Showing papers by "Warren L. Butler published in 1972"
TL;DR: These experiments indicate that the fluorescence yield follows the dark reduction of the primary electron donor of Photosystem II, not the photoreduction of the acceptor, which would account for the recent results of Mauzerall showing that thefluorescence yield of chloroplasts at room temperature requires about 20 musec to reach a maximum after a very brief flash.
Abstract: Absorbance changes of C-550 and cytochrome b559, and fluorescence-yield changes were measured during irradiation of chloroplasts at -196°. The photo-reduction of C-550 proceeded more rapidly than the photo-oxidation of cytochrome b559, and the fluorescence-yield change had similar kinetics to the cytochrome b559 change. The fluorescence yield of chloroplasts exposed to a 16-μsec flash at -196° did not increase during the flash, but increased in the dark after the flash. Both of these experiments indicate that the fluorescence yield follows the dark reduction of the primary electron donor of Photosystem II, not the photoreduction of the acceptor. This explanation would also account for the recent results of Mauzerall [Proc. Nat. Acad. Sci. USA (1972) 69, 1358-1362] showing that the fluorescence yield of chloroplasts at room temperature requires about 20 μsec to reach a maximum after a very brief flash.
119 citations
TL;DR: It is suggested that a relatively strong oxidant associated with the water-splitting side of Photosystem II, possibly the primary electron donor, can chlorophyll fluorescence of Photos System II as well as thePrimary electron acceptor.
65 citations
TL;DR: Hill activity, light-induced absorbance changes at liquid nitrogen temperature associated with the primary activity of photosystem II, and fluorescence yield changes at both low temperature and room temperature were measured with lyophilized spinach chloroplasts before and after extraction with hexane and reconstitution with beta-carotene and plastoquinone A.
Abstract: Hill activity (oxygen evolution with ferricyanide as the electron acceptor), light-induced absorbance changes at liquid nitrogen temperature associated with the primary activity of photosystem II, and fluorescence yield changes at both low temperature and room temperature were measured with lyophilized spinach chloroplasts before and after extraction with hexane and reconstitution with beta-carotene and plastoquinone A. Extraction eliminated the Hill activity, and both beta-carotene and plastoquinone A were required for maximal restoration of activity to the reconstituted chloroplasts.Extraction also eliminated the light-induced absorbance changes at -196 C due to the photoreduction of C-550 and photooxidation of cytochrome b(559), and reconstitution with beta-carotene and plastoquinone A restored the low temperature photoreactions. However, only beta-carotene was essential for the restoration of the photoreactions. Cytochrome b(559) was modified, as a result of the extraction, to a lower redox potential, autooxidizable form and remained as such after reconstitution with beta-carotene. The beta-carotene-restored chloroplasts showed the photoreduction of C-550 but not the photooxidation of cytochrome b(559) because the cytochrome was already oxidized. When beta-carotene-reconstituted chloroplasts were suspended in buffer containing ascorbate prior to freezing, the cytochrome b(559) was reduced and could be photooxidized by irradiation at low temperature. After reconstitution with beta-carotene plus plastoquinone A the cytochrome b(559) was partially restored to its original high potential form and was in the reduced state so that both the photoreduction of C-550 and the photooxidation of cytochrome b(559) occurred on irradiation of the beta-carotene plus plastoquinone A-reconstituted chloroplasts. Reconstitution with plastoquinone A alone had essentially no effect on restoring the photoreactions.The fluorescence yield of dark-adapted lyophilized chloroplasts at -196 C showed an irreversible increase of about 2.5-fold during irradiation. After extraction the fluorescence yield of the chloroplasts was high (at the maximal light-induced level of the lyophilized control chloroplasts) and showed very little change in the light. Reconstitution with beta-carotene alone restored some fluorescence quenching which was relieved by irradiation at low temperature. Reconstitution with plastoquinone A alone restored a high degree of quenching, but this quenching was not relieved by light at low temperature. Fluorescence emission spectra at -196 C showed that the fluorescence of variable yield in the lyophilized and beta-carotene-reconstituted chloroplasts involved only the 680 and 695 nm emission bands but not the larger 730 nm emission band, whereas the irreversible quenching in plastoquinone A-reconstituted chloroplasts involved all wavelengths of emission. Extraction of the chloroplasts also eliminated the sharp 695 nm emission band at low temperature, and reconstitution with beta-carotene partially restored it.The fluorescence yield changes at room temperature differed from the low temperature measurements in that the strong fluorescence quenching restored to the plastoquinone A-reconstituted chloroplasts was relieved by light and reappeared in the dark. Thus plastoquinone A appeared to be much more effective than beta-carotene in restoring the fluorescence of variable yield in room temperature measurements. However, it is argued from the results at low temperature that the quenching in plastoquinone A-reconstituted chloroplasts, which is probably due to the oxidized form of the quinone, is nonspecific and a different quenching mechanism from that which obtains in normal chloroplasts.The results suggest that extraction with hexane removes plastoquinone A, which interrupts electron transport, and beta-carotene, which disrupts the primary photochemical activity of photosystem II. Reconstitution of the extracted chloroplasts with beta-carotene alone restores C-550 and the primary photochemical activity of photosystem II, and when the photosystem II reaction centers are restored the additional requirement of plastoquinone A for the Hill reaction can be demonstrated.
63 citations
TL;DR: The experiments reported here were undertaken to obtain additional evidence for the site of inhibition by DBMIB and can be interpreted to indicate the size of the pool of reducible electron carriers, largely plastoquinone, that equilibrates with Q, the primary electron acceptor and fluorescence quencher of Photosystem II.
47 citations
TL;DR: Spinach chloroplasts suspended in a mixture of redox buffers were titrated under anaerobic conditions by adding small amounts of oxidant (potassium ferricyanide) or reductant (reduced methyl viologen) to determine the extent of the low temperature light-induced reduction of C-550 and oxidation of cytochrome b 559.
47 citations
TL;DR: Three b -type cytochromes have been recognized in beef heart mitochondria and ETPH and they fractionate into complexes II and III, which are functionally and spectrally comparable to b T and b K.
38 citations
22 citations
TL;DR: Erixon and Butler showed that the light-induced absorbance change of C-550 did represent a reduction and could be achieved chemically in the dark with strong reductants such as dithionite or borohydride but not with ascorbate.
13 citations
TL;DR: The data indicate that there exist two functionally distinct pools of ascorbate-reducible cytochrome b559 both of which function in the water-splitting oxygen-evolving apparatus and the lfd mutant strains are unable to split water and evolve oxygen because they lack one of the two pools.
12 citations
01 Jan 1972
TL;DR: The initial report by KNAFF et al. as mentioned in this paper that cyt b559 was photooxidized by PS II at liquid nitrogen temperature and that a new component, C-550, was photoreduced by PSII, also at low temperature, were confirmed in two other laboratories (ERIXON & BUTLER 1971b, BOARDMAN et al 1971).
Abstract: The initial report by KNAFF & ARNON (1969) that cyt b559 was photooxidized by PS II at liquid nitrogen temperature and that a new component, C-550, was photoreduced by PS II, also at low temperature, were confirmed in two other laboratories (ERIXON & BUTLER 1971b, BOARDMAN et al 1971). In the present paper we will summarize some of the additional work carried out in our laboratory on these two PS II mediated photoreactions at liquid nitrogen temperature. Most of the data presented here will appear in separate publications with greater detail as to experimental methods.
1 citations