Showing papers on "Porphyrin published in 1990"
TL;DR: Resistance of Gram negative bacteria to porphyrin photosensitization is the main impediment to its use as a broad spectrum antibacterial method.
Abstract: Photoactivated porphyrins display a potent cytotoxic activity towards a variety of Gram positive bacteria, mycoplasma and yeasts, but not Gram negative cells. The prerequisite for photosensitization of a microbial cell is the binding of porphyrin to the cytoplasmic membrane in a pH-dependent manner. On illumination, the membrane bound, and possibly, cytoplasmic porphyrin molecules generate singlet oxygen and radicals which sensitize biomolecules and lead to cell death. The immediate inhibition of cell growth on photodynamic treatment is accompanied by alterations in cell wall and membrane synthesis, leading to the formation of large mesosomes adjacent to the unaccomplished septa. Hemin bound to microbial cells exerts cytotoxic activity by peroxidative and oxidative reactions independent of light. Future research in the field may enhance the possibility of using porphyrin photosensitization for treatment of microbial infections. Such clinical use will be unrelated to the antibiotic resistance of the pathogen. Resistance of Gram negative bacteria to porphyrin photosensitization is the main impediment to its use as a broad spectrum antibacterial method.
312 citations
TL;DR: In this paper, the resonance Raman spectra with variable-wavelength excitation were reported for nickel octaethylporphyrin and its isotopomers containing {sup 15}N, and {sup 2}H at the methine (meso-d{sub 4}) and methylene (methylene-d-sub 16}) carbon atoms.
Abstract: Resonance Raman spectra with variable-wavelength excitation are reported for nickel octaethylporphyrin and its isotopomers containing {sup 15}N, and {sup 2}H at the methine (meso-d{sub 4}) and methylene (methylene-d{sub 16}) carbon atoms. The {sup 15}N, meso-d{sub 4} double isotopomer is also examined. The infrared spectrum of the methylene-d{sub 16} isotopomer is reported, and the frequencies are combined with recently published infrared results for the other isotopomers. Essentially all of the porphyrin skeletal modes have been assigned and have been allocated to local coordinates which recognize the pyrrole rings as cooperative vibrational units. The assignments are supported by a normal-coordinate analysis with a valence force field involving standard ethyl force constants and porphyrin in-plane force constants which are transferred nearly intact from Ni porphine and Ni tetraphenylporphine. Many vibrational modes of the NiOEP ethyl substituents have also been located in the spectra and assigned. Bands assignable to ethyl C-C stretching and C-H bending modes are surprisingly strong in the resonance Raman spectra and suggest appreciable involvement of the ethyl groups in the porphyrin {pi}-{pi}{sup *} excited states. The conformations of the ethyl substituents have a marked influence on the low-frequency vibrational spectra.
282 citations
259 citations
TL;DR: In this paper, an improved synthesis of C 2 symmetric sapphyrins was reported, and their first crystallography characterization was carried out in the first half of 2013.
Abstract: We wish to report here an improved synthesis of C 2 symmetric sapphyrins as well as their first crystallography characterization
254 citations
TL;DR: A synthetic five-part molecular device has been prepared that uses a multistep electron transfer strategy similar to that of photosynthetic organisms to capture light energy and convert it to chemical potential in the form of long-lived charge separation.
Abstract: A synthetic five-part molecular device has been prepared that uses a multistep electron transfer strategy similar to that of photosynthetic organisms to capture light energy and convert it to chemical potential in the form of long-lived charge separation. It consists of two covalently linked porphyrin moieties, one containing a zinc ion (PZn) and the other present as the free base (P). The metailated porphyrin bears a carotenoid polyene (C) and the other a diquinone species (QA-QB). Excitation of the free-base porphyrin in a chloroform solution of the pentad yields an initial charge-separated state, C-PZn-P.+.-QA--QB, with a quantum yield of 0.85. Subsequent electron transfer steps lead to a final charge-separated state, C.+-PZn-P-QA-QB.-, which is formed with an overall quantum yield of 0.83 and has a lifetime of 55 microseconds. Irradiation of the free-base form of the pentad, C-P-P-QA-QB, gives a similar charge-separated state with a lower quantum yield (0.15 in dichloromethane), although the lifetime is increased to ∼340 microseconds. The artificial photosynthetic system preserves a significant fraction (∼1.0 electron volt) of the initial excitation energy (1.9 electron volts) in the long-lived, charge-separated state.
218 citations
TL;DR: In this article, the synthesis of trimeric and pentameric porphyrins bridged by rigid aromatic spacers is presented, where the Soret absorption bands of anthracene-linked series were blue shifted, while those of p-phenylene series were split, which can be explained by the exciton coupling theory.
