Synthesis of asymmetric tetraarylporphyrins and their ytterbium complexes

The synthesis of asymmetric meso-aryl-substituted porphyrins containing three 4-methoxycarbo-nylphenyl groups, and 4-hydroxyphenyl or 4-hydroxy-3-methoxyphenyl radicals or isomeric 3-and 4-pyridyl radicals as a forth substitute, is described. 4-Oxyalkyl derivatives are obtained. The ytterbium complexes of these porphyrins have been synthesized, and their spectral luminescence properties have been studied. A significant difference in the lifetimes of the excited state of ytterbium complexes of the esters and acids of asymmetric porphyrins has been shown.     

Interaction of cationic porphyrins with DNA: importance of the number and position of the charges and minimum structural requirements for intercalation

Thirty-three porphyrins or metalloporphyrins corresponding to the general formula [meso-[N-methyl-4(or 3 or 2)-pyridiniumyl]n(aryl)4-nporphyrin]M (M = H2, CuII, or ClFeIII), with n = 2-4, have been synthesized and characterized by UV-visible and 1H 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. In particular, they contain 0, 1, 2, 3, or 4 meso-aryl substituents not able to rotate. 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 (Kapp between 1.2 x 10(7) and 5 x 10(4) M-1 under our conditions), and a linear decrease of log Kapp 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 calf thymus DNA. Moreover, the cis dicationic meso-bis(N-methyl-2-pyridiniumyl)diphenylporphyrin, which involved only two freely rotating meso-aryl groups in a cis position, was also able to intercalate. The other meso-(N-methyl-2-pyridiniumyl)n(phenyl)4-nporphyrins, which involved either zero, one, or two trans freely rotating meso-aryl groups, could not intercalate into DNA. These results show that only half of the porphyrin ring is necessary for intercalation to occur.     

Chemical properties of water-soluble porphyrins. 5. Reactions of some manganese (III) porphyrins with the superoxide and other reducing radicals

Solution properties of three manganese porphyrins, in monomeric form, were investigated. These were the 'picket-fence-like' porphyrin Mn(III)-alpha,alpha,alpha,beta- tetra-ortho(N-methylisonicotinamidophenyl)porphyrin (Mn(III)PFP) and two 'planar unhindered' porphyrins, the Mn(III)TMPyP (tetrakis (4-N-methylpyridyl)porphyrin) and Mn(III)TAP (tetra(4-N,N,N-trimethylanilinium)porphyrin). The porphyrin properties studied were: the absorption spectra in their manganic and manganous forms; acid/base properties of the aquo complexes; the effect of potential axial ligands (up to a concentration of 0.1 mol dm-3) and their one electron reduction potentials. Knowing these properties, the reaction of the Mn(III) porphyrins with the superoxide radical and other reducing radicals were studied using the pulse radiolysis technique. The second-order reaction rate constant of O2- with the Mn(III) porphyrins, which governs the catalytic efficiency of the metalloporphyrins upon the disproportionation of the superoxide radical, was 5.1 X 10(7) to 4.0 X 10(5) dm3 mol-1 s-1, depending on the pH and the nature of the metalloporphyrin. These values are at least one order of magnitude lower than found for Fe(III)TMPyP. One electron reduction of the three Mn(III) porphyrins by eaq-, CO2-, CH2OH and (CH3)2COH had similar second-order rate constants (10(9)-10(10) dm3 mol-1 s-1). That for (CH3)2(CH2)COH was about 10(5) dm3 mol-1 s-1. Reduction in all cases produced the corresponding Mn(II) porphyrin and no intermediate was found. The oxidation reaction of the Mn(II) porphyrins by O2- was approximately two orders of magnitude faster when compared to the reduction of Mn(III) porphyrins with the same radical. Since the reactivities of O2- towards the three manganese (III) compounds follow their reduction potentials, it is suggested that these reactions are governed by an outer-sphere mechanism. This suggestion is corroborated by the finding that water molecules acting as axial ligands, in these aqueous solution systems, are not replaced by another potential ligand when the latter is in the concentration range of 100 mM or less.     

