Mesoporphyrin IX Dimethyl Ester Research Articles

Comparison of light-induced formation of reactive oxygen species and the membrane destruction of two mesoporphyrin derivatives in liposomes

The photodynamic effect requires the simultaneous presence of light, photosensitizer (PS) and molecular oxygen. In this process, the photoinduced damage of cells is caused by reactive oxygen species (ROS). Besides DNA, the other target of ROS is the membranes, separating internal compartments in living cells. Hence, the ability of ROS formation of porphyrins as PSs, in liposomes as simple models of cellular membranes is of outstanding interest. Earlier we compared the binding parameters and locations of mesoporphyrin IX dihydrochloride (MPCl) and mesoporphyrin IX dimethyl ester (MPE), in small unilamellar vesicles (SUV) made from various saturated phosphatidylcholines. In this study, we used the same kinds of samples for comparing the ROS forming ability. Triiodide production from potassium iodide because of light-induced ROS in the presence of molybdate catalyst was applied, and the amount of product was quantitatively followed by optical spectrometry. Furthermore, we demonstrated and carefully studied SUVs disruption as direct evidence of membrane destruction by the methods of dynamic light scattering (DLS) and fluorescence correlation spectroscopy (FCS), applying unsaturated phosphatidylcholines as membrane components. Although the ROS forming ability is more pronounced in the case of MPCl, we found that the measured disruption was more effective in the samples containing MPE.

Comparison of Reactive Oxygen Species Production Activity and Binding Ability of Porphyrins in Cell Membrane Models

Photo dynamic therapy (PDT) is a widespread medical treatment based on the light-triggered generation of reactive oxygen species (ROS) by porphyrin derivatives. ROS may cause oxidative damage to membranes as well as to DNA and, in consequence, ultimately kill cells. Hence, the binding ability, the location within liposomes as simple cellular membrane models, and the ROS production ability of porphyrins are of outstanding interest. Earlier we determined the location of mesoporphyrin IX dimethyl ester (MPE) and its non-esterified form, mesoporphyrin IX dihydrochloride (MPCl) in small unilamellar vesicles (SUV) with fluorescence line narrowing spectroscopy (FLN). Here we investigated the production of ROS by the photosensitizers in the aqueous medium of the vesicles and in the lipid bilayer environment. The monocomponent vesicles were formed of various saturated phosphatidylcholines. The amount of generated oxygen radicals in the aqueous media was measured on the basis of the produced tri-iodide (I3-) from potassium iodide (KI) in the presence of molybdenum (MoO4) catalyst, which was followed by absorption spectrophotometry. The ROS in the lipophilic membranes and in near-membrane regions was measured with a dihydrorhodamine derivative by fluorescence spectroscopy. We observed in general that the binding ability of MPE is considerably higher than that of MPCl. In aqueous media (without liposomes) MPCl was highly effective in ROS formation whereas in case of MPE no similar effect was observed. Liposome-incorporated MPCl produced ROS in much higher amounts than the MPE in the aqueous medium of the liposomes. In near-membrane regions MPE produced ROS in the same amount as MPCl.

Comparison of Binding Ability and Location of Two Mesoporphyrin Derivatives in Liposomes Explored with Conventional and Site-Selective Fluorescence Spectroscopy

Application of porphyrins as photosensitizers is based on their light-triggered generation of reactive oxygen species (ROS) that may cause oxidative tissue damage and ultimately kill cells. Cellular membranes are the action grounds of many sensitizers due to their hydrophobic or amphiphilic character as well as the location of many of the targets attacked by ROS. Hence, the binding ability and location of porphyrins in liposomes as simple models of cellular membranes are of outstanding interest. Here we compare mesoporphyrin IX dimethyl ester (MPE) and its nonesterified form, mesoporphyrin IX dihydrochloride (MPCl). Monocomponent small unilamellar vesicles formed of various saturated phosphatidylcholines with incorporated mesoporphyrins were investigated. We determined the binding parameters and the inhomogeneous distribution functions (IDFs) by different fluorescence techniques. We found in general that the binding ability of MPE is considerably greater than that of MPCl. In the case of MPCl, the IDFs suggest that only one of the two binding site types identified earlier for MPE ("site II") exists; the other one ("site I") vanishes while a new one appears ("site III"). We can confirm that "site I" is located between the two lipid layers, "site II" is situated between the hydrocarbon chains, while the location of the novel "site III" is along the outer part of the hydrocarbon chains partially inserted between the lipid head groups.

