Ligand‐binding in Porphyrin Systems*

Gallagher, W. A.; Elliott, W.B.

doi:10.1111/j.1749-6632.1973.tb43230.x

Cited by 45 publications

(19 citation statements)

References 23 publications

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“…1 that with the increase of the concentration the molar extinction coefficient decreases, the spectral shape of the Soret band changes from two peaks at 372 and 390 nm to a single peak at 363 nm, and a red-shift of four peaks in the Q-band occurs. This behavior is very similar to the change from the absorption spectra of the monomer to those of the E dimer of HPIX, DPIX, and PPDC in an aqueous solution [7] - [lo], except that the peak at the shorter wavelength of the Soret band still remains at the most diluted concentration. This suggests that in the HPD solution at high concentration the D aggregate including mainly the E dimer exists, while at the diluted concentration, in addition to the monomer, another molecular species independent of the concentration exists.…”

Section: A Steady-state Absorption and Fluorescence Excitation Spectrasupporting

confidence: 55%

“…In order to confirm the latter part of this suggestion, we measured how the relative intensity of the fluorescence peaks at 615 or 680 nm depends on the wavelength of the excitation light. A typical excitation spec- Favorable comparison of this spectrum with the absorption spectrum of the monomer of HPIX and DPIX already known [7] - [9] indicates that both the spectra are almost the same.…”

Section: A Steady-state Absorption and Fluorescence Excitation Spectramentioning

confidence: 99%

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Picosecond time-resolved fluorescence spectroscopy of hematoporphyrin derivative

Yamashita¹,

Nomura²,

Kobayashi³

et al. 1984

IEEE J. Quantum Electron.

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Section: A Steady-state Absorption and Fluorescence Excitation Spectrasupporting

confidence: 55%

Section: A Steady-state Absorption and Fluorescence Excitation Spectramentioning

confidence: 99%

Picosecond time-resolved fluorescence spectroscopy of hematoporphyrin derivative

Yamashita¹,

Nomura²,

Kobayashi³

et al. 1984

IEEE J. Quantum Electron.

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“…Fe(III) PP (ImH)2 in aqueous solutions without dispersing agent (detergent or solvent) exhibits an absorption spectrum characteristic of n-aggregation (Gallagher and Elliott 1973). The frequency of the Fe-[N(ImH)]2 stretching mode of aqueous Fe (III)PP (ImH)2 which has been characterized at 200_+ 1 cm-1 (Desbois and Lutz 1983;Choi and Spiro 1983;Mitchell et al 1987) is not significantly affected by a pH increase from 7.5 to 11.3 (figure not shown).…”

Section: Absorption Spectroscopy Of Iron (Iii) Derivativesmentioning

confidence: 99%

Redox control of proton transfers in membrane b-type cytochromes: an absorption and resonance Raman study on bis(imidazole) and bis(imidazolate) model complexes of iron-protoporphyrin

