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Dewey Holten - One of the best experts on this subject based on the ideXlab platform.
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a perspective on the redox properties of tetrapyrrole macrocycles
Physical Chemistry Chemical Physics, 2021Co-Authors: James R Diers, Christine Kirmaier, David F Bocian, Jonathan S Lindsey, Masahiko Taniguchi, Dewey HoltenAbstract:Tetrapyrrole macrocycles serve a multitude of roles in biological systems, including oxygen transport by heme and light harvesting and charge separation by chlorophylls and bacteriochlorophylls. Synthetic Tetrapyrroles are utilized in diverse applications ranging from solar-energy conversion to photomedicine. Nevertheless, students beginning tetrapyrrole research, as well as established practitioners, are often puzzled when comparing properties of related Tetrapyrroles. Questions arise as to why optical spectra of two Tetrapyrroles often shift in wavelength/energy in a direction opposite to that predicted by common chemical intuition based on the size of a π-electron system. Gouterman's four-orbital model provides a framework for understanding these optical properties. Similarly, it can be puzzling as to why the oxidation potentials differ significantly when comparing two related Tetrapyrroles, yet the reduction potentials change very little or shift in the opposite direction. In order to understand these redox properties, it must be recognized that structural/electronic alterations affect the four frontier molecular orbitals (HOMO, LUMO, HOMO−1 and LUMO+1) unequally and in many cases the LUMO+1, and not the LUMO, may track the HOMO in energy. This perspective presents a fundamental framework concerning tetrapyrrole electronic properties that should provide a foundation for rational molecular design in tetrapyrrole science.
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electronic structure and excited state dynamics of rylene tetrapyrrole panchromatic absorbers
Journal of Physical Chemistry A, 2021Co-Authors: Jie Rong, Dariusz M Niedzwiedzki, Christine Kirmaier, David F Bocian, Jonathan S Lindsey, Masahiko Taniguchi, James R Diers, Nikki Cecil M Magdaong, Dewey HoltenAbstract:Panchromatic absorbers have potential applications in molecular-based energy-conversion schemes. A prior porphyrin-perylene dyad (P-PMI, where "MI" denotes monoimide) coupled via an ethyne linker exhibits panchromatic absorption (350-700 nm) and a tetrapyrrole-like lowest singlet excited state with a relatively long singlet excited-state lifetime (τS) and increased fluorescence quantum yield (Φf) versus the parent porphyrin. To explore the extension of panchromaticity to longer wavelengths, three arrays have been synthesized: a chlorin-terrylene dyad (C-TMI), a bacteriochlorin-terrylene dyad (B-TMI), and a perylene-porphyrin-terrylene triad (PMI-P-TMI), where the terrylene, a π-extended homologue of perylene, is attached via an ethyne linker. Characterization of the spectra (absorption and fluorescence), excited-state properties (lifetime, yields, and rate constants of decay pathways), and molecular-orbital characteristics reveals unexpected subtleties. The wavelength of the red-region absorption band increases in the order C-TMI (705 nm) < PMI-P-TMI (749 nm) < B-TMI (774 nm), yet each array exhibits diminished Φf and shortened τS values. The PMI-P-TMI triad in toluene exhibits Φf = 0.038 and τS = 139 ps versus the all-perylene triad (PMI-P-PMI) for which Φf = 0.26 and τS = 2000 ps. The results highlight design constraints for auxiliary pigments with Tetrapyrroles to achieve panchromatic absorption with retention of viable excited-state properties.
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probing electronic communication for efficient light harvesting functionality dyads containing a common perylene and a porphyrin chlorin or bacteriochlorin
Journal of Physical Chemistry B, 2014Co-Authors: Eunkyung Yang, Dariusz M Niedzwiedzki, Christine Kirmaier, David F Bocian, Jonathan S Lindsey, Jieqi Wang, James R Diers, Dewey HoltenAbstract:The synthesis, photophysical, redox, and molecular-orbital characteristics of three perylene-tetrapyrrole dyads were investigated to probe the efficacy of the arrays for use as light-harvesting constituents. Each dyad contains a common perylene-monoimide that is linked at the N-imide position via an arylethynyl group to the meso-position of the tetrapyrrole. The Tetrapyrroles include a porphyrin, chlorin, and bacteriochlorin, which have zero, one, and two reduced pyrrole rings, respectively. The increased pyrrole-ring reduction results in a progressive red shift and intensification of the lowest-energy absorption band, as exemplified by benchmark monomers. The arylethyne linkage affords moderate perylene-tetrapyrrole electronic coupling in the dyads as evidenced by the optical, molecular-orbital, and redox properties of the components of the dyads versus the constituent parts. All three dyads in nonpolar solvents exhibit relatively fast (subpicosecond) energy transfer from the perylene to the tetrapyrrole. Competing charge-transfer processes are also absent in nonpolar solvents, but become active for both the chlorin and bacteriochlorin-containing dyads in polar solvents. Calculations of energy-transfer rates via the Forster, through-space mechanism reveal that these rates are, on average, 3-fold slower than the observed rates. Thus, the Dexter through-bond mechanism contributes more substantially than the through-space mechanism to energy transfer in the dyads. The electronic communication between the perylene and tetrapyrrole falls in a regime intermediate between those operative in other classes of perylene-tetrapyrrole dyads that have previously been studied.
