The aim of this work was a reinvestigation of the role of Cl('-) ions in the reactions on the oxidizing side of photosystem II in chloroplasts. It was found that thylakoid membranes retained photosynthetically active Cl('-) during their isolation in Cl('-)-free media. This Cl('-) was readily released only when the thylakoids were incubated in uncoupler-containing media at alkaline pH in the dark. Once the residual Cl('-) was released by such treatment, photosynthetic electron transport became dependent on added Cl('-) under all conditions. / The effect of Cl('-) deficiency on the stability of the higher oxidation states of the Mn-containing water photooxidase was investigated. While at least two oxidizing equivalents were accumulated on this enzyme in the absence of Cl('-), they were not as stable in the dark as when Cl('-) was present. The postulate that Cl('-) serves only as a counter ion to positively charged oxidation states of the water splitting enzyme could not be supported. / In addition to facilitating the release of Cl('-) from thylakoids, uncouplers were found to also accelerate the release of bound Mn from PS II in dark-adapted chloroplasts. This suggested that a metastable proton gradient could persist in thylakoids form some time in the dark. It is postulated that both the photosystem II Cl('-) site and the water splitting enzyme reside in a special proton sequestering domain located within the thylakoid membrane which is isolated from the bulk solutions by barriers that are nearly impermeable to protons. The experimental evidence suggests that this domain may be identical to that postulated by Dilley's research group (Baker, G. M., Bhatnager, D. and Dilley, R. A., 1980, Biochemistry 20: 2307-2315). / Source: Dissertation Abstracts International, Volume: 42-09, Section: B, page: 3520. / Thesis (Ph.D.)--The Florida State University, 1981.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_74606 |
| Contributors | THEG, STEVEN MARTIN., Florida State University |
| Source Sets | Florida State University |
| Detected Language | English |
| Type | Text |
| Format | 184 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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