SEARCH · Search PubMed

Results for “PORPHYRINS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 757 records · Page 42Linked to original sources

PubMed1996

Meso-substituted cationic porphyrins as efficient photosensitizers of gram-positive and gram-negative bacteria.

Previous studies on the photosensitization of bacterial cells with different neutral or negatively charged porphyrins and phthalocyanines have demonstrated that, although Gram-positive bacteria are efficiently photoinactivated, Gram-negative bacteria become photosensitive only after modification of the permeability of their outer membrane. The results described in this paper show that two meso-substituted cationic porphyrins, namely tetra(4N-methyl-pyridyl)porphine tetraiodide and tetra(4N,N,N-trimethyl-anilinium)porphine, efficiently photosensitize the inactivation of Gram-negative bacteria, such as Vibrio anguillarum and Escherichia coli. A negatively charged meso-substituted porphyrin, tetra(4-sulphonatophenyl)porphine, has no appreciable photosensitizing activity towards Gram-negative bacteria, although all three porphyrins exhibit a similar subcellular distribution pattern, being mainly localized in the protoplasts or spheroplasts. Moreover, the three porphyrins show similar efficiency in the photoinactivation of the Gram-positive bacterium Entorecoccus seriolicida.

Dose-Response Relationship, Radiation↗

PubMed1995

Photophysical properties of porphyrins in biological membranes.

This review illustrates the photophysical properties of some porphyrins, especially those used for biomedical applications, in relation to their photosensitizing efficiency in biological membranes. Porphyrin absorption and luminescence properties are mainly examined. The factors influencing the affinity of porphyrins for biological membranes, including the dye hydrophobicity, the charge and aggregation state, the pH of the medium and the physicochemical properties of the dye environment, are discussed. These factors determine the differences in the photophysical properties of porphyrins in biological membranes. Particular attention is paid to the porphyrin aggregation state: only monomeric species and possibly planar end-to-end aggregates are endowed with significant photosensitizing ability. Many conclusions presented are based on data obtained on membrane model systems such as micelles or liposomes which can mimic specific situations occurring in cells.

Animals↗

PubMed1996

The role of membrane-bound porphyrin-type compound as endogenous sensitizer in photodynamic damage to yeast plasma membranes.

The effect of visible light (400-600 nm) on Candida guilliermondii and Saccharomyces cerevisiae was studied, and irradiation fluences killing the yeast cells without exogenous sensitizers were determined. The lethal effects are strongly oxygen-dependent, suggesting the involvement of photodynamic reactions mediated by endogenous sensitizer(s). Repair-deficient strains of S. cerevisiae show the same photosensitivity as the wild-type strain indicating that visible light does not photosensitize repairable DNA lesions. As was demonstrated using the microfluorometric method with the fluorochrome primulin, photodestruction of plasma membrane permeability barriers is important for yeast cell lethality. Visible light at cell-killing fluences induces lipid peroxidation in plasma membrane ghosts isolated from C. guilliermondii. Data obtained suggest the important role of singlet oxygen photogenerated by endogenous sensitizer(s) in initiating oxidative reactions. A spectrofluorometric analysis of the plasma membrane ghosts revealed one compound fluorescent in the visible spectral region at 683 nm. Its fluorescence excitation and absorption spectra have structures typical for porphyrins. The plasma membrane-bound porphyrin-like compound is different in some fluorescence properties from mitochondrial porphyrins. Estimation of its amount gives a value of 0.1 nmol porphyrin per milligram of protein of the plasma membrane ghosts. This porphyrin-type compound is considered to be the most probable candidate for the role of the sensitizer in photodynamic damage to yeast plasma membrane and cell inactivation by visible light.

Candida↗

PubMed1995

Absence of circadian variations in urinary porphyrin excretion in normal subjects.

The hypothesis that urinary porphyrins could be excreted in a circadian rhythm was examined. A group of 20 healthy subjects, 10 males and 10 females, aged 20-40 years, were used in this study. Urine was collected at 4-hr intervals over three 24-hr periods. Median porphyrin concentrations (microgram l-1 or microgram g-1 of creatinine) were similar in the six groups, but significant differences were observed in that excreted. Highest porphyrin excretion was detected in the afternoon (12.00-16.00 hr) and, in the evening (16.00-20.00 hr). pH values were also increased at evening but did not correlate with porphyrin excretion. Despite these temporal variations, no cycles indicating circadian periodicity were observed. Therefore, a 24-hr collection of urine is not necessary for the initial evaluation of porphyrin metabolism.

