Presence Of Porphyrins Research Articles

Fluorescence Switching of Quantum Dot in Quantum Dot–Porphyrin–Cucurbit [7] Uril Assemblies

The fluorescence switching of alloy (Cd1–xZnxS) quantum dot (QD) in the presence of porphyrin and cucurbit [7] uril has been demonstrated using steady-state and time-resolved spectroscopy. The assemblies of Cd1–xZnxS QD, 5-(4-aminophenyl)-10,15,20-triphenyl-21H,23H-porphyrin (APTPP), have been prepared by electrostatically attaching the negatively charged QD with positively charged APTPP. The drastic photoluminescence (PL) quenching and the shortening of decay time of alloy QD in the presence of porphyrin indicate the efficient energy transfer from QD to porphyrin. It is interesting to note that the PL quenching varies with changing the alloy composition, which reveals that the quenching of QD luminescence by porphyrin could be used as a probe for detection of porphyrin. Furthermore, in the presence of cucurbit [7] uril, CB[7] acts as a receptor to bind the porphyrin (quencher) and restore the luminescence of the QD by preventing the energy transfer from QD to porphyrin. Encapsulation of APTPP molecules w...

87 The melting of DNA in the presence of meso-tetra-pyridyl porphyrins with different peripheral substituents

The influence of water-soluble cationic 3N- and 4N-pyridyl porphyrins with different peripheral substituents (oxyethyl, buthyl, allyl, and metallyl) on melting parameters of DNA has been studied. Results indicate that the presence of porphyrin changes the shape and parameters of DNA melting curve. The increase of porphyrins concentration results in the increase of the melting temperature (Tm) and the melting interval (ΔT) of DNA. At the porphyrin-DNA concentration ratio r = 0.01, changes in the melting temperature have not been observed. The melting intervals almost do not change upon adding of the 4N-porphyrins, while the decrease of ΔT, in the presence of 3N-porphyrins, is observed. Because the intercalation binding mechanism occurs in GC-rich regions of DNA, we assume that 3N-porphyrins, intercalated in GC-rich regions, reduce the thermal stability of these sites, bringing them closer to the thermal stability of the AT-sites, which is the reason for the decrease in the melting interval. While at the relative concentration r = 0.01 for 4-N porphyrins, already the external binding mechanism “turns on” and the destabilizing effect of porphyrins on GC-pairs compensates stabilizing effect on AT-pairs, as a result of which change in the melting of DNA upon complexation with these porphyrins is not observed. The decrease of the hypochromic effect also indicates the intercalation of investigated porphyrins in the DNA structure, which weakens the staking interaction of base pairs of DNA. The increase of the hypochromic effect of DNA upon binding with porphyrin depends on the type of peripheral substituents of the porphyrin. The results show that porphyrins with butyl and allyl substituents weaken staking interaction of base pairs less than porphyrins with other substituents. The largest change was observed for metallyl porphyrins. It can be the result of bulky peripheral substituents, which make significant local changes in DNA structure.

Construction of a controllable Förster resonance energy transfer system based on G-quadruplex for DNA sensing

Conjugations of oligonucleotides, chromophores, and gold nanoparticles (GNPs) can be used for energy transfer assays to detect DNA. Herein, a homogenous Förster resonance energy transfer (FRET) system employing two-step modification of oligonucleotide on GNPs was reported. The distance between the donor (fluorescein attached onto DNA) and the acceptor (GNPs) was controlled by using the G-rich DNA. In the presence of porphyrin or berberine, which can act as ligands of G-quadruplexes, the G-rich DNA spacer can result into G-quadruplex structure. Therefore, the intimate contact between the fluorophore and the GNP results in efficient energy transfer and fluorescence quenching. After hybridization with target DNA, the G-quadruplex stretched and resulted in an enhancement of fluorescence. So the present FRET system can be used for target DNA sensing with detection limit as low as 40pM (S/N=3). In this study, a relation between the fluorescence quenching efficiency and GNP sizes was found and bigger GNPs had higher fluorescence enhancement after hybridization with target DNA.

Copper chlorophyllin: A food colorant with bioactive properties?

Copper chlorophyllin (Cu-Chl) is a chlorophyll-derived food colorant, commercially available as a complex mixture of different chlorin molecules. Several studies have reported great variability in the composition of the mixture as well as the presence of porphyrins and uncoppered chlorin derivatives. The intake of chlorophyllin and its relationship with possible health benefits have been also the subject of several studies and the results have drawn attention to the possibility that this compound may serve not just as a food colorant, but also as a potential bioactive product with antimutagenic, anticarcinogenic and antioxidant activities; however, its mechanisms of action are not yet well understood. Attaining knowledge of its mechanisms of absorption, bioavailability and consequent bioactivity is essential for the exploration of its potential health-related applications. The purpose of this paper is to present an overview of bioactivities concerning Cu-Chl and provide a discussion on the latest scientific research findings on its human health benefits.

