Biological proton pumping in an oscillating electric field.

Abstract

Time-dependent external perturbations provide powerful probes of the function of molecular machines. Here we study biological proton pumping in an oscillating electric field. The protein cytochrome c oxidase is the main energy transducer in aerobic life, converting chemical energy into an electric potential by pumping protons across a membrane. With the help of master-equation descriptions that recover the key thermodynamic and kinetic properties of this biological "fuel cell," we show that the proton pumping efficiency and the electronic currents in steady state depend significantly on the frequency and amplitude of the applied field, allowing us to distinguish between different microscopic mechanisms of the machine. A spectral analysis reveals dominant reaction steps consistent with an electron-gated pumping mechanism.

AI evidence extraction

Main findings

Using master-equation modeling of cytochrome c oxidase proton pumping under an applied oscillating electric field, the authors report that steady-state proton pumping efficiency and electronic currents depend significantly on the frequency and amplitude of the applied field. Spectral analysis indicates dominant reaction steps consistent with an electron-gated pumping mechanism.

Outcomes measured

• proton pumping efficiency
• electronic currents (steady state)
• dominant reaction steps / microscopic mechanism (spectral analysis)

Limitations

• Appears to be a theoretical/modeling study (master-equation descriptions) rather than an experimental exposure study.
• No specific field parameters (e.g., frequency values, amplitude, exposure duration) are provided in the abstract.
• No biological population or sample size is described.

{
    "study_type": "other",
    "exposure": {
        "band": null,
        "source": "external oscillating electric field",
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": null
    },
    "population": null,
    "sample_size": null,
    "outcomes": [
        "proton pumping efficiency",
        "electronic currents (steady state)",
        "dominant reaction steps / microscopic mechanism (spectral analysis)"
    ],
    "main_findings": "Using master-equation modeling of cytochrome c oxidase proton pumping under an applied oscillating electric field, the authors report that steady-state proton pumping efficiency and electronic currents depend significantly on the frequency and amplitude of the applied field. Spectral analysis indicates dominant reaction steps consistent with an electron-gated pumping mechanism.",
    "effect_direction": "unclear",
    "limitations": [
        "Appears to be a theoretical/modeling study (master-equation descriptions) rather than an experimental exposure study.",
        "No specific field parameters (e.g., frequency values, amplitude, exposure duration) are provided in the abstract.",
        "No biological population or sample size is described."
    ],
    "evidence_strength": "insufficient",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "oscillating electric field",
        "cytochrome c oxidase",
        "proton pumping",
        "molecular machines",
        "master equation",
        "frequency dependence",
        "amplitude dependence",
        "spectral analysis",
        "electron-gated pumping mechanism"
    ],
    "suggested_hubs": []
}

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