Adult↗

PubMed2005

Meso-substituted tetra-cationic porphyrins photosensitize the death of human fibrosarcoma cells via lysosomal targeting.

In this paper we present a study on the intracellular localisation and the efficiency of cell photoinactivation of a series of derivatives of 5,10,15,20-tetrakis-(4-N-methylpyridyl)-porphine (C1), whose degree of lipophilicity was varied through replacement of one methyl group with an alkyl chain of various length. Human HT1080 fibrosarcoma cells exposed to the various C1 derivatives (0.25 microM) for 24 h and irradiated with increasing doses of red-light (0.45-27 J/cm2) were inactivated with different efficiencies. The efficiency of cell photoinactivation increased with the increasing length of the hydrocarbon tail and lipophilicity and correlated with the efficiency of the porphyrin accumulation into the cells. Despite the presence of positive charges, these porphyrins did localise rather selectively in lysosomes while mitochondrial localisation was not evident, as demonstrated by fluorescence microscopy studies. Studies on isolated mitochondria provided evidence that the porphyrin uptake and distribution in these organelles were not modulated by the transmembrane potential but were exclusively controlled by partitioning phenomena which might have prevented mitochondria localization in whole cells. Our findings demonstrated that these porphyrins entered the cells through the endocytotic pathway and were transported to lysosomes whose pH increased rapidly upon irradiation. Lysosomal damage did not cause any intracellular redistribution of the porphyrin and represented the primary event causing cell death, very likely via necrosis.

Cations↗

PubMed2006

Optical properties of porphyrin molecules immobilized in nano-porous silicon.

The paper aims at studying optical properties of porous silicon powders and thin films which were impregnated with different porphyrin molecules. It has been shown that introducing porphyrins into porous silicon matrix results in quenching of luminescence from porous silicon, while luminescence of porphyrins survives, though its structure changes. At the same time, porphyrins in porous silicon matrix which was preliminarily oxidized does not alter luminescence from porphyrins. Generation of singlet oxygen by illuminated porphyrin/porous silicon composite is confirmed by additional oxidation of porous silicon and by the observation of characteristic 1270 nm luminescence band.

Adsorption↗

PubMed2006

Detection of organics using porphyrin embedded nanoporous organosilicas.

Molecularly imprinted polymers and silica have been studied as receptor binding site mimics for use in a wide range of separation, catalysis, and detection applications employing transduction mechanisms including conductometric, amperometric, and capacitance. Porphyrins are also well known as sensor components due to the extreme sensitivity of their spectrophotometric characteristics to changes in their immediate environment. We have developed periodic mesoporous organosilicas (PMO) which incorporate a porphyrin into the material for use as an optical indicator of target binding. This material combines the stability, selectivity, and high density of binding sites characteristic of the molecularly imprinted PMO with the sensitivity and selectivity of the porphyrin. We demonstrate binding of p-nitrophenol, p-cresol, 2,4,6-trinitrotoluene, and RDX by the porphyrin-embedded PMOs with selective adsorption of TNT over the other analytes. In addition, the binding of each of the organics by the PMO results in unique changes in the spectrophotometric characteristics of the incorporated porphyrin. These changes can be observed by visual inspection or through the use of fluorescence spectra collected in 96-well format.

Nanostructures↗

PubMed2004

Interaction of phospholipid dispersions with water-soluble porphyrins as monitored by their Raman temperature profiles.

Raman scattering spectra of 1,2-dipalmitoyl-sn-glycero-3-phospho-rac-(1-glycerol) (DPPG) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) dispersions, mixed with water-soluble porphyrins, i.e. cationic copper(II)-5,10,15,12-tetrakis(4-N-methylpyridyl) and anionic silver(II)-5,10,15,20-tetrakis(4-carboxyphenyl)porphyrins, were measured in the 2800-3100 cm(-1) C-H stretching vibration region as a function of the temperature within the 5-55 degrees C range. Temperature profiles of Raman data were constructed from a quantitative data treatment based on factor analysis. This method is shown to be more efficient than the commonly used approach employing peak intensity ratios. Parameters of the gel phase to liquid crystal phase transition determined from Raman temperature profiles were used to monitor the porphyrin influence on DPPG and DPPC structures. Both negatively and positively charged porphyrins significantly perturb DPPC and DPPG dispersions, causing significant downshift of the transition temperature and broadening of the transition region. Water-soluble porphyrins are assumed to set at the outside part of phospholipid dispersions and interact via coulombic forces with charged lipid heads. For the cationic CuTMPyP, the strongest effect has been observed for negatively charged DPPG. In contrast, anionic AgTPPC4 has been found to interact more efficiently with DPPC possessing both positive and negative charges.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed2006

An improved method for isolation and purification of sedimentary porphyrins by high-performance liquid chromatography for compound-specific isotopic analysis.

