Temperature-independent electron transfer in mixed-metal hemoglobin hybrids

Debasish Kuila; Wade W. Baxter; Michael J. Natan; Brian M. Hoffman

doi:10.1021/j100154a001

Temperature-independent electron transfer in mixed-metal hemoglobin hybrids

Debasish Kuila, Wade W. Baxter, Michael J. Natan, Brian M. Hoffman^*

^*Corresponding author for this work

Chemistry

Research output: Contribution to journal › Article › peer-review

24 Scopus citations

Abstract

Long-range electron transfer (ET) in mixed-metal hemoglobin hybrids [(MP),Fe(CN^-)P] (M = Mg, Zn) is measured as a function of temperature from ambient to 100 K. Triplet-state quenching of ³(MP) is found to be inadequate to determine ET rate constants when the quenching rate is low, as it is in these hybrids at low temperature. Direct observation of the ET intermediate, [(MP)⁺,Fe²⁺(CN^-)P], has allowed us to determine the temperature response of the ET rate constants k_t and k_b for the ³(MP) → Fe³⁺(CN^-)P and Fe²⁺(CN^-)P → (MP)⁺ electron-transfer steps, respectively. The ET process is not affected by the freezing of the cryosolvent, which may indicate that coupling of ET to low-frequency solvent modes may be minimal. For both M, but especially for M = Mg, k_b is nearly temperature independent. Calculation of the electron coupling matrix element gives H_AB ≈ 10^-3 cm^-1. Comparison with results for ruthenated myoglobin indicates that the Hb interface exhibits efficient electronic coupling even across the noncovalent interface between the subunits.

Original language	English (US)
Pages (from-to)	1-3
Number of pages	3
Journal	Journal of physical chemistry
Volume	95
Issue number	1
DOIs	https://doi.org/10.1021/j100154a001
State	Published - 1991

ASJC Scopus subject areas

General Engineering
Physical and Theoretical Chemistry

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title = "Temperature-independent electron transfer in mixed-metal hemoglobin hybrids",

abstract = "Long-range electron transfer (ET) in mixed-metal hemoglobin hybrids [(MP),Fe(CN-)P] (M = Mg, Zn) is measured as a function of temperature from ambient to 100 K. Triplet-state quenching of 3(MP) is found to be inadequate to determine ET rate constants when the quenching rate is low, as it is in these hybrids at low temperature. Direct observation of the ET intermediate, [(MP)+,Fe2+(CN-)P], has allowed us to determine the temperature response of the ET rate constants kt and kb for the 3(MP) → Fe3+(CN-)P and Fe2+(CN-)P → (MP)+ electron-transfer steps, respectively. The ET process is not affected by the freezing of the cryosolvent, which may indicate that coupling of ET to low-frequency solvent modes may be minimal. For both M, but especially for M = Mg, kb is nearly temperature independent. Calculation of the electron coupling matrix element gives HAB ≈ 10-3 cm-1. Comparison with results for ruthenated myoglobin indicates that the Hb interface exhibits efficient electronic coupling even across the noncovalent interface between the subunits.",

author = "Debasish Kuila and Baxter, {Wade W.} and Natan, {Michael J.} and Hoffman, {Brian M.}",

year = "1991",

doi = "10.1021/j100154a001",

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publisher = "American Chemical Society",

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T1 - Temperature-independent electron transfer in mixed-metal hemoglobin hybrids

AU - Kuila, Debasish

AU - Baxter, Wade W.

AU - Natan, Michael J.

AU - Hoffman, Brian M.

PY - 1991

Y1 - 1991

N2 - Long-range electron transfer (ET) in mixed-metal hemoglobin hybrids [(MP),Fe(CN-)P] (M = Mg, Zn) is measured as a function of temperature from ambient to 100 K. Triplet-state quenching of 3(MP) is found to be inadequate to determine ET rate constants when the quenching rate is low, as it is in these hybrids at low temperature. Direct observation of the ET intermediate, [(MP)+,Fe2+(CN-)P], has allowed us to determine the temperature response of the ET rate constants kt and kb for the 3(MP) → Fe3+(CN-)P and Fe2+(CN-)P → (MP)+ electron-transfer steps, respectively. The ET process is not affected by the freezing of the cryosolvent, which may indicate that coupling of ET to low-frequency solvent modes may be minimal. For both M, but especially for M = Mg, kb is nearly temperature independent. Calculation of the electron coupling matrix element gives HAB ≈ 10-3 cm-1. Comparison with results for ruthenated myoglobin indicates that the Hb interface exhibits efficient electronic coupling even across the noncovalent interface between the subunits.

AB - Long-range electron transfer (ET) in mixed-metal hemoglobin hybrids [(MP),Fe(CN-)P] (M = Mg, Zn) is measured as a function of temperature from ambient to 100 K. Triplet-state quenching of 3(MP) is found to be inadequate to determine ET rate constants when the quenching rate is low, as it is in these hybrids at low temperature. Direct observation of the ET intermediate, [(MP)+,Fe2+(CN-)P], has allowed us to determine the temperature response of the ET rate constants kt and kb for the 3(MP) → Fe3+(CN-)P and Fe2+(CN-)P → (MP)+ electron-transfer steps, respectively. The ET process is not affected by the freezing of the cryosolvent, which may indicate that coupling of ET to low-frequency solvent modes may be minimal. For both M, but especially for M = Mg, kb is nearly temperature independent. Calculation of the electron coupling matrix element gives HAB ≈ 10-3 cm-1. Comparison with results for ruthenated myoglobin indicates that the Hb interface exhibits efficient electronic coupling even across the noncovalent interface between the subunits.

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Temperature-independent electron transfer in mixed-metal hemoglobin hybrids

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