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PubMed2002

Steric control of organic transformation by a dendrimer cage: organocobalt dendrimer porphyrins as novel coenzyme B(12) mimics.

Cobalt(II) complexes of poly(aryl ester) dendrimer porphyrins (m-[Gn]TPP)Co(II) and (p-[Gn]TPP)Co(II) (n = 0-3) underwent AIBN-initiated alkylation (AIBN = 2,2'-azobis(isobutyronitrile)) at the metal center with propargyl alcohol in CDCl(3) at 60 degrees C, where the dendritic substituents did not affect the overall conversion rate but selectivity of the alkylation. With the largest (m-[G3]TPP)Co(II), a single organocobalt(III) species (Co(III)-C(=CH(2))CH(2)OH, 4) was selectively formed in 91% yield, due to a steric protection of 4 by the large dendrimer cage from the access of another molecule of cobalt porphyrin species. In contrast, with other cobalt(II) porphyrins, isomerized compounds such as Co(III)-C(CH(3))=CHOH (5) and Co(III)-CH(CH(3))CHO (6) were formed in addition to 4. A stereochemical investigation with (m-[G3]TPP)Co(II) using AIBN-d(12), in place of nondeuterated AIBN, demonstrated that the alkylation (cobalt(III) hydride addition to propargyl alcohol) is selective to a trans adduct. Results also indicated that this addition step does not involve external activation of propargyl alcohol.

Alkylation↗

PubMed2004

One-pot synthesis of cyanuric acid-bridged porphyrin-porphyrin dyads.

Stepwise amination of cyanuric chloride (1) with 5-(4-aminophenyl)-10,15,20-triphenylporphyrin (2) and/or its zinc(II) complex (3) enables the synthesis of porphyrin-porphyrin dyads with predetermined free base-free base forms or free base-zinc and zinc-zinc metalation states. Furthermore, the use of aminopropyl-silanized silica gel as a scavenger for unwanted byproducts allowed the one-pot synthesis of title porphyrin compounds in high yield and purity with minimum use of preparative column chromatography.

Journal Article↗

PubMed1999

Synthesis of meso-tetra-(3,5-dibromo-4-hydroxylphenyl)-porphyrin and its application to second-derivative spectrophotometric determination of lead in clinical samples.

A new very sensitive and selective chromogenic reagent, meso-tetra-(3,5-dibromo-4-hydroxylphenyl)porphyrin [T(DBHP)P], was synthesized and studied for the determination of trace lead in detail. In 0.10 mol l-1 NaOH medium, lead reacts with T(DBHP)P to form a 1:2 yellow complex, which gives a maximum absorption at 479 nm; 0-0.48 microgram ml-1 Pb(II) obeyed Beer's law. The molar absorptivity of the complex and Sandell's sensitivity are 2.5 x 10(5) 1 mol-1 cm-1 and 0.000812 microgram cm-2, respectively. Second-derivative spectrophotometry is better than conventional spectrophotometry in sensitivity and selectivity, and its limit of quantification, limit of detection and relative standard deviation are 0.70 ng ml-1, 0.21 ng ml-1 and 1.0%, respectively. Ca (3250-fold), Mg (2000-fold), Sr (1000-fold), Ba (750-fold), Al (1000-fold), Bi (500-fold), Fe (2000-fold), Co (750-fold), Ni (1000-fold), Cu (750-fold), Zn (1250-fold), Cd (2500-fold) and Ag (550-fold) do not interfere with the determination of lead. The chromogenic system is remarkably superior to other reagents, especially porphyrin compounds. The influence caused by oxygen in air or in solution can be easily eliminated by adding Na2SO3. The reaction is very stable, the stability constant of the complex being 1.2 x 10(45). The chromogenic reaction is completed within 1 min at room temperature when 8-hydroxylquinoline is used as catalyst. The proposed method has been applied to the direct determination of trace lead in clinical samples. The accuracy and precision are both very satisfactory.

Humans↗

PubMed2005

A comparative study of water soluble 5,10,15,20-tetrakis(2,6-dichloro-3-sulfophenyl)porphyrin and its metal complexes as efficient sensitizers for photodegradation of phenols.

