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PubMed2006

Investigation of stepwise covalent synthesis on a surface yielding porphyrin-based multicomponent architectures.

Porphyrins have been shown to be a viable medium for use in molecular-based information storage applications. The success of this application requires the construction of a stack of components ("electroactive surface/tether/charge-storage molecule/linker/electrolyte/top contact") that can withstand high-temperature conditions during fabrication (up to 400 degrees C) and operation (up to 140 degrees C). To identify suitable chemistry that enables in situ stepwise synthesis of covalently linked architectures on an electroactive surface, three sets of zinc porphyrins (22 altogether) have been prepared. In the set designed to form the base layer on a surface, each porphyrin incorporates a surface attachment group (triallyl tripod or vinyl monopod) and a distal functional group (e.g., pentafluorophenyl, amine, bromo, carboxy) for elaboration after surface attachment. A second set designed for in situ dyad construction incorporates a single functional group (alcohol, isothiocyanato) that is complementary to the functional group in the base porphyrins. A third set designed for in situ multad construction incorporates two identical functional groups (bromo, alcohol, active methylene, amine, isothiocyanato) in a trans configuration (5,15-positions in the porphyrin). Each porphyrin that bears a surface attachment group was found to form a good quality monolayer on Si(100) as evidenced by the voltammetric and vibrational signatures. One particularly successful chemistry identified for stepwise growth entailed reaction of a surface-tethered porphyrin-amine with a dianhydride (e.g., 3,3',4,4'-biphenyltetracarboxylic dianhydride), forming the monoimide/monoanhydride. Subsequent reaction with a diamine (e.g., 4,4'-methylene-bis(2,6-dimethylaniline)) gave the bis(imide) bearing a terminal amine. Repetition of this stepwise growth process afforded surface-bound oligo-imide architectures composed of alternating components without any reliance on protecting groups. Taken together, the ability to prepare covalently linked constructs on a surface without protecting groups in a stepwise manner augurs well for the systematic preparation of a wide variety of functional molecular devices.

Journal Article↗
PubMed2005

Aggregation behavior of tetrakis(4-sulfonatophenyl)porphyrin in AOT/water/decane microemulsions.

AOT/water/decane microemulsions have been used to entrap the water-soluble 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS4). Quasi-elastic light scattering technique has confirmed the confinement of the porphyrin and its various aggregates into the inner water pool. Various species have been detected as function of the size of the microemulsions, concentration of the porphyrin, pH, and aging of the solutions by using a combination of UV-vis absorption, steady fluorescence emission, fluorescence lifetime measurements, and time-resolved fluorescence anisotropy. Under neutral pH conditions, the porphyrin is present as the free base monomer (S414) in the inner water compartment, and it is free to rotate when the size of the droplet is large enough and the porphyrin concentration is low. On increasing the concentration and/or decreasing the microemulsion size, a H-dimer of the free base (S406) is prevalently formed. Aging both the S414 and S406 species leads to the formation of a new species (S424), which has been postulated as a H-type dimer of the diacid porphyrin. On decreasing the pH, the species S414 and S406 almost instantaneously convert into the diacid porphyrin, which is monomeric (S434). This latter is an intermediate in the eventual formation of J-aggregated TPPS4 (S490). A marked stability has been observed for the S424 species, which do not interconvert on changing the pH of the bulk aqueous phase.

Journal Article↗
PubMed2005

Interaction of porphyrins with a dendrimer template: self-aggregation controlled by pH.

The interaction between self-aggregated porphyrins such as 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS) and 5,10,15,20-tetrakis(4-phosphonatophenyl)porphyrin (TPPP), and a generation 5 (G5) PAMAM dendrimer template is governed by minute differences of porphyrin acido-basic properties. While at neutral pH both monomeric TPPS and TPPP form complexes with G5, decreasing pH did not lead to porphyrin ring protonation (pK(a) approximately 5) but rather to the preferential formation of H-aggregates (probably H-dimers), most likely due to protonation of the G5. Upon further acidification of the solution, this face-to-face orientation of the porphyrin units is being converted to edge-to-edge aligned J-aggregates with a tightly defined structure. This process starts by protonation of the porphyrin ring at pH below 2.3 and 2.8 for TPPS and TPPP, respectively. The AFM imaging of porphyrin/G5 nanostructures obtained at pH 0.7 shows the formation of long nanorods of TPPS with partially aggregated G5 and small aggregates of TPPP connected to individual G5 molecules.

