Photoreduction of Self-Assembled Lipidporphyrinato-iron(III) Chloride with Hyaluronic Acid under Semi-Physiological Conditions

Komatsu, Teruyuki; Yanagimoto, Tetsuya; Nakagawa, Akito; Tsuchida, Eishun

doi:10.1246/cl.2000.84

Cited by 3 publications

(5 citation statements)

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“…Apparently, the binding of CO to the deoxyHb inhibits a back reaction for conversion to metHb. The rate of photoreduction of metHb to form deoxyHb seems comparable with that of the tetraphenylporphyrin derivatives in organic solvents that showed completion of the reduction within 50 ns (17,30,31). The host macromolecular globin chain does not seem to retard the reaction.…”

Section: Discussionmentioning

confidence: 72%

“…It is suggested that the electron transfer from a distal histidine to a ferric iron would be the primary step (), which was supported by the facts that the photoreduction of hemin was accelerated with the increasing amount of pyridine as a base () and that the synthetic heme underwent photoreduction in the presence of 2-methylimidazole ( − ). In the absence of base ligands, on the other hand, irradiation at a halide anion ligand-to-metal charge-transfer (LMCT) band may induce photoreduction as the result of halide radical formation ( − ). It has also been confirmed that the addition of alcohols such as 2-propanol or glycerol facilitates the photoreduction of hemoprotein () and synthetic hemes ( 6 , 18 , 19 ).…”

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confidence: 99%

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Photoreduction of Methemoglobin by Irradiation in the Near-Ultraviolet Region

et al. 2000

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Ferric metHb can be photoreduced to the ferrous state by direct photoexcitation in the near-ultraviolet region. In this research, we studied the mechanism and facilitating conditions for the photoreduction and the resulting restoration of O(2) binding. MetHb in phosphate-buffered saline or pure water in a CO atmosphere was photoreduced to form HbCO by illuminating the N band (365 nm), one of the porphyrin pi --> pi transitions, whereas the photoreduction did not occur in Ar, N(2), or O(2). The transient absorption spectrum exhibited the generation of deoxyHb within 30 ns in both the CO and Ar atmospheres; however, only in CO did the subsequent CO binding inhibit the back reaction. The photoreduction rate was dependent on the pH and ligand anions, showing that aquametHb in the high-spin state was predominant for the photoreduction. Axial ligand-to-metal charge-transfer (LMCT) bands overlap with the Soret and Q bands in metHb; however, the excitation of these bands showed little photoreduction, indicating that the contribution of these LMCT bands is minimal. Excitation of the N band significantly contributes to the photoreduction, and this is facilitated by the external addition of mannitol, hyaluronic acid, Trp, Tyr, etc. Especially, Trp allowed the photoreduction even in an Ar atmosphere, and the reduced Hb can be converted to HbO(2) by O(2) bubbling. One mechanism of the metHb photoreduction that is proposed on the basis of these results consists of a charge transfer from the porphyrin ring to the central ferric iron to form the porphyrin pi cation radical and ferrous iron by the N band excitation, and the contribution of the amino acid residues in the globin chain as an electron donor or an electron pathway.

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Section: Discussionmentioning

confidence: 72%

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confidence: 99%

Photoreduction of Methemoglobin by Irradiation in the Near-Ultraviolet Region

et al. 2000

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“…For example, for Fe III TPPX (Fig. 2: M Fe III X; X F, Cl, Br, I, N 3 ; Ar Ph) [69] and its derivatives carrying both long lipid chains and a chain with an imidazole terminal [70], only irradiation of the LMCT band at 350-400 nm effects cleavage of the Fe-X bond in the presence of hydrogen donors, but irradiation of the B band or Q band in the longer-wavelength region is completely ineffective. Thus the excited LMCT state can undergo reactions competing with internal conversion.…”

Section: Resultsmentioning

confidence: 99%

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

Tokumaru

2001

J. Porphyrins Phthalocyanines

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Photochemical irradiation of porphyrins or phthalocyanines with violet or ultraviolet light absorbed by their second or higher absorption bands populates their higher excited states. These higher excited states generally dissipate very rapidly, but, competing with such rapid deactivation, often show unique behaviour different from the lowest excited states populated under visible light irradiation of the first absorption band, namely wavelength-dependent reactions or emission. The higher excited states often exhibit characteristic emission and enhanced reactivity in electron transfer, energy transfer and so on, competing with rapid deactivation. This paper attempts to summarize our work, perfomed particularly by means of femtosecond spectroscopy, and recent progress in this area.

