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Hitoshi Tamiaki - One of the best experts on this subject based on the ideXlab platform.
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In situ formation of photoactive B-ring reduced chlorophyll isomer in photosynthetic protein LH2
Scientific Reports, 2020Co-Authors: Yoshitaka Saga, Yuji Otsuka, Daichi Funakoshi, Yuto Masaoka, Yu Kihara, Tsubasa Hidaka, Hiroka Hatano, Hitoshi Asakawa, Yutaka Nagasawa, Hitoshi TamiakiAbstract:Natural chlorophylls have a D-ring reduced chlorin π-system; however, no naturally occurring photosynthetically active B-ring reduced chlorins have been reported. Here we report a B-ring reduced chlorin, 17,18-didehydro-bacteriochlorophyll (BChl) a , produced by in situ oxidation of B800 bacteriochlorophyll (BChl) a in a light-harvesting protein LH2 from a purple photosynthetic bacterium Phaeospirillum molischianum . The regioselective oxidation of the B-ring of B800 BChl a is rationalized by its molecular orientation in the protein matrix. The formation of 17,18-didehydro-BChl a produced no change in the local structures and circular arrangement of the LH2 protein. The B-ring reduced 17,18-didehydro-BChl a functions as an energy donor in the LH2 protein. The photoactive B-ring reduced Chl isomer in LH2 will be helpful for understanding the photofunction and evolution of photosynthetic Cyclic Tetrapyrrole pigments.
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Effects of Cyclic Tetrapyrrole rings of aggregate-forming chlorophyll derivatives as hole-transporting materials on performance of perovskite solar cells
ACS Applied Energy Materials, 2017Co-Authors: Gang Chen, Hitoshi Tamiaki, Shin-ichi Sasaki, Kotowa Sakai, Toshitaka Ikeuchi, Tsutomu Miyasaka, Xiao-feng WangAbstract:Organic hole-transporting materials (HTMs) are essential components of high-performance perovskite solar cells (PSCs). Three zinc-coordinated chlorophyll derivatives with bacteriochlorin, chlorin, and porphyrin macrocycles, namely, ZnBChl, ZnChl, and ZnPor, respectively, were newly synthesized and employed as HTMs in PSCs. The difference in the π backbones of these HTMs causes differences in their photophysical properties, and thus different hole-extraction abilities, as revealed by steady-state photoluminescence spectra. The power conversion efficiencies (PCEs) of PSCs with a typical mesoporous structure, fluorine-doped tin oxide/compact TiO2/mesoporous TiO2/CH3NH3PbI3/HTM/Ag, are 8.26%, 11.88%, and 0.68% for ZnBChl, ZnChl, and ZnPor, respectively. The small PCE of the ZnPor-based PSC is partially attributed to the small energy gap of the highest occupied molecular orbital (HOMO) levels between ZnPor and CH3NH3PbI3 perovskite. Therefore, we increased this energy gap slightly by shifting the HOMO level of...
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the 17 propionate esterifying variants of bacteriochlorophyll a and bacteriopheophytin a in purple photosynthetic bacteria
Journal of Photochemistry and Photobiology B-biology, 2015Co-Authors: Tadashi Mizoguchi, Megumi Isaji, Yusuke Tsukatani, Jiro Harada, Hitoshi TamiakiAbstract:Most purple photosynthetic bacteria contain bacteriochlorophyll(BChl)-a (a magnesium complex) and bacteriopheophytin(BPhe)-a (its free base) as their photoactive pigments. These pigments are composed of two parts: a Cyclic Tetrapyrrole as the chromophore and a long hydrocarbon-chain as the propionate-type esterifying group at the 17-position. The hydrocarbon-chain is usually an isoprenoid-type C20 phytyl (Phy) group in both the pigments. In the ester group of BChl-a, several variants such as geranylgeranyl (GG), dihydrogeranylgeranyl (DHGG) and tetrahydrogeranylgeranyl (THGG) groups were found in the final stage of BChl-a biosynthesis. On the other hand, the esterifying variants in BPhe-a have not been studied as much due to the lower levels of this pigment relative to BChl-a. The esterifying group does not affect the electronic absorption properties of such pigments in the monomeric state, but drastically alters the hydrophobicity. In this study, BChl-a and BPhe-a in the six phylogenetically distinct classes of purple bacteria were analyzed in terms of their esterifying groups in the 17-propionate residues, using high-performance liquid chromatography. Both BChls-a and BPhes-a carrying GG, DHGG and THGG in addition to the usual Phy were found for all the bacterial species studied at measurable levels. In some of the species, the ratio of BPhes-a esterified with GG, DHGG and THGG over the total BPhe-a drastically decreased in comparison with that of the corresponding BChls-a. Especially, the relative content of BPhe-a with GG largely decreased. This observation might indicate that BPhe-a as a cofactor of reaction centers was preferentially esterified with partially reduced and flexible chains (THGG and Phy) rather than less reduced and rigid ones (GG and DHGG).