Is Dye Mixture More Suitable Rather Than Single Dye to Fabricate Dye Sensitized Solar Cell?

The steady state and time resolved spectroscopic studies reveal that two xanthene dyes Rhodamine 6G (R6G) and Rhodamine B (RB), used in the present investigations, form ground state hydrogen -bonded complexes with meso-tetrakis(4-carboxyphenyl) porphyrin (TCPP). However, it is apparent that upon photoexcitation the H-bonding complexes formed in the ground state decompose into the individual reacting components. This presumption was confirmed from the observation of the presence of only static quenching mode in the steady state fluorescence of the dyes in presence of porphyrin. The photoelectrochemical properties of the free dyes and the mixtures of each dye with porphyrin are investigated by measuring incident photon-to-current conversion efficiency (IPCE) using ZnO electrode and also with TiO2 electrode. It is seen that Rhodamine B-porphyrin mixture has attained maximum IPCE among the four samples studied at approximately 550 nm using ZnO electrode. Using TiO2 electrode, slight improvement in the value of IPCE was found for the same mixture. Therefore Rhodamine B-porphyrin mixture may act as a good sensitizer for converting solar energy to electrical energy.

ChemInform Abstract: Highly Selective, Economical and Efficient Oxidation of Alcohols to Aldehydes and Ketones by Air and Sunlight or Visible Light in the Presence of Porphyrins Sensitizers.

In this work, a new aerobic route is introduced for the selective oxidation of a variety of aromatic and aliphatic alcohols to the corresponding aldehyde and ketone derivatives by molecular oxygen in the presence of free base porphyrins and metalloporphyrins as sensitizers using white light or sunlight in an organic solvent. The method shows a wide scope, exhibits chemoselectivity and proceeds under mild reaction conditions. The resulting products are obtained in good conversions in a reasonable time.

Photooxygenation of alkenes by molecular oxygen in the presence of porphyrins and chlorin sensitizers under visible light irradiation

Photooxidation of alkenes by molecular oxygen and visible light in the presence of tetraphenylporphyrin (H2TPP) , tetramesitylporphyrin (H2TMP) , tetrakis pentafluorophenylporphyrin (H2TPFPP) and tetrakis(2,3-dimetoxyphenyl)porphyrin T(2,3-OMeP)P and metalloporphyrins such as ClFeTPP , ClMnTMP , ClMnTPP , ClMnTPFPP , ClCoTPP and ZnTPP has been performed. Photooxidation of alkenes with tetraphenylchlorin (H2TPC) as the sensitizer with visible light has also been studied. The conversion rates for alkene oxidation were in the order of free-base porphyrins > chlorin > metalloporphyrins. In the presence of NaN3/Na2SO3 the yield of oxidation products and conversion percentage is considerably reduced, confirming involvement of 1O2 in the mechanism.

Aqueous extraction of glucuronoxylans from chestnut wood: New strategy for lignin oxidation using phthalocyanine or porphyrin/H 2O 2 system

Hardwood 4- O-methylglucuronoxylans (MGX) are classically isolated by a delignification step, using a sodium chlorite solution, followed by alkaline extraction, an efficient, although potentially polluting process. In this work, we propose a chlorine-free environmentally-friendly process for MGX extraction from Castanea sativa Mill. Chestnut sawdust was first delignified using metalled phthalocyanine or porphyrin in presence of hydrogen peroxide. Then, MGX were easily extracted by hot water. This protocol, repeated with different incubation times and temperatures, led to the selective extraction of acetylated MGX with decent yields reaching 12%. The best results were obtained after delignification using iron tetrapyrrole macrocycles. However, lower degrees of polymerization of MGX were observed in comparison to the classical method, suggesting that this new process affects the structures of xylans.

Photocatalytic properties and structure of chitosan-based porphyrin-containing systems

The photocatalytic activity of the disodium salt of substituted hematoporphyrin in a model reaction of tryptophan oxidation in the presence of chitosan with different molecular masses and a block copolymer of ethylene and propylene oxides (Pluronic F-127) is studied. It is shown that, in the presence of the Pluronic, the catalytic activity of the chitosan-porphyrin system increases. The structure of chitosan-Pluronic systems, depending on the molecular mass of chitosan and the presence of porphyrin, is examined by AFM. A pleasible mechanism of the influence of the Pluronic on the photocatalytic activity of chitosan-por-phyrin systems is proposed.

