Hemin intercalated in micellar cetyltrimethylammonium bromide and Triton X-100. Kinetic, spectral, and equilibrium study with cyanide

Simplicio, Jon; Schwenzer, Kathryn

doi:10.1021/bi00734a014

Cited by 64 publications

(45 citation statements)

References 23 publications

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“…Fe CT band at 644 nm. The band positions are in good agreement with those reported in the literature 4 and distinctly different from the absorption spectrum of hemin dimer, which shows a split Soret band at 368 and 385 nm and Q bands at 494 and 530 nm. 28 Therefore, hemin in TX-100 micelles remains essentially as a monomer species.…”

Section: Resultssupporting

confidence: 84%

“…Although the RR spectral features of hemin under these experimental conditions almost correspond to five-coordinated, high-spin species, a six-coordinated species with a weakly coordinated water molecule at the sixth coordination site has been proposed in alkaline aqueous micellar systems. 4 The 10 mode wavenumber is sensitive to the coordination and spin state in ferric octaethylporphyrin (Fe III OEP). 31 For six-coordinated highspin Fe III OEP, the 10 mode is observed between 1618 and 1625 cm 1 , when two alcoholic oxygens (including oxygen of H 2 O) or one alcoholic oxygen and one tetrahydrofuran oxygen bind asymmetrically from both sides of the porphyrin plane.…”

Section: Resultsmentioning

confidence: 99%

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Photoreduction of iron protoporphyrin IX chloride in non‐ionic triton X‐100 micelle studied by electronic absorption and resonance Raman spectroscopy

Shantha

Saini

Thanga

et al. 2001

J Raman Spectroscopy

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Resonance Raman and electronic absorption studies of iron protoporphyrin IX chloride (hemin) in non-ionic Triton X-100 micelle in the absence and presence of hindered imidazole (2-methylimidazole and 1,2-dimethylimidazole) and unhindered imidazole under various experimental conditions are reported. Hemin undergoes photoreduction at the metal center, both in the absence and presence of hindered imidazole, in anaerobic, alkaline and neutral pH conditions on photoexcitation by laser radiation at 441.6 and 457.9 nm. It is inferred from this study that only the monomer hemin encapsulated within the micelle under the alkaline pH conditions is photoreducible. The photoreduction of hemin in this micelle occurs from an electron transfer as a result of dissociation of coordinated hydroxyl ion to the iron atom in the photoexcited state, which may also involve the OH ! Fe charge transfer transition around 360 nm.

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Section: Resultssupporting

confidence: 84%

Section: Resultsmentioning

confidence: 99%

Photoreduction of iron protoporphyrin IX chloride in non‐ionic triton X‐100 micelle studied by electronic absorption and resonance Raman spectroscopy

Shantha

Saini

Thanga

et al. 2001

J Raman Spectroscopy

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“…39 To prevent heme dimerization, it is possible to use micelles formed from materials such as CTAB (cetyltrimethylammonium bromide), which stabilize the hemes in a monodispersed solution. 40,41 Model compound kinetic studies have been performed in CTAB under conditions where an imidazole ligand is bound to the heme. 18,23 However, for such compounds, the CO ligand escape rate is much larger than its geminate rebinding rate, so the latter process is difficult or impossible to detect.…”

Section: Introductionmentioning

confidence: 99%

CO Rebinding to Protoheme: Investigations of the Proximal and Distal Contributions to the Geminate Rebinding Barrier

et al. 2005

J. Am. Chem. Soc.

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The rebinding kinetics of CO to protoheme (FePPIX) in the presence and absence of a proximal imidazole ligand reveals the magnitude of the rebinding barrier associated with proximal histidine ligation. The ligation states of the heme under different solvent conditions are also investigated using both equilibrium and transient spectroscopy. In the absence of imidazole, a weak ligand (probably water) is bound on the proximal side of the FePPIX-CO adduct. When the heme is encapsulated in micelles of cetyltrimethylammonium bromide (CTAB), photolysis of FePPIX-CO induces a complicated set of proximal ligation changes. In contrast, the use of glycerol-water solutions leads to a simple two-state geminate kinetic response with rapid (10-100 ps) CO recombination and a geminate amplitude that can be controlled by adjusting the solvent viscosity. By comparing the rate of CO rebinding to protoheme in glycerol solution with and without a bound proximal imidazole ligand, we find the enthalpic contribution to the proximal rebinding barrier, H p , to be 11 ± 2 kJ/mol. Further comparison of the CO rebinding rate of the imidazole bound protoheme with the analogous rate in myoglobin (Mb) leads to a determination of the difference in their distal free energy barriers: ΔG D ≈ 12 ± 1 kJ/mol. Estimates of the entropic contributions, due to the ligand accessible volumes in the distal pocket and the xenon-4 cavity of myoglobin (~3 kJ/mol), then lead to a distal pocket enthalpic barrier of H D ≈ 9 ± 2 kJ/mol. These results agree well with the predictions of a simple model and with previous independent room-temperature measurements (Tian et al. Phys. Rev. Lett. 1992, 68, 408) of the enthalpic MbCO rebinding barrier (18 ± 2 kJ/mol).

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“…As interações entre porfirinas e tensoativos podem ser tais que i) as repulsões não permitem a formação de qualquer agregado, independentemente da concentração do tensoativo; ii) a micelização ocorre sem a formação de agregados pré-micelares e iii) a micelização é precedida por agregados pré-micelares. 74 A formação de agregados entre hemina e tensoativos é favorável, uma vez que são reportados agregados entre hemina e tensoativos catiônicos 76 , aniônicos 77 e neutros. 76,78 No caso da solução de hemina em CTAB os espectros de absorção sugerem que a interação entre hemina e CTAB provoca a dissociação do dímero heminahemina, pois o deslocamento observado é condizente com o espectro do monômero.…”

Section: Discussionunclassified

“…74 A formação de agregados entre hemina e tensoativos é favorável, uma vez que são reportados agregados entre hemina e tensoativos catiônicos 76 , aniônicos 77 e neutros. 76,78 No caso da solução de hemina em CTAB os espectros de absorção sugerem que a interação entre hemina e CTAB provoca a dissociação do dímero heminahemina, pois o deslocamento observado é condizente com o espectro do monômero.…”

Section: Discussionunclassified

Oxidação quimiluminescente do luminol em meios micelares: desenvolvimento de uma ensaio para determinação da capacidade anti-radicalar

Santos¹

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Hemin intercalated in micellar cetyltrimethylammonium bromide and Triton X-100. Kinetic, spectral, and equilibrium study with cyanide

Cited by 64 publications

References 23 publications

Photoreduction of iron protoporphyrin IX chloride in non‐ionic triton X‐100 micelle studied by electronic absorption and resonance Raman spectroscopy

Photoreduction of iron protoporphyrin IX chloride in non‐ionic triton X‐100 micelle studied by electronic absorption and resonance Raman spectroscopy

CO Rebinding to Protoheme: Investigations of the Proximal and Distal Contributions to the Geminate Rebinding Barrier

Oxidação quimiluminescente do luminol em meios micelares: desenvolvimento de uma ensaio para determinação da capacidade anti-radicalar

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