We describe an improved method for purification of sedimentary vanadyl and nickel porphyrins (i.e., naturally occurring metalloalkylporphyrins). For the purpose of compound-specific isotopic analyses, various sedimentary porphyrins were purified from the complex natural mixtures by the dual-step high-performance liquid chromatography (HPLC) method. The high-sample-capacity reversed-phase HPLCs by adding N,N-dimethylformamide to the mobile phase allow an efficient collection of fractions containing the target compounds even using analytical-scale columns. Furthermore, this method achieved improved chromatographic resolutions but significantly reduced the overall retention time down to 60% compared with the previous work. The target compounds were then isolated with the normal-phase HPLC with the baseline-resolution, which is necessary to avoid chromatographic isotopic fractionation. One of the advantages of this method is that it requires neither derivatization nor demetallation. The purity of these isolated compounds was demonstrated by various HPLC online detection methods utilizing a photodiode-array detector, a mass selective detector. The overall recoveries of Ni porphyrin, VO porphyrin, and porphyrin-free base, respectively, were estimated to be approximately 50-60%, 65%, and 85%.

Chromatography, High Pressure Liquid↗

PubMed2004

Determination of porphyrins and biliverdin in bile and excreta of birds by a single liquid chromatography-ultraviolet detection analysis.

Methods developed for porphyrin analysis have low recoveries and/or poor precision for the less polar protoporphyrin IX. We describe a simple method of analysis of porphyrins and biliverdin in bile and excreta of birds based on extraction with HCl 3N: acetonitrile and HPLC/UV analyses. Recoveries were good for protoporphyrin IX and other porphyrins (>79%). Applications of this method showed that porphyrins and biliverdin in birds excreta are mainly of biliary-fecal origin rather than urinary origin. Biliverdin and protoporphyrin IX increased proportionately more than the rest of the porphyrins and coproporphyrin III increased more than coproporphyrin I in the bile of Pb-poisoned mallards.

Animals↗

PubMed2005

First insight into catalytic activity of anionic iron porphyrins immobilized on exfoliated layered double hydroxides.

Mg-Al layered double hydroxide (LDH) intercalated with glycinate anions was synthesized through co-precipitation and exfoliated in formamide and the single-layer suspension was reacted with aqueous iron porphyrin solutions (Fe(TDFSPP) and Fe(TCFSPP)). The obtained materials were characterized by X-ray powder diffraction, UV-vis, and electron paramagnetic resonance and investigated in the oxidation reaction of cyclooctene and cyclohexane using iodosylbenzene as oxidant. The iron porphyrin seems to be immobilized at the surface of the glycinate intercalated LDH. The catalytic activities obtained in heterogeneous media for iron porphyrin, Fe(TDFSPP), was superior to the results obtained under homogeneous conditions, but the opposite effect was observed on the Fe(TCFSPP), indicating that, instead of the structural similarity of both iron porphyrins (second-generation porphyrins), the immobilization of each one produced different catalysts. The best catalytic activity of the Fe(TDFSPP)/Gly-LDH, compared to Fe(TCFSPP)/Gly-LDH, can be explained by the easy access of the oxidant and the substrate to the catalytic sites in the former, probably located at the surface of the layered double hydroxide pillared with glycinate anions. A model for the immobilization and a mechanism for the oxidation reaction will be discussed.

Aluminum Hydroxide↗

PubMed2006

A novel pH-controlled transfer process of 5,10,15-tri(4-hydroxyphenyl)-20-(4-hexadecyloxyphenyl) porphyrin in CTAB micelles.

By analysis of the UV-visible and fluorescence spectra of 5,10,15-tri(4-hydroxyphenyl)-20-(4-hexadecyloxyphenyl)porphyrin (P) in different microenvironments of micelle and solvent solutions, a novel pH-controlled transfer process of P in CTAB micelle was reported. In neutral CTAB micelles, porphyrins may locate at the inner layers of micelles. With pH increases to 11.19, the porphyrin can be completely deprotonated and transfers to the outer surface of CTAB micelle. The investigation of kinetics of porphyrin complexing with Cu(II) indicates that the metallation rate of porphyrins in CTAB micelles could also be controlled by changing pH.