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Demetalation kinetics of the zinc chlorophyll derivative possessing two formyl groups: effects of formyl groups conjugated to the chlorin macrocycle on physicochemical properties of photosynthetic pigments
Journal of Porphyrins and Phthalocyanines, 2013Co-Authors: Kana Sadaoka, Hitoshi Tamiaki, Shigenori Kashimura, Toru Oba, Yoshitaka SagaAbstract:Demetalation kinetics of zinc chlorophyll derivative 1 possessing two formyl groups directly linked to the A- and B-rings of the chlorin macrocycle, which was synthesized from chlorophyll b, was examined under acidic conditions and compared with those of Zn chlorins 2 and 3 possessing a single formyl group in the A- and B-ring, respectively, as well as Zn chlorin 4 lacking any formyl group to unravel the substitution effects on demetalation properties of chlorophyllous pigments. Demetalation kinetics of diformylated Zn chlorin 1 was slower than those of monoformylated Zn chlorins 2 and 3, indicating that the effect of the electron-withdrawing formyl group on demetalation kinetics was amplified by introduction of two formyl groups to the chlorin macrocycle. High correlations were observed between demetalation rate constants of Zn chlorins 1–4 and the sum of Hammett σ parameters of the 3- and 7-substituents on the chlorin macrocycle, indicating that the combination of electron-withdrawing abilities of the substituents linked directly to the Cyclic Tetrapyrrole was responsible for demetalation properties of zinc chlorophyll derivatives.
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Demetalation of Chlorophyll Pigments
Chemistry & Biodiversity, 2012Co-Authors: Yoshitaka Saga, Hitoshi TamiakiAbstract:Natural chlorophylls (Chls) and bacteriochlorophyll (BChls), which are major pigments in photosynthesis, possess a central Mg (or Zn) in their Cyclic Tetrapyrrole macrocycles. Removal of the central metal atom from chlorophyllous pigments, called pheophytinization, is a biologically important reaction in that it allows production of the primary electron acceptors in photosystem II(-type) reaction centers and is one of the crucial steps in the Chl degradation pathway. Pheophytinization in processed and postharvest foods derived from vegetables and fruits has attracted considerable attention in agricultural and food chemistry from the viewpoints of maintenance of their color level and evaluation by consumers. In this review, we focus on in vivo demetalation reactions and demetalated products of chlorophyllous pigments. In addition, we summarize kinetic studies on in vitro demetalation of natural (B)Chl molecules and their synthetic analogs under acidic conditions.
Robert J Desnick - One of the best experts on this subject based on the ideXlab platform.
