• Journal of Microbiology and Biotechnology
• /
• v.23 no.5
• /
• pp.668-673
• /
• 2013

A recombinant E. coli co-expressing ALA synthase (hemA), NADP-dependent malic enzyme (maeB), and dicarboxylic acid transporter (dctA) was reported to synthesize porphyrin derivatives including iron-containing heme. To enhance the synthesis of bacterial heme, five genes of the porphyrin biosynthetic pathway [pantothenate kinase (coaA), ALA dehydratase (hemB), 1-hydroxymethylbilane synthase (hemC), uroporphyrinogen III synthase (hemD), and uroporphyrinogen III decarboxylase (hemE)] were amplified in the recombinant E. coli co-expressing hemA-maeB-dctA. Pantothenate kinase expression enabled the recombinant E. coli to accumulate intracellular CoA. Intracellular ALA was the most enhanced by uroporphyrinogen III synthase expression, porphobilinogen was the most enhanced by ALA dehydratase expression, uroporphyrin and coproporphyrin were the most enhanced by 1-hydroxymethylbilane synthase expression. The strain co-expressing coaA, hemA, maeB, and dctA produced heme of $0.49{\mu}mol/g$-DCW, which was twice as much from the strain without coaA expression. Further pathway gene amplifications for the porphyrin derivatives are discussed based on the results.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2008.10a
• /
• pp.1411-1413
• /
• 2008

We developed $Sn^{4+}$-porphyrin complexes that show thermally activated delayed fluorescence (TADF). TADF intensities increased with an increase of temperature because of an acceleration of the reverse intersystem crossing from triplet to singlet excited states by heat activation. TADF component provides a novel pathway for high efficiency OLEDs.

• Proceedings of the Korean Fiber Society Conference
• /
• 2003.10b
• /
• pp.100-103
• /
• 2003

The basic structure of porphyrin consists of four pyrrole units linked by four methine bridges. It reveals that the cyclic 16-atom is the preferred cyclic system for n-electron delocalization since this pathway exhibits the highest degree of bond equalization. Scheme 1 (a) shows the 16-center system is the chromogen of the porphyrins, which allows 18-electron delocalization that could produce aromatic characteristics (1,2). (omitted)

• Bulletin of the Korean Chemical Society
• /
• v.33 no.2
• /
• pp.636-640
• /
• 2012

We modify ZnO nanorods with Zn-porphyrin to obtain the improved characteristics of energy transfer, which is further investigated for the applicability to photovoltaic devices. A nitrogen heterocyclic ligand containing a thiol group is covalently grafted onto the surface of finely structured ZnO nanorods with a length of 50-250 nm and a diameter of 15-20 nm. Zn-porphyrin is then attached to the ligand molecules by the mechanism of metalligand axial coordination. The resulting energy band diagram suggests that the porphyrin-modified ZnO nanorods might provide an efficient pathway for energy transfer upon being applied to photovoltaic devices.

• Bulletin of the Korean Chemical Society
• /
• v.19 no.2
• /
• pp.183-188
• /
• 1998

Incorporation of metalloporphyrins into polypyrrole (PPy) film was achieved either by electropolymerization of pyrrole in the presence of metal-tetra(sulfonatophenyl)porphyrin anion (MTSPP, M=Co, Fe) or by metalizing hydrogenated tetra(4-sulfonatophenyl)porphyrin anion (H2TSPP) doped into PPy through ion-exchange. Electrochemical reduction of oxygen on the PPy doped with metallo porphyrin (PPy-MTSPP) was studied in acidic and basic solutions. Oxygen reduction on PPy-MTSPP electrodes appeared to proceed through a 4-electron pathway as well as a 2-electron path. In acidic solutions, the overpotential for O2 reduction on PPy-CoTSPP electrode was smaller than that on gold by about 0.2 V. In basic solutions the overpotential of the PPy-CoTSPP electrode in the activation range was close to those of Au and Pt. The limiting current was close to that of Au. However, polypyrrole doped with cobalt-tetra(sulfonatophenyl)porphyrin anion (PPy-CoTSPP) or with iron-tetra(sulfonatophenyl)porphyrin anion (PPy-FeTSPP) was found to have limited potential windows at high temperatures (above 50 ℃), and hence the electrode could not be held at the oxygen reduction potentials in basic solutions (pH 13) without degradation of the polymer.