5,10,15,20-Tetrakis(2,6-dichloro-3-chlorosulfophenyl)porphyrin and its tin and zinc complexes were synthesized with high yields and fully characterized. The corresponding water-soluble 5,10,15,20-tetrakis(2,6-dichloro-3-sulfophenyl)porphyrins were obtained by hydrolysis with water. An extensive photophysical study of the new water soluble porphyrinic compounds was carried out including absorption and fluorescence spectra, fluorescence quantum yields, triplet absorption spectra, triplet lifetimes, triplet and singlet oxygen quantum yields. These sensitizers were successfully used in the photodegradation of 4-chlorophenol and 2,6-dimethylphenol. A comparison is made of their efficiencies, and some mechanistic considerations are highlighted.

Journal Article↗

PubMed1995

Fluorescence spectroscopic identification of 7,12-dimethylbenz[a]anthracene-induced hamster buccal pouch carcinogenesis.

An attempt was made to study whether light-induced fluorescence spectroscopy could be exploited to discriminate premalignant and malignant tissues of hamster buccal pouch carcinogenesis from normal tissues during a 16 week regimen of tri-weekly topical application of 7,12-dimethylbenz[a]anthracene (DMBA) in liquid paraffin. Histologically, the DMBA-treated buccal mucosa showed hyperplastic changes at 4-6 weeks, papillomas at 8-10 weeks, early invasive carcinomas at 11-13 weeks and finally well-differentiated squamous cell carcinomas at 14-16 weeks of treatment. Acetone extracts of these different staged tissues with age matched control tissues were excited at 405 and 420 nm and the emissions were scanned from 430 and 440 to 700 nm respectively. The spectral profiles of control and transformed tissues were found to be different, each displaying their own characteristic prominent maxima and other spectral marks. The spectra of transformed tissues showed characteristic peaks around 620-630 nm which did not appear in control tissues and the fluorescent intensities at 630 nm [FI(630)nm] were significantly increased from early stages onwards when compared to controls. The spectra of DMBA carcinomas developed at the 18th week after withdrawal of DMBA application at the 10th week and carcinoma extract spiked with DMBA confirmed the peak around 620-630 could be attributed only to porphyrin compounds accumulated in transformed tissues. Furthermore, the ratios of FI(520)nm/FI(630)nm of transformed tissues were also significantly decreased when compared to control tissues. This diagnostic test had a very close resemblance with respect to histological studies. These results suggest that this technique using conventional light-induced fluorescence spectroscopy may be useful for early diagnosis of premalignant and malignant lesions of oral cavity.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed1996

Inhibitory effect of dietary flavonol quercetin on 7,12-dimethylbenz[a]anthracene-induced hamster buccal pouch carcinogenesis.

The inhibitory effect of dietary supplementation with flavonol quercetin on 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch carcinogenesis was investigated. Dietary quercetin inhibited the incidence of both papillomas and tumors induced by DMBA. The fluorescence spectra of papillomas and tumors showed different prominent maxima and a characteristic peak around 620-630 nm, which could be attributed to the accumulation of porphyrin compounds. Further, the fluorescence intensities at 630 nm (FI630nm) were elevated, whereas the ratio FI530nm/FI630nm was decreased in DMBA-induced lesions. Quercetin treatment significantly decreased FI630nm and increased the ratio FI520nm/FI630nm when compared with DMBA-induced lesions. It is therefore evident that quercetin has an inhibitory effect on DMBA-induced carcinogenesis and further studies will throw more light on its use as a chemopreventive agent against oral cancer.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed1994

Characterization of a family of chlorophyll-deficient wheat (Triticum) and barley (Hordeum vulgare) mutants with defects in the magnesium-insertion step of chlorophyll biosynthesis.