Cetrimonium↗

PubMed2006

Reductive nitrosylation of water-soluble iron porphyrins by S-nitroso-N-acetylpenicillamine: rate constants and EPR characterization.

Reductive nitrosylation of the water-soluble iron derivatives of the cationic Fe(III)(TMPyP) and anionic Fe(III)(TPPS) porphyrins [where TMPyP=tetra-meso-(4-N-methylpyridiniumyl)porphinate and TPPS=tetra-meso-(4-sulfonatophenyl)porphinate] by the nitric oxide donor S-nitroso-N-acetylpenicillamine (SNAP) was studied using optical absorption spectroscopy and electron paramagnetic resonance. Nitrosylation rates were obtained, the reaction was found to be first order in the SNAP concentration and the stoichiometry of the reaction was one to one. The similarity between the obtained second-order rate constants for both porphyrins, k(TMPyP)=0.84 x 10(3)M(-1)s(-1) and k(TPPS)=0.97 x 10(3)M(-1)s(-1), suggested that the reaction mechanism is approximately independent of the nature of the porphyrin meso-substituents. A mechanism was proposed involving the hydrolysis of SNAP by an out of plane liganded H(2)O yielding the sulfenic acid of N-acetylpenicillamine and the transfer of NO(-) to Fe(III). The EPR (electron paramagnetic resonance) spectra of the SNAP- and gaseous NO-treated porphyrins were obtained and compared. The difference between the spectra of the cationic and anionic porphyrins indicates different local symmetry and Fe-N-O bond angle. SNAP-treatment produced much more resolved hyperfine structures than gaseous NO-treatment.

Electron Spin Resonance Spectroscopy↗

PubMed2006

The effect of skin permeation enhancers on the formation of porphyrins in mouse skin during topical application of the methyl ester of 5-aminolevulinic acid.

The influence of skin permeation enhancers, such as dimethyl sulphoxide (DMSO) and 1-[2-(decylthio)ethyl]azacyclopentan-2-one (HPE-101), Labrafac CC, Labrafil, Labrasol and Transcutol in a concentration of 10% (wt./wt.) on the formation of porphyrins in normal mouse skin from topical application of creams with methyl 5-aminolevulinate (MAL) was studied. The concentration of porphyrins in the mouse skin was determined by direct fluorescence measurements. The results show that studied permeation enhancers increase the formation of porphyrins, and therefore also the skin penetration 2% MAL whereas for 10% and 20% (wt./wt.) MAL concentrations only DMSO, HPE-101 and Labrafac CC increased the porphyrin formation. At all studied MAL concentrations DMSO gave the largest enhancing effect, similarly to that of HPE-101. This suggests that in 2-20% MAL creams HPE-101 may be substituted by Labrafac CC to reduce skin irritation induced by HPE-101 without impairing the porphyrin formation.

Administration, Topical↗

PubMed2006

Photodynamic therapy: regulation of porphyrin synthesis and hydrolysis from ALA esters.

Photodynamic therapy (PDT) is a tool for the treatment of certain cancerous and pre-cancerous conditions. The natural precursor of porphyrins 5-aminolevulinic acid (ALA) has been extensively used as a pro-photosensitiser in PDT. ALA's poor permeability has been enhanced by chemical esterification with aliphatic alcohols. Some of the ALA esters proved to be more efficient than ALA for porphyrin synthesis. In the present work we studied the nature of porphyrin synthesis regulation from the ALA esters Hexyl-ALA (He-ALA) and R,S-ALA-2-(hydroxymethyl)tetrahydropyranyl ester (THP-ALA) in an adenocarcinoma cell line. We found that He-ALA is incorporated into the cells at a higher rate, followed by THP-ALA and ALA, whereas ALA and ALA esters efflux at the same rate mediated by passive diffusion. Although ALA entrance to the cell might be regulatory at low concentrations, ALA derivative uptake is not a limiting factor. At high concentrations, the regulation of ALA conversion into porphyrins is driven by the enzyme porphobilinogenase, whereas ALA esters hydrolysis is regulated by esterases. The key conclusion of this contribution is that the use of ALA esters has to be limited to low concentrations where no regulation on porphyrin synthesis takes place.