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Probing Electronic Communication for Efficient Light-Harvesting Functionality: Dyads Containing a Common Perylene and a Porphyrin, Chlorin, or Bacteriochlorin
2014Co-Authors: Eunkyung Yang, Dariusz M Niedzwiedzki, Christine Kirmaier, David F Bocian, Jonathan S Lindsey, Jieqi Wang, James R Diers, Dewey HoltenAbstract:The synthesis, photophysical, redox, and molecular-orbital characteristics of three perylene–tetrapyrrole dyads were investigated to probe the efficacy of the arrays for use as light-harvesting constituents. Each dyad contains a common perylene–monoimide that is linked at the N-imide position via an arylethynyl group to the meso-position of the tetrapyrrole. The Tetrapyrroles include a porphyrin, chlorin, and bacteriochlorin, which have zero, one, and two reduced pyrrole rings, respectively. The increased pyrrole-ring reduction results in a progressive red shift and intensification of the lowest-energy absorption band, as exemplified by benchmark monomers. The arylethyne linkage affords moderate perylene–tetrapyrrole electronic coupling in the dyads as evidenced by the optical, molecular-orbital, and redox properties of the components of the dyads versus the constituent parts. All three dyads in nonpolar solvents exhibit relatively fast (subpicosecond) energy transfer from the perylene to the tetrapyrrole. Competing charge-transfer processes are also absent in nonpolar solvents, but become active for both the chlorin and bacteriochlorin-containing dyads in polar solvents. Calculations of energy-transfer rates via the Förster, through-space mechanism reveal that these rates are, on average, 3-fold slower than the observed rates. Thus, the Dexter through-bond mechanism contributes more substantially than the through-space mechanism to energy transfer in the dyads. The electronic communication between the perylene and tetrapyrrole falls in a regime intermediate between those operative in other classes of perylene–tetrapyrrole dyads that have previously been studied
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distinct photophysical and electronic characteristics of strongly coupled dyads containing a perylene accessory pigment and a porphyrin chlorin or bacteriochlorin
Journal of Physical Chemistry B, 2013Co-Authors: Jieqi Wang, Dariusz M Niedzwiedzki, Christine Kirmaier, David F Bocian, Jonathan S Lindsey, Eunkyung Yang, James R Diers, Dewey HoltenAbstract:The synthesis, photophysical, redox, and molecular-orbital characteristics of three perylene–tetrapyrrole dyads were investigated to elucidate characteristics favorable for use in next-generation light-harvesting assemblies. Each dyad contains a common perylene-monoimide that is linked at the 9-position via an ethynyl group to the meso-position of the tetrapyrrole. The Tetrapyrroles include a porphyrin, chlorin, and bacteriochlorin, which have zero, one, and two reduced pyrrole rings, respectively. The increased pyrrole-ring reduction results in a progressive red shift and intensification of the lowest-energy absorption band, as exemplified by benchmark monomers. The direct ethyne linkage and accompanying strong perylene–tetrapyrrole electronic coupling in the dyads is evident by significant differences in optical absorption versus the sum of the features of the constituents. The perturbations decrease for the tetrapyrrole constituent along the series porphyrin > chlorin > bacteriochlorin. This trend is e...
Martin J. Warren - One of the best experts on this subject based on the ideXlab platform.