Journal Article↗
PubMed2006

Spectroelectrochemical evidence for communication within a laterally-bridged dimanganese(III) bis-porphyrin.

Electronic coupling between the porphyrin units of a laterally-bridged dimanganese(III) bis-porphyrin 2 is explored using electrochemistry, spectroelectrochemistry and resonance-Raman spectroscopy. It is found that strong electronic interactions between the manganese(III) ion and the porphyrin macrocycle enhance the perturbations experienced by these bis-porphyrin systems when compared to related monomer porphyrin systems. In turn this leads to effective electronic communication between the manganese ions in the bis-porphyrin. This finding has importance in the design of molecular wires based on laterally-bridged oligo-metallo-porphyrins.

Journal Article↗
PubMed1988

Differential cell photosensitivity following porphyrin photodynamic therapy.

Experiments were performed to determine if differences in porphyrin photosensitivity could be observed for cells with varying efficiency in DNA damage repair, as well as for cells which make up components of the vasculature. Photofrin II is undergoing current clinical evaluation for photodynamic therapy of solid tumors, and therefore the retention, dark toxicity, and photosensitizing effects of this drug on human DNA repair-deficient fibroblasts (ataxia telangiectasia and xeroderma pigmentosum) were compared to normal human fibroblasts. In addition, bovine cells of endothelial, smooth muscle, and fibroblast origin were compared for porphyrin retention, toxicity, and photosensitivity. All human fibroblasts exhibited porphyrin-induced dark toxicity, but there were no significant differences in photosensitization or porphyrin retention for any of these cell lines. However, bovine endothelial cells were considerably more photosensitive than smooth muscle or fibroblast cells treated under identical conditions. All bovine cells accumulated similar levels of porphyrin, and therefore the increased sensitivity of the endothelial cells was not due to differences in porphyrin retention. These results provide additional evidence that nuclear damage and/or repair is not a dominant factor in the cytotoxicity induced by porphyrin photosensitization. In addition, these results indicate that endothelial cell photosensitivity may play a role in the vascular damage observed following photodynamic therapy.

Animals↗
PubMed1998

Are porphyrin mixtures favorable photodynamic anticancer drugs? A model study with combinatorial libraries of tetraphenylporphyrins.

Reported here is the preparation of tetraphenylporphyrin libraries via efficient combinatorial solution-phase syntheses, their purification, and preliminary results from a bioorganic study on their uptake in liposome membranes. Libraries with up to 666 components were prepared with substituents including Br, CF3, Cl, CN, CO2Me, Et, F, OAc, and Ph. Further, a first example for the synthesis of more diverse libraries via a "latent libraries" approach is presented. This involves masking polar groups with lipophilic protecting groups. After purification of the latent library, the masking protecting groups are removed in a quantitative reaction that produces the library compounds as the only non-volatile components. Libraries were characterized by laser desorption time-of-flight mass spectrometry, NMR, and UV-vis spectroscopy. In vitro uptake into membranes of small sonicated liposomes was measured, both in terms of total porphyrin incorporation and in terms of structure-incorporation relationships. The latter were determined from isotopically-resolved laser-desorption mass spectra under conditions that yield quantitative results. Smaller libraries showed increased uptake of porphyrins bearing OH and CF3 substituents and lower uptake of ester-, alkyl-, and halide-bearing porphyrins. This structure-dependent selectivity disappears for larger libraries, however, where uniformly high uptake is observed, i.e., at a constant lipid:porphyrin ratio the total porphyrin incorporation is higher for libraries than for single compounds of similar polarity. We propose that the decreased concentration of individual compounds in large libraries is responsible for this effect. Membrane incorporation has previously been shown to correlate with photodynamic activity in vitro and in vivo.16 Therefore, these results may help to explain why photodynamic therapy of tumors, a modern anti-cancer treatment modality, is successfully performed with a complex mixture of porphyrins.

