Über enolisierte Derivate der Chlorophyllreihe. 132‐Desmethoxycarbonyl‐173‐desoxy‐132,173‐cyclochlorophyllid a‐enol und eine Methode zur Einführung von Magnesium in porphinoide Ligandsysteme unter milden Bedingungen. (Vorläufige Mitteilung)

Isenring, Hans-Peter; Zaß, Engelbert; Smith, Keith; Falk, H.; LUISIER, JEAN-LUC; Eschenmoser, Albert

doi:10.1002/hlca.19750580816

Cited by 51 publications

(12 citation statements)

References 29 publications

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“…We conclude therefore that the slower The fraction containing [3-vinyl]-132-OH-BChl-a at site BA is called [3-vinyl]RCs. (27)(28)(29) and its potential functional importance in photosynthesis (30)(31)(32)(33) [3-vinyl]BChl-a at the monomeric site BA while -35% of the RCs have BChl-a at this position.tt The fraction containing [3-vinyl]BChl-a at site BA exhibits a slower decay of the excited electronic level P* (X' 32 ps). The additional observation of a long-lasting bleaching of the Q.…”

Section: P+b P+h-p+q- This Model Ismentioning

confidence: 99%

Primary electron transfer kinetics in bacterial reaction centers with modified bacteriochlorophylls at the monomeric sites BA,B.

Finkele

Lauterwasser

Struck

et al. 1992

Proc. Natl. Acad. Sci. U.S.A.

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The primary electron transfer has been investigated by femtosecond time-resolved absorption spectroscopy in two chemically modified reaction centers (RC) of Rhodobacter sphaeroides, in which the monomeric bacteriochlorophylls BA and BB have both been exchanged by 132-hydroxybacteriochlorophyll a or [3-vinylJ-132-hydroxybac-teriochlorophyll a. The kinetics of the primary electron transfer are not influenced by the 132-hydroxy modification. In RCs containing [3-vinyl]-132-hydroxybacteriochlorophyll a the primary rate is reduced by a factor of 10. HThe three known x-ray structures of bacterial reaction centers (RCs) show basically the same arrangement of the cofactors (see refs. 1-4). They form two branches [A (active) and B (inactive)], which are arranged in an approximate twofold symmetry. Surprisingly, the electron transfer (ET) has been found to proceed exclusively along the A branch (5-7). From the primary donor, P870 or P960, an electron is transferred to the acceptor quinone (QA) The structural arrangement of the chromophores suggests an ET via the two intervening pigments-i.e., the monomeric bacteriochlorophyll (BChl) BA and the bacteriopheophytin (BPhe) HAWhile there is general agreement that the BPhe HA is an intermediate electron acceptor (5-9), the role of the BChl BA located between the BChl dimer P and the BPhe HA is still controversially discussed. First studies with sufficient time resolution and an appropriate excitation wavelength led to the conclusion that the state P+B-(P, primary donor) is not a real intermediate in the ET (5,10,11). However, a direct ET from P* to HA over an edge-to-edge distance of '10 A can be accounted for only by a "superexchange" transfer via a virtual intermediate P+B-(12-15 Kinetic measurements were performed at T 298 K in cuvettes of 1-mm path length under stirring. The sample volume was 0.2-0.3 ml. The transmission was between T 10%o and 50% at A = 860 nm (80-25 ,uM The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

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Section: P+b P+h-p+q- This Model Ismentioning

confidence: 99%

Primary electron transfer kinetics in bacterial reaction centers with modified bacteriochlorophylls at the monomeric sites BA,B.

Finkele

Lauterwasser

Struck

et al. 1992

Proc. Natl. Acad. Sci. U.S.A.

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“…1) is a major detoxification pathway for protists feeding on unicellular algae and, in particular, on photosynthetic picoplankton. Although the tetrapyrrole macrocycle is retained in the process, Chl enols are nonfluorescent and nonphototoxic (2,15,16). They contribute up to 43% of the total chlorophyllous pigments in a water column and up to 81% in sediments, making them a major breakdown product on a global scale.…”

Section: Conversion Of Chl a To Cyclopheophorbidementioning

confidence: 99%

“…The enzymology needs to be worked out; ring closure between the 17-propionic acid side chain and the isocyclic ring in the test tube requires a strong base (10,16). It is also unclear if the protist predators produce the enzyme or if it is Author contributions: H.S.…”

Section: Conversion Of Chl a To Cyclopheophorbidementioning

confidence: 99%

Chlorophyll breakdown in aquatic ecosystems

Scheer¹

2012

Proc. Natl. Acad. Sci. U.S.A.

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“…6 While Keith was in Switzerland, Andrew Pelter moved to Swansea University to take up a position as Professor of Organic Chemistry and a lectureship became available there. Keith was appointed to the position from October 1972 and rejoined his collaboration with Pelter on organoboron chemistry.…”

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confidence: 99%

A tribute to Prof. Keith Smith

El‐Hiti¹

2012

Arkivoc

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A male child born in Walsall, England, on January 15 1947 to a family in difficult circumstances was adopted by a miner and his wife from North Staffordshire and his name became Keith Smith. As a result, Keith grew up in the rural village of Brown Edge, close to the pottery city of Stoke-on-Trent. Following the death of his mother when he was five years old, his father re-married and Keith acquired two older step-siblings. He attended the local primary school in Brown Edge, but as one of the fortunate few from the village to pass the "eleven-plus" examination his secondary education was at Leek High School, necessitating a 7 mile each way daily bus trip to Leek. It was during his time at Leek High School that he met his future wife, Lynn, who attended the neighboring high school for girls. It was also there that his interest in science, and in chemistry in particular, was stimulated. When he left Leek High in 1965 he was awarded the Mathematics, Chemistry and University Entrance Prizes.He then attended Manchester University, where he studied Chemistry. He was awarded the A F Edwards Memorial Prize at the end of his first year and went on to achieve a BSc with First Class Honors in 1968. Following his graduation, two of the most significant events that would influence his future life occurred. In August he married Lynn and in October he began research studies under the supervision of Dr Andrew Pelter, then a young member of staff in the Chemistry Department at Manchester University.His initial research project involved continuation of recent work of the Pelter group, which depended upon reactions of acyloxyboron compounds. This was successful and his first paper, on synthesis of thioesters, was submitted just a few months after he started his studies. 1 However, around that time H C Brown's seminal work into the hydroboration reaction had demonstrated that many different organoboron compounds could be easily synthesised and the first useful synthetic reactions of such compounds were beginning to emerge. With

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Über enolisierte Derivate der Chlorophyllreihe. 13²‐Desmethoxycarbonyl‐17³‐desoxy‐13²,17³‐cyclochlorophyllid a‐enol und eine Methode zur Einführung von Magnesium in porphinoide Ligandsysteme unter milden Bedingungen. (Vorläufige Mitteilung)

Cited by 51 publications

References 29 publications

Primary electron transfer kinetics in bacterial reaction centers with modified bacteriochlorophylls at the monomeric sites BA,B.

Primary electron transfer kinetics in bacterial reaction centers with modified bacteriochlorophylls at the monomeric sites BA,B.

Chlorophyll breakdown in aquatic ecosystems

A tribute to Prof. Keith Smith

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