Comparison of Binding Ability and Location of Two Mesoporphyrin Derivatives in Liposomes by Conventional and Site-Selective Fluorescence Spectroscopy

Application of porphyrins as photosensitizers is based on their light-triggered generation of reactive oxygen species (ROS) that may cause oxidative tissue damage and ultimately kill cells. Cellular membranes are the action grounds of many sensitizers due to their hydrophobic or amphiphilic character as well as the location of many of the targets attacked by ROS. Hence, the binding ability and location of porphyrins in liposomes as simple models of cellular membranes are of outstanding interest. Here we compare mesoporphyrin IX dimethyl ester (MPE) and its nonesterified form, mesoporphyrin IX dihydrochloride (MPCl). Monocomponent small unilamellar vesicles formed of various saturated phosphatidylcholines with incorporated mesoporphyrins were investigated. We determined the binding parameters and the inhomogeneous distribution functions (IDFs) by different fluorescence techniques. We found in general that the binding ability of MPE is considerably greater than that of MPCl. In the case of MPCl, the IDFs suggest that only one of the two binding types identified earlier for MPE (site II) exists; the other one (site I) vanishes while a new one appears (site III). We can confirm that site I is located between the two lipid layers, site II is situated between the hydrocarbon chains, while the location of the novel site III is along the outer part of the hydrocarbon chains partially inserted between the lipid head groups.

Polarization‐sensitive CARS spectroscopy on free‐base porphyrins: coproporphyrin I tetramethyl ester

AbstractThe application of polarization‐sensitive (PS) coherent anti‐Stokes Raman scattering (CARS) spectroscopy for the investigation of highly luminescent free‐base porphyrins under Qx band resonance is discussed. For coproporphyrin I tetramethyl ester (CP‐I‐TME), PS CARS spectra involving resonances with the electronic Qx absorption band as well as polarized spontaneous Raman spectra involving B band resonance are presented. A quantitative evaluation of the CP‐I‐TME spectra is performed and the results are compared to our previously presented data on free‐base octaethylporphine (OEP) and mesoporphyrin IX dimethyl ester (MP‐IX‐DME), which were obtained under identical excitation conditions. This comprehensive analysis reveals several spectral differences that can be attributed to the different β–substitution pattern of the porphyrin macrocycle. Additionally, the strong resonance enhancement of totally symmetric modes under Qx band excitation is identified as a common property for OEP, CP‐I‐TME, and MP‐IX‐DME; this enhancement selectivity distinguishes the investigated substances from what is generally observed for metallo porphyrins. Copyright © 2008 John Wiley & Sons, Ltd.

Symmetry Properties of Vibrational Modes in Mesoporphyrin IX Dimethyl Ester Investigated by Polarization-Sensitive Resonance Raman and CARS Spectroscopy

The symmetry properties of selected vibrational modes of mesoporphyrin IX dimethyl ester (MP-IX-DME) in solution are investigated under different electronic resonance conditions. The Raman band parameters of the macrocycle modes nu(2), nu(10), nu(11), and nu(19) are determined from a quantitative analysis of polarized spontaneous resonance Raman (RR) and polarization-sensitive (PS) multiplex coherent anti-Stokes Raman scattering (CARS) spectra obtained with pre-resonant B band and resonant Qx band excitation, respectively. Additionally, the molecular geometry and the vibrational modes of MP-IX-DME are calculated by employing density functional theory (DFT) on the B3LYP/6-31G(d) level. Both the DFT-derived structure and the Raman spectroscopic parameters of MP-IX-DME indicate minor deviations from an ideal D2h macrocycle symmetry. To assess the influence of the beta substitution pattern on the in-plane symmetry, calculated normal-mode vectors and several experimentally detected parameters, such as peak positions, depolarization ratios, and coherent phases, are analyzed. The effects of the macrocycle substitution pattern are different for the selected vibrational modes: nu(2) in particular is very sensitive to subtle perturbations of the in-plane symmetry. The considerable activity of totally symmetric vibrations observed in the PS CARS spectra of MP-IX-DME and the correlation of mode symmetries with coherent phases confirm earlier PS CARS results on octaethylporphine (OEP) acquired under the same electronic resonance conditions.

