Probing native‐like orientation of pigments in modified reaction centers from <i>Rhodobacter sphaeroides</i> R26 by linear dichroism

Meyer, Michaela; Scheer, Hugo; Breton, Jacques

doi:10.1016/0014-5793(96)00869-1

Cited by 10 publications

(8 citation statements)

References 16 publications

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“… a Obtained in toluene at room temperature. b Relative intensity of the indicated peak versus that of the Q y (0,0) band. c Mixture of the B x (0,0) and B y (0,0) absorption bands. d Absorption data (in diethyl ether) from ref . e Fluorescence data (in toluene) from ref . f Data from ref . …”

Section: Resultsmentioning

confidence: 99%

Construction of the Bacteriochlorin Macrocycle with Concomitant Nazarov Cyclization To Form the Annulated Isocyclic Ring: Analogues of Bacteriochlorophyll a

Zhang

Lindsey

2017

J. Org. Chem.

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Bacteriochlorophylls contain a bacteriochlorin macrocycle bearing an annulated fifth ring. The fifth ring, termed the isocyclic ring or ring E, is equipped with 13-oxo and 13-carbomethoxy substituents. Herein, a general route to stable, synthetic bacteriochlorophyll analogues is described. Knoevenagel condensation (∼40 mM, rt, CHCl, piperidine/AcOH/molecular sieves) of a dihydrodipyrrin-carboxaldehyde (AD half) and a dihydrodipyrrin substituted with a β-ketoester (BC half) forms a propenone bearing the two halves (a hydrobilin analogue). Subsequent treatment (0.2 mM) with acid (Yb(OTf), CHCN, 80 °C) promotes a double ring-closure process: (i) condensation between the α-position of pyrrole ring A and the α-acetal unit attached to pyrroline ring B forms the bacteriochlorin macrocycle, and (ii) Nazarov cyclization of the β-(propenoyl)-substituted ring C forms the isocyclic ring (E). Five new bacteriochlorins bearing various substituents (alkyl/alkyl, aryl, and alkyl/ester) at positions 2 and 3 (β-pyrrole sites, ring A) and 13 carboalkoxy groups (R = Me or Et) were constructed in 37-61% yield from the hydrobilin analogues. The BC half and AD half are available in five and eight steps, respectively, from the corresponding pyrrole-2-carboxaldehyde and unsaturated ketone. The bacteriochlorins exhibit absorption spectra typical of bacteriopheophytins (free base bacteriochlorophylls), with a strong near-infrared absorption band (707-751 nm).

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Section: Resultsmentioning

confidence: 99%

Construction of the Bacteriochlorin Macrocycle with Concomitant Nazarov Cyclization To Form the Annulated Isocyclic Ring: Analogues of Bacteriochlorophyll a

Zhang

Lindsey

2017

J. Org. Chem.

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“…This question will be further addressed by using Rb. sphaeroides (R26) RCs in which H A has been exchanged for 12 C-or 13 C-labeled plant pheophytin (Meyer & Scheer, 1995;Meyer et al, 1996).…”

Section: Discussionmentioning

confidence: 99%

Electrostatic Influence of Q_A Reduction on the IR Vibrational Mode of the 10a-Ester CO of H_A Demonstrated by Mutations at Residues Glu L104 and Trp L100 in Reaction Centers from Rhodobacter sphaeroides

et al. 1997

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The light-induced QA-/QA FTIR difference spectrum of the photoreduction of the primary quinone (QA) in reaction centers (RCs) from Rhodobacter sphaeroides exhibits a set of complex differential bands between 1750 and 1715 cm(-1). Several of these features correspond in frequency to bands that bleach in the HA-/HA FTIR difference spectra of the photoreduction of the bacteriopheophytin electron acceptor (HA). Since the 10a-ester C==O from HA and the side chains of protonated carboxylic acids would be expected to contribute in this spectral region, mutations were designed at Trp L100 and Glu L104, which have been proposed to form hydrogen bonds to the 10a-ester and the 9-keto carbonyls on ring V of HA, respectively. The QA/-/QA spectra measured in IH2O and 2H2O of RCs from wild type (WT) were compared to those of RCs with the mutation Trp to Phe at L100 [WF(L100)], Glu to Leu at L104 [EL(L104)], or both mutations [EL(L104)/WF(L100)]. The spectra of the mutants in the 1800-1400 cm(-1) frequency range exhibit only limited perturbations compared to those of WT, indicating the absence of significant structural changes due to the mutations. Part of a differential signal centered around 1732 cm(-1) in the spectrum of WT RCs is downshifted by approximately 7 cm(-1) in EL(L104), while it is upshifted by approximately 11 cm(-1) in WF(L100). This upshift of the differential signal is assigned to the frequency change of the 10a-ester C==O of HA induced by the rupture of the hydrogen bond with Trp L100. The 1H2O-minus-2H2O double-difference spectrum of WT RCs exhibits a characteristic differential signal positive at 1730 cm-1 and negative at 1724 cm-1 that is absent in the corresponding spectra of EL(L104) and of the double mutant, implicating Glu L104 in the QA-/QA spectral changes. This differential signal is strongly modified in frequency and amplitude in the 1H2O-minus-2H2O spectrum of WF(L100), indicating that it does not correspond to a direct response of the C==O mode of the Glu L104 side chain upon QA reduction. Instead, perturbation of the hydrogen bond of the 9-keto C==O with Glu L104 is proposed to induce a change of electron density on ring V of HA, thereby altering the frequency of the 10a-ester C==O that is in partial conjugation with ring V. The loss of the hydrogen bond to the 9-keto C==O of HA due to the Glu L104 to Leu mutation or the alteration of the strength of the hydrogen bond by 1H/2H exchange on Glu L104 appears to produce such effects. Thus, the QA-/QA spectra above 1700 cm-1 are dominated by contributions from the 10a-ester C==O of HA, with most of the differential signals assigned to a small frequency downshift of the 10a-ester C==O of HA in response to QA reduction. The complexity of the signals implies a structural heterogeneity of the conformation and hydrogen bonding of the 10a-ester C==O of HA, which may be related to the functional heterogeneity observed in electron transfer kinetics. The present FTIR results show that the reduction of QA can induce a pronounced electrostatic effect on molecula...