Photodynamic effect of meso-(aryl)porphyrins and meso-(1-methyl-4-pyridinium)porphyrins on HaCaT keratinocytes

Sixteen porphyrins, including neutral, anionic and cationic meso-(aryl)porphyrins and meso-(1-methyl-4-pyridinium)porphyrins were herein evaluated in terms of their photosensitizing properties against HaCaT keratinocytes. After an initial screening, the cationic porphyrins were studied in more details, by both determining their log P_OW and performing PDT assays in lower porphyrin concentrations. Porphyrins presenting two or more adjacent positively charged groups, directly linked to the macrocycle meso positions, appeared to be the most effective photosensitizers. The present study also included the dicationic 5,10-diphenyl-15,20-di(1-methylpyridinium-4-yl)porphyrin (14b), which has previously shown promising results on a psoriasis-like in vivo model. Overall results indicated that the beneficial effect related to porphyrins on psoriasis can be related to the decreasing of keratinocyte viability. Furthermore, some of the cationic porphyrins studied appeared as candidates to be utilized as photosensitizers for psoriasis treatment.     

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

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

Study on synthesis,characterization and biological activity of some new nitrogen heterocycle porphyrins

Seven new nitrogen heterocycle porphyrins, 5,10,15,20-tetra[4-(N-pyrrolidinyl)phenyl]porphine (TBPPH(2)), 5,10,15,20-tetra[4-(4'-ethylpiperazinyl)phenyl]porphine (TEPPH(2)), 5,10,15,20-tetra [4-(4'-butylpiperazinyl)phenyl]porphine (TUPPH(2)), 5,10,15,20-tetra[4-(4'-heptylpiperazinyl) phenyl]porphine (THPPH(2)), 5-[4-(4'-ethylpiperazinyl)phenyl]-10,15,20-triphenylporphine (MEPPH(2)), 5-[4-(4'-buthylpiperazinyl)phenyl]-10,15,20-triphenylporphine (MUPPH(2)) and piperazine bridge porphine dimer N,N'-di(5,10,15,20-tetraphenylporphinato)piperazine (DiPPH(2)) have been synthesized by the direct condensation of nitrogen heterocycle substituted benzaldehydes with pyrrole. Each porphine bears one or four substituted pyrrolidine or piperazine moieties that have been used as drugs. Their structures were characterized by elementary analysis, MS, 1H NMR, IR and UV-vis. These nitrogen heterocycle porphyrins aggregates in water and THF solution were studied by the spectrophotofluorimetry. The anticancer activity of these porphines for the liver cancer cells, the stomach tumor cells and the nasopharyngeal carcinoma cancer cells were tested by the MTT assay. Compared with cis-platinum (cis-Pt) and 5-Fluorouracil (5-Fu), the nitrogen heterocycle porphyrins have the better biological activity and might have potential application in medicine.     

Reactions of manganese porphyrins with peroxynitrite and carbonate radical anion

We have studied the reaction kinetics of ten manganese porphyrins, differing in their meso substituents, with peroxynitrite (ONOO-) and carbonate radical anion (CO3.) using stopped-flow and pulse radiolysis, respectively. Rate constants for the reactions of Mn(III) porphyrins with ONOO- ranged from 1 x 10(5) to 3.4 x 10(7) m(-1) s(-1) and correlated well with previously reported kinetic and thermodynamic data that reflect the resonance and inductive effects of the substituents on the porphyrin ring. Rate constants for the reactions of Mn(III) porphyrins with CO3. ranged from 2 x 10(8) to 1.2 x 10(9) m(-1)s(-1) at pH 相似文献   

Photodynamic inactivation of Escherichia coli by novel meso-substituted porphyrins by 4-(3-N,N,N-trimethylammoniumpropoxy)phenyl and 4-(trifluoromethyl)phenyl groups.