Adenocarcinoma↗

PubMed1998

Kinetics of the interactions of a dicarboxylic porphyrin with unilamellar lipidic vesicles: interplay between bilayer thickness and pH in rate control.

The transfer of a dicarboxylic porphyrin from phosphatidylcholine fluid-phase unilamellar vesicles towards albumin is studied focusing on bilayer thickness and pH effects. The kinetics of this process yield the rate constants for the porphyrin flip-flop from the inner to the outer hemileaflet and its exit towards aqueous medium. Phospholipids with monounsaturated 14-22 carbon chains are used. Interplay between bilayer thickness and pH for the control of the rate constants is observed. This results in the amplification, at physiological pH, of the effect of membrane thickness on the flip-flop and exit rates as compared to pH 8.5 and 6.5. These data are explained by the degree of porphyrin burying within the bilayer resulting from a compromise between favorable hydrophobic interactions with the hydrocarbon phase and unfavorable penetration of the polar carboxylic chains. The balance between the two effects depends particularly on the neutralization of one carboxylic chain. Considering the bilayer hydrophobicity profile and the porphyrin size, the optimization of hydrophobic interactions appears dependent on the bilayer thickness. The flip-flop and the exit are governed by neutralization and deprotonation of the carboxylic chains, respectively, the rate of these proton exchanges being dependent on the porphyrin location within the bilayer.

Albumins↗

PubMed1986

Mode of interaction and apparent binding constants of meso-tetraaryl porphyrins bearing between one and four positive charges with DNA.

Meso-substituted porphyrins, ((4-N-methyl-pyridyl)n(Ph)4-n)PH2, n = 1 to 4, bearing between 1 and 4 positive charges have been synthetized and studied for their interaction with Calf Thymus DNA. Competition binding experiments using ethidium bromide or one of its dimers show that these porphyrins and some of their Cu(II) or Fe(III)Cl complexes have apparent binding constants between 3 10(5) and 5 10(7) M-1. Fluorescence energy transfer experiments show that not only the tetracationic previously described porphyrin but also the tri- and dicationic porphyrins are able to intercalate into DNA. These data indicate a greater importance of the polyaromatic porphyrin ring than of the number or position of the positive charges for meso-tetra-arylporphyrin interaction with DNA.

Binding, Competitive↗

PubMed1997

Halogenated aromatic hydrocarbon-mediated porphyrin accumulation and induction of cytochrome P4501A in chicken embryo hepatocytes.

Concentration-dependent induction of cytochrome P4501A (CYP1A) and intracellular porphyrin accumulation were observed following treatment of chicken embryo hepatocyte (CEH) cultures with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 2,3,7,8-tetrachlorodibenzofuran (TCDF), 3,3',4,4'-tetrachlorobiphenyl (PCB 77, IUPAC nomenclature), 2,3',4,4',5-pentachlorobiphenyl (PCB 118), 3,3',4,4',5-pentachlorobiphenyl (PCB 126), 3,3',4,4',5,5'-hexachlorobiphenyl (PCB 169), and a commercial mixture of PCBs (Aroclor 1254). For these halogenated aromatic hydrocarbons (HAHs), or mixture, maximal CYP1A activity [measured as ethoxyresorufin-O-deethylase (EROD) activity] and immunodetectable protein were observed at concentrations just prior to, or coincident with, the concentrations at which porphyrin accumulation became evident. Both immunodetectable CYP1A protein and catalytic activity decreased at high concentrations of these compounds, but the rate and extent of decrease of immunodetectable CYP1A protein varied. Time-course studies with PCB 77 indicated a decrease in potency and an increase in maximal CYP1A induction between 24 and 48 hr of exposure which may indicate in vitro metabolism of this HAH. Intracellular accumulation of total porphyrins without CYP1A induction, was observed for 2,2',5,5'-tetrachlorobiphenyl (PCB 52), 2,2',6,6'-tetrachlorobiphenyl (PCB 54), 2,2',3,5',6-pentachlorobiphenyl (PCB 95), 2,2',4,5,5'-pentachlorobiphenyl (PCB 101), 2,2',3,3',6,6'-hexachlorobiphenyl (PCB 136), and 2,2',4,4',5,5'-hexachlorobiphenyl (PCB 153). Overall, these results are consistent with a role for CYP1A induction and/or Ah receptor activation in porphyrin accumulation mediated by HAHs with a planar configuration, whereas those that are not planar may mediate porphyrin accumulation by a mechanism not involving induction of CYP1A.

Animals↗