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Recent advances in the biosynthesis of modified Tetrapyrroles: the discovery of an alternative pathway for the formation of heme and heme d _1
Cellular and Molecular Life Sciences, 2014Co-Authors: Shilpa Bali, David J. Palmer, Susanne Schroeder, Stuart J Ferguson, Martin J. WarrenAbstract:Hemes ( a , b , c , and o ) and heme d _1 belong to the group of modified Tetrapyrroles, which also includes chlorophylls, cobalamins, coenzyme F_430, and siroheme. These compounds are found throughout all domains of life and are involved in a variety of essential biological processes ranging from photosynthesis to methanogenesis. The biosynthesis of heme b has been well studied in many organisms, but in sulfate-reducing bacteria and archaea, the pathway has remained a mystery, as many of the enzymes involved in these characterized steps are absent. The heme pathway in most organisms proceeds from the cyclic precursor of all modified Tetrapyrroles uroporphyrinogen III, to coproporphyrinogen III, which is followed by oxidation of the ring and finally iron insertion. Sulfate-reducing bacteria and some archaea lack the genetic information necessary to convert uroporphyrinogen III to heme along the “classical” route and instead use an “alternative” pathway. Biosynthesis of the isobacteriochlorin heme d _1, a cofactor of the dissimilatory nitrite reductase cytochrome cd _1, has also been a subject of much research, although the biosynthetic pathway and its intermediates have evaded discovery for quite some time. This review focuses on the recent advances in the understanding of these two pathways and their surprisingly close relationship via the unlikely intermediate siroheme, which is also a cofactor of sulfite and nitrite reductases in many organisms. The evolutionary questions raised by this discovery will also be discussed along with the potential regulation required by organisms with overlapping tetrapyrrole biosynthesis pathways.
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molecular hijacking of siroheme for the synthesis of heme and d1 heme
Proceedings of the National Academy of Sciences of the United States of America, 2011Co-Authors: Shilpa Bali, Susana A L Lobo, BERNARD THOMAS GOLDING, Mark J Howard, Ligia M Saraiva, David Palmer, A Lawrence, Stuart J Ferguson, Martin J. WarrenAbstract:Modified Tetrapyrroles such as chlorophyll, heme, siroheme, vitamin B12, coenzyme F430, and heme d1 underpin a wide range of essential biological functions in all domains of life, and it is therefore surprising that the syntheses of many of these life pigments remain poorly understood. It is known that the construction of the central molecular framework of modified Tetrapyrroles is mediated via a common, core pathway. Herein a further branch of the modified tetrapyrrole biosynthesis pathway is described in denitrifying and sulfate-reducing bacteria as well as the Archaea. This process entails the hijacking of siroheme, the prosthetic group of sulfite and nitrite reductase, and its processing into heme and d1 heme. The initial step in these transformations involves the decarboxylation of siroheme to give didecarboxysiroheme. For d1 heme synthesis this intermediate has to undergo the replacement of two propionate side chains with oxygen functionalities and the introduction of a double bond into a further peripheral side chain. For heme synthesis didecarboxysiroheme is converted into Fe-coproporphyrin by oxidative loss of two acetic acid side chains. Fe-coproporphyrin is then transformed into heme by the oxidative decarboxylation of two propionate side chains. The mechanisms of these reactions are discussed and the evolutionary significance of another role for siroheme is examined.
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Vitamin B12: Biosynthesis of the Corrin Ring
Tetrapyrroles, 2009Co-Authors: Ross M. Graham, Evelyne Deery, Martin J. WarrenAbstract:Vitamin B12 is a cobalt-containing modified tetrapyrrole, whose structural complexity and beguiling chemistry has fascinated scientists for over 80 years. As with all modified Tetrapyrroles, its structure is derived from uroporphyrinogen III. This transformation requires a large number of enzyme-mediated steps that result in peripheral methylation, cobalt chelation, ring contraction, decarboxylation, amidation and adenosylation. There are two related though genetically distinct routes for cobalamin biosynthesis, which are referred to as the aerobic and anaerobic pathways. In this chapter the biosynthesis of the corrin ring component of vitamin B12 along these two routes is described.