Selective photocatalytic epoxidation of cyclooctene by molecular oxygen in the presence of porphyrin sensitizers

Photooxidation of cyclooctene by molecular oxygen in the presence of tetraphenyl porphyrin (H2TPP), tetramesityle porphyrin (H2TMP), tetrakis dichlorophenyl porphyrin (H2TDCPP) and ClFeTMP, ClFeTPP, tetrakis pentaflouro phenyl porphyrin iron chloride (ClFeTPFPP), ClFeTDCPP, ClMnTPP, ClMnTPFPP, ZnTDCPP, ClMnTDCPP, ClCoTDCPP, ClCoTPP and ZnTPP as sensitizers has been studied. 98% cyclooctene conversion with 97% selectivity toward cyclooctene oxide was obtained by H2TDCPP and ZnTDCPP sensitizers. The effect of electron-donating and withdrawing groups on the porphyrin macrocycle ring showed that non-metalled porphyrins with electron-withdrawing groups have higher reactivity (H2TDCPP > H2TPP > H2TMP). The order of reactivity for metalloporphyrins is Zn > Mn > Fe > Co for the same porphyrin ligand. A turnover number (TON) up to 6,000 with selectivity up to 95% was obtained by ClMnTDCPP. In free-base porphyrins and Zn porphyrins, singlet oxygen production is the major route for oxidation, whereas in Mn and Fe porphyrins, two parallel pathways for oxidation products is proposed.

Bioavailability of organically bound Fe to model phytoplankton of the Southern Ocean

Abstract. Iron (Fe) is known to be mostly bound to organic ligands and to limit primary productivity in the Southern Ocean. It is thus important to investigate the bioavailability of organically bound Fe. In this study, we used four phytoplankton species of the Southern Ocean (Phaeocystis sp., Chaetoceros sp., Fragilariopsis kerguelensis and Thalassiosira antarctica Comber) to measure the influence of various organic ligands on Fe solubility and bioavailability. Short-term uptake Fe:C ratios were inversely related to the surface area to volume ratios of the phytoplankton. The ratio of extracellular to intracellular Fe is used to discuss the relative importance of diffusive supply and uptake to control Fe bioavailability. The effect of excess organic ligands on Fe bioavailability cannot be solely explained by their effect on Fe solubility. For most strains studied, the bioavailability of Fe can be enhanced relative to inorganic Fe in the presence of porphyrin, catecholate siderophore and saccharides whereas it was decreased in presence of hydroxamate siderophore and organic amine. For Thalassiosira, iron bioavailability was not affected by the presence of porphyrin, catecholate siderophore and saccharides. The enhancement of Fe bioavailability in presence of saccharides is presented as the result from both the formation of bioavailable (or chemically labile) organic form of Fe and the stabilisation of Fe within the dissolved phase. Given the ubiquitous presence of saccharides in the ocean, these compounds might represent an important factor to control the basal level of soluble and bioavailable Fe. Results show that the use of model phytoplankton is promising to improve mechanistic understanding of Fe bioavailability and primary productivity in HNLC regions of the ocean.

Development of novel formulations for photodynamic therapy on the basis of amphiphilic polymers and porphyrin photosensitizers. Pluronic influence on photocatalytic activity of porphyrins

Effect of ethylene and propylene oxide tri-block copolymers (Pluronics) on the photocatalytic activity of tree porphyrins differing by their hydrophobicity was studied. It was shown that Pluronics induce considerable increase in the photocatalytic activity of the tetraphenylporphyrin, hematoporphyrin disodium salt (Dimegine) and relatively hydrophilic N-methyl-bis-glucamine salt of chlorine e6 (Photoditazine) in the reaction of photooxidation of tryptophan in water solution. This effect was maximal for Pluronics F127 and P85 with intermediate hydrophobicity, while more hydrophilic F68 and more hydrophobic L61 were less effective. Pluronic effect on the photocatalytic activity of tetraphenylporphyrin and dimegine is attributed to their disaggregation in water solution, while PD activity is elevated due to the local concentrating of the photocatalyst and the substrate within micellar volume. It was found by AFM that the structure of Pluronic F127 thin films prepared by water solution evaporation on mica surface significantly changed in the presence of porphyrin. This effect can be attributed to the interaction of Pluronics with porphyrins in water solution.

