Neue Methoden zur Einführung von Metallen in Chlorophyll‐derivate

Strell, Martin; Urumow, Todor

doi:10.1002/jlac.197719770609

Cited by 12 publications

(7 citation statements)

References 8 publications

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“…On the contrary, a strongly absorbing complex of Cu II was observed in MeOH at high concentrations of CuAc 2 . A slight blue-shift of the absorption maximum (not shown) points to dimer formation in reaction (5), although the coordination of a second Ac -by CuAc + to form CuAc 2 in reaction (4) can also be expected to take place. In both solvents, and in the absence of other potential ligands, Cu II exists usually as [Cu(Solv) 6 ] 2+ [29,30] but CuAc 2 forms dimeric species, both in the crystalline state [31] and in solution.…”

Section: Coordination Forms Of Cu II In Meoh and Mecnmentioning

confidence: 90%

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Mechanistic Information on Cu^II Metalation and Transmetalation of Chlorophylls

et al. 2009

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Chlorophyll a and pheophytin a have been treated with various metal salts in solution. As a result, metallo derivatives of photosynthetic pigments were formed, or the chlorine ring was oxidized. These studies showed that both effects can be caused by Cu II ions depending on the redox potential of its complexes formed in specific media. In this report the results of studies on metal insertion and exchange reactions are presented. According to the common use of the "acetate method" in the synthesis of metallotetrapyrroles, and the fact that acetates coordinated to Cu II ions protect chlorophylls from oxidative degradation, Cu II acetate monohydrate was selected as main reagent. The metalation and transmetalation processes were investigated with spectroscopic (UV/ Vis absorption and emission) and kinetic (conventional and high-pressure) techniques. It turned out that differences in solvent properties can significantly affect not only the rates (metalation), but also the course (transmetalation) of the reaction. The most pronounced effect was found for the trans-

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Section: Coordination Forms Of Cu II In Meoh and Mecnmentioning

confidence: 90%

“…[4,5] The metal exchange reactions of Chls and BChls are of both theoretical and practical interest. For instance, a spontaneous insertion of transition metals, such as Cu and Ni (soil pollutants), may occur in vivo and lead to the irreversible impairment of photosynthetic activity in plants.…”

Section: Introductionmentioning

confidence: 99%

Mechanistic Information on Cu^II Metalation and Transmetalation of Chlorophylls

et al. 2009

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“…We have found that direct metalation methods for chlorins , were successful with only a few metals when applied to the free base analogues of bacteriochlorins, the bacteriopheophytins. 16a,, However, Strell and Urumov's principle of transmetalation to indirectly prepare different metal-substituted chlorins could be adapted for preparing additional metal-substituted bacteriochlorophylls ([M]-BChl). Starting from [Cd]-BChl ( 8a , or its 13 2 -OH derivative, 8b ), Pd 2+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ , and Mn 2+ were incorporated into BPhe ( 1a , b ), to yield the pigments 2a , b to 6a , b and 9a , b (Figure ).…”

Section: Introductionmentioning

confidence: 99%

Metal-Substituted Bacteriochlorophylls. 1. Preparation and Influence of Metal and Coordination on Spectra

et al. 1998

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In contrast to porphyrins and chlorins, the direct metalation of bacteriochlorins is difficult. Nevertheless, Cu2+ and Zn2+ can be introduced into bacteriopheophytin in acetic acid, whereas Cd2+ can be inserted in dimethylformamide. The former reactions depend on the substituents of the isocyclic ring: they are facilitated if enolization of the β-ketoester system is inhibited. Starting with [Cd]-bacteriochlorophyll-a or its 132-hydroxy derivative, a series of metallo-bacteriochlorins with central divalent ions Pd2+, Co2+, Ni2+, Cu2+, Zn2+, and Mn2+ have been obtained by transmetalation. Like in the parent Mg complex, the four principal optical transitions are well-separated in these complexes, and their responses to changes in the central metal and its coordination state can be followed in detail. The energies of the Q y and B x transitions are almost independent of the central metal, whereas the Q x and B y transition energies change significantly, depending on the central metal as well as the presence of additional axial ligands. If the complexes are grouped by their coordination number, empirical linear correlations exist between these shifts and the ratio / , where is Pauling's electronegativity value and is the ionic radius of the metal. A similar correlation was found for those 1H NMR signals influenced mainly by the ring current and for the redox potentials. This observation was in contrast with the linear relationships with alone, found for metal-substituted porphyrins. The spectral variations influenced by the central metal and its state of ligation are attributed, within the framework of the four-orbital model, to the electrostatic interaction of the electron densities in the four orbitals with the effective charge of the central metal ions, which is most pronounced for the a2u orbital (HOMO-1). Ligation studies have revealed that addition of the first axial ligand decreases the effective charge of the central metal by approximately 50% and addition of the second axial ligand by another 20% with respect to the absence of axial ligands. The singlet−triplet splitting deduced from fluorescence and phosphorescence measurements is similar for [Pd]-, [Cu]-, [Zn]-, and [Mg]-BChl (4550 ± 100 cm-1).