The photodynamic effect of novel cationic porphyrins, with different pattern of meso-substitution by 4-(3-N,N,N-trimethylammoniumpropoxy)phenyl (A) and 4-(trifluoromethyl)phenyl (B) groups, have been studied in both solution bearing photooxidizable substrates and in vitro on a typical Gram-negative bacterium Escherichia coli. In these sensitizers, the cationic groups are separated from the macrocycle ring by a propoxy spacer. Thus, the charges have a high mobility and a minimal influence on photophysical properties of the porphyrin. These compounds produce singlet molecular oxygen, O2(1Delta(g)), with quantum yields of approximately 0.41-0.53 in N,N-dimethylformamide. In methanol, the l-tryptophan photodecomposition increases with the number of cationic charges in the sensitizer. In vitro investigations show that cationic porphyrins are rapidly bound to E. coli cells in approximately 5 min. A higher binding was found for A3B3+ porphyrin, which is tightly bound to cells still after three washing steps. Photosensitized inactivation of E. coli cellular suspensions follows the order: A3B3+ > A44+> ABAB2+ > AB3+. Under these conditions, a negligible effect was found for 5,10,15,20-tetra(4-sulfonatophenyl)porphyrin (TPPS4(4-)) that characterizes an anionic sensitizer. Also, the results obtained for these new cationic porphyrins were compared with those of 5,10,15,20-tetra(4-N,N,N-trimethylammonium phenyl)porphyrin (TTAP4+), which is a standard active sensitizer established to eradicate E. coli. The photodynamic activity of TTAP4+ is quite similar to that produced by A4(4+). Studies in an anoxic condition indicate that oxygen is necessary for the mechanism of action of photodynamic inactivation of bacteria. The higher photodynamic activity of A3B3+ was confirmed by growth delay experiments. Photodynamic inactivation capacities of these sensitizers were also evaluated in E. coli cells immobilized on agar surfaces. Under these conditions, A3B3+ porphyrin retains a high activity to inactivate localized bacterial cells. Therefore, tricationic porphyrin A3B3+ is an interesting sensitizer with potential applications in photodynamic inactivation of bacteria in liquid suspensions or on surfaces.     

Conformational investigation of two isomeric chiral porphyrins: a convergent approach with different techniques

The conformation in solution of two atropisomeric meso-tetrabinaphthyl porphyrins, used as catalytic precursors in asymmetric synthesis, was studied by means of experimental ((1)H-NMR ROESY, UV-Vis, and circular dichroism) and computational (semiempirical structure optimization, DeVoe's coupled oscillators calculations) methods. UV-Vis and CD spectra are calculated for several molecular models, with a systematic sampling of the conformational space, and compared to the experimental ones, leading to a structural hypothesis which is confirmed by NMR and PM3.     

Photoinactivation of Escherichia coli using porphyrin derivatives with different number of cationic charges

The photodynamic effect of meso-substituted cationic porphyrins, 5-[4-(trimethylammonium)phenyl]-10,15,20-tris(2,4,6-trimethoxyphenyl)porphyrin iodide 1, 5,10-di(4-methylphenyl)-15,20-di(4-trimethylammoniumphenyl)porphyrin iodide 2 and 5-(4-trifluorophenyl)-10,15,20-tris(4-trimethylammoniumphenyl)porphyrin iodide 3, have been investigated in both homogeneous medium bearing photooxidizable substrates and in vitro on a typical gram-negative bacterium Escherichia coli. Absorption and fluorescence spectroscopic studies were compared in N,N-dimethylformamide. Fluorescence quantum yields (varphiF) of 0.10, 0.06 and 0.08 were calculated for porphyrins 1, 2 and 3, respectively. The singlet molecular oxygen, O2(1Deltag), production was evaluated using 9,10-dimethylanthracene yielding values of 0.66, 0.36 and 0.42 for porphyrins 1, 2 and 3, respectively. Guanosine 5'-monophosphate was used as biological substrate model. Similar decomposition of guanosine 5'-monophosphate was obtained using these cationic porphyrins as sensitizer. In biological medium, photosensitized inactivation of E. coli was analyzed using cells without and with one washing step. E. coli cultures were treated with sensitizer at 37 degrees C for 30 min in dark. In both procedures, a higher photoinactivation of cells (>99.999%) was found for cells treated with 10 microM of tricationic porphyrin 3 and irradiated for 5 min with visible light. Porphyrins 1 and 2 only show an important photodamage when the cells are irradiated without washing step. These results indicated that the tetracationic porphyrin 3 could be a promising sensitizer with potential applications in the photoinactivation of bacterial cells by photodynamic therapy.     