Abstract: Synthesis, UV-visible absorption, and fluorescence emission properties are presented for the trimeric and pentameric porphyrins bridged by rigid aromatic spacers (m- or p-phenylene, anthracene-1,8-diyl, etc.). The synthetic method utilized here is based on the previously reported synthesis of 5,15-diaryloctaalkylporphyrins, with several important improvements. The new method can be generally utilized for preparation of conformationally constrained oligomeric porphyrins sequentially linked with aromatic spacers. The Soret absorption bands of anthracene-linked series were blue shifted, while those of p-phenylene series were split, which can be explained in terms of the exciton coupling theory. The relative fluorescence intensity was observed to decrease for higher oligomers. These porphyrin oligomers will be useful for synthetic model studies on photosynthetic charge separation.
196 citations
TL;DR: Results show that only half of the porphyrin ring is necessary for intercalation to occur in calf thymus DNA, and their apparent affinity binding constants were relatively high.
Abstract: Thirty-three porphyrins or metalloporphyrins corresponding to the general formula (meso-(N-methyl-4(or 3 or 2)-pyridiniumyl){sub n}(aryl){sub 4-n}porphyrin)M (M = H{sub 2}, Cu{sup II}, or ClFe{sup III}), with n = 2-4, have been synthesized and characterized by UV-visible and {sup 1}H NMR spectroscopy and mass spectrometry. These porphyrins differ not only in the number (2-4) and position of their cationic charges but also in the steric requirements to reach even temporarily a completely planar geometry. Interaction of these porphyrins or metalloporphyrins with calf thymus DNA has been studied and their apparent affinity binding constants have been determined by use of a competition method with ethidium bromide which was applicable not only for all the free base porphyrins but also for their copper (II) or iron (III) complexes. Whatever their mode of binding may be, their apparent affinity binding constants were relatively high and a linear decrease of log K{sub app} with the number of porphyrin charges was observed. Studies of porphyrin-DNA interactions by UV and fluorescence spectroscopy, viscosimetry, and fluorescence energy transfer experiments showed that not only the tetracationic meso-tetrakis(N-methyl-4(or 3)-pyridiniumyl)porphyrins, which both involved four freely rotating meso-aryl groups, but also the corresponding tri- and dicationic porphyrins were able to intercalate into calfmore » thymus DNA. These results show that only half of the porphyrin ring is necessary for intercalation to occur.« less
183 citations
TL;DR: The antibody has high affinity for several metalloporphyrins, suggesting an approach to developing antibody-heme catalysts for redox or electron transfer reactions.
Abstract: An antibody elicited to a distorted N-methyl porphyrin catalyzed metal ion chelation by the planar porphyrin. At fixed Zn2+ and Cu2+ concentrations, the antibody-catalyzed reaction showed saturation kinetics with respect to the substrate mesoporphyrin IX (2) and was inhibited by the hapten, N-methylmesoporphyrin IX (1). The turnover number of 80 hour-1 for antibody-catalyzed metallation of 2 with Zn2+ compares with an estimated value of 800 hour-1 for ferrochelatase. The antibody also catalyzed the insertion of Co2+ and Mn2+ into 2, but it did not catalyze the metallation of protoporphyrin IX (3) or deuteroporphyrin IX (4). The antibody has high affinity for several metalloporphyrins, suggesting an approach to developing antibody-heme catalysts for redox or electron transfer reactions.
177 citations
TL;DR: The complete synthesis of chlorophyll a starting from Knorr's pyrrole was described in detail in this article, with full experimental detail, in which the four pyrroles which are required for rings A, B, C and D were elaborated largely by known reactions, although with considerable improvements.
172 citations
TL;DR: In this article, the binding of bis-amine ligands to a series of cyclic zinc porphyrin dimers was characterized by NMR and electronic spectroscopy, and the binding parameters were defined.
Abstract: The binding of bis-amine ligands to a series of cyclic zinc porphyrin dimers has been characterized by NMR and electronic spectroscopy. The cavity within the flexible dimers is kept closed by {pi}-{pi} interactions between the porphyrin and aromatic bridging groups but can be opened by ligands whose binding is strong enough to overcome this energetic barrier. Analysis of the binding of these bifunctional and the corresponding monofunctional ligands to the porphyrin dimers and corresponding monomeric porphyrins allowed definition of the parameters {Delta}{Delta}G, {Delta}{Delta}H, and {Delta}{Delta}S. These are specifically associated with the energetic costs of conformational switching and yield information about the strength of the {pi}-{pi} interactions that hold the cavity closed.