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Tetrapyrroles birth life and death
2009Co-Authors: Martin J. Warren, Alison G SmithAbstract:Preface.- 1. An Historical Introduction to Porphyrin and Chlorophyll Synthesis.- 2. Biosynthesis of 5-Aminolevulinic Acid.- 3. 5-Aminolaevulinic Acid Dehydratase, Porphobilinogen Deaminase and Uroporphyrinogen III Synthase.- 4. Transformation of Uroporphyrinogen III into Protohaem.- 5. Inherited Disorders of Haem Synthesis: The Human Porphyrias.- 6. Heme Degradation: Mechanistic and Physiological Implications.- 7. Regulation of Mammalian Heme Biosynthesis.- 8. Tetrapyrroles in Photodynamic Therapy.- 9. Heme Transport and Incorporation into Proteins.- 10. Heme and Hemoproteins.- 11. Novel Heme-Protein Interactions-Some More Radical Than Others.- 12.Synthesis and Role of Bilins in Photosynthetic Organisms.- 13. Phytochromes: Bilin-Linked Photoreceptors in Bacteria and Plants.- 14. Biosynthesis of Chlorophyll and Bacteriochlorophyll.- 15. Regulation of Tetrapyrrole Synthesis in Higher Plants.- 16. Regulation of the Late Steps of Chlorophyll Biosynthesis.- 17. Chlorophyll Breakdown.- 18. Vitamin B12 Biosynthesis of the Corrin Ring.- 19. Conversion of Cobinamide into Coenzyme B12.- 20. The Regulation of Cobalamin Biosynthesis.- 21. Coenzyme B12-Catalyzed Radical Isomerizations.- 22. Biosynthesis of Siroheme and Coenzyme F430.- 23. Role of Coenzyme F430 in Methanogenesis.- 24. The Role of Siroheme in Sulfite and Nitrite Reductases.- 25. The Role of Heme d1 in Denitrification.
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the biosynthesis of hemes siroheme vitamin b12 and linear Tetrapyrroles in pseudomonads
2004Co-Authors: Nicole Frankenberg, Ross Graham, Max Schobert, Evelyne Raux, Jürgen Moser, Martin J. Warren, Dieter JahnAbstract:Structure and function of Tetrapyrroles. Tetrapyrroles are characterized by their four five-membered pyrrole rings usually linked together via single atom bridges (Figure 1). The four rings of the macrocycle are labeled clockwise A-D starting with the first of the three symmetric rings with regard to the ring substituents. Two principal classes of cyclic Tetrapyrroles are found in pseudomonads. The porphyrins, including various hemes, are characterized by their completely saturated ring system. The porphinoids are more reduced cyclic Tetrapyrroles and include vitamin B12 (corrinoids), siroheme and heme d 1. In cyclic Tetrapyrroles, the nitrogen atoms of the four pyrrole rings are used to chelate a variety of divalent cations. Tetrapyrroles are very distinct in color. The pink cobalt-containing vitamin B12 derivatives are the most complex known Tetrapyrroles1. They are involved in complex enzymatic reactions like radical-dependent nucleotide reduction, rearrangements and methyl transfer.
Tatsuru Masuda - One of the best experts on this subject based on the ideXlab platform.
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the role of tetrapyrrole and gun1 dependent signaling on chloroplast biogenesis
Plants (Basel Switzerland), 2021Co-Authors: Takayuki Shimizu, Tatsuru MasudaAbstract:Chloroplast biogenesis requires the coordinated expression of the chloroplast and nuclear genomes, which is achieved by communication between the developing chloroplasts and the nucleus. Signals emitted from the plastids, so-called retrograde signals, control nuclear gene expression depending on plastid development and functionality. Genetic analysis of this pathway identified a set of mutants defective in retrograde signaling and designated genomes uncoupled (gun) mutants. Subsequent research has pointed to a significant role of tetrapyrrole biosynthesis in retrograde signaling. Meanwhile, the molecular functions of GUN1, the proposed integrator of multiple retrograde signals, have not been identified yet. However, based on the interactions of GUN1, some working hypotheses have been proposed. Interestingly, GUN1 contributes to important biological processes, including plastid protein homeostasis, through transcription, translation, and protein import. Furthermore, the interactions of GUN1 with Tetrapyrroles and their biosynthetic enzymes have been revealed. This review focuses on our current understanding of the function of tetrapyrrole retrograde signaling on chloroplast biogenesis.