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human uroporphyrinogen iii synthase nmr based mapping of the active site
Proteins, 2008Co-Authors: Luis F Cunha, Miklos Kuti, David F Bishop, Mihaly Mezei, Lei Zeng, Mingming Zhou, Robert J DesnickAbstract:Uroporphyrinogen III synthase (URO-synthase) catalyzes the cyclization and D-ring isomerization of hydroxymethylbilane (HMB) to uroporphyrinogen (URO'gen) III, the Cyclic Tetrapyrrole and physiologic precursor of heme, chlorophyl, and corrin. The deficient activity of human URO-synthase results in the autosomal recessive cutaneous disorder, congenital erythropoietic porphyria. Mapping of the structural determinants that specify catalysis and, potentially, protein-protein interactions is lacking. To map the active site and assess the enzyme's possible interaction in a complex with hydroxymethylbilane-synthase (HMB-synthase) and/or uroporphyrinogen-decarboxylase (URO-decarboxylase) by NMR, an efficient expression and purification procedure was developed for these cytosolic enzymes of heme biosynthesis that enabled preparation of special isotopically-labeled protein samples for NMR characterization. Using an 800 MHz instrument, assignment of the URO-synthase backbone (13)C(alpha) (100%), (1)H(alpha) (99.6%), and nonproline (1)H(N) and (15)N resonances (94%) was achieved as well as 85% of the side-chain (13)C and (1)H resonances. NMR analyses of URO-synthase titrated with competitive inhibitors N(D)-methyl-1-formylbilane (NMF-bilane) or URO'gen III, revealed resonance perturbations of specific residues lining the cleft between the two major domains of URO synthase that mapped the enzyme's active site. In silico docking of the URO-synthase crystal structure with NMF-bilane and URO'gen III was consistent with the perturbation results and provided a 3D model of the enzyme-inhibitor complex. The absence of chemical shift changes in the (15)N spectrum of URO-synthase mixed with the homogeneous HMB-synthase holoenzyme or URO-decarboxylase precluded occurrence of a stable cytosolic enzyme complex.
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uroporphyrinogen iii synthase molecular cloning nucleotide sequence expression of a mouse full length cdna and its localization on mouse chromosome 7
Genomics, 1995Co-Authors: Christine A Kozak, Robert J DesnickAbstract:Abstract Uroporphyrinogen-III synthase (URO-S; EC 4.2.1.75), the fourth enzyme in the heme biosynthetic pathway, is responsible for the conversion of hydroxymethylbilane to the Cyclic Tetrapyrrole, uroporphyrinogen III. The deficient activity of URO-S is the enzymatic defect in congenital erythropoietic porphyria (CEP), an autosomal recessive disorder. For the generation of a mouse model of CEP, the human URO-S cDNA was used to screen 2 × 10 6 recombinants from a mouse adult liver cDNA library. Ten positive clones were isolated, and dideoxy sequencing of the entire 1.6-kb insert of clone pmUROS-1 revealed 5′ and 3′ untranslated sequences of 144 and 623 bp, respectively, and an open reading frame of 798 bp encoding a 265-amino-acid polypeptide with a predicted molecular mass of 28,501 Da. The mouse and human coding sequences had 80.5 and 77.8% nucleotide and amino acid identity, respectively. The authenticity of the mouse cDNA was established by expression of the active monomeric enzyme in Escherichia coli . In addition, the analysis of two multilocus genetic crosses localized the mouse gene on chromosome 7, consistent with the mapping of the human gene to a position of conserved synteny on chromosome 10. The isolation, expression, and chromosomal mapping of this full-length cDNA should facilitate studies of the structure and organization of the mouse genomic sequence and the development of a mouse model of CEP for characterization of the disease pathogenesis and evaluation of gene therapy.
Hong Boon Lee - One of the best experts on this subject based on the ideXlab platform.