Antineoplastic Agents↗
PubMed2000

Peptide design based on an antibody complementarity-determining region (CDR): construction of porphyrin-binding peptides and their affinity maturation by a combinatorial method.

We have utilized sequence information from an antiheme monoclonal antibody to develop novel porphyrin-binding peptides. Several peptides which have an intramolecular disulfide bond in different positions and different chain lengths were prepared. The affinities of peptides for meso-tetrakis(4-carboxyphenyl)porphyrin were increased by an appropriate conformational restraint using a disulfide bond. Detailed studies with a representative 12-peptide, 12C4, whose length was reduced from 20 residues of the complementarity-determining region (CDR), indicated that both the hydrophobic and electrostatic interactions were essential factors in the peptide-porphyrin binding. Moreover, two-dimensional 1H NMR spectroscopy revealed the conformation of the peptide and the critical residues for the porphyrin-binding. According to the obtained results, a further minimized 9-peptide, 9L, was successfully redesigned with a sequence capable of forming a beta-turn instead of a disulfide bond. Furthermore, affinity maturation studies of 9L were performed by using a combinatorial approach such as the spot-synthesis method. Peptides with an improved affinity for porphyrins were prepared by systematic amino acid replacement. Thus, the design of peptides targeted to porphyrins was demonstrated by the combination of antibody information and the rationally designed combinatorial method.

Amino Acid Sequence↗
PubMed1986

Solid phase extraction and isocratic separation of urinary porphyrins by HPLC.

A method for determining urine porphyrins by HPLC is described. In the preliminary step, porphyrins are purified in high yields and concentrated by low pressure reverse-phase chromatography on C18 (octadecylsilane bonded silica) cartridge. Porphyrins are stable for 10 days after adsorption on C18 cartridge. The separation of porphyrin esters is performed on an aminopropyl-bonded silica column with an eluting system containing n-heptane and ethyl acetate. The system enables rapid isocratic separation of porphyrin methyl esters with high selectivity. The simplicity and reproducibility of the whole procedure allows its application to the routine analysis of urinary porphyrins in the clinical laboratory.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

Porphyrin profiles in blood, urine and faeces by HPLC/electrospray ionization tandem mass spectrometry.

A high-resolution high-performance liquid chromatography/electrospray ionization quadrupole time-of-flight tandem mass spectrometry method is described for the analysis of porphyrins in blood, urine and faeces. The gradient elution reversed-phase HPLC system using acetonitrile-methanol-1 m ammonium acetate/acetic acid buffer (pH 5.16) as gradient solvent mixtures was able to separate all porphyrin metabolites, including the type I and type III isomers of uroporphyrin, hepta-, hexa- and penta-carboxylic acid porphyrins and coproporphyrin. The porphyrins were positively identified by the protonated molecules [M+H](+) and further characterized by tandem mass spectrometric analysis with each porphyrin giving a characteristic collisioninduced dissociation product ion spectrum. The mass chromatograms obtained by HPLC/ESI MS are useful for the differential diagnosis of the porphyrias, since each type of porphyria has a typical porphyrin excretion pattern.

Chromatography, High Pressure Liquid↗
PubMed1985

The interaction of tumour-localizing porphyrins with collagen, elastin, gelatin, fibrin and fibrinogen.

We have already reported in Balb C mouse transplantable mammary carcinoma, that uroporphyrin I and III are superior as tumour localizers when compared to hematoporphyrin derivative and a derivative thereof, photofrin II. This study compares the binding of porphyrins to proteins which may be found in tumour cells or stroma to investigate whether there is a common binding determinant. Coproporphyrin III and deuteroporphyrin IX which are non-tumour localizing porphyrins, were also part of the comparative study. The interaction of these porphyrins with acid soluble collagen and acid insoluble collagen, elastin, and fibrin was evaluated, and the binding of uroporphyrin isomers I and III and deuteroporphyrin IX to gelatin and fibrinogen, was also determined. The results suggest that collagen, especially the acid soluble form, and gelatin preferentially bind the four porphyrins which localize in mammary carcinoma tissue. The well reported observations that malignant epithelial cells, including breast cancer, produce collagen and contain a rate-limiting enzyme in collagen biosynthesis would support the notion that de novo synthesis of this protein may in part govern the tumour uptake and retention of porphyrins. Elastin, fibrinogen and fibrin showed non-discriminant binding to the porphyrins under study.

