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Studies on the electron transfer from Tyr-161 of polypeptide D-1 to P680+ in PS II membrane fragments from spinach (1989)

Renger, G. ; Eckert, H-J. ; Völker, M.

Springer

Photosynthesis research 22 (1989), S. 247-256

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ISSN: 1573-5079

Keywords: photosystem II ; P680+ reduction ; reorganisation energy ; Ca2+ effect

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract The functional connection between redox component Y z identified as Tyr-161 of polypeptide D-1 (Debus et al. 1988) and P680+ was analyzed by measurements of laser flash induced absorption changes at 830 nm in PS II membrane fragments from spinach. It was found that neither DCMU nor the ADRY agent 2-(3-chloro-4-trifluoromethyl) anilino-3,5-dinitrothiophene (ANT 2p) affects the rate of P680+ reduction by Y z under conditions where the catalytic site of water oxidation stays in the redox state S1. In contrast to that, a drastic retardation is observed after mild trypsin treatment at pH=6.0. This effect which is stimualted by flash illumination can be largely reversed by Ca2+. The above mentioned data lead to the following conclusions: (a) the segment of polypeptide D-1 containing Tyr-161 and coordination sites of P680 is not allosterically affected by structural changes due to DCMU binding at the QB-site which is also located in D-1. (b) ANT 2p as a strong protonophoric uncoupler and ADRY agent does not modify the reaction coordinate of P680+ reduction by Y z , and (c) Ca2+ could play a functional role for the electronic and vibrational coupling between the redox groups Y z and P680. The electron transport from Y z to P680+ is discussed within the framework of a nonadiabatic process. Based on thermodynamic considerations the reorganization energy is estimated to be in the order of 0.5 V.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00048303

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Quantitative HPTLC determination of selenium (1986)

Funk, W. ; Dammann, V. ; Couturier, T. ; [et al.]

Weinheim : Wiley-Blackwell

Journal of High Resolution Chromatography 9 (1986), S. 224-235

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ISSN: 0935-6304

Keywords: Thin-layer chromatography, HPTLC ; Biological matrices ; Fluorimetric detection ; Selenium ; Chemistry ; Analytical Chemistry and Spectroscopy

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The present determination of selenium in biological matrices by HPTLC with in situ fluorimetric detection is an accurate alternative method, comparable to other established methods such as photometry, polarography, neutron activation, or X-ray fluorescence analysis, gas chromatography, and atomic absorption spectrometry.The excellent sensitivity of this procedure is proved by the detection limit of 250 fg of selenium per spot (using purified 2,3,1-naphthoselenodiazole). The oxidation of organic matrices, applying a novel digestion procedure, may be carried out with little instrumental expenditure.Sample preparation steps, such as the oxidation of selenium to Se (VI) and subsequent reduction to Se (IV) do not lead to significant random or systematic errors, nor does the digestion step, if an optimized procedure is used.A recovery rate of 103% and nearly parallel calibration curves for digested selenocysteine standards compared with spiked human serum samples demonstrate the accurate quantitative preparation of a biological matrix. Any interfering metal ions can be masked by addition of chelate-forming reagents.

Additional Material: 24 Ill.