NMR spectrometric studies of complexation of [60]fullerene with series of meso-tetraphenylporphyrins

Extensive 1H NMR spectrometric studies have been done to gain information on the nature of molecular interactions of the supramolecular complexes of [60]fullerene with a series of meso-tetraphenylporphyrins, namely, meso-5,10,15,20-tetraphenylporphyrin ( 1), meso-5,10,15,20-tetra-2-bromophenyl-porphyrin ( 2) and meso-5,10,15,20-tetra-2-chlorophenyl-porphyrin ( 3) in toluene medium. [60]Fullerene has been shown to form 1:1 adducts with the above series of meso-tetraphenylporphyrins. Formation constants ( K) for all the complexes have been determined from the systematic variation of the NMR chemical shifts of beta proton of the porphyrin in presence of [60]fullerene. It has been observed that 3 acts as a better donor in forming supramolecular complex with [60]fullerene.

Drug-Induced Protoporphyria in Beagle Dogs

As part of regulatory safety testing program, a 13-week oral toxicity study with a new antipsychotic drug candidate was performed in beagle dogs. During this study, dark red/brown feces were recorded in treated dogs and increases in liver parameters (alanine aminotransferase, alkaline phosphatase, bilirubin) were measured biochemically. At the end of the study, livers of high-dose (50 mg/kg) animals were (mottled) dark brown, sometimes with pale foci. Histopathological examination of these livers showed dark globular pigment deposits in the hepatocellular cytoplasm and within the bile canaliculi. Varying numbers of inflammatory cell infiltrates were additionally present in association with the deposits. These pigment deposits showed birefringency with characteristic "Maltese Cross"-like structures under polarized light. Electronmicroscopy revealed the typical, so-called "sunburst" pattern with radiating double-lined crystalline structures. These morphologic characteristics strongly indicated at the presence of porphyrins, which was definitely confirmed biochemically. Published reports of drug-induced hepatic porphyria in dogs are rare. The possible underlying mechanism in the dog and man is discussed.

How Finsen's light cured lupus vulgaris

In 1903, Niels Ryberg Finsen was awarded the Nobel Prize for his invention of light therapy for skin tuberculosis (lupus vulgaris). The mechanism of action has not been shown; thus, we wanted to elucidate the mechanism of Finsen's light therapy. We measured radiation that could be transmitted through his lens systems and absorption of the stain solution filters in the lamps, and related the obtained results to the possible biological effects on Mycobacterium tuberculosis. Judged from transmission characteristics all tested lens systems were glass lenses (absorbing wavelength < 340 nm). The tested filters likewise absorbed wavelengths < 340 nm. The methylene blue solution used to absorb heat, blocked out wavelengths below 340 nm and between 550 and 700 nm. Furthermore, fluorescence of M. tuberculosis indicated the presence of porphyrins and HPLC analysis of sonicated M. marinum showed that coproporphyrin III was present, which highly justified that porphyrins were present in M. tuberculosis. Production of singlet oxygen through radiation of porphyrins with light of e.g. 400 nm seems to be a most plausible explanation why Finsen's therapy worked in spite of the lack of shortwave ultraviolet radiation, which Finsen believed was the most effective radiation for treating skin tuberculosis.

Novel heterotopic colloids of anionic porphyrins entangled in cationic amphiphilic cyclodextrins: spectroscopic investigation and intracellular delivery.

The entanglement process between water-soluble 5,10,15,20-tetrakis(4-sulfonatophenyl)-21H,23H-porphine and the amphiphilic cyclodextrin (CD) heptakis(2-omega-amino-O-oligo(ethylene oxide)-6-hexylthio)-beta-CD and the occurrence of various species at different porphyrin:CD ratios were studied by a combination of UV/Vis absorption, fluorescence anisotropy, time-resolved fluorescence, resonance light scattering, and circular dichroism. The effect of the entanglement process on the mean vesicle diameter was investigated over a wide concentration range by quasielastic light-scattering techniques. The experimental results indicate that the presence of porphyrins in this colloidal system promotes some structural rearrangements, essentially driven by charge interaction, which are responsible for a sensitive change of vesicle dimensions. In the range of porphyrin:CD molar ratios between 1:10 and 1:50, the porphyrin is solubilized in monomeric form (tau(1)=11.5 ns) and photosensitizes the production of singlet oxygen ((1)O(2)). At the same molar ratio the ability of this amphiphilic cyclodextrin to transport porphyrins into tumor cells indicates specificity at the nuclear-compartment level. These findings may be of potential interest for the of development agents for photodynamic therapy of tumors.