During thylakoid membrane biogenesis, chlorophyll (Chl) biosynthesis and the accumulation of Chl-binding proteins are tightly linked, light-regulated processes. We have investigated the consequences faced by mutant plants with defects in Chl biosynthesis by studying a series of five homeologous allelic chlorina mutants in wheat (Triticum) and one phenotypically related barley (Hordeum vulgare) mutant that express the same pleiotropic mutant phenotype but to different extents. These mutants accumulate Chl at different rates, with the most severely affected plants having the slowest rate of Chl accumulation. Analysis of precursor pools in the Chl synthesis pathway indicates they have a partial block in Chl synthesis and accumulate protoporphyrin IX (Proto), the last porphyrin compound common to both heme and Chl synthesis. The affected plants with the most severe phenotypes accumulate the most Proto. Chloroplasts isolated from these mutants exhibit a lower activity of the enzyme Mg-chelatase, which catalyzes the first committed step in Chl synthesis. The most severely affected plants exhibit the greatest reduction in Mg-chelatase activity. Heme levels and protoporphyrinogen oxidase activity were the same for mutant and wild-type plants. We suggest that a block in Mg-chelatase activity in these mutants could account for the other traits of their pleiotropic phenotype previously described in the literature.

Alleles↗

PubMed1988

Possible control of transcript levels by chlorophyll precursors in Chlamydomonas.

Steady-state mRNA levels of the three nuclear genes cab1, rbcS1 and rbcS2 (coding for the light-harvesting chlorophyll-binding protein (LHCP) and the small subunit of ribulose 1,5-bisphosphate carboxylase, respectively) and of the two plastid-encoded genes rbcL and psaA2 (coding for the large subunit of the carboxylase and a member of the P700 chlorophyll a protein, respectively) have been investigated in synchronized Chlamydomonas cells in response to light and inhibitors interfering with chlorophyll synthesis. The accumulation of cab1, rbcS1 and psaA2 transcripts is light-dependent, whereas transcripts from rbcS2 and rbcL genes are present in high amounts in the light and in the dark. Dioxoheptanoic acid, an inhibitor blocking chlorophyll synthesis prior to porphyrin formation, does not affect the accumulation of all five mRNAs. However, inhibition of chlorophyll synthesis by incubating cells with dipyridyl, cycloheximide or nitrogen promotes the accumulation of porphyrin compounds, but specifically prevents the accumulation of light-dependent transcripts. Although functionally unrelated, these inhibitors are known to block an Fe-dependent oxygenase, which is involved in the formation of the isocyclic ring in the chlorophyll molecule. The data are explained as a control by chlorophyll precursors over the accumulation of light-dependent transcripts.

2,2'-Dipyridyl↗

PubMed2003

Oxygen tension imaging in the mouse retina.

A newly developed microscope-based imaging system was used to measure the oxygen tension (PO2) inside the retinal and choroidal vessels of mice and to generate in vivo maps of retinal PO2. These maps were generated from the phosphorescence lifetimes of an injected palladium-porphyrin compound using a frequency-domain measurement. The system was fully calibrated and used to produce retinal PO2 maps at different inspiratory oxygen fractions. PO2 rose accordingly and predictably as inspiratory O2 was stepped from hypoxic to hyperoxic conditions. Important experimental and acquisition parameters necessary for applying phosphorescence lifetime imaging to the mouse eye were investigated, including camera exposure and intensifier gain settings. Because of a need to limit light exposure to the retina, PO2 map quality as measured by the coefficient of determination was investigated as a function of signal-to-noise and accumulated excitation energy deposition. With the development of this technology for use in mice, the potential for investigating the oxygen dynamics in genetically engineered mouse models of retinal disease, including diabetic retinopathy, glaucoma, and age-related macular degeneration, is advanced.

Animals↗

PubMed1967

Carbon monoxide production associated with ineffective erythropoiesis.

