. Bacterial photosynthesis. Bacteria -- Physiology; Photosynthesis. 400 PHOTOMECHANICAL CONSIDERATIONS other ions used hitherto), while a partial (20 per cent) reversibility of the bleaching could be demonstrated by addition of ascorbic acid or sodium dithionite. In solutions other than alcoholic ones a change analogous to the one represented by Fig. 1-^Fig, 2 was not observed with bacteriochloro- phyll. Dilution of a concentrated methanolic bacteriochlorophyll solu- tion with water yields a colloidal nonfluorescent solution. The near- infrared spectrum of such a solution may show a complex st
. Bacterial photosynthesis. Bacteria -- Physiology; Photosynthesis. 400 PHOTOMECHANICAL CONSIDERATIONS other ions used hitherto), while a partial (20 per cent) reversibility of the bleaching could be demonstrated by addition of ascorbic acid or sodium dithionite. In solutions other than alcoholic ones a change analogous to the one represented by Fig. 1-^Fig, 2 was not observed with bacteriochloro- phyll. Dilution of a concentrated methanolic bacteriochlorophyll solu- tion with water yields a colloidal nonfluorescent solution. The near- infrared spectrum of such a solution may show a complex structure (cf. , Komen, 4) under favourable conditions (crude pigment solution, quick dilution). Addition of oxidants affects the two bands in a different way (Fig, 3).. 400 500 600 700 800 900 mu Fig. 3. Absorption spectrum and reversible bleaching of colloidal bacterio- chlorophyll, formed by addition of water to a concentrated methanolic pigment solution. The absorption band with maximum around 785 mju is bleached re- versibly to some extent; the band around 845 mju is very unstable. It also dis- appeared upon a slight heating or illumination. Reversible oxidation by addition of oxidising and reducing ions can also be demonstrated with in vivo bacteriochlorophyll. In Fig. 4, re- versible oxidation of Rho do spirillum r?/6r?/;;/chromatophores is shown. The weak absorption band at about 800 m/i is not bleached reversibly, but shows a marked stability against oxidation. Its position, however, is reversibly shifted about 5 m/i towards the blue (cf. Goedhccr, 5). This band disappears completely at a pH below 4 (cf. Thomas, Goed- heer, Komen, 6). A prerequisite for the occurrence of reversible oxidation is the presence of the central magnesium atom. No reversible oxidation could be demonstrated with Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these i
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