Benzoylation at the meso Position of a Zinc(II) Deuteroporphyrin

By short treatment of zinc(II) deuteroporphyrin-IX dimethyl ester with benzoic anhydride/SnCl4, a mixture of benzoylated derivatives was obtained from which a tribenzoyl derivative with benzoyl groups at the 2, 4, and γ-meso positions could be isolated in low yield. Except for the known Vilsmeier formylation, this constitutes the first example of a Friedel-Crafts acylation taking place at the meso position of a porphyrin chelate. The expected lack of regioselectivity of this reaction, even at low conversion rates, and the difficulty to separate the products limit, of course, its synthetic value for the preparation of the particular benzoyl derivatives. This limitation cannot be overcome by starting with a completely β-substituted porphyrin or with a symmetrically substituted porphyrin, since attempts to benzoylate Zn(II) mesoporphyrin-IX dimethyl ester lead exclusively to demetallation. However, these findings add to the knowledge of the fundamental properties of porphyrin reactivity. A rationalization based on calculations at a semiempirical level, which are in acceptable agreement with the experimental results, is presented.

Solvent Effects on Rate Constants for One-Electron Oxidation of Porphyrins

Absolute rate constants for one-electron oxidation of free base porphyrins (hematoporphyrin-IX, mesoporphyrin-IX dimethyl ester) by the trichloromethylperoxyl radical and by the radical cation of N-methylindole have been determined in a variety of solvents by the pulse radiolysis technique. All solvents were air-saturated and contained CCl[sub 4] as a source for the CCl[sub 3]O[sub 2][sup [sm bullet]] radicals. The rate constants for reactions of these radicals were measured by following the formation of the porphyrin [pi]-radical cation optical absorption at 700 nm as a function of porphyrin concentration. The rate constants for reaction of CCl[sub 3]O[sub 2][sup [sm bullet]] with the porphyrin were found to vary by an order of magnitude in the different solvents and were correlated with the solvent cohesive energy density. In the second set of experiments, N-methylindole was used in addition to CCl[sub 4] so that CCl[sub 3]O[sub 2][sup [sm bullet]] radicals oxidize this solute to its radical cation, which in turn oxidizes the porphyrin. The variations of the rate constants for oxidation of the porphyrin by the N-methylindole radical cation in the different solvents exhibited different trends than those for oxidation by CCl[sub 3]O[sub 2][sup [sm bullet]] radicals. 39 refs., 1 fig., 6 tabs.

EPR detection of heterodimer species between copper(II), silver (II) and oxovanadium(IV) porphyrins

The EPR spectra of glassy solutions in tetrachloroethane containing equimolar amounts of two metalloporphyrins were measured at 77 K. The metalloporphyrins are CuP, AgP and VOP, where P is mesoporphyrinIX dimethyl ester. The spectra show evidence of heterodimer formation: in the case of CuPAgP the EPR spectrum of the heterodimer was obtained through computer manipulation and the EPR parameters determined. The spectra of CuPVOP and AgPVOP are consistent with the presence of two heterodimeric species.

The reaction of metalloporphyrins with nitrogen dioxide

The octaethylporphyrin(OEP) complexes of iron(III) chloride, iron(III) acetate, thallium(III) hydroxide, zinc(II), and cobalt(II) and the mesoporphyrin IX dimethyl ester (MPDME) complexes of zinc(II) and iron(III) chloride were reacted with a 20:1 ratio of NO 2 to metalloporphyrin in CH 2Cl 2. The +3 metalloporphyrins gave products which had a nitromethyl group in each of the four meso positions of the porphyrin ring and a chloride ion bound to the metal atom. The products of +2 metalloporphyrin reaction had a nitro group bound in each of the meso positions. The spectral and electrochemical properties of some of the products were measured. 36Cl labelled OEPFeCl was reacted with NO 2 in CH 2Cl 2. The product, meso-tetranitromethyl OEPFeCl, had 17% of the original activity which indicates that the chloride ion bound to the iron is exchanged with chloride ions formed in the reaction. The nitromethylation reaction appears to involve initially the displacement of chloride from iron(III) by NO 2 and solvent attack on the bound NO 2. The meso-nitration of the +2 metalloporphyrin by NO 2 has been proposed to proceed by a π-cation radical mechanism (E.C. Johnson and D. Dolphin, Tetrahedron Letters 2197 (1976).