Animals↗
PubMed2005

Effect of axial ligation or pi-pi-type interactions on photochemical charge stabilization in "two-point" bound supramolecular porphyrin-fullerene conjugates.

Two types of structurally well-defined, self-assembled zinc porphyrin-fullerene conjugates were formed by "two-point" binding strategies to probe the effect of axial ligation or pi-pi-type interactions on the photochemical charge stabilization in the supramolecular dyads. To achieve this, meso-tetraphenylporphyrin was functionalized to possess one or four [18]crown-6 moieties at different locations on the porphyrin macrocycle while fullerene was functionalized to possess an alkyl ammonium cation, and a pyridine or phenyl entities. As a result of the crown ether-ammonium cation complexation, and zinc-pyridine coordination or pi-pi-type interactions, stable zinc porphyrin-fullerene conjugates with defined distance and orientation were formed. Evidence for the zinc-pyridine complexation or pi-pi-type interactions was obtained from the spectral and computational studies. Steady-state and time-resolved emission studies revealed efficient quenching of the zinc-porphyrin singlet excited state in these dyads, and the measured rates of charge separation, k(CS) were found to be slightly better in the case of the dyads held by axial coordination and crown ether-cation complexation. Nanosecond transient absorption studies provided evidence for the electron transfer reactions, and these studies also revealed charge stabilization in these dyads. The lifetimes of the radical ion pairs were found to depend upon the type of porphyrins utilized to form the dyads, that is, porphyrin possessing the crown ether moiety at the ortho position of one of the phenyl rings yielded prolonged charge stabilized states. Addition of pyridine to the supramolecular dyads eliminated the zinc-pyridine coordination or pi-pi-type interactions of the "two-point" bound systems due to the formation of a new zinc-pyridine axial bond thus giving a unique opportunity to probe the effect of axial coordination or pi-pi interactions on k(CS) and k(CR). Under these conditions, the measured electron transfer rates revealed faster k(CS) and slower k(CR) as compared to those obtained in the absence of added pyridine. The evaluated lifetimes of the radical ion-pairs were found to be hundreds of nanoseconds and were longer in the presence of pyridine.

Electrochemistry↗
PubMed2004

Effects of ion-carrier substituents on the potentiometric-response characteristics in anion-selective membrane electrodes based on iron porphyrins.

The potentiometric response characteristics with respect to salicylate anion of several membrane electrodes based on iron(III) tetraphenylporphyrin chloride (FeTPPCl) and derivatives with electrophilic and nucleophilic substituents, incorporated into plasticized polyvinylchloride (PVC) membranes were investigated. Complexes tetraphenyl porphyrin iron(III) chloride (FeTPPCl; A), tetrakis (4-methoxyphenyl) porphyrin iron(III) chloride (Fe(TOCH3PP)Cl; B), tetrakis (2,6-dichlorophenyl) porphyrin iron(III) chloride (Fe(TDClPP)Cl; C), tetrakis (4-nitrophenyl) porphyrin iron(III) chloride (Fe(TNO2PP)Cl; D), and tetrakis (pentafluorophenyl) porphyrin iron(III) chloride (Fe(TPFPP)Cl; E) were used as anion carriers in the membrane electrodes. The sensitivity, working range, detection limit, response mechanism, and selectivity of the membrane sensor toward interference shows a considerable dependence on the type of carrier substituent and the pH value of the sample solution. Potentiometric investigations in solutions of various pH show that the carrier complex containing fluoro substituents (E), which have very strong electron-accepting properties and a high ability to form hydrogen bonds, is capable of serving as a positively charged ionophore. Some other ionophores are capable of serving as both charged and neutral carriers under different conditions. The electrodes prepared in this work show super-Nernstian slopes with respect to salicylate concentration, which tend to a Nernstian response (slope near to -59 mV decade-1) upon an increase of the pH of the test solution. The results of UV/Vis absorption spectroscopy are used for interpretation of the formation of an oxene complex between salicylate and iron porphyrins.