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

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

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

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

Photodynamic and light independent action of 8 to 2 carboxylic free porphyrins on some haem-enzymes

Backgrounds and aims: skin lesions in cutaneous porphyrias appear to be determined by the structural properties of the porphyrins accumulated. To better understand the relationship between the structure and physicochemical properties of porphyrins and their specific effect on protein configuration, the action of a whole range of 8 to 2 carboxylic porphyrins has been studied. Materials and methods: δ-aminolevulinic acid dehydratase (ALA-D) and porphobilinogen deaminase (PBG-D) partially purified from bovine liver, were exposed to 10 μM uroporphyrin (Uro), phyriaporphyrin (Phyria), hexaporphyrin (Hexa), pentaporphyrin (Penta), coproporphyrin (Copro) or protoporphyrin (Proto), either in the dark or under UV light. All experiments were performed in the enzyme solutions after removing the porphyrins. Results: under both illuminating conditions, all porphyrins inactivated the enzymes (20–70% under control values), indicating photodynamic action mediated by oxidative reactions and conformational changes due to direct binding of porphyrins to the protein. Total thiol content in ALA-D was not significantly changed by most porphyrins under UV light, while all porphyrins increase total sulfhydryl groups in PBG-D (23–52% over the control values) indicating changes in the redox status of SH residues. Free amino groups were reduced by all porphyrins in ALA-D (23–56% under controls), instead they were enhanced in PBG-D (23–51% over controls), suggesting protein fragmentation. The formation of molecular aggregates would be the consequence of cross-links between oxidation products, while fragmentation can be attributed to either rupture of disulphur bridges and/or enhancement of free amino groups on the protein enzyme. Conclusions: the effect of the porphyrins on enzyme activity, total SH groups and free amino groups content, was different for ALA-D and PBG-D, even under the same illuminating conditions. On the basis of these results, no correlation between enzyme alterations and the physico-chemical properties of porphyrins could be established.     

DNA binding specificity of a series of cationic metalloporphyrin complexes

The sequence specificities of a series of cationic metalloporphyrins toward a 139 base pair restriction fragment of pBR-322 DNA have been studied by DNase I footprinting methodology. Analysis using controlled digests and quantitative autoradiography/microdensitometry revealed that the 5- and 6-coordinate complexes of meso-tetrakis(N-methyl-4-pyridiniumyl)porphine, MT4MPyP, where M is Mn, Fe, Co, and Zn, were found to bind to AT regions of DNA. Footprinting analysis involving the radiolabel on the opposing strand of restriction fragment showed site skewing in the direction of the 3' end of the fragment, indicating that the porphyrins bind in the minor groove of DNA. The significant increase in DNase I catalyzed hydrolysis observed in various regions of the fragment appeared to be primarily due to a decrease in available substrate DNA upon porphyrin binding with possible contributions from structural changes in DNA caused by ligand binding. The complexes NiT4MPyP and CuT4MPyP were found to bind to both AT and GC regions of the fragment, producing different degrees of inhibition in the two regions. Since the outside-binding porphyrins can neither intercalate or effectively hydrogen bond to DNA, they appear to read sequence by responding to steric and/or electrostatic potential effects located in the minor groove of DNA.     

Interaction of metallopyrazoliumylporphyrins with calf thymus DNA.

