The photochemical properties of two basic easily synthesized isatin N(2)-phenylhydrazones were investigated. Contrary to the corresponding isatin N(2)-diphenylhydrazones, only Z-isomers were isolated from the reaction mixtures during the synthesis due to their stabilization by intramolecular hydrogen bonding. Although the presence of the C=N double bond creates conditions for the formation of a...

SPPA1 is a protease in the plastids of plants, located in non-appressed thylakoid regions. In this study, T-DNA insertion mutants of the single-copy SPPA1 gene in Arabidopsis thaliana (At1g73990) were examined. Mutation of SPPA1 had no effect on the growth and development of plants under moderate, non-stressful conditions. It also did not affect the quantum efficiency of photosynthesis as measu...

Phylloquinone (vitamin K(1)) is synthesized in cyanobacteria and in chloroplasts of plants, where it serves as electron carrier of photosystem I. The last step of phylloquinone synthesis in cyanobacteria is the methylation of 2-phytyl-1,4-naphthoquinone by the menG gene product. Here, we report that the uncharacterized Arabidopsis gene At1g23360, which shows sequence similarity to menG, functio...

The quantum yield of photoisomerisation of the photoactive yellow protein (PYP) strongly depends on peak power and wavelength with femtosecond optical excitation. Using systematic power titrations and addition of second order dispersion resulting in 140, 300 and 600 fs pulse durations, the one and multi-photon cross-sections at 400, 450 and 490 nm have been assessed from transient absorption sp...

The relationship between thylakoid membrane fluidity and the process of photoinhibition at room and low (4 degrees C) temperature was investigated. Two different membrane perturbing agents--cholesterol and benzylalcohol were applied to manipulate the fluidity of isolated pea thylakoids. The photochemical activity of photosystem I (PSI) and photosystem II (PSII), polarographically determined, we...

The structural, functional, and evolutionary relationships between photosystem II and the purple nonsulfur bacterial reaction center have been recognized for several years. These can be classified as "quinone type" (type II) photosystems because the terminal electron acceptor is a mobile quinone molecule. The analogous relationship between photosystem I and the green sulfur bacterial (and helic...

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-car...