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Transcriptional regulation of tetrapyrrole biosynthesis in Arabidopsis thaliana
Frontiers Media S.A., 2016Co-Authors: Koichi Kobayashi, Tatsuru MasudaAbstract:Biosynthesis of chlorophyll (Chl) involves many enzymatic reactions that share several first steps for biosynthesis of other Tetrapyrroles such as heme, siroheme and phycobilins. Chl allows photosynthetic organisms to capture light energy for photosynthesis but with simultaneous threat of photooxidative damage to cells. To prevent photodamage by Chl and its highly photoreactive intermediates, photosynthetic organisms have developed multiple levels of regulatory mechanisms to coordinate tetrapyrrole biosynthesis (TPB) with the formation of photosynthetic and photoprotective systems and to fine-tune the metabolic flow with the varying needs of Chl and other Tetrapyrroles under various developmental and environmental conditions. Among a wide range of regulatory mechanisms of TPB, this review summarizes transcriptional regulation of TPB genes during plant development,with focusing on several transcription factors characterized in Arabidopsis thaliana.Key TPB genes are tightly coexpressed with other photosynthesis-associated nuclear genes and are induced by light, oscillate in a diurnal and circadian manner, are coordinated with developmental and nutritional status, and are strongly downregulated in response to arrested chloroplast biogenesis. LONG HYPOCOTYL 5 and PHYTOCHROME-INTERACTING FACTORs, which are positive and negative transcription factors with a wide range of light signaling, respectively, target many TPB genes for light and circadian regulation. GOLDEN2-LIKE transcription factors directly regulate key TPB genes to fine-tune the formation of the photosynthetic apparatus with chloroplast functionality. Some transcription factors such as FAR-RED ELONGATED HYPOCOTYL3, REVEILLE1, and scarecrow-like transcription factors may directly regulate some specific TPB genes, whereas other factors such as GATA transcription factors are likely to regulate TPB genes in an indirect manner. Comprehensive transcriptional analyses of TPB genes and detailed characterization of key transcriptional regulators help us obtain a whole picture of transcriptional control of TPB in response to environmental and endogenous cues
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tetrapyrrole metabolism in arabidopsis thaliana
The Arabidopsis Book, 2011Co-Authors: Ryouichi Tanaka, Koichi Kobayashi, Tatsuru MasudaAbstract:Higher plants produce four classes of Tetrapyrroles, namely, chlorophyll (Chl), heme, siroheme, and phytochromobilin. In plants, Tetrapyrroles play essential roles in a wide range of biological activities including photosynthesis, respiration and the assimilation of nitrogen/sulfur. All four classes of Tetrapyrroles are derived from a common biosynthetic pathway that resides in the plastid. In this article, we present an overview of tetrapyrrole metabolism in Arabidopsis and other higher plants, and we describe all identified enzymatic steps involved in this metabolism. We also summarize recent findings on Chl biosynthesis and Chl breakdown. Recent advances in this field, in particular those on the genetic and biochemical analyses of novel enzymes, prompted us to redraw the tetrapyrrole metabolic pathways. In addition, we also summarize our current understanding on the regulatory mechanisms governing tetrapyrrole metabolism. The interactions of tetrapyrrole biosynthesis and other cellular processes including the plastid-to-nucleus signal transduction are discussed.
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the cell biology of Tetrapyrroles a life and death struggle
Trends in Plant Science, 2010Co-Authors: Nobuyoshi Mochizuki, Bernhard Grimm, Michael Moulin, Alison G Smith, Ryouichi Tanaka, Tatsuru Masuda, Ayumi Tanaka, Matthew J TerryAbstract:Tetrapyrroles such as chlorophyll and heme are co-factors for essential proteins involved in a wide variety of crucial cellular functions. Nearly 2% of the proteins encoded by the Arabidopsis thaliana genome are thought to bind Tetrapyrroles, demonstrating their central role in plant metabolism. Although the enzymes required for tetrapyrrole biosynthesis are well characterized, there are still major questions about the regulation of the pathway, and the transport of Tetrapyrroles within cells. These issues are important, as misregulation of tetrapyrrole metabolism can lead to severe photo-oxidative stress, and because Tetrapyrroles have been implicated in signaling pathways coordinating interactions between plant organelles. In this review, we discuss the cell biology of tetrapyrrole metabolism and its implications for Tetrapyrroles as signaling molecules.