Anions↗
PubMed1989

Bromocriptine prevents the castration-induced rise in porphyrin concentration in the harderian glands of the male Syrian hamster, Mesocricetus auratus.

The Harderian glands in Syrian hamsters exhibit a striking sexual dimorphism. Male Harderian glands show two cell types and low levels of porphyrins and melatonin. Of the enzymes involved in the synthesis of melatonin, N-acetyltransferase (NAT) and hydroxyindole-O-methyltransferase (HIOMT) show high and low activity levels, respectively. Female Harderian glands show but one cell type and have high porphyrin and melatonin levels, low NAT activity, and high HIOMT activity. In castrated males, the Harderian glands exhibit a female pattern of morphology, porphyrin levels, and indoleamine metabolism. In an attempt to determine whether prolactin in involved in this sexually dimorphic response of the Harderian glands, intact and castrated male and intact female hamsters were injected daily with 500 micrograms of bromocriptine, a dopamine agonist. Bromocriptine led to reduced serum prolactin levels in all groups. It had no apparent effect on the Harderian glands of intact males. In contrast, in castrated males bromocriptine prevented the postcastrational rise in porphyrin levels but had no effect on NAT or HIOMT activities. In females, bromocriptine treatment had no effect on porphyrin concentrations or HIOMT activity; it led to a statistically significant increase in NAT activity. We propose that testosterone inhibits Harderian porphyrin synthesis while dopamine or prolactin stimulates it.

Animals↗
PubMed2002

Detection of water-soluble vitamins by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry using porphyrin matrices.

The detection of water-soluble vitamins B(1), B(2), B(6), B(12) and C by matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry (TOFMS) was attempted by studying 17 porphyrin matrices. Comparative studies of porphyrin matrices, useful mass spectral window, matrix/analyte molar ratio (M/A), ultraviolet-visible absorption characteristics and quantitative results were made. Most porphyrin matrices provide a useful mass spectral window in the low-mass range. The optimal M/A increases with increasing molecular mass of the vitamin. Vitamin B(12) possesses the highest molecular mass and requires a higher M/A. The presence of hydroxyl or carboxyl groups in the porphyrin is an indicator of a useful MALDI matrix. Vitamins B(2) and B(6) were readily ionized upon irradiation with a 337 nm laser without the use of any porphyrin matrix. Improved linearity and sensitivity of the calibration curves were obtained with samples prepared with a constant M/A. The limits of detection and quantitation are at the picomole level. The results indicate that MALDI-TOFMS with porphyrin matrices is a rapid and viable technique for the detection of low molecular mass water-soluble vitamins.

Indicators and Reagents↗
PubMed1997

Photodynamic effects induced by meso-tetrakis[4-(carboxymethyleneoxy)phenyl]porphyrin using rat hepatic microsomes as model membranes.

Porphyrins, in combination with light, offer an alternate approach to the treatment of cancer, in the form of photodynamic therapy (PDT). With a view to locate new porphyrins for use in PDT, we evaluated the ability of a novel water-soluble porphyrin, meso-tetrakis[4-(carboxymethyleneoxy)phenyl]porphyrin (T4CPP) to induce photodamage in membranes, using rat hepatic microsomes as a model system. Hepatic microsomes treated with T4CPP and exposed to visible light showed significant lipid peroxidation, as assessed by the formation of conjugated dienes, lipid hydroperoxides, and thiobarbituric acid-reactive substances. The peroxidation induced was both time- and concentration-dependent. T4CPP plus light also resulted in the destruction of the microsomal enzymes adenosine triphosphatase and glucose-6-phosphatase. Analysis of the products of peroxidation and selective inhibition by specific inhibitors showed that the oxidative damage induced was mainly due to singlet oxygen and partly due to hydroxyl radical. The porphyrin T4CPP was efficiently labeled with 99mTc. When this 99mTc-labeled porphyrin was injected into a mammary-tumor-bearing rat, it accumulated in the tumor. Our studies suggest that T4CPP, due to its potential to localize in tumors and to induce membrane damage as exemplified by alteration in rat liver microsomes, may have possible applications in this new modality of cancer treatment.