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“…The UV-vis absorption spectrum of the final compound showed maxima at 330, 423, and 565 nm. We have reported that the amphiphilic Fe(III)TPP derivative formed a five-coordinated high-spin complex with a chloride anion (Cl -) in phosphate-buffered saline solution (Fleischer et al, 1971;Komatsu et al, 2000b). However, this is not true for rHSA-Fe(III)P. On the basis of the absorption pattern, we determined that the dominant species of Fe(III)P in rHSA is an octahedral sixcoordinate high-spin ferric complex with a Cland an intramolecularly coordinated imidazole nitrogen (Figure 1, 3) (Shantha et al, 1998;Walker et al, 1976).…”

Section: Resultsmentioning

confidence: 99%

“…In aqueous media, however, the produced radicals easily react with the formed porphyrinatoiron(II), so that the ferrous complex is not accumulated. Only when hyaluronic acid coexists in phosphate-buffered saline solution, the self-organized fibers of amphiphilic Fe(III)TPP derivative could be reduced by the LMCT irradiation (Komatsu et al, 2000b).…”

Section: Introductionmentioning

confidence: 99%

Photoreduction of Autooxidized Albumin−Heme Hybrid in Saline Solution: Revival of Its O₂-Binding Ability

2001

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Recombinant human serum albumin (rHSA) incorporating 2-[8-[N-(2-methylimidazolyl)]octanoyloxymethyl]-5,10,15,20-tetrakis(alpha,alpha,alpha,alpha-o-pivalamido)phenylporphinatoiron(II)s (Fe(II)Ps) [rHSA-Fe(II)P] is a synthetic hemoprotein which can bind and release O(2) reversibly under physiological conditions (saline solution [NaCl]: 150 mM, pH 7.3) as do hemoglobin and myoglobin. However, the central ferrous ions of Fe(II)Ps are slowly oxidized to O(2)-inactive ferric forms. Based on the UV-vis. absorption spectroscopy, the majority of the autooxidized Fe(III)Ps in albumin are determined to be six-coordinate high-spin complexes with a proximal imidazole and a chloride anion, which show ligand-to-metal charge transfer (LMCT) absorption at 330 nm. Interestingly, photoirradiation of this LMCT band under an argon atmosphere led to reduction of the central ferric iron of Fe(III)P, allowing the revival of the O(2)-binding ability. The ratio of the photoreduction reached a maximum of 83%, which is probably due to the partial dissociation of the axial imidazole. The same photoirradiation under a CO atmosphere provides the corresponding carbonyl rHSA-Fe(II)P. Laser flash photolysis experiments revealed that the reduction was completed within 100 ns. The quantum yields (Phi) of these photoreductions were approximately 0.01.

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Photoreduction of Self-Assembled Lipidporphyrinato-iron(III) Chloride with Hyaluronic Acid under Semi-Physiological Conditions

Cited by 3 publications

References 17 publications

Photoreduction of Methemoglobin by Irradiation in the Near-Ultraviolet Region

Photoreduction of Methemoglobin by Irradiation in the Near-Ultraviolet Region

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

Photoreduction of Autooxidized Albumin−Heme Hybrid in Saline Solution: Revival of Its O₂-Binding Ability

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Photoreduction of Self-Assembled Lipidporphyrinato-iron(III) Chloride with Hyaluronic Acid under Semi-Physiological Conditions

Cited by 3 publications

References 17 publications

Photoreduction of Methemoglobin by Irradiation in the Near-Ultraviolet Region

Photoreduction of Methemoglobin by Irradiation in the Near-Ultraviolet Region

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

Photoreduction of Autooxidized Albumin−Heme Hybrid in Saline Solution: Revival of Its O2-Binding Ability

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Photoreduction of Autooxidized Albumin−Heme Hybrid in Saline Solution: Revival of Its O₂-Binding Ability