The rate of endogenous carbon monoxide production ( Vco), determined by the closed rebreathing system technique, was elevated above the normal range in four of five patients studied with ineffective erythropoiesis (four patients with primary refractory anemia, one with thalassemia). The mean molar ratio of Vco to Vheme (rate of circulating heme catabolism, determined from (51)Cr red cell survival curves) was 3.0 +/- 0.6 (SE), indicating that most of the CO originated from sources other than circulating erythrocyte hemoglobin, in contrast to previous findings in patients with hemolytic anemia, where Vco paralleled Vheme closely.After administration of glycine-2-(14)C to these patients, endogenous CO was isolated by washout of body CO stores at high pO(2) or by reacting peripheral venous blood samples with ferricyanide. The CO was then oxidized to CO(2) by palladium chloride and trapped for counting in a liquid scintillation spectrometer. "Early labeled" peaks of (14)CO were demonstrated which paralleled "early labeled" peaks of stercobilin and preceded maximal labeling of circulating heme. Production of "early labeled" (14)CO in patients with ineffective erythropoiesis was greatly increased, up to 14 times that found in a normal subject. The increased Vco and "early (14)CO" production shown by these patients are presumably related mainly to heme catabolism in the marrow. The possibility exists that hepatic heme and porphyrin compounds may also contribute significantly to Vco, as suggested by the finding of a high Vco in an additional patient with porphyria cutanea tarda.

Adolescent↗

PubMed2005

Determinants of oxidative phosphorylation onset kinetics in isolated myocytes.

At the onset of constant-load exercise, pulmonary oxygen uptake (VO(2)) exhibits a monoexponential increase, following a brief time delay, to a new steady state. To date, the specific factors controlling VO(2) onset kinetics during the transition to higher rates of work remain largely unknown. To study the control of respiration in the absence of confounding factors such as blood flow heterogeneity and fiber type recruitment patterns, the onset kinetics of mitochondrial respiration were studied at the start of contractions in isolated single myocytes. Individual myocytes were microinjected with a porphyrin compound to allow phosphorescent measurement of intracellular PO(2) (P(i)O(2), an analog of VO(2)). Peak tension and P(i)O(2) were continuously monitored under a variety of conditions designed to test the role of work intensity, extracellular PO(2), cellular metabolites, and enzyme activation on the regulation of VO(2) onset kinetics.

Animals↗

PubMed2003

Biomolecules linked to transition metal complexes--new chances for chemotherapy.

From the synthetic point of view the fast developing fields of medicine and biology offer new opportunities for the design of very effective drugs with high selectivity. Especially in the field of anticancer therapy many efforts have been made to deliver drugs to specific tissues. Sugar substituted porphyrin compounds, bile acid conjugates, and pH-sensitive immunoliposomes are only some examples. Although there are many different approaches to exploit biomolecules as shuttles only a start has been made. Since the targeting of a drug is a very complex process, a successful design of a new compound has to consider chemical as well as biological aspects and requires a multidisciplinary cooperation with physicians and biologists. Three interesting concepts are evaluated exemplarily: antibodies, molecules with binding affinity to hormone receptors, and bile acids. The main issues are: selection of the drug and the carrier, ways of linking the pharmacological active compound to the biomolecule, the optimal way of linking the drug to the spacer, and cytotoxicity, apoptosis, and drug resistance.

Animals↗

PubMed1988

[Phototherapy of tumors using photosensitizing agents].

The experimental and clinical data on a new method of cancer treatment--photodestruction of tumours treated with the photosensitizing preparations--are reviewed. Particular emphasis is given to porphyrin compounds. The problems are considered dealing with accumulation of these compounds in cells and tissues, with the mechanism of photoalteration of sensitized tumours, with testing of the method on transplanted and spontaneous animal tumours as well as with the data on the phototherapy of human tumours with a hematoporphyrin-derivative used as a photosensitizer. The prospects for the method development are evaluated.

Animals↗

PubMed1985

Early detection of lung cancer by means of hematoporphyrin derivative fluorescence and laser photoradiation.

In recent years hematoporphyrin derivative (HpD), a mixture of porphyrin compounds that have an increased affinity for malignant tissue, has been used as an endobronchial tumor indicator to facilitate the bronchoscopic localization of early squamous cell carcinoma of the central tracheobronchial tree. In this article the authors describe four different bronchoscopic fluorescence detection systems that have facilitated the bronchoscopic localization of HpD-labeled early squamous cell carcinoma of the trachea and central bronchi.

Adenocarcinoma↗

PubMed1993

Purification of forensic specimens for the polymerase chain reaction (PCR) analysis.