Generation of homologous porphyrins under simulated geochemical conditions

Crude oils generally contain at least one symmetrical homologous series of porphyrins, which is usually centered at m/ e 476 (DPEP) or m/ e 478 (etioporphyrin). Simulated geochemical conditions in the present study resulted in decarboxylations and alkylations which ultimately led to the synthesis of homologous porphyrins from a single porphyrin. In several series of closed tube experiments, mesoporphyrin IX dimethylester (MPDME) was mixed with a variety of constituents including benzene, acetic acid, propionic acid, water and clay; the experiments were performed at temperatures between 135°C and 400°C at time intervals up to 80 days. Dealkylation, alkylation, hydrolysis, decarboxylation and metallation products were observed. An unsymmetrical homologous series of porphyrins was produced from MPDME. The dominant mass was m/ e 478 (corresponding to a double deoarboxylation). Dealkylation products in multiples of 14 amu below the m/ e 478 peak comprised the other members of the series. Cu-MPDME also produced homologous porphyrins. These, however, exhibited symmetry about the dominant members, similar to the symmetry found for the porphyrins of most petroleums and oil shales.

ChemInform Abstract: POLAROGRAPHIC STUDIES OF SOME PORPHYRINS AND METALLOPORPHYRINS IN N,N‐DIMETHYLFORMAMIDE

Electrochemical behavior of protoporphyrin IX dimethylester (PPDM), mesoporphyrin IX dimethylester(MPDM), Fe(III)Cl-protoporphyrin, Ni(II)-, Cu(II)-, Co(II)-, Zn(II)- and Mn(III)Cl·H2O–PPDM was investigated in dimethylformamide by use of AC polarography, cyclic voltammetry and DC polarography. These porphyrins and divalent metal complexes of PPDM gave, for the most part, three reduction waves. The first and second waves were reversible one-electron steps in each case, but the third step was an irreversible one. Mn(III)-complex gave four reduction waves and one oxidation wave. The first three reduction waves were one-electron steps and the oxidation wave was identified as that due to chloride anion. Fe(III)-complex gave five reduction waves and one oxidation wave. The first two reduction waves were one-electron steps. All these compounds showed specific adsorption at the potential more positive than −1.1 V vs. SCE. Assignment of the reduction steps of the metalloporphyrins is described. The observed order ...

Polarographic Studies of Some Porphyrins and Metalloporphyrins in N,N-Dimethylformamide

Abstract Electrochemical behavior of protoporphyrin IX dimethylester (PPDM), mesoporphyrin IX dimethylester(MPDM), Fe(III)Cl-protoporphyrin, Ni(II)-, Cu(II)-, Co(II)-, Zn(II)- and Mn(III)Cl·H2O–PPDM was investigated in dimethylformamide by use of AC polarography, cyclic voltammetry and DC polarography. These porphyrins and divalent metal complexes of PPDM gave, for the most part, three reduction waves. The first and second waves were reversible one-electron steps in each case, but the third step was an irreversible one. Mn(III)-complex gave four reduction waves and one oxidation wave. The first three reduction waves were one-electron steps and the oxidation wave was identified as that due to chloride anion. Fe(III)-complex gave five reduction waves and one oxidation wave. The first two reduction waves were one-electron steps. All these compounds showed specific adsorption at the potential more positive than −1.1 V vs. SCE. Assignment of the reduction steps of the metalloporphyrins is described. The observed order of increasing negative half-wave potentials is discussed in terms of Zerner and Gouterman’s molecular orbital calculation.

Pyrroles and related compounds. Part XIII. Porphyrin synthesis through b-oxobilanes and oxophlorins (oxyporphyrins)

Condensation of 5′-benzyloxycarbonylpyrromethane-5-carboxamides with 5-benzyloxycarbonylpyrromethanes by means of phosphoryl chloride yeilds imine salts, which can be hydrolysed to well defined, crystalline b-oxobilanes. Hydrogenolysis of the two benzyloxycarbonyl groups in these compounds, followed by cyclisation with methyl orthoformate under acidic catalysis and aeration, yields oxophlorins. These oxophlorins are efficiently converted into porphyrins by acetylation, hydrogenation with elimination of acetic acid, and dehydrogenation. Three examples of this porphyrin synthesis are given, including coproporphyrin-III tetramethyl ester and mesoporphyrin-IX dimethyl ester, and its generality is discussed.