Aqueous–membrane partitioning of β-substituted porphyrins encompassing diverse polarity

Soares, Ana Raquel; Thanaiah, Yugaananthy; Taniguchi, Masahiko; Lindsey, Jonathan S.

doi:10.1039/c3nj41042k

Cited by 19 publications

(28 citation statements)

References 39 publications

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“…Among amphiphilic tetrapyrrole macrocycles that have been studied in surfactant assemblies, the vast majority contain the porphyrin chromophore (40,41), with substantially fewer chlorins examined (for an overview, see Reference 32). Even fewer studies of bacteriochlorophylls (and derivatives thereof) in micelles have been reported (42)(43)(44)(45)(46)(47)(48), whereas studies of synthetic bacteriochlorins in micelles have only appeared quite recently (32,49).…”

Section: Chromophoresmentioning

confidence: 99%

Enhanced Light‐Harvesting Capacity by Micellar Assembly of Free Accessory Chromophores and LH1‐like Antennas

Harris

Sahin

Jiang

et al. 2014

Photochem & Photobiology

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Biohybrid light-harvesting antennas are an emerging platform technology with versatile tailorability for solar-energy conversion. These systems combine the proven peptide scaffold unit utilized for light harvesting by purple photosynthetic bacteria with attached synthetic chromophores to extend solar coverage beyond that of the natural systems. Herein, synthetic unattached chromophores are employed that partition into the organized milieu (e.g. detergent micelles) that house the LH1-like biohybrid architectures. The synthetic chromophores include a hydrophobic boron-dipyrrin dye (A1) and an amphiphilic bacteriochlorin (A2), which transfer energy with reasonable efficiency to the bacteriochlorophyll acceptor array (B875) of the LH1-like cyclic oligomers. The energy-transfer efficiencies are markedly increased upon covalent attachment of a bacteriochlorin (B1 or B2) to the peptide scaffold, where the latter likely acts as an energy-transfer relay site for the (potentially diffusing) free chromophores. The efficiencies are consistent with a Förster (through-space) mechanism for energy transfer. The overall energy-transfer efficiency from the free chromophores via the relay to the target site can approach those obtained previously by relay-assisted energy transfer from chromophores attached at distant sites on the peptides. Thus, the use of free accessory chromophores affords a simple design to enhance the overall light-harvesting capacity of biohybrid LH1-like architectures.

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Section: Chromophoresmentioning

confidence: 99%

Enhanced Light‐Harvesting Capacity by Micellar Assembly of Free Accessory Chromophores and LH1‐like Antennas

Harris

Sahin

Jiang

et al. 2014

Photochem & Photobiology

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“…For the reaction with 0.046 mM pyrrole and 0.39 mM micelles, the mean occupancy number m = 0.12 pyrrole/micelles. S14 †), but the calculated values for these and related molecules exhibit profound variation across programs, 18 and hence are not reliable for quantitative evaluation. In other words, only 1 of ∼130 000 micelles contains four pyrrole molecules, yet the yield of porphyrin at this concentration is 15 or 35% (CTAC or SDS micelles).…”

Section: Discussionmentioning

confidence: 99%

“…12 While the reaction of formaldehyde with a 3,4-dialkylpyrrole is a well-known path to an octaalkylporphyrin (Scheme 1), [13][14][15] the conditions in the synthesis lab employ strong acids and high concentrations. Given the lipophilic nature of such porphyrins, 18 and the fact that extant photosynthetic machinery is localized in membranes, the reactions were carried out in aqueous-surfactant assemblies. 16) or 10 mM.…”