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characterization of cytosolic tetrapyrrole binding proteins in arabidopsis thaliana
Photochemical and Photobiological Sciences, 2008Co-Authors: Shigekazu Takahashi, Takuro Ogawa, Kazuhito Inoue, Tatsuru MasudaAbstract:In plant cells, Tetrapyrroles are synthesized in plastids and distributed to numerous organelles to function in various vital activities. However, molecular mechanisms of Tetrapyrroles trafficking in plant cells are poorly understood. In animal cells, experimental evidence suggests that the p22HBP/SOUL family are cytosolic heme carrier proteins functioning in heme trafficking. In this study, we characterized Arabidopsis cytosolic heme-binding proteins (cHBPs) homologous to the p22HBP/SOUL family. Six homologous genes were identified in the complete genome of Arabidopsis. Deduced amino acid sequences of two genes contained N-terminal amino acid extensions, presumably functioning as signal peptides to organelles. No such extension was observed in the other four genes, but one gene contained a ten-base deletion in its open reading frame, suggesting it maybe a pseudogene. The remaining three genes encoding putative cHBPs, designated cHBP1, cHBP2 and cHBP3, were further analyzed. Semiquantitative RT-PCR analysis showed that cHBP1 was preferentially expressed in leaves, while cHBP2 was predominantly expressed in roots. A tetrapyrrole binding assay using recombinant proteins of cHBP1 and cHBP2 revealed that both cHBPs bind to heme, protoporphyrin IX, and Mg-protoporphyrin IX dimethyl ester with distinct dissociation constants (Kd) of approximately submicro molar concentrations. Low temperature electron spin resonance (ESR) spectra showed that both cHBP1 and cHBP2 bind high-spin type heme. When mixed with apo-horse radish peroxidase (HRP), heme-bound cHBP1 and cHBP2 showed comparable abilities for reconstitution of HRP activity, showing that both cHBPs bind heme reversibly. These results suggest that both cHBP1 and cHBP2 have properties suitable for tetrapyrrole carrier proteins and function in distinct organs in plant cells.
Jonathan S Lindsey - One of the best experts on this subject based on the ideXlab platform.
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a perspective on the redox properties of tetrapyrrole macrocycles
Physical Chemistry Chemical Physics, 2021Co-Authors: James R Diers, Christine Kirmaier, David F Bocian, Jonathan S Lindsey, Masahiko Taniguchi, Dewey HoltenAbstract:Tetrapyrrole macrocycles serve a multitude of roles in biological systems, including oxygen transport by heme and light harvesting and charge separation by chlorophylls and bacteriochlorophylls. Synthetic Tetrapyrroles are utilized in diverse applications ranging from solar-energy conversion to photomedicine. Nevertheless, students beginning tetrapyrrole research, as well as established practitioners, are often puzzled when comparing properties of related Tetrapyrroles. Questions arise as to why optical spectra of two Tetrapyrroles often shift in wavelength/energy in a direction opposite to that predicted by common chemical intuition based on the size of a π-electron system. Gouterman's four-orbital model provides a framework for understanding these optical properties. Similarly, it can be puzzling as to why the oxidation potentials differ significantly when comparing two related Tetrapyrroles, yet the reduction potentials change very little or shift in the opposite direction. In order to understand these redox properties, it must be recognized that structural/electronic alterations affect the four frontier molecular orbitals (HOMO, LUMO, HOMO−1 and LUMO+1) unequally and in many cases the LUMO+1, and not the LUMO, may track the HOMO in energy. This perspective presents a fundamental framework concerning tetrapyrrole electronic properties that should provide a foundation for rational molecular design in tetrapyrrole science.
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electronic structure and excited state dynamics of rylene tetrapyrrole panchromatic absorbers
Journal of Physical Chemistry A, 2021Co-Authors: Jie Rong, Dariusz M Niedzwiedzki, Christine Kirmaier, David F Bocian, Jonathan S Lindsey, Masahiko Taniguchi, James R Diers, Nikki Cecil M Magdaong, Dewey HoltenAbstract:Panchromatic absorbers have potential applications in molecular-based energy-conversion schemes. A prior porphyrin-perylene dyad (P-PMI, where "MI" denotes monoimide) coupled via an ethyne linker exhibits panchromatic absorption (350-700 nm) and a tetrapyrrole-like lowest singlet excited state with a relatively long singlet excited-state lifetime (τS) and increased fluorescence quantum yield (Φf) versus the parent porphyrin. To explore the extension of panchromaticity to longer wavelengths, three arrays have been synthesized: a chlorin-terrylene dyad (C-TMI), a bacteriochlorin-terrylene dyad (B-TMI), and a perylene-porphyrin-terrylene triad (PMI-P-TMI), where the terrylene, a π-extended homologue of perylene, is attached via an ethyne linker. Characterization of the spectra (absorption and fluorescence), excited-state properties (lifetime, yields, and rate constants of decay pathways), and molecular-orbital characteristics reveals unexpected subtleties. The wavelength of the red-region absorption band increases in the order C-TMI (705 nm) < PMI-P-TMI (749 nm) < B-TMI (774 nm), yet each array exhibits diminished Φf and shortened τS values. The PMI-P-TMI triad in toluene exhibits Φf = 0.038 and τS = 139 ps versus the all-perylene triad (PMI-P-PMI) for which Φf = 0.26 and τS = 2000 ps. The results highlight design constraints for auxiliary pigments with Tetrapyrroles to achieve panchromatic absorption with retention of viable excited-state properties.