166 citations
TL;DR: In this article, more comprehensive geometric effects in an extensive array of hybrid metal complexes consisting of ZnP and ferric porphyrin chloride (Fe{sup III}PCl) were investigated.
Abstract: Despite the crucial role of photoinduced electron transfer (ET) reactions in photosynthetic energy conversion, the factors that control this reactivity remain poorly understood. Recent theoretical work indicates the importance of orientation effects on the rates of the nonadiabatic ET process between diporphyrin pairs. This paper reports more comprehensive geometric effects in an extensive array of hybrid metal complexes consisting of zinc porphyrin (ZnP) and ferric porphyrin chloride (Fe{sup III}PCl). Diporphyrin models studied here include a variety of mutual orientations and different kinds of aromatic spacers such as benzene, naphthalene, and spirobiindan.
06 Mar 1990
TL;DR: In this paper, a tripyrrole dimethine-derived "expanded porphyrin" (texaphyrin), the synthesis of such compounds, their analogs or derivatives and their uses are discussed.
Abstract: The present invention involves a novel tripyrrole dimethine-derived "expanded porphyrin" (texaphyrin), the synthesis of such compounds, their analogs or derivatives and their uses. These expanded porphyrin-like macrocycles are efficient chelators of divalent and trivalent metal ions. Metal complexes of these compounds are active as photosensitizers for the generation of singlet oxygen and thus potentially for inactivation or destruction of human immunodeficiency virus (HIV-1), mononuclear or other cells infected with such virus and tumor cells as well. A variety of texaphyrin derivatives have been produced and many more are readily obtainable. Various metal (e.g., transition, main group, and lanthanide) complexes with the texaphyrin and texaphyrin derivatives of the present invention have unusual water solubility and stability which render them particularly useful. These metallotexaphyrin complexes have optical properties making them unique as compared to existing porphyrin-like or other macrocycles. For example, they absorb light strongly in a physiologically important region (i.e. 690-880 nm). These complexes also form long-lived triplet states in high yield and act as efficient photosensitizers for the formation of singlet oxygen. These properties, coupled with their high chemical stability and appreciable solubility in polar media such as water, add to their usefulness.
TL;DR: In this paper, the synthesis and characterization of a variety of selectively metalated quinone-substituted zinc-containing octaalkyl porphyrin dimers, designed to mimic certain key electronic and structural aspects of the photosynthetic reaction centers of Rhodopseudomonas viridis and Rhodobacter sphaeroides, and appropriate control monomers and dimers are described.
Abstract: The synthesis and characterization of a variety of selectively metalated quinone-substituted zinc-containing octaalkyl porphyrin dimers, designed to mimic certain key electronic and structural aspects of the photosynthetic reaction centers of Rhodopseudomonas viridis and Rhodobacter sphaeroides, and appropriate control monomers and dimers are described. These new compounds have been characterized by {sup 1}H NMR, {sup 13}C NMR, UV-visible spectroscopy, mass spectrometry, and microanalysis. Electrochemical data are also given for representative dimers and monomers and X-ray structural information is provided for a 1,3-phenyl-linked and a 1,4-phenyl-linked functionalized copper-containing dimer and for a quinone-substituted metal-free monomer.
TL;DR: The crystal structure of the ferric form of myoglobin from the mollusc Aplysia limacina has been refined at 1.6 A resolution, by restrained crystallographic refinement methods, and indicates that a hydroxyl ion is bound to the Fe sixth co-ordination position.
TL;DR: This work has synthesized a porphyrin encased within a protective barrier that is circumscribed by a hydrophobic groove and forms an inclusion complex upon exposure to 10 equiv of heptakis (2,6-di-O-methyl)-β-cyclodextrin in aqueous solution at pH 6.0.
Abstract: Heme-dependent proteins participate in a diverse array of biochemical phenomena including oxygen transport (hemoglobin) and activation (cytochrome P-450 enzymes). The proteinoid appendage of these species serves as a steric impediments that precludes μ-oxo oligomer formation, as a protective barrier that prevents oxidative decomposition of the porphyrin periphery, as a water-soluble carrier of the heme, and as an entity that maintains the hydrophobic nature of the active site, we have synthesized a porphyrin encased within a protective barrier that is circumscribed by a hydrophobic groove. The tetraamino porphyrin (prepared in three steps from p-hydroxybenzaldehyde) forms an inclusion complex upon exposure to 10 equiv of heptakis (2,6-di-O-methyl)-β-cyclodextrin in aqueous solution at pH 6.0
TL;DR: The photophysical properties of tetrakis(4‐sulfonatophenyl)porphyrin, its tin (IV) complex (SnTSPP), aluminium(III) trisulfon atophthalocyanine (A1PCS), and the corresponding zinc(II) complex(ZnPCS) have been measured in H2O, D2O and upon binding to human serum albumin (HSA).