Section: Introductionmentioning

confidence: 99%

Paley's watchmaker analogy and prebiotic synthetic chemistry in surfactant assemblies. Formaldehyde scavenging by pyrroles leading to porphyrins as a case study

et al. 2015

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The formation of elaborate molecules is regarded as an essential first step in prebiotic chemistry, but how such transformations could spontaneously occur, particularly in dilute aqueous conditions, remains poorly understood. Here, micromolar concentrations of a 3,4-dialkylpyrrole and excess formaldehyde in aqueous micellar solution (pH 7) at 25 or 50 °C were found to give good yield (up to 40%) of the lipophilic octaalkylporphyrin. The reaction occurs despite a mean occupancy number of ∼0.1 pyrrole molecules/micelle, and <1 of 10,000 micelles initially containing the requisite 4 pyrrole molecules to form the porphyrin assuming a (random) Poisson distribution. Yields of up to 13% were observed in large, unilamellar phosphatidylcholine vesicles, wherein there are ∼15,000 pyrrole molecules per vesicle membrane. Double-labeling crossover experiments (of 3,4-diethylpyrrole and 3,4-dimethylpyrrole) examined by mass spectrometry revealed facile exchange processes of reactive constituents among both micelle and vesicle surfactant assemblies. Together, the exchange of pyrrolic reactants among micelles and the thermodynamic driving force for tetrapyrrole formation overcome the apparent statistical odds against reaction. The fruitful exchange, accumulation and reaction of minute quantities of reactants in aqueous-surfactant assemblies suggest a general means for formation of prebiotically valuable constituents, even when the statistical odds at the outset are overwhelmingly improbable.

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“…One of the classic examples of a structure-directed reaction of proposed prebiotic relevance is the conversion of hydrogen cyanide to heterocycles including adenine. [7][8][9][10][11][12][13][14] Tetrapyrrole macrocycles have been suggested as valuable photoactive constituents in the evolution if not the origin of life. 5 A more recent example concerns the formation of nucleotides from simple constituents.…”

Section: Introductionmentioning

confidence: 99%

“…The a-methoxymethyl group enables self-condensation of the pyrrole leading to uroporphyrinogens; the latter upon dehydrogenation afford uroporphyrins, which have been proposed as ideal prebiotic photosensitizers. 10,12,13 The success of the combinatorial reactions raised a nagging question: what happens when one of the reactants is defective? 40,41 A second pyrrole, known as the Fischer-Fink pyrrole (FF-1), is blocked toward self-condensation and hence does not lead to uroporphyrinogens.…”

Section: Introductionmentioning

confidence: 99%

Complexity in structure-directed prebiotic chemistry. Effect of a defective competing reactant in tetrapyrrole formation

et al. 2015

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Chemical reactions in prebiotic environments likely entailed complex combinatorial processes with mixtures of reactants. As a case study, the effect of a defective reactant has been examined in a chemical model for the prebiogenesis of tetrapyrrole macrocycles (uroporphyrins). The latter are formed by a multistep process that includes (1) condensation of a b-diketone and an a-aminoketone to form a pyrrole, (2) self-condensation of the pyrrole to form a bilane (tetrapyrromethane), (3) cyclization of the bilane to form a porphyrinogen, and (4) oxidation of the porphyrinogen to form the porphyrin. A defective b-diketone (acetylacetone) affords a pyrrole that can react with nascent oligopyrromethane chains and in so doing terminate chain growth. Quantitative studies show that the porphyrin yield decreases with the fourth power of the mole fraction of the non-defective reactant. Mass spectral examination of the reaction mixture revealed the presence of the pyrrole and of end-capped oligomers derived from the defective diketone. Taken together, the results show the poisoning effect of a small amount of defective reactant in repetitive, irreversible structure-directed reactions, which have been a mainstay in thinking about chemistry leading to the origin of life.Scheme 1 Abiotic pathway to tetrapyrrole macrocycles.Chart 1 Pyrrole structural features required for self-condensation (top) and pyrroles lacking such features (bottom).

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Aqueous–membrane partitioning of β-substituted porphyrins encompassing diverse polarity

Cited by 19 publications

References 39 publications

Enhanced Light‐Harvesting Capacity by Micellar Assembly of Free Accessory Chromophores and LH1‐like Antennas

Enhanced Light‐Harvesting Capacity by Micellar Assembly of Free Accessory Chromophores and LH1‐like Antennas

Paley's watchmaker analogy and prebiotic synthetic chemistry in surfactant assemblies. Formaldehyde scavenging by pyrroles leading to porphyrins as a case study

Complexity in structure-directed prebiotic chemistry. Effect of a defective competing reactant in tetrapyrrole formation

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