Animals↗
PubMed2001

Analysis of urinary porphyrins in rats exposed to aluminum and iron.

The mechanism by which excess aluminum induces anemia may be aluminum overload resulting from a reversible block in heme synthesis due either to a defect in porphyrin synthesis or to impaired iron utilization. Studies were conducted to define the specific changes in the urinary porphyrin excretion pattern (porphyrin profile) and the time course of those changes in rats exposed to aluminum. In these studies, aluminum chloride (AlCl3) was orally administered to female Wistar rats at the dose of 100 mg Al/kg for 35 days with or without FeCl2 (4 mg Fe/kg). Control rats were treated with 0.9% NaCl or with FeCl2 (4 mg/kg). The dynamics of urine porphyrins (8-, 7-, 6-, 5-, and 4-carboxyporphyrins) was determined by HPLC on the 7th, 14th, 21st, 28th, and 35th days in both exposed and control groups of rats. The results of the experiment indicate that aluminum induced a statistically significant increase in the percentage of uroporphyrin and a decrease in coproporphyrin in urine (cumulative dose, 2100 mg Al/kg). Changes in urinary porphyrins were observed when the concentration of aluminum in serum was at 48 microg Al/L on average. Administration of iron together with aluminum diminished the described changes in porphyrins metabolism caused by aluminum itself.

Administration, Oral↗
PubMed1995

The effects of bromocriptine and prolactin on porphyrin biosynthesis in the harderian gland of the male hamster, Mesocritecus auratus.

Porphyrin biosynthesis was examined in the Harderian gland of the male golden hamster by fluorometric assays of gland porphyrin content and by measuring the activity of a rate-limiting enzyme for haem biosynthesis, 5-aminolaevulinic acid synthase. Both porphyrin content and enzyme activity are low in normal male glands but were greatly raised in males castrated for 6 weeks. However, porphyrin synthesis remained at basal levels in castrates given the dopamine agonist bromocriptine; this suppression could be reversed by simultaneous prolactin administration, and castrated males receiving prolactin alone exhibited very high enzyme activity and porphyrin content. Bromocriptine also prevents the morphological feminisation of the Harderian gland which would normally occur after castration; again, the simultaneous administration of prolactin permits feminisation to occur. The results support the hypothesis that, while androgens have an inhibitory effect on porphyrin synthesis within this model, other factors, including prolactin, are permissive.

5-Aminolevulinate Synthetase↗
PubMed2001

Porphyrin levels in excreta of sea birds of the Chilean coasts as nondestructive biomarker of exposure to environmental pollutants.

In this preliminary study on sea birds we propose the use of porphyrins in excreta as a biomarker of exposure to contaminants. Samples of excreta were obtained from colonies of brown pelicans (Pelecanus occidentalis thagus), neotropic cormorants (Phalacrocorax olivaceus), and kelp gulls (Larus dominicanus) in three areas of the south coast of Chile with different human impact (Tubul, Talcahuano, and Valdivia). They were analyzed for porphyrin content (copro-, uro-, and protoporphyrins and total porphyrins) by a rapid fluorimetric method and by HPLC. The main outcomes of the study were: (a) kelp gulls and neotropic cormorants living in areas with high human impact showed a clear capacity to accumulate and eliminate porphyrins in the excreta; (b) species-related accumulation capacities are likely, as shown by the different levels found in different species living in the same area; (c) the porphyrin profile obtained by fluorimetry and HPLC showed a higher percentage of protoporphyrin than the other porphyrins; (d) although the fluorimetric method of Grandchamp is semiquantitative, it was found to be sensitive enough to detect differences in samples from field studies. The positive results of this preliminary study make it possible to propose this nondestructive method for a variety of field applications.

Animals↗