Behavior Of Porphyrins Research Articles

Molecular Dynamics of Cobalt Protoporphyrin Antagonism of the Cancer Suppressor REV-ERBβ.

Nuclear receptor REV-ERBβ is an overexpressed oncoprotein that has been used as a target for cancer treatment. The metal-complex nature of its ligand, iron protoporphyrin IX (Heme), enables the REV-ERBβ to be used for multiple therapeutic modalities as a photonuclease, a photosensitizer, or a fluorescence imaging agent. The replacement of iron with cobalt as the metal center of protoporphyrin IX changes the ligand from an agonist to an antagonist of REV-ERBβ. The mechanism behind that phenomenon is still unclear, despite the availability of crystal structures of REV-ERBβ in complex with Heme and cobalt protoporphyrin IX (CoPP). This study used molecular dynamic simulations to compare the effects of REV-ERBβ binding to Heme and CoPP, respectively. The initial poses of Heme and CoPP in complex with agonist and antagonist forms of REV-ERBβ were predicted using molecular docking. The binding energies of each ligand were calculated using the MM/PBSA method. The computed binding affinity of Heme to REV-ERBβ was stronger than that of CoPP, in agreement with experimental results. CoPP altered the conformation of the ligand-binding site of REV-ERBβ, disrupting the binding site for nuclear receptor corepressor, which is required for REV-ERBβ to regulate the transcription of downstream target genes. Those results suggest that a subtle change in the metal center of porphyrin can change the behavior of porphyrin in cancer cell signaling. Therefore, modification of porphyrin-based agents for cancer therapy should be conducted carefully to avoid triggering unfavorable effects.

Synthesis and Solution Self-Assembly Behavior of Porphyrin Tethered by Fullerene C<sub>60</sub>

This paper focuses on the synthesis, spectroscopic studies and self-assembly behavior of porphyrin phenyl linked fullerene C60 dyad, which included COOH groups in its fullerene unit so as to promote its adsorption onto TiO2. UV-Vis spectrum and steady-state fluorescence spectrum measurement, showed that the self-assembly of this compound in different solvents with different polarities. The results show that the soret absorption peak slightly blue shifted by 5 nm in acetonitrile and 2 nm in tetrahydrofuran, while the soret peaks in toluene solution was the same as in chloroform. Increasing concentration from 1x10-6 mol/L to 2x10-5 mol/L in chloroform resulted into aggregation, also the slight red shifting on cooling from 900C to 100C was observed from a temperature dependant UV-Vis absorption spectra, thus indicates aggregation. All these features may indicate presence of J-type aggregation happening in 4-methylphenyl-H2porhyrin-fullerene C60-COOH. In addition, the fluorescence of 4-methylphenyl-H2Porhyrin-fullerene C60-COOH has been quenched compared to that of pure 4-methylphenyl-H2porhyrin-OH under the same concentration. Therefore, this novel material design may find good application in photoelectric devices.

1,3-Dipolar Cycloaddition Reactions of Porphyrins with Azomethine Ylides

[reaction: see text] The behavior of porphyrins as dipolarophiles in 1,3-dipolar cycloadditions with azomethine ylides was studied. Depending on the nature of the substituent groups on the porphyrin macrocycles, the reaction can give monoadducts (chlorins) or bisadducts (isobacteriochlorins and bacteriochlorins). When a large excess of azomethine ylide is used, trisadducts can also be obtained. Mixed isobacteriochlorin derivatives were prepared from the reaction of azomethine ylides with the chlorin monoadducts previously obtained via Diels-Alder reactions.

Influence of isomerism on the chromatographic behaviour of porphyrins

The chromatographic behaviour of some porphyrins and their complexes with zinc has been studied by HPLC on 150×3.9 mm and 300×3.9 mm columns packed with Nova-Pak C18 and μ-Bondapak C18, respectively, and on a microcolumn (64×2 mm) packed with Nucleosil C18. The effect of the nature and the arrangement of side substituents in the porphyrin molecules on retention is considered. It is demonstrated that HPLC can be used for the separation ofcis-andtrans-isomers (atropisomers) of the zinc complex of 5,15-di(phenyl-2-CH3O)-3,7,13,17-tetramethyl-2,8,12,18-tetrabutylporphyrin and other porphyrins with a similar structure. The efficiency of separation has been compared on different columns.

Photochemical and photophysical behaviour of porphyrins and phthalocyanines irradiated with ­violet or ultraviolet light

Photochemical and photophysical behaviour of porphyrins and phthalocyanines irradiated with ­violet or ultraviolet light

Porphyrins and phthalocyanines as model compounds for detoxification of tumor chemotherapeutic drugs

The fluorescence behavior of porphyrins and phthalocyanines allows one to discriminate between monomeric and associated states of the dyes. These criteria are necessary prerequisites to decide about the inclusion behaviour of the dyes in oligomeric cyclodextrins. Masking the hydrophobic portion of the dyes by cyclodextrins allows one to transport these substances as inert through the body of an animal. The story is depicted here of how to proceed from functionalized porphyrinoids to tumor therapeutic drugs.

Investigation on the behavior of porphyrins at the surface of the colloidal silver particles

The behavior of meso-tetra(4′-hydroxyphenyl) porphyrin (T(4-HP)P) and meso-5-(4′-hydroxyphenyl)-10,15,20-triphenylporphyrin (HPTPP) in a Ag sol system was investigated by UV-vis spectra, surface enhanced scattering (SERS), fluorescence spectra and the measurements of luminescence lifetime. There was an obvious SERS effect when the porphyrins were adsorbed on the surface of colloidal silver particles. Meanwhile, a new peak was observed at about 460 nm in the absorption spectra. The evidence suggests that T(4-HP)P and HPTPP chemisorbed on the particle surface of Ag sol to produce complex life metalloporphyrins. The apparent association constants for the two porphyrins and silver sol were 3.16 × 10 4M −1, 2.79 × 10 4M −1, respectively. It was found that silver sol was a fluorescence quencher by which above 90% of the fluorescence emission of T(4-HP)P and HPTPP could be quenched. The mechanism for fluorescence quenching was proposed to be a static process based upon the measurements of fluorescence lifetimes.

Spectral study of mono‐meso‐(hydroxyphenyl)octamethylporphyrins

AbstractThe behaviour of porphyrins [mono‐meso‐(2‐hydroxyphenyl)octamethylporphyrin, mono‐meso‐(4‐hydroxyphenyl)octamethylporphyrin and mono‐meso‐(3,4‐dihydroxyphenyl)octamethylporphyrin] in basic solution is examined by UV‐Visible and 1H NMR spectroscopy. The unusual nature of the spectra may be explained by the formation of porphomethene moieties in which the porphyrin chromophore is modified by interruption of the π‐system. The porphyrins in bases are less susceptible to oxidation in contrast with meso‐tetrakis‐(4′‐hydrooxyphenyl)porphyrins.