Purification methods of deoxyribonucleic acid (DNA) from degraded and contaminated forensic samples were investigated for polymerase chain reaction (PCR) analysis. DNA extracted from putrefied tissue or bloodstains sometimes contained the copurified contaminant, that was identified as the porphyrin compound (hematin). When contaminated but less degraded DNA was analyzed by PCR, it was necessary to eliminate the impurity by anion exchange column chromatography or chelating resin preparation, and ultrafiltration using Centricon microconcentrators. When highly degraded DNA was analyzed, trace amounts of high molecular weight DNA was recovered by electroelution method, and then further purified by both column chromatography and ultrafiltration. From thus purified samples, the amelogenin gene for sex determination could be amplified by dual PCR technique.

Adipose Tissue↗

PubMed1998

Synthesis of protoporphyrin IX induced by 5-aminolevulinic acid in yeast cells in the presence of 2,2;-dipyridyl

5-Aminolevulinic acid (ALA), a precursor of porphyrin synthesis, increased the production of various porphyrin compounds in Candida guilliermondii cells. Metalloporphyrins and protoporphyrin IX (PPIX) were predominantly accumulated, respectively, at ALA concentrations of 0.2-0.4 mM and at those higher than 1.5 mM. 2,2;-Dipyridyl which complexed with bivalent metals significantly increased the content of endogenous PPIX even at ALA concentrations lower than 0.5 mM. Under these conditions, the yeast sensitivity to photodynamic effect of visible light (400-600 nm) dramatically increased due to photosensitization by endogenous PPIX.

Journal Article↗

PubMed1983

X-ray absorption spectroscopic studies of high valent iron porphyrins. Horseradish peroxidase compounds I and II and synthetic models.

X-ray absorption edge and extended x-ray absorption fine structure studies have been undertaken on resting (ferric) horseradish peroxidase, HRP compound I (HRP-I), HRP compound II (HRP-II), and several highly oxidized synthetic iron porphyrins that may have relevance as models for the iron site in horseradish peroxidase. The energies of the absorption edges are consistent with an Fe(IV) formulation for the highly oxidized species. The shapes of the absorption edges further support the assignment of HRP-I and one of the model compounds as Fe(IV)-porphyrin pi-cations. The edge shapes also demonstrate that the iron sites in the model porphyrins are not identical to the iron sites in the enzyme. Preliminary curve fitting analysis of the extended x-ray absorption fine structure clearly indicates the presence of two different nearest neighbor distances for the iron, both in HRP-I and HRP-II, as well as in two of the highly oxidized model porphyrins. These distances are interpreted as an iron-porphyrin nitrogen distance and as a short (approximately 1.6 A) iron-oxygen distance.

Electron Probe Microanalysis↗

PubMed2006

Assessment of the performance of density-functional methods for calculations on iron porphyrins and related compounds.

The behaviors of a large number of GGA, meta-GGA, and hybrid-GGA density functionals in describing the spin-state energetics of iron porphyrins and related compounds have been investigated. There is a large variation in performance between the various functionals for the calculations of the high-spin state relative energies. Most GGA and meta-GGA functionals are biased toward lower-spin states and so fail to give the correct ground state for the high-spin systems, for which the meta-GGA functionals show more or less improvement over the GGA ones. The GGA functionals that use the OPTX correction for exchange show remarkably high performance for calculating the high-spin state energetics, but their results for the intermediate-spin states are somewhat questionable. A heavily parameterized GGA functional, HCTH/407, provides results which are in qualitative agreement with the experimental findings for the iron porphyrins [FeP, FeP(Cl), FeP(THF)2], but its relative energies for the high-spin states are probably somewhat too low. The high-spin state relative energies are then even more underestimated by the corresponding meta-GGA functional tau-HCTH. For the hybrid-GGA functionals, the Hartree-Fock (HF)-type (or exact) exchange contribution strongly stabilizes the high-spin states, and so the performance of such functionals is largely dependent upon the amount of the HF exchange admixture in them. The B3LYP, B97, B97-1, and tau-HCTH-hyb functionals are able to provide a satisfactory description of the energetics of all the systems considered.

Iron↗