Abstract: The photophysical properties of tetrakis(4-sulfonatophenyl)porphyrin (H2TSPP), its tin (IV) complex (SnTSPP), aluminium(III) trisulfonatophthalocyanine (AIPCS), and the corresponding zinc(II) complex (ZnPCS), have been measured in H2O, D2O, and upon binding to human serum albumin (HSA). The triplet excited states of the various macrocyclic dyes generate singlet molecular oxygen, O2(1 delta g) in high quantum yield upon illumination in O2-saturated solution, even in the presence of HSA. The triplet states also abstract an electron from 4-aminophenol, forming the radical anion of the macrocycle. Quenching rate constants and quantum yields have been measured for the various processes in the presence and absence of HSA. It is found that HSA binds all the dyes at nonspecific sites close to the interface in such a manner that the dyes remain accessible to species residing in the solution phase. Dyes that do not possess axial ligands complexed to the central cation (e.g. H2TSPP, ZnPCS) are able to bind also at a deeper, more specific site on the protein where they are protected from species in solution. Under such conditions, triplet quenching by 4-aminophenol is restricted to long-distance electron tunnelling, for which the rate is relatively slow.
TL;DR: As the size of the cycloalkenyl ring in synthetic C5-C7 tetracycloenyl-meso-tetraphenylporphyrins (TCnTPP) increases, the porphyrin core changes from planar to non-planar as mentioned in this paper.
TL;DR: In this paper, the authors calculated overlap integrals of phthalocanine (Pc) and porphyrin (Pp) dimers on changing the distance and rotation angle between two macrocycles.
TL;DR: In this paper, spontaneous adsorption of iron tetrakis(4-N-methylpyridyl) porphyrin on edge plane pyrolytic graphite electrodes from aqueous solutions of the soluble porphrin produces an adsorbed species that catalyzes the electroreduction of O 2 at potentials notably more positive than can be obtained with electrodes on which the porphyn does not adsorb (e.g., glassy carbon)
Abstract: Spontaneous adsorption of iron tetrakis(4-N-methylpyridyl) porphyrin on edge plane pyrolytic graphite electrodes from aqueous solutions of the soluble porphyrin produces an adsorbed species that catalyzes the electroreduction of O 2 at potentials notably more positive than can be obtained with electrodes on which the porphyrin does not adsorb (e.g., glassy carbon)
TL;DR: The authors have discovered a relatively short route from His-39 to the heme in the Candida krusei (C.k.) protein, and extracted donor-acceptor electronic coupling constants from an analysis of the driving-force dependence of ET rates in Ru(His-39)-modified C.k. zinc cytochrome c.
Abstract: Experiments in several laboratories have shown that electron transfer (ET) can take place at appreciable rates over long distances (> 10 {angstrom}) in organic and inorganic molecules and in proteins. There is a bewildering array of potential ET pathways in proteins; interestingly, the through-peptide routes (if there are any) generally involve so many bonds that they cannot possibly account for the observed rates. In searching for good pathways through cytochrome c, the authors discovered a relatively short route from His-39 to the heme in the Candida krusei (C.k.) protein. Along this route, the crucial shortcut is a hydrogen bond that bridges Gly-41 and the heme. Since experimental information relevant to protein pathway models is lacking, they have extracted donor-acceptor electronic coupling constants from an analysis of the driving-force dependence of ET rates in Ru(His-39)-modified C.k. zinc cytochrome c.
TL;DR: A theoretical description of the observed phenomena corroborates that lipophilic complexes of Co(III) (e.g. aquacyano[heptakis(2-phenylethyl)]Co(III), cobyrinate perchlorate and Mn(III)-porphyrin complexes act as positively charged carriers for anions as discussed by the authors.
Abstract: Zero-current counter-transport studies as well as electrodialytic transport experiments on solvent polymeric membranes doped with ionophores for anions have been carried out and were compared with potentiometric measurements on the same membranes. A theoretical description of the observed phenomena corroborates that lipophilic complexes of Co(III) (e. g. aquacyano[heptakis(2-phenylethyl)]Co(III) cobyrinate perchlorate) and Mn(III) (e. g. lipophilic Mn(III)porphyrin complexes) act as positively charged carriers for anions, whereas a lipophilic Ru(II)porphyrin complex has to be described as an electrically neutral carrier for anions.