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“…Under these conditions allomerisation products can nearly completely be avoided. The cadmium ion only catalyses the insertion reaction (Strell and Urumov, 1977) by forming an intermediate sitting-atop complex. No cadmium complex can be detected after extraction of the pigment.…”

Section: Investigation Of Zinc-pheophorbidesmentioning

confidence: 99%

Chlorophyll synthetase cannot synthesize chlorophyll a′

Helfrich¹,

Schoch²,

Lempert³

et al. 1994

European Journal of Biochemistry

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Chlorophyll synthetase catalyzes the last step of chlorophyll biosynthesis, namely prenylation (esterification) of chlorophyllide with phytyl diphosphate or geranylgeranyl diphosphate. During investigation of various chlorophyllide derivatives as potential substrates we observed lower esterification with increasing percentages of chlorophyllide a' in epimeric mixtures of chlorophyllides a and a: To avoid epimerization during esterification, we studied the reaction in detail with model compounds [zinc-1 32(R)-methoxy-pheophorbide a and zinc-1 3'(S)-rnethoxy-pheophorbide a, zinc-1 32(R)-methoxy-pyropheophorbide a and zinc-chlorin e,-l3', 1 5'-dimethylester]. We conclude that compounds which have the 13'-carbomethoxy group at the same side of the macrocycle as the propionic side chain of ring D are neither substrates nor competitive inhibitors. Only compounds having the 132-carbomethoxy group at the opposite site are substrates for the enzyme. Naturally occuring chlorophyll a ' must be formed by epimerization after esterification.Chlorophyll a' [a-'prime', 13Z(S)-chlorophyll a ] has been known since 1942 (Strain and Manning, 1942) as a byproduct of isolation of chlorophyll a [13'(R)-chlorophyll a]. Due to the easy epimerization of chlorophyll at C-13' (Hynninen, 1991) it is generally believed that it is formed from chlorophyll a during the extraction procedure. However, increasing evidence has accumulated during the last decade that chlorophyll a' is a natural constituent of higher plants and cyanobacteria (Watanabe et al., 1985 a,b;Kobayashi et al., 1988). Investigations on pigment composition of Chlamydomonas reinhardtii (Maroc and Tremolieres, 1990) and of P700-enriched chloroplasts of higher plants (Maeda et al., 1992) revealed that two chlorophyll a' molecules are situated in the core of photosystem I. Furthermore, the presence of two bacteriochlorophyll g 'molecules in the reaction center of heliobacteria was also described (Kobayashi et al., 1990(Kobayashi et al., , 1991. The question now arises, at which stage of the biosynthetic pathway of the chlorophylls is the prime pigment synthesized, especially whether it is formed before or after esterification of chlorophyllide a.Chlorophyll synthetase catalyzes prenylation of chlorophyllides with geranylgeranyl diphosphate (GerGerP,) or phytyl diphosphate (PhyP,), the last step of chlorophyll biosynthesis (Rudiger et al., 1980). This step is essential for translation and accumulation of chlorophyll a apoproteins (Eichacker et al., 1990(Eichacker et al., , 1992 and probably for stable assembly also for other components of the thylakoid membrane (Paulsen et al., 1990; Rudiger 1992 Rudiger , 1993. Chlorophyll synthetase catalyzes prenylation not only of chlorophyllide a, but also of chlorophyllide b and some modified derivatives (Benz and Rudiger, 1981 and Rudiger, 1992;Vezitskii and Sherbakov, 1987). During our studies on the substrate specificity of chlorophyll synthetase, we observed fractions of chlorophyllide a with a greatly reduced ability for esterificat...

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Neue Methoden zur Einführung von Metallen in Chlorophyll‐derivate

Cited by 12 publications

References 8 publications

Mechanistic Information on Cu^II Metalation and Transmetalation of Chlorophylls

Mechanistic Information on Cu^II Metalation and Transmetalation of Chlorophylls

Metal-Substituted Bacteriochlorophylls. 1. Preparation and Influence of Metal and Coordination on Spectra

Chlorophyll synthetase cannot synthesize chlorophyll a′

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Neue Methoden zur Einführung von Metallen in Chlorophyll‐derivate

Cited by 12 publications

References 8 publications

Mechanistic Information on CuII Metalation and Transmetalation of Chlorophylls

Mechanistic Information on CuII Metalation and Transmetalation of Chlorophylls

Metal-Substituted Bacteriochlorophylls. 1. Preparation and Influence of Metal and Coordination on Spectra

Chlorophyll synthetase cannot synthesize chlorophyll a′

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Mechanistic Information on Cu^II Metalation and Transmetalation of Chlorophylls

Mechanistic Information on Cu^II Metalation and Transmetalation of Chlorophylls