The interaction of transition metal complexes of cationic porphyrins bearing five membered rings, meso-tetrakis(1,2-dimethylpyrazolium-4-yl)porphyrin (MPzP, M=Mn(III), Ni(II), Cu(II) or Zn(II)), with calf thymus DNA (ctDNA) has been studied. Metalloporphyrins NiPzP and CuPzP are intercalated into the 5'GC3' step of ctDNA. MnPzP is bound edge-on at the 5'TA3' step of the minor groove of ctDNA, while ZnPzP is bound face-on at the 5'TA3' step of the major groove of ctDNA. The binding constants of the metalloporphyrins to ctDNA range from 1.05x10(5) to 2.66x10(6) M(-1) and are comparable to those of other reported cationic porphyrins. The binding process of the metallopyrazoliumylporphyrins to ctDNA is endothermic and entropically driven. These results have revealed that the kind of central metal ions of metalloporphyrins influences the binding characteristics of the porphyrin to DNA.     

Optical absorption and fluorescence spectroscopy studies of ground state melanin-cationic porphyrins complexes.

Optical absorption and fluorescence spectroscopies were employed in the study of the interaction between synthetic L-dopa (dihydroxyphenylalanine) melanin and the cationic porphyrins tetrakis(4-N-methylpyridyl) porphyrin (TMPyP), tetrakis(4-N-benzylpyridyl)porphyrin (TBzPyP), zinc tetrakis(4-N-methylpyridyl)porphyrin (ZnTMPyP) and zinc tetrakis (4-N-benzylpyridyl)porphyrin (ZnTBzPyP). Optical absorption and fluorescence properties of the porphyrins were dependent on the symmetry of the central ring. No evidence was found for dimerization of the porphyrins in phosphate buffer, pH 7, in the concentration range between 4 x 10(-8) to 5 x 10(-5) M. Addition of L-dopa melanin red shifted the optical absorption spectra of porphyrins, concomitant to broadening and reduction in intensity of the bands. L-Dopa melanin also strongly quenched the fluorescence of the porphyrins. Time resolution of the fluorescence decay of porphyrins showed at least two lifetimes that were only slightly modified in the presence of melanin. The interaction between melanin and porphyrin resulted in the formation of non-fluorescent ground state complexes. It was found that there are two different classes of binding sites in melanin for complexation with cationic porphyrins and the values of dissociation constants are of the order of 10(-8) M. These values and the number of binding sites are dependent on the nature of the porphyrins. It was shown that the binding has electrostatic origin, but it is also affected by metal coordination and hydrophobic interaction.     

Surface-enhanced resonance Raman scattering of porphyrins on gold nanoparticles attached to silanized glass plates

Surface-enhanced resonance Raman scattering (SERRS) spectra of cationic 5,10,15,20-tetrakis(1-methyl-4-pyridyl) porphyrin (TMPyP) and anionic 5,10,15,20-tetrakis(4-sulfonatophenyl) porphyrin (TSPP) were measured from gold surfaces prepared by attaching citrate-reduced colloidal nanoparticles to glass slides silanized by 3-aminopropyltrimethoxysilane. SERRS spectra of both porphyrins obtained in a large concentration range (1 x 10(-4) to 1 x 10(-7)M) of primary solution do not show any sign of porphyrin metalation or perturbation of its native structure. Optimal adsorption time (15-20 min) and covering concentration limit (lower than 1 x 10(-5)M) of porphyrins have been estimated from the concentration and soaking time dependences of SERRS spectra.     

Electron paramagnetic resonance of the excited triplet state of metal-free and metal-substituted cytochrome c.