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The Porphobilinogen Conundrum in Prebiotic Routes to Tetrapyrrole Macrocycles
Origins of Life and Evolution of Biospheres, 2017Co-Authors: Masahiko Taniguchi, Marcin Ptaszek, Vanampally Chandrashaker, Jonathan S LindseyAbstract:Attempts to develop a credible prebiotic route to Tetrapyrroles have relied on enzyme-free recapitulation of the extant biosynthesis, but this process has foundered from the inability to form the pyrrole porphobilinogen ( PBG ) in good yield by self-condensation of the precursor δ-aminolevulinic acid ( ALA ). PBG undergoes robust oligomerization in aqueous solution to give uroporphyrinogen (4 isomers) in good yield. ALA , PBG , and uroporphyrinogen III are universal precursors to all known tetrapyrrole macrocycles. The enzymic formation of PBG entails carbon-carbon bond formation between the less stable enolate/enamine of one ALA molecule (3-position) and the carbonyl/imine (4-position) of the second ALA molecule; without enzymes, the first ALA reacts at the more stable enolate/enamine (5-position) and gives the pyrrole pseudo-PBG. pseudo-PBG cannot self-condense, yet has one open α-pyrrole position and is proposed to be a terminator of oligopyrromethane chain-growth from PBG . Here, 23 analogues of ALA have been subjected to density functional theoretical (DFT) calculations, but no motif has been identified that directs reaction at the 3-position. Deuteriation experiments suggested 5-(phosphonooxy)levulinic acid would react preferentially at the 3- versus 5-position, but a hybrid condensation with ALA gave no observable uroporphyrin. The results suggest efforts toward a biomimetic, enzyme-free route to Tetrapyrroles from ALA should turn away from structure-directed reactions and focus on catalysts that orient the two aminoketones to form PBG in a kinetically controlled process, thereby avoiding formation of pseudo-PBG .
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probing electronic communication for efficient light harvesting functionality dyads containing a common perylene and a porphyrin chlorin or bacteriochlorin
Journal of Physical Chemistry B, 2014Co-Authors: Eunkyung Yang, Dariusz M Niedzwiedzki, Christine Kirmaier, David F Bocian, Jonathan S Lindsey, Jieqi Wang, James R Diers, Dewey HoltenAbstract:The synthesis, photophysical, redox, and molecular-orbital characteristics of three perylene-tetrapyrrole dyads were investigated to probe the efficacy of the arrays for use as light-harvesting constituents. Each dyad contains a common perylene-monoimide that is linked at the N-imide position via an arylethynyl group to the meso-position of the tetrapyrrole. The Tetrapyrroles include a porphyrin, chlorin, and bacteriochlorin, which have zero, one, and two reduced pyrrole rings, respectively. The increased pyrrole-ring reduction results in a progressive red shift and intensification of the lowest-energy absorption band, as exemplified by benchmark monomers. The arylethyne linkage affords moderate perylene-tetrapyrrole electronic coupling in the dyads as evidenced by the optical, molecular-orbital, and redox properties of the components of the dyads versus the constituent parts. All three dyads in nonpolar solvents exhibit relatively fast (subpicosecond) energy transfer from the perylene to the tetrapyrrole. Competing charge-transfer processes are also absent in nonpolar solvents, but become active for both the chlorin and bacteriochlorin-containing dyads in polar solvents. Calculations of energy-transfer rates via the Forster, through-space mechanism reveal that these rates are, on average, 3-fold slower than the observed rates. Thus, the Dexter through-bond mechanism contributes more substantially than the through-space mechanism to energy transfer in the dyads. The electronic communication between the perylene and tetrapyrrole falls in a regime intermediate between those operative in other classes of perylene-tetrapyrrole dyads that have previously been studied.
