the typical absorption shift of the antenna (B 800/1020 —» B 800/960). The results are discussed quantitatively a containing organisms. | | | |
Reference
| Z. Naturforsch. 41c, 873—880 (1986); received July 17 1986 | | | |
Published
| 1986 | | | |
Keywords
| Bacterial Photosynthesis, Ectothiorhodospira, Reaction Center, Proteolysis, Difference Spectro scopy Photosynthetic membranes | | | |
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| default:Reihe_C/41/ZNC-1986-41c-0873.pdf | | | | Identifier
| ZNC-1986-41c-0873 | | | | Volume
| 41 | |
| 6 | Author
| Bengt Svensson, Imre Vass, Stenbjörn Styring | Requires cookie* | | | Title
| Sequence Analysis of the D 1 and D 2 Reaction Center Proteins of Photosystem II | | | | Abstract
| A com pilation o f 38 sequences for the D1 and 15 sequences for the D 2 reaction center pro teins o f photosystem II is presented. The sequences have been compared and a similarity index that takes into account the degree o f conservation and the quality o f the changes in each posi tion has been calculated. The similarity index is used to identify and describe functionally im portant domains in the D 1 /D 2 heterodimer. Comparative hydropathy plot are presented for the aminoacid sidechains that constitute the binding domain o f the tyrosine radicals, Tyrz and TyrD, in photosystem II. The structure around Tyrz is more hydrophilic than the structure around TyrD. The hydrophilic residues are clustered in the part o f the binding pocket for Tyrz that is turned towards the lumenal side o f the thylakoid membrane. M ost prominent is the presence o f two conserved carboxylic am inoacids, D l-A sp 170 and D l-G lu 189. Their respec tive carboxyl-groups com e close in space and are proposed to constitute a metal binding site together with D l-G ln 165. The distance between the proposed metal binding site and the cen ter o f the ring o f Tyrz is approximately 7Ä . The cavity that constitutes the binding site for TyrD is com posed o f residues from the D 2 protein. Its character is more hydrophobic than the Tyrz site and the environment around TyrD lacks the cluster o f putative metal binding side chains. | | | |
Reference
| Z. Naturforsch. 46c, 765 (1991); received March 13 1991 | | | |
Published
| 1991 | | | |
Keywords
| Photosystem II, D1 Protein, D 2 Protein, Tyrosine, M anganese, Reaction Center | | | |
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| default:Reihe_C/46/ZNC-1991-46c-0765.pdf | | | | Identifier
| ZNC-1991-46c-0765 | | | | Volume
| 46 | |
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