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W L Butler

Publications and source records attributed to W L Butler.

At least 55 records · Page 3Linked to original sources
PubMed1972

A spectroscopic analysis of a high fluorescent mutant of Chlamydomonas reinhardi.

Chloroplast fragments of a high fluorescent mutant of Chlamydomonas reinhardi, hfd 91, were compared against those of Acl(+), a low chlorophyll variant of the wild type. The chloroplast fragments of the mutant which have a high invariant fluorescence yield lacked photochemical activities associated with photosystem II (PSII) but retained normal photosystem I (PSI) activities. The mutant fragments also lacked the low temperature (-196 degrees C) light-induced absorbance changes due to the photoreduction of C-550 and the photooxidation of cytochrome (cyt) b-559 which are PSII-mediated reactions. A fourth-derivative analysis of the absolute spectra of the chloroplast fragments at different stages of reduction (obtained with ferricyanide, ascorbate, and dithionite) showed both the oxidized and reduced forms of C-550 and the reduced forms of cyt c-553, b-559, and b-564 in wild-type fragments. The mutant fragments lacked C-550 and an ascorbate-reducible cyt b-559 but contained cyt c-553, a dithionite-reducible cyt b-559, and cyt b-564.

Ascorbic Acid↗
PubMed1969

Cytochrome a3: destruction by light.

Spectroscopic measurements on cultures of Prototheca zopfii irradiated with blue light revealed that inhibition of respiration was accompanied by destruction of cytochrome a(3). One of the three b-type cytochromes and one of the two c-type cytochromes of this organism were also affected. Cytochrome oxidase of yeast (not resolved into the a and a(3) components) and cytochrome a(3) of beef-heart mitochondria were also destroyed by blue light.

Cytochromes↗
PubMed1969

Photooxidation by photosystem II of tris-washed chloroplasts.

Irradiation of tris-washed chloroplasts with moderate intensities of red light caused a partial bleaching of chloroplast pigments and an inhibition of the hydroquinone-supported photoreduction of NADP. The presence of an electron donor for photosystem 2 (PS2) during the irradiation prevented the bleaching and inhibition. It is concluded that the strong oxidant produced by PS2 accumulates in tris-washed chloroplasts during irradiation and an electron donor for PS2 protects against the photooxidation reactions.

Chloroplasts↗
PubMed1968

Photoreduction and photophosphorylation with tris-washed chloroplasts.

The artificial electron donor compounds p-phenylenediamine (PD), N, N, N', N'-tetramethyl-p-phenylenediamine (TMPD), and 2,6-dichlorophenol-indophenol (DCPIP) restored the Hill reaction and photophosphorylation in chloroplasts that had been inhibited by washing with 0.8 m tris (hydroxymethyl) aminomethane (tris) buffer, pH 8.0. The tris-wash treatment inhibited the electron transport chain between water and photosystem II and electron donation occurred between the site of inhibition and photosystem II. Photoreduction of nicotinamide adenine dinucleotide phosphate (NADP) supported by 33 mum PD plus 330 mum ascorbate was largely inhibited by 1 mum 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) while that supported by 33 mum TMPD or DCPIP plus ascorbate was relatively insensitive to DCMU. Experiments with the tris-washed chloroplasts indicated that electron donors preferentially donate electrons to photosystem II but in the presence of DCMU the donors (with the exception of PD at low concentrations) could also supply electrons after the DCMU block. The PD-supported photoreduction of NADP showed the relative inefficiency in far-red light characteristic of chloroplast reactions requiring photosystem II. With phosphorylating systems involving electron donors at low concentrations (33 mum donor plus 330 mum ascorbate) photophosphorylation, which occurred with P/e(2) ratios approaching unity, was completely inhibited by DCMU but with higher concentrations of the donor systems, photophosphorylation was only partially inhibited.

Chloroplasts↗
PubMed1968

Inhibition of chloroplasts by UV-irradiation and heat-treatment.

The site of inhibition in UV-irradiated and heat-treated chloroplasts was examined by using artificial electron donor compounds such as p-phenylenediamine and hydroquinone which donated electrons specifically to photosystem II. In both cases the electron donors restored the photoreduction of nicotinamide adenine dinucleotide phosphate and the restored activity was inhibited by 3-(3,4-dichlorophenyl)-1,1-dimethyl urea. The fluorescence of variable yield was eliminated by both inhibitory treatments and was partially restored by the electron donors in the heat-treated but not the UV-irradiated chloroplasts. The results suggest that the sites of inhibition of UV-radiation and heat treatment are in the photosynthetic electron transport chain between water and photosystem II.

Chloroplasts↗