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Probing Electronic Communication for Efficient Light-Harvesting Functionality: Dyads Containing a Common Perylene and a Porphyrin, Chlorin, or Bacteriochlorin
2014Co-Authors: Eunkyung Yang, Dariusz M Niedzwiedzki, Christine Kirmaier, David F Bocian, Jonathan S Lindsey, Jieqi Wang, James R Diers, Dewey HoltenAbstract:The synthesis, photophysical, redox, and molecular-orbital characteristics of three perylene–tetrapyrrole dyads were investigated to probe the efficacy of the arrays for use as light-harvesting constituents. Each dyad contains a common perylene–monoimide that is linked at the N-imide position via an arylethynyl group to the meso-position of the tetrapyrrole. The Tetrapyrroles include a porphyrin, chlorin, and bacteriochlorin, which have zero, one, and two reduced pyrrole rings, respectively. The increased pyrrole-ring reduction results in a progressive red shift and intensification of the lowest-energy absorption band, as exemplified by benchmark monomers. The arylethyne linkage affords moderate perylene–tetrapyrrole electronic coupling in the dyads as evidenced by the optical, molecular-orbital, and redox properties of the components of the dyads versus the constituent parts. All three dyads in nonpolar solvents exhibit relatively fast (subpicosecond) energy transfer from the perylene to the tetrapyrrole. Competing charge-transfer processes are also absent in nonpolar solvents, but become active for both the chlorin and bacteriochlorin-containing dyads in polar solvents. Calculations of energy-transfer rates via the Förster, through-space mechanism reveal that these rates are, on average, 3-fold slower than the observed rates. Thus, the Dexter through-bond mechanism contributes more substantially than the through-space mechanism to energy transfer in the dyads. The electronic communication between the perylene and tetrapyrrole falls in a regime intermediate between those operative in other classes of perylene–tetrapyrrole dyads that have previously been studied
Eileen K Jaffe - One of the best experts on this subject based on the ideXlab platform.
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control of tetrapyrrole biosynthesis by alternate quaternary forms of porphobilinogen synthase
Nature Structural & Molecular Biology, 2003Co-Authors: Sabine Breinig, Andrew Wasson, Alexander Zdanov, Alexander Wlodawer, Jukka Kervinen, Robert Fairman, Linda Stith, Eileen K JaffeAbstract:Porphobilinogen synthase (PBGS) catalyzes the first common step in the biosynthesis of Tetrapyrroles (such as heme and chlorophyll). Although the predominant oligomeric form of this enzyme, as inferred from many crystal structures, is that of a homo-octamer, a rare human PBGS allele, F12L, reveals the presence of a hexameric form. Rearrangement of an N-terminal arm is responsible for this oligomeric switch, which results in profound changes in kinetic behavior. The structural transition between octamer and hexamer must proceed through an unparalleled equilibrium containing two different dimer structures. The allosteric magnesium, present in most PBGS, has a binding site in the octamer but not in the hexamer. The unprecedented structural rearrangement reported here relates to the allosteric regulation of PBGS and suggests that alternative PBGS oligomers may function in a magnesium-dependent regulation of tetrapyrrole biosynthesis in plants and some bacteria.
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porphobilinogen synthase from pea expression from an artificial gene kinetic characterization and novel implications for subunit interactions
Biochemistry, 2000Co-Authors: Jukka Kervinen, Samuel Litwin, Jacob Martins, Marina Volin, Robert C Scarrow, And Erica Yoon, Anthony T. Yeung, Roland L Dunbrack, Eileen K JaffeAbstract:Porphobilinogen synthase (PBGS) is present in all organisms that synthesize Tetrapyrroles such as heme, chlorophyll, and vitamin B12. The homooctameric metalloenzyme catalyzes the condensation of two 5-aminolevulinic acid molecules to form the tetrapyrrole precursor porphobilinogen. An artificial gene encoding PBGS of pea (Pisum sativum L.) was designed to overcome previous problems during bacterial expression caused by suboptimal codon usage and was constructed by recursive polymerase chain reaction from synthetic oligonucleotides. The recombinant 330 residue enzyme without a putative chloroplast transit peptide was expressed in Escherichia coli and purified in 100-mg quantities. The specific activity is protein concentration dependent, which indicates that a maximally active octamer can dissociate into less active smaller units. The enzyme is most active at slightly alkaline pH; it shows two pKa values of 7.4 and 9.7. Atomic absorption spectroscopy shows maximal binding of three Mg(II) per subunit; kine...
