| | 2 | Author
| H. Heithier, H.-J Galla, H. Möhwald | Requires cookie* | | | Title
| Fluorescence Spectroscopic and Thermodynamic Studies of Chlorophyll Containing Monolayers and Vesicles. Part I: Mixed Monolayers of Pheophytin A and Lecithin  | | | | Abstract
| Mixed monolayers of pheophytin a and a-L-dimyristoyl lecithin (DML) are investigated on the water surface. The studies gain their special value from the simultaneous measurement of surface pressure and fluorescence intensity as a function of the covered area per molecule. A phase separation in the liquid state of the monolayer is established. Phase 1 exists almost exclusively of pheophytin molecules. Phase 2 exists essentially of D M L domains solubilizing pheo phytin in a concentration of 15 mol%. During the D M L main transition the pheophytin solubility decreases to about 2 mol%, the excess pheophytin being precipitated within the surface layer. During the pheophytin main transition an ordered structure below the surface layer is formed. A stabilizing interaction between the pheophytin domains and their environment is observed and discussed. A sharp fluorescence change at a pressure below 0.5 dyn/cm indicates another phase transition. It very probably involves an unwrapping of pheophytin from water molecules. | | | |
Reference
| Z. Naturforsch. 33c, 382 (1978); received March 15/April 3 1978 | | | |
Published
| 1978 | | | |
Keywords
| Monolayers, Chlorophyll, Energy Transfer, Fluorescence Spectroscopy, Phase Transitions | | | |
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| default:Reihe_C/33/ZNC-1978-33c-0382.pdf | | | | Identifier
| ZNC-1978-33c-0382 | | | | Volume
| 33 | |
| 5 | Author
| U. Kreibig, C. W. Etter | Requires cookie* | | | Title
| Light Diffraction of in vitro Crystals of Six Tobacco Mosaic Viruses | | | | Abstract
| Iridescent gels o f the common, tomato mosaic, para-tobacco mosaic, ribgrass mosaic, sunnhemp mosaic, and cucumber 4 tobacco mosaic virus strains were prepared using the purification method of Boedtker and Simmons (J. Amer. Chem. Soc. 1958). Macrocrystals which were stable for many months could be grown from iridescent gels of all viruses when stored at 0 -1 0 °C. The gels exhibited various structural phases (nematic and smectic) differing in density. The structure of the microcrystalline gels and of macrocrystals was investigated by means of optical diffraction. Distinct Bragg reflections were observed from which a mean periodicity of 340 nm was derived for all virus strains. The results indicate a crystalline multilayer structure as first proposed by Oster (J. Gen. Physiol. 33, 445, [1950]). The angular positions and widths of the Bragg reflections depended on the concentration of virus and the ionic strength. The periodicity decreased from 365 nm at 30 mg/ml virus to about 315 nm at 109 mg/ml virus, i.e. the periodicity approached the 300 nm length o f the virion. Model calculations taking into account Debye-Hückel repulsive and van der Waals attractive forces gave a qualitative explanation for the crystalline structure and its observed concentration dependence. The in vitro crystals resemble immature crystal forms observed in the living cell. | | | |
Reference
| Z. Naturforsch. 35c, 750—762 (1980); received March 7 1980 | | | |
Published
| 1980 | | | |
Keywords
| Tobacco Mosaic Viruses, Crystallization, Phase Transitions, Light Diffraction, Crystal Structure, Model Calculations | | | |
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| default:Reihe_C/35/ZNC-1980-35c-0750.pdf | | | | Identifier
| ZNC-1980-35c-0750 | | | | Volume
| 35 | |
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