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RESEARCH ARTICLE Open Access Cyclic
2013-07-09, 2013Co-Authors: Tetrapyrrolic Photosensitisers From The, Pei Jean Tan, Cheng Yi Ong, Asma Dazni Danial, Hirzun Mohd Yusof, Bee Keat Neoh, Hong Boon LeeAbstract:Background: Twenty-seven extracts from 26 plants were identified as photo-cytotoxic in the course of our bioassay guided screening program for photosensitisers from 128 extracts prepared from 64 terrestrial plants in two different collection sites in Malaysia- Royal Belum Forest Reserve in the State of Perak and Gunung Nuang in the State of Selangor. One of the photo-cytotoxic extracts from the leaves of Phaeanthus ophtalmicus was further investigated. Results: The ethanolic extract of the leaves from Phaeanthus ophtalmicus was able to reduce the in vitro viability of leukaemic HL60 cells to < 50 % when exposed to 9.6 J/cm 2 of a broad spectrum light at a concentration of 20 μg/ mL. Dereplication of the photo-cytotoxic fractions from P. ophthalmicus extracts based on TLC Rf values and HPLC co-injection of reference tetrapyrrolic compounds enabled quick identification of known photosensitisers, pheophorbide-a, pheophorbide-a methyl ester, 13 2-hydroxypheophorbide-a methyl ester, pheophytin-a and 15 1-hydroxypurpurin 7-lactone dimethyl ester. In addition, compound 1 which was not previously isolated as a natural product was also identified as 7-formyl-15 1-hydroxypurpurin-7-lactone methyl ester using standard spectroscopic techniques. Conclusions: Our results suggest that the main photosensitisers in plants are based on the Cyclic Tetrapyrrole
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Validation of Quantitative Structure-Activity Relationship (QSAR) Model for Photosensitizer Activity Prediction
International Journal of Molecular Sciences, 2011Co-Authors: Neni Frimayanti, Hong Boon Lee, Mun Li Yam, Rozana Othman, Sharifuddin M. Zain, Noorsaadah Abd RahmanAbstract:Photodynamic therapy is a relatively new treatment method for cancer which utilizes a combination of oxygen, a photosensitizer and light to generate reactive singlet oxygen that eradicates tumors via direct cell-killing, vasculature damage and engagement of the immune system. Most of photosensitizers that are in clinical and pre-clinical assessments, or those that are already approved for clinical use, are mainly based on Cyclic Tetrapyrroles. In an attempt to discover new effective photosensitizers, we report the use of the quantitative structure-activity relationship (QSAR) method to develop a model that could correlate the structural features of Cyclic Tetrapyrrole-based compounds with their photodynamic therapy (PDT) activity. In this study, a set of 36 porphyrin derivatives was used in the model development where 24 of these compounds were in the training set and the remaining 12 compounds were in the test set. The development of the QSAR model involved the use of the multiple linear regression analysis (MLRA) method. Based on the method, r(2) value, r(2) (CV) value and r(2) prediction value of 0.87, 0.71 and 0.70 were obtained. The QSAR model was also employed to predict the experimental compounds in an external test set. This external test set comprises 20 porphyrin-based compounds with experimental IC(50) values ranging from 0.39 μM to 7.04 μM. Thus the model showed good correlative and predictive ability, with a predictive correlation coefficient (r(2) prediction for external test set) of 0.52. The developed QSAR model was used to discover some compounds as new lead photosensitizers from this external test set.
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Cyclic Tetrapyrrolic Photosensitisers from the leaves of Phaeanthus ophthalmicus
Chemistry Central Journal, 2011Co-Authors: Pei Jean Tan, Cheng Yi Ong, Asma Dazni Danial, Hirzun Mohd Yusof, Bee Keat Neoh, Hong Boon LeeAbstract:Twenty-seven extracts from 26 plants were identified as photo-cytotoxic in the course of our bioassay guided screening program for photosensitisers from 128 extracts prepared from 64 terrestrial plants in two different collection sites in Malaysia - Royal Belum Forest Reserve in the State of Perak and Gunung Nuang in the State of Selangor. One of the photo-cytotoxic extracts from the leaves of Phaeanthus ophtalmicus was further investigated. The ethanolic extract of the leaves from Phaeanthus ophtalmicus was able to reduce the in vitro viability of leukaemic HL60 cells to < 50% when exposed to 9.6 J/cm2 of a broad spectrum light at a concentration of 20 μg/mL. Dereplication of the photo-cytotoxic fractions from P. ophthalmicus extracts based on TLC Rf values and HPLC co-injection of reference tetrapyrrolic compounds enabled quick identification of known photosensitisers, pheophorbide-a, pheophorbide-a methyl ester, 132-hydroxypheophorbide-a methyl ester, pheophytin-a and 151-hydroxypurpurin 7-lactone dimethyl ester. In addition, compound 1 which was not previously isolated as a natural product was also identified as 7-formyl-151-hydroxypurpurin-7-lactone methyl ester using standard spectroscopic techniques. Our results suggest that the main photosensitisers in plants are based on the Cyclic Tetrapyrrole structure and photosensitisers with other structures, if present, are present in very minor amounts or are not as active as those with the Cyclic Tetrapyrrole structure.