Desbois

Lutz

1992

Eur Biophys J

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Abstract. Optical absorption spectra and resonance Raman (RR) spectra, obtained with Soret excitation, are reported for bis(imidazole) and bis(imidazolate) complexes of iron(II)-and iron(III)-protoporphyriri IX, prepared in aqueous conditions. Perdeuteration experiments on the axial ligands permitted the assignment of the symmetric Fe-(ligand)2 stretching mode of Fe[x]PP(L)2 to RR bands at 203 (x=II; L=ImH), 212 (x=II; L=Im-), 201 (x=III; L=ImH) and 226 cm -1 (x = III; L = Im-). These frequency differences indicate a strengthening of the axial bonds when the imidazole deprotonations occur. The larger difference observed for the ferric derivatives reflects the stronger a-donor capability of the Ira-anion for iron(III) over iron(II). For the ferrous derivatives, the frequencies of several skeletal porphyrin modes (v4, Vlo, vll and V3s ) are downshifted by 2-10 cm-J upon deprotonation of the ligands. This effect corresponds to an increased back-bonding from the metal atom to the porphyrin ring when the axial ligand decreases its n-acid strength. Bringing further support to this interpretation, an inverse linear relationship is established between the frequencies of v (Fe(II)-L2) and v~t. This correlation is expected to monitor the overall Hbonding state of histidine ligands of reduced cytochromes b. On the other hand, absorption measurements have characterized large pK~ differences for the sequential imidazole ionizations of Fe Abbreviations: RR, resonance Raman; EPR, electron paramagnetic resonance; PP, protoporphyrin IX; ImH, imidazole; Ira-, imidazolate; Im*, imidazole or imidazolate; 1Melm, t-methylimidazole; HisH, histidine; His-, histidinate; CTABr, cetyltrimethylammonium bromide; NaDS, sodium dodecylsulphate; VLP, very low potential; LP, low potential; HP, high potential good proton-acceptor and proton-donor, respectively, and suggest a model by which heme, located in a favorable environment inside a cytochrome, could couple a cycle of electron transfer with a proton transfer. Based on sequence data and structural models, it is further proposed that, in several membrane cytochromes b (b, b6, b559) , a positively charged amino acid residue and an imidazolate ligand of the ferriheme could form an ion pair involved in a redox control of proton transfer.

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“…However, the large spectral changes with concentration occur in the Soret band. The four visible absorption bands (Q bands) show spectral shifts about 100-300 cm-' from 10 to 1000 pM with small extinction decreases (Gallagher and Elliott, 1973). The Soret band (B transitions) and Q transitions arise from the same pairs of nearly degenerate highest filled and lowest unfilled molecular orbitals, where the intensity of the weakly allowed Q bands originates from vibrational mixing with B states of the same polarization (Gouterman, 1978).…”

Section: Hematoporphyrinmentioning

confidence: 99%

SINGLET OXYGEN GENERATION BY HEMATOPORPHYRIN IX, UROPORPHYRIN I and HEMATOPORPHYRIN DERIVATIVE AT 546 nm IN PHOSPHATE BUFFER and IN THE PRESENCE OF EGG PHOSPHATIDYLCHOLINE LIPOSOMES

Blum

Grossweiner

1985

Photochem & Photobiology

122

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Abstract— The quantum yield of singlet oxygen generation (φ) was measured at 546 nm with the p‐nitrosodimethylaniline (RNO) method. The results obtained in pH 7.4 phosphate buffer (PB) were: φ(HP) = 0.44 ± 0.05: φ= 0.71 ± 0.07: φ(HpD‐A) = 0.06 ± 0.02. The value of φ was constant from 3 to 67 μM, attributed to the dominance of HP dimers; φ (HP) increased to 0.77 ± 0.13 in the presence of small egg phosphatidylcholine liposomes (SUV), attributed to solubilization and monomerization: φ (HpD‐A) increased to 0.87 ± 0.17 in the presence of SUV. attributed to monomerization of the impurity porphyrins and unfolding of the covalent dimer constituents. The quantum efficiency of the RNO system (100 μM RNO plus 10 mM histidine) was approximately 0.015 at pH 7.4 and increased significantly at lower pH.

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Ligand‐binding in Porphyrin Systems*

Cited by 45 publications

References 23 publications

Picosecond time-resolved fluorescence spectroscopy of hematoporphyrin derivative

Picosecond time-resolved fluorescence spectroscopy of hematoporphyrin derivative

Redox control of proton transfers in membrane b-type cytochromes: an absorption and resonance Raman study on bis(imidazole) and bis(imidazolate) model complexes of iron-protoporphyrin

SINGLET OXYGEN GENERATION BY HEMATOPORPHYRIN IX, UROPORPHYRIN I and HEMATOPORPHYRIN DERIVATIVE AT 546 nm IN PHOSPHATE BUFFER and IN THE PRESENCE OF EGG PHOSPHATIDYLCHOLINE LIPOSOMES

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