• Journal of Microbiology and Biotechnology
• /
• v.25 no.6
• /
• pp.880-886
• /
• 2015

Bacterial heme was produced from a genetic-engineered Escherichia coli via the porphyrin pathway and it was useful as an iron resource for animal feed. The amount of the E. coli-synthesized heme, however, was only few milligrams in a culture broth and it was not enough for industrial applications. To analyze heme biosynthetic pathways, an engineered E. coli artificially overexpressing ALA synthase (hemA from Rhodobacter sphaeroides) and pantothenate kinase (coaA gene from self geneome) was constructed as a bacterial heme-producing strain, and both the transcription levels of pathway genes and the intermediates concentrations were determined from batch and continuous cultures. Transcription levels of the pathway genes were not significantly changed among the tested conditions. Intracellular intermediate concentrations indicated that aminolevulinic acid (ALA) and coenzyme A (CoA) were enhanced by the hemA-coaA co-expression. Intracellular coproporphyrinogen I and protoporphyrin IX accumulation suggested that the bottleneck steps in the heme biosynthetic pathway could be the spontaneous conversion of HMB to coproporphyrinogen I and the limited conversion of protoporphyrin IX to heme, respectively. A strategy to increase the conversion of ALA to heme is discussed based on the results.

• Korean Journal of Environmental Biology
• /
• v.26 no.2
• /
• pp.115-120
• /
• 2008

Earlier we have described new water-soluble Ag- and Zn-derivatives of tetrachloride meso-tetra (4-N-oxiethylpyridyl) porphyrin (TOEtPyP) as potential anticancer drugs. In this work the effect of one of these metal porphyrins, TOEtPyP Ag, on the cell population kinetics was studied in vitro using morphological and biochemical techniques. The results suggested that TOEtPyP Ag action consisted in the simultaneous suppression of the cell growth and activation of the cell death. About 40% of the cells were shown to die via apoptotic pathway. So, the porphyrin studied may be attributed to inducers of both necrotic and apoptotic processes. The results obtained support our previous assertion that TOEtPyP Ag may be considered as a potential chemotherapeutic agent.

• Bulletin of the Korean Chemical Society
• /
• v.20 no.11
• /
• pp.1303-1308
• /
• 1999

Conducting poly(3,4-ethylenedioxythiophene) (PEDT) films with metalloporphyrins incorporated as the counter ions were prepared by electropolymerization of the monomer in the presence of metal-tetra(sulfonatophenyl) porphyrin anions. Cathodic reduction of oxygen on the resulting conducting polymer films was studied. The overpotential for O2 reduction on electrodes with cobalt-porphyrin complex was significantly smaller in acidic solutions than on gold. In basic solutions, the overpotential at low current densities was close to those on platinum and gold. Polymer electrode with Co-complex yielded higher limiting currents than with Fe-complex, although the Co-complex polymer electrode was a poorer electrocatalyst for O2 reduction in the activation range of potential than the Fe counterpart. From the rotating ring-disk electrode experiments, oxygen reduction was shown to proceed through either a 4-electron pathway or a 2-electron pathway. In contrast to the polypyr-role-based electrodes, the PEDT-based metalloporphyrin electrodes were stable with wider potential windows, including the oxygen reduction potential. Their electrocatalytic properties were maintained at temperatures up to 80℃ in KOH solutions.

• Applied Chemistry for Engineering
• /
• v.5 no.1
• /
• pp.37-43
• /
• 1994

Mononitrotoluenes were reduced to aminotoluenes using porphyrin as a catalyst in the presence of several types of reductants including hydrogen sulfide and 1, 4-dithiothreitol(DTT). Intermediates and final products of porphyrin-catalyzed reduction of mononitrotoluenes were identified and a pathway for the reduction of the nitro group to the corresponding amino group was proposed. The optimum pH for the reduction was determined. The catalytic activity of the porphyrin was confirmed by UV/VIS absorption spectra and basic kinetics of porphyrin-catalyzed reduction were studied. Of several types of reductants tested, DTT sodium hydrosulfite, and hydrogen sulfide were seen to give significant reduction of nitrobodies. When hydrogen sulfide was used as a reductant hydrogen sulfide and nitrotoluenes were removed simultaneously.

• Bulletin of the Korean Chemical Society
• /
• v.17 no.6
• /
• pp.515-520
• /
• 1996

Simple conditions were discovered to afford tripyrranes by reaction of 2,5-bis(α-hydroxymethyl)furan or 2,5-bis(α-hydroxy-α-phenylmethyl)thiophene with excess pyrrole in the presence of acid catalyst. Stepwise synthesis of porphyrins with core-ligand modification and synthesis of meso-tetraarylporphyrins bearing two different substituents in cis orientation have developed as building blocks for the various porphyrin-based model systems. Consequently, 21-thia-23-oxa-10,15-diphenylporphyrin (28), 21-oxa-10,15-diphenylporphyrin (29) and 21-oxa-23-carba-12-aza-10,15-diphenylporphyrin (30) were synthesized by acid-catalyzed [3+1] condensation between tripyrranes and 2,5-bis(α-hydroxymethyl)pyrrole or 2,5-bis(α-hydroxy-α-phenylmethyl)thiophene. The synthetic pathway described here gave regioisomerically pure porphyrins and thus overcame the synthetic problems associated with separation and purification of regioisomeric mixture.