The photoactivated metastable triplate states of the porphyrin (free-base, i.e., metal-free) zinc and tin derivatives of horse cytochrome c were investigated using electron paramagnetic resonance. Zero-field splitting parameters, line shape, and Jahn-Teller distortion in the temperature range 3.8-150 K are discussed in terms of porphyrin-protein interactions. The zero-field splitting parameters D for the free-base, Zn and Sn derivatives are 465 x 10(-4), 342 x 10(-4) and 353 x 10(-4) cm-1, respectively, and are temperature invariant over the temperature ranges studied. AN E value at 4 K of 73 x 10(-4) cm-1 was obtained for Zn cytochrome c, larger than any previously found for Zn porphyrins derivatives of hemeproteins, showing that the heme site of cytochrome c imposes an asymmetric field. Though the E value for Zn cytochrome c is large, the geometry of the site appears quite constrained, as indicated by a spectral line shape showing a single species. Intersystem crossing occurred predominantly to the T2 > zero-field spin sublevel. EPR line shape changes with respect to temperature of Zn cyt c are interpreted in terms of vibronic coupling, and a maximum Jahn-Teller crystal-field splitting of approximately 180 cm-1 is obtained. Sn cytochrome c in comparison with the Zn protein exhibits a photoactivated triplet line shape that is less well resolved in the X-Y region. The magnitude of E value is approximately 60 x 10(-4) cm-1 at 4 K; its value rapidly tends toward zero with increasing temperature, from which a value for the Jahn-Teller crystal-field splitting of > or = 40 cm-1 is estimated. In contrast to those for the metal cytochromes, the magnitude of E value for the free-base derivative was essentially zero at all temperatures studied. This finding is discussed as a consequence of an excited-state tautomerization process that occurs even at 4 K.     

Interaction of cationic <Emphasis Type="Italic">meso</Emphasis>-porphyrins with liposomes,mitochondria and erythrocytes

Two series of cationic porphyrins meso-(3N-methylpyridinium)phenylporphyrin (3P1, 3P2c, 3P2t, 3P3 and 3P4) and meso-(4N-methylpyridinium)phenylporphyrin (4P1, 4P2c, 4P2t, 4P3 and 4P4) were studied to obtain a comprehensive understanding of factors that influence the binding of cationic porphyrins to liposomes and mitochondria, as well as their photodynamic efficiencies in erythrocytes. Binding and photodynamic efficiency were found to be inversely proportional to the number of positively charged groups and directly proportional to n-octanol/water partition coefficients (log P_OW), except for the cis molecules 3P2c and 4P2c. In the cis molecules, binding and photodynamic efficiency were much higher than expected, indicating that specific interactions not accounted by log P_OW enhance photodynamic efficiency. The effect of mitochondrial transmembrane electrochemical potentials on cationic porphyrin binding constants was estimated to be as large as 15%, and may be useful to selectively target this organelle when promoting photodynamic therapy to induce apoptosis.     

Solid-phase purification and analysis of dicarboxylic porphyrins extracted from cultured tumor cells

We describe here a sensitive method for the purification and analysis of porphyrins present in hematoporphyrin derivative. Hematoporphyrin derivative is a solution containing a complex mixture of dicarboxylic porphyrins such as hematoporphyrin IX, monohydroxyethyl monovinyl deuteroporphyrin isomers, and protoporphyrin IX in addition to porphyrin aggregates of variable molecular sizes. This mixture is known for its ability to be selectively retained by tumor cells and for its cytotoxicity in the presence of light. In order to study the mechanisms of hematoporphyrin derivative uptake and its cellular metabolism, extraction methods are required that combine high recoveries with minimum changes of very labile components. Extraction with perchloric acid: methanol mixtures recovered only some 60% of the porphyrins taken up by tumor cells and artifactual fluorescent spots were seen on thin-layer chromatograms. Improved yields were obtained upon extraction with dimethyl sulfoxide or Triton X-100:4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (Hepes) buffer mixture, but the extracts were not suitable for reverse-phase thin-layer chromatography (RTLC). The procedure described here consists of extracting porphyrins from cultured tumor cells with a buffered detergent followed by sequential chromatography on DEAE-cellulose columns and on reverse-phase octadecylsilyl cartridges. Identification of the isolated free dicarboxylic porphyrins is conveniently done by RTLC.