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Cyclic Tetrapyrrolic Photosensitisers from the leaves of Phaeanthus ophthalmicus
Chemistry Central Journal, 2011Co-Authors: Pei Jean Tan, Cheng Yi Ong, Asma Dazni Danial, Hirzun Mohd Yusof, Bee Keat Neoh, Hong Boon LeeAbstract:Background Twenty-seven extracts from 26 plants were identified as photo-cytotoxic in the course of our bioassay guided screening program for photosensitisers from 128 extracts prepared from 64 terrestrial plants in two different collection sites in Malaysia - Royal Belum Forest Reserve in the State of Perak and Gunung Nuang in the State of Selangor. One of the photo-cytotoxic extracts from the leaves of Phaeanthus ophtalmicus was further investigated. Results The ethanolic extract of the leaves from Phaeanthus ophtalmicus was able to reduce the in vitro viability of leukaemic HL60 cells to < 50% when exposed to 9.6 J/cm^2 of a broad spectrum light at a concentration of 20 μg/mL. Dereplication of the photo-cytotoxic fractions from P. ophthalmicus extracts based on TLC R_f values and HPLC co-injection of reference tetrapyrrolic compounds enabled quick identification of known photosensitisers, pheophorbide- a , pheophorbide- a methyl ester, 13^2-hydroxypheophorbide- a methyl ester, pheophytin- a and 15^1-hydroxypurpurin 7-lactone dimethyl ester. In addition, compound 1 which was not previously isolated as a natural product was also identified as 7-formyl-15^1-hydroxypurpurin-7-lactone methyl ester using standard spectroscopic techniques. Conclusions Our results suggest that the main photosensitisers in plants are based on the Cyclic Tetrapyrrole structure and photosensitisers with other structures, if present, are present in very minor amounts or are not as active as those with the Cyclic Tetrapyrrole structure.
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www.mdpi.com/journal/ijms Validation of Quantitative Structure-Activity Relationship (QSAR) Model for Photosensitizer Activity Prediction
2011Co-Authors: Neni Frimayanti, Hong Boon Lee, Mun Li Yam, Rozana Othman, Sharifuddin M. Zain, Noorsaadah Abd RahmanAbstract:Abstract: Photodynamic therapy is a relatively new treatment method for cancer which utilizes a combination of oxygen, a photosensitizer and light to generate reactive singlet oxygen that eradicates tumors via direct cell-killing, vasculature damage and engagement of the immune system. Most of photosensitizers that are in clinical and pre-clinical assessments, or those that are already approved for clinical use, are mainly based on Cyclic Tetrapyrroles. In an attempt to discover new effective photosensitizers, we report the use of the quantitative structure-activity relationship (QSAR) method to develop a model that could correlate the structural features of Cyclic Tetrapyrrole-based compounds with their photodynamic therapy (PDT) activity. In this study, a set of 36 porphyrin derivatives was used in the model development where 24 of these compounds were in the training set and the remaining 12 compounds were in the test set. The development of the QSAR model involved the use of the multiple linear regression analysis (MLRA) method. Based on the method, r 2 value, r 2 (CV) value and r 2 prediction value of 0.87, 0.71 and 0.70 wer
Roseanne J Sension - One of the best experts on this subject based on the ideXlab platform.
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Ultrafast Excited State Dynamics and Fluorescence from Vitamin B12 and Organometallic [Co]-C≡C-R Cobalamins.