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“…As with B-band normalization, the I B / I Qy ratio for ZnTPC (5.28) versus H 2 TPC (4.12) implies greater relative red-region absorption for H 2 TPC , but again, the known molar absorption coefficient values show that ZnTPC > H 2 TPC in terms of the intensity of the respective Q y bands. This pitfall is hardly restricted to synthetic chlorins ZnTPC and H 2 TPC ; as one example, the same phenomenon occurs with pheophytin a and 3-desvinyl-3-acetyl pheophytin a (not shown) …”

Section: Abcs Of Chlorophylls and Chlorinsmentioning

confidence: 93%

“…This pitfall is hardly restricted to synthetic chlorins ZnTPC and H 2 TPC; as one example, the same phenomenon occurs with pheophytin a and 3-desvinyl-3-acetyl pheophytin a (not shown). 66 A superior approach may be to make comparisons on the basis of integrated spectra. The integration can treat the respective B and Q y band regions whereupon a ratio of the integrated areas (ΣB/ΣQ y ) is obtained for comparison.…”

Section: Chlorin Absorption Spectramentioning

confidence: 99%

Synthetic Chlorins, Possible Surrogates for Chlorophylls, Prepared by Derivatization of Porphyrins

2016

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Chlorophylls make Earth green, are the central constituents in the engine of photosynthesis, and not surprisingly have garnered immense attention. A chlorin, the core chromophore of a chlorophyll, is a dihydroporphyrin macrocycle that contains one pyrroline ring and three pyrrole rings. The dominant method for the synthesis of chlorins has entailed the derivatization of porphyrins. The present review covers the ostensibly simple conversion of porphyrins, regardless of synthetic or biological origin, to chlorins. The period covered encompasses the entire history since the beginnings of chlorin synthetic chemistry in the early 20th century through 2015. Representative transformations include hydrogenation, cycloaddition, annulation, and diverse "breaking and mending" approaches. Altogether, the synthesis of >1000 chlorins or chlorin-like compounds (containing >50 distinct pyrroline motifs) is described. Such diversity animates the question "what structural features are essential for a chlorin to resemble chlorophyll?" To begin to address the structure-spectrum relationship, > 250 absorption spectra are provided for representative structures. The synthesis and spectral properties of the vast collection of compounds described herein are expected to illuminate the scope to which synthetic chlorins can serve as surrogates for chlorophylls and be exploited in diverse ways.

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Probing native‐like orientation of pigments in modified reaction centers from Rhodobacter sphaeroides R26 by linear dichroism

Cited by 10 publications

References 16 publications

Construction of the Bacteriochlorin Macrocycle with Concomitant Nazarov Cyclization To Form the Annulated Isocyclic Ring: Analogues of Bacteriochlorophyll a

Construction of the Bacteriochlorin Macrocycle with Concomitant Nazarov Cyclization To Form the Annulated Isocyclic Ring: Analogues of Bacteriochlorophyll a

Electrostatic Influence of Q_A Reduction on the IR Vibrational Mode of the 10a-Ester CO of H_A Demonstrated by Mutations at Residues Glu L104 and Trp L100 in Reaction Centers from Rhodobacter sphaeroides

Synthetic Chlorins, Possible Surrogates for Chlorophylls, Prepared by Derivatization of Porphyrins

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Probing native‐like orientation of pigments in modified reaction centers from Rhodobacter sphaeroides R26 by linear dichroism

Cited by 10 publications

References 16 publications

Construction of the Bacteriochlorin Macrocycle with Concomitant Nazarov Cyclization To Form the Annulated Isocyclic Ring: Analogues of Bacteriochlorophyll a

Construction of the Bacteriochlorin Macrocycle with Concomitant Nazarov Cyclization To Form the Annulated Isocyclic Ring: Analogues of Bacteriochlorophyll a

Electrostatic Influence of QA Reduction on the IR Vibrational Mode of the 10a-Ester CO of HA Demonstrated by Mutations at Residues Glu L104 and Trp L100 in Reaction Centers from Rhodobacter sphaeroides

Synthetic Chlorins, Possible Surrogates for Chlorophylls, Prepared by Derivatization of Porphyrins

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Electrostatic Influence of Q_A Reduction on the IR Vibrational Mode of the 10a-Ester CO of H_A Demonstrated by Mutations at Residues Glu L104 and Trp L100 in Reaction Centers from Rhodobacter sphaeroides