Photocatalytic degradation of 4-nitrophenol in aqueous suspension by using polycrystalline TiO 2 impregnated with functionalized Cu(II)–porphyrin or Cu(II)–phthalocyanine

The photocatalytic activity of polycrystalline TiO 2 samples impregnated with functionalized Cu(II)- or metal-free porphyrins has been investigated. A probe reaction, i.e., 4-nitrophenol (4-NP) photodegradation in aqueous suspension, has been used. The results indicated that the presence of the sensitizers is beneficial for the photoactivity and suggest an important role of Cu(II). A comparison with similar samples impregnated with modified Cu(II)- and metal-free phthalocyanines showed that the presence of porphyrin is more beneficial both for the decomposition rate of 4-nitrophenol and for the disappearance of nonpurgeable organic carbon (NPOC). Experiments were carried out by using cutoff and interference filters and a cooperative mechanism involving the photoactivation of both TiO 2 and sensitizer is proposed.

The photodynamic and non-photodynamic actions of porphyrins.

Porphyrias are a family of inherited diseases, each associated with a partial defect in one of the enzymes of the heme biosynthetic pathway. In six of the eight porphyrias described, the main clinical manifestation is skin photosensitivity brought about by the action of light on porphyrins, which are deposited in the upper epidermal layer of the skin. Porphyrins absorb light energy intensively in the UV region, and to a lesser extent in the long visible bands, resulting in transitions to excited electronic states. The excited porphyrin may react directly with biological structures (type I reactions) or with molecular oxygen, generating excited singlet oxygen (type II reactions). Besides this well-known photodynamic action of porphyrins, a novel light-independent effect of porphyrins has been described. Irradiation of enzymes in the presence of porphyrins mainly induces type I reactions, although type II reactions could also occur, further increasing the direct non-photodynamic effect of porphyrins on proteins and macro-molecules. Conformational changes of protein structure are induced by porphyrins in the dark or under UV light, resulting in reduced enzyme activity and increased proteolytic susceptibility. The effect of porphyrins depends not only on their physico-chemical properties but also on the specific site on the protein on which they act. Porphyrin action alters the functionality of the enzymes of the heme biosynthetic pathway exacerbating the metabolic deficiencies in porphyrias. Light energy absorption by porphyrins results in the generation of oxygen reactive species, overcoming the protective cellular mechanisms and leading to molecular, cell and tissue damage, thus amplifying the porphyric picture.

Chronology of the Apoptotic Events Induced in the K562 Cell Line by Photodynamic Treatment with Hematoporphyrin and Monoglucosylporphyrin

Photodynamic treatment of promyelocytic K562 cells in the presence of a monoglucosylporphyrin or hematoporphyrin leads to a sequence of events recognized as hallmarks of apoptosis: a drop in mitochondrial potential, concurrent with a drop in ATP level and a decrease in cell respiration, translocation of phosphatidylserine of the plasma membrane, DNA fragmentation, appearance of apoptotic bodies and eventually loss of plasma membrane integrity. The chronology of these events is in accordance with sequential events induced by other known proapoptotic agents; in contrast to these agents that induce apoptosis in a restricted part of the cell population, we observed that the entire cell population (apart from a small percentage of cells that endured rapid necrosis during phototreatment) underwent apoptosis after irradiation in the presence of porphyrins. It appears that photodynamic treatment allows the bypass of early apoptotic signals in K562 cells that are otherwise renowned for their resistance to drug-induced apoptosis (A. McGahon, R. Bissonnette, M. Schmitt, K. M. Cotter, D. R. Green and T. G. Cotter, Blood 83, 1179-1187, 1994). Singlet oxygen is believed to be the proximate reactive species generated by porphyrin illumination. Because this molecule reacts with almost every cellular constituent, the way that singlet oxygen or its reactive oxygen species byproducts trigger apoptosis remains to be elucidated.

Fluorescence of Dental Calculus from Cats, Dogs, and Humans and of Bacteria Cultured from Dental Calculus

Recently we reported that feline and canine dental calculus fluoresced pink to red under long wavelength ultraviolet light due to the presence of porphyrin. Here we report the observation of such fluorescence in 30 of 30 cats, 30 of 30 dogs, and 8 of 13 supragingival samples and 5 of 5 subgingival samples of humans. The fluorescence spectra of the calculus dissolved in 9 M HCl show that it is due to three distinct metal-free porphyrins. Similar fluorescence is obtained from bacterial cultures grown from calculus deposits of cats and dogs and bacteria grown on blood agar containing hemin and vitamin K1. The results of the bacterial culture study suggest that the metal-free porphyrin is produced by bacteria in the mouth. The clinical observation of fluorescence can be used for diagnosis.