The Journal of Physical Chemistry B, 2020Co-Authors: Elvin V. Salerno, Nicholas A. Miller, Arkaprabha Konar, Christoph Kieninger, Bernhard Kräutler, Roseanne J SensionAbstract:Cobalamins are cobalt-centered Cyclic Tetrapyrrole ring-based molecules that provide cofactors for exceptional biological processes and possess unique and synthetically tunable photochemistry. Typical cobalamins are characterized by a visible absorption spectrum consisting of peaks labeled α, β, and sh. The physical basis of these peaks as having electronic origin or as a vibronic progression is ambiguous despite much investigation. Here, for the first time, cobalamin fluorescence is identified in several derivatives. The fluorescence lifetime is ca. 100-200 fs with quantum yields on the order of 10-6-10-5 because of rapid population of "dark" excited states. The results are compared with the fluorescent analogue with zinc replacing the cobalt in the corrin ring. Analysis of the breadth of the emission spectrum provides evidence that a vibrational progression in a single excited electronic state makes the dominant contribution to the visible absorption band.
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energy cascades excited state dynamics and photochemistry in cob iii alamins and ferric porphyrins
Accounts of Chemical Research, 2015Co-Authors: Aaron S Rury, Theodore E Wiley, Roseanne J SensionAbstract:CONSPECTUSPorphyrins and the related chlorins and corrins contain a Cyclic Tetrapyrrole with the ability to coordinate an active metal center and to perform a variety of functions exploiting the oxidation state, reactivity, and axial ligation of the metal center. These compounds are used in optically activated applications ranging from light harvesting and energy conversion to medical therapeutics and photodynamic therapy to molecular electronics, spintronics, optoelectronic thin films, and optomagnetics. Cobalt containing corrin rings extend the range of applications through photolytic cleavage of a unique axial carbon–cobalt bond, permitting spatiotemporal control of drug delivery.The photochemistry and photophysics of Cyclic Tetrapyrroles are controlled by electronic relaxation dynamics including internal conversion and intersystem crossing. Typically the electronic excitation cascades through ring centered ππ* states, ligand to metal charge transfer (LMCT) states, metal to ligand charge transfer (MLCT...
Christine A Kozak - One of the best experts on this subject based on the ideXlab platform.
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uroporphyrinogen iii synthase molecular cloning nucleotide sequence expression of a mouse full length cdna and its localization on mouse chromosome 7
Genomics, 1995Co-Authors: Christine A Kozak, Robert J DesnickAbstract:Abstract Uroporphyrinogen-III synthase (URO-S; EC 4.2.1.75), the fourth enzyme in the heme biosynthetic pathway, is responsible for the conversion of hydroxymethylbilane to the Cyclic Tetrapyrrole, uroporphyrinogen III. The deficient activity of URO-S is the enzymatic defect in congenital erythropoietic porphyria (CEP), an autosomal recessive disorder. For the generation of a mouse model of CEP, the human URO-S cDNA was used to screen 2 × 10 6 recombinants from a mouse adult liver cDNA library. Ten positive clones were isolated, and dideoxy sequencing of the entire 1.6-kb insert of clone pmUROS-1 revealed 5′ and 3′ untranslated sequences of 144 and 623 bp, respectively, and an open reading frame of 798 bp encoding a 265-amino-acid polypeptide with a predicted molecular mass of 28,501 Da. The mouse and human coding sequences had 80.5 and 77.8% nucleotide and amino acid identity, respectively. The authenticity of the mouse cDNA was established by expression of the active monomeric enzyme in Escherichia coli . In addition, the analysis of two multilocus genetic crosses localized the mouse gene on chromosome 7, consistent with the mapping of the human gene to a position of conserved synteny on chromosome 10. The isolation, expression, and chromosomal mapping of this full-length cDNA should facilitate studies of the structure and organization of the mouse genomic sequence and the development of a mouse model of CEP for characterization of the disease pathogenesis and evaluation of gene therapy.