TL;DR: Four structural analogs of benzoporphyrin derivative have been studied and compared for photosensitizing activity in vitro and showed that the monoacid derivatives had equivalent cytotoxicity and were about five‐fold more active than the diacid forms.
Abstract: Four structural analogs of benzoporphyrin derivative (BPD) have been studied and com- pared for photosensitizing activity in vim. All analogs have an identical reduced tetrapyrrol porphyrin ring, and differ by the position of a cyclohexadiene ring (fused at either ring A or ring B of the porphyrin) and the presence of either two acid groups or one acid and one ester group at rings C and D of the porphyrin. Photosensitizer activity was tested with the M1 tumor cell line using an assay (the MTT assay) which detects mitochondria1 hydrogenases as a measure of cell viability. This assay was shown to be equivalent to the standard clonogenicity or ('Hlthymidine uptake assay. Comparative studies with the BPD analogs showed that the monoacid derivatives had equivalent cytotoxicity and were about five-fold more active than the diacid forms. This was the case whether the assays were performed in the presence or absence of fetal calf serum.
TL;DR: In this paper, the synthesis and properties of a series of fixed-distance chlorophyll-porphyrin molecules are described, which consist of a methyl pyrochlorophyllide a moiety which is directly bonded at its 2-position to the 5-position of a 2,8,12,18,tetraethyl-3,7,13,17,17-tetramethyl-15-(p-tolyl)porphrin.
Abstract: The synthesis and properties of a series of fixed-distance chlorophyll-porphyrin molecules are described. These molecules consist of a methyl pyrochlorophyllide a moiety which is directly bonded at its 2-position to the 5-position of a 2,8,12,18-tetraethyl-3,7,13,17-tetramethyl-15-(p-tolyl)porphyrin. Steric hindrance between adjacent substituents rigidly positions the {pi} systems of both macrocycles perpendicular to one another. The macrocycles were selectively metalated with zinc to give the four possible derivatives, HCHP, ZCHP, HCZP, and ZCZP, where H, Z, C, and P denote free base, Zn derivative, chlorin, and porphyrin, respectively. The lowest excited singlet states of HCHP and ZCHP, which are localized on HC and ZC, respectively, exhibit lifetimes and fluorescence quantum yields that are solvent polarity independent and do not differ significantly from those of chlorophyll itself. ZCZP, however, displays a lowest excited singlet state and lifetime and fluorescence quantum yield that are strongly solvent polarity dependent.
TL;DR: In this paper, a series of conformationally restricted por-phyrins bridged by aromatic spacers has been synthesized, and the geometry-dependence of the intramolecular singlet excita- tion energy transfer (EN) in the zinc-free base diporphyrin system and the intra-molecular electron transfer (ET) in zinc-ferric hybrid diporphrin system were studied by the pico-second time-resolved fluorescence spectroscopy.
Abstract: A series of conformationally restricted dimeric por- phyrins bridged by aromatic spacers has been synthesized. Soret bands of their bis-zinc complexes are split due to the exciton coupling, depending upon the geometrical relationship of the two porphyrin rings. With these dimeric porphyrins, the geometry-dependence of the intramolecular singlet excita- tion energy transfer (EN) in the zinc-free base diporphyrin system and the intramolecular electron transfer (ET) in the zinc-ferric hybrid diporphyrin system were studied by the pico-second time-resolved fluorescence spectroscopy and pico- second time-resolved transient absorption spectroscopy. It has been shown that the former process proceeds via Forster mechanism. In the latter system, both rates of the forward and backward ET were determined. The rates of the forward ET decreased upon the increase of the center-to-center distance of the two porphyrins, while the rates of the backward ET were nearly constant through the series in the range of 8-22 A of the center-to-center distance. An improved procedure has been developed for the synthesis of conformationally restricted trimeric and pentameric porphyrins as well as quinone-linked porphyrin aggregates, which will be very useful in studying the sequential and long-distance EN and ET processes.
TL;DR: The porphyrias may present in ways that mimic other disorders, and because different types of porphyria share identical clinical features, accurate diagnosis depends on identifying patterns of haem precursor overproduction.
Abstract: The porphyrias are a group of disorders of haem biosynthesis in which overproduction of haem precursors is associated with characteristic clinical features. Two main forms of clinical manifestation may occur together or separately: lifethreatening attacks of acute porphyria and photosensitization of the skin. • Because the porphyrias may present in ways that mimic other disorders, and because different types of porphyria share identical clinical features, accurate diagnosis depends on identifying patterns of haem precursor overproduction. This requires correct selection, performance and interpretation