Dynamics of intramolecular electron transfer reaction of FAD studied by magnetic field effects on transient absorption spectra.

The journal of physical chemistry. A · 2005 · Unclear · Insufficient evidence

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UnclearInsufficient evidencePaper 3585

Study snapshot

PublicationThe journal of physical chemistry. A · 2005

Study typein_vitro

Reported directionUnclear

Evidence ratingInsufficient

Abstract

The kinetics of intermediates generated from intramolecular electron-transfer reaction by photo irradiation of the flavin adenine dinucleotide (FAD) molecule was studied by a magnetic field effect (MFE) on transient absorption (TA) spectra. Existence time of MFE and MFE action spectra have a strong dependence on the pH of solutions. The MFE action spectra have indicated the existence of interconversion between the radical pair and the cation form of the triplet excited state of flavin part. All rate constants of the triplet and the radical pair were determined by analysis of the MFE action spectra and decay kinetics of TA. The obtained values for the interconversion indicate that the formation of cation radical promotes the back electron-transfer reaction to the triplet excited state. Further, rate constants of spin relaxation and recombination have been studied by the time profiles of MFE at various pH. The drastic change of those two factors has been obtained and can be explained by SOC (spin-orbit coupling) induced back electron-transfer promoted by the formation of a stacking conformation at pH > 2.5.

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AI evidence extraction

Structured fields below were generated from the paper’s abstract and metadata to make the evidence easier to inspect. Automated extraction may be incomplete or incorrect; verify important details against the original paper.

Study typein_vitro

Effect directionunclear

PopulationNot supplied

Sample sizeNot supplied

ExposureNot supplied

Evidence strengthInsufficientConfidence: 74% · Peer reviewed: yes

Main findings

Magnetic field effects on transient absorption spectra were used to analyze intermediates and kinetics in photoinduced intramolecular electron transfer of FAD. MFE existence time and action spectra depended strongly on solution pH, and the action spectra indicated interconversion between a radical pair and a cation form of the triplet excited state; derived rate constants suggested cation radical formation promotes back electron transfer to the triplet excited state, with changes in spin relaxation and recombination profiles across pH.

Outcomes measured

Magnetic field effects (MFE) on transient absorption spectra
Kinetics/rate constants of triplet and radical pair intermediates in FAD intramolecular electron transfer
Spin relaxation and recombination rate constants
pH dependence of MFE existence time and action spectra

Limitations

Magnetic field exposure parameters (field strength, frequency/waveform, duration) not reported in the abstract
In vitro chemical/photophysical system (FAD in solution), not a health or organismal outcome
Sample size and experimental replication not described in the abstract

View raw extracted JSON

{
  "study_type": "in_vitro",
  "exposure": {
    "band": null,
    "source": "magnetic field (laboratory)",
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": null
  },
  "population": null,
  "sample_size": null,
  "outcomes": [
    "Magnetic field effects (MFE) on transient absorption spectra",
    "Kinetics/rate constants of triplet and radical pair intermediates in FAD intramolecular electron transfer",
    "Spin relaxation and recombination rate constants",
    "pH dependence of MFE existence time and action spectra"
  ],
  "main_findings": "Magnetic field effects on transient absorption spectra were used to analyze intermediates and kinetics in photoinduced intramolecular electron transfer of FAD. MFE existence time and action spectra depended strongly on solution pH, and the action spectra indicated interconversion between a radical pair and a cation form of the triplet excited state; derived rate constants suggested cation radical formation promotes back electron transfer to the triplet excited state, with changes in spin relaxation and recombination profiles across pH.",
  "effect_direction": "unclear",
  "limitations": [
    "Magnetic field exposure parameters (field strength, frequency/waveform, duration) not reported in the abstract",
    "In vitro chemical/photophysical system (FAD in solution), not a health or organismal outcome",
    "Sample size and experimental replication not described in the abstract"
  ],
  "evidence_strength": "insufficient",
  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "flavin adenine dinucleotide",
    "FAD",
    "intramolecular electron transfer",
    "magnetic field effect",
    "transient absorption",
    "radical pair",
    "triplet excited state",
    "spin relaxation",
    "recombination",
    "pH dependence",
    "spin-orbit coupling"
  ],
  "suggested_hubs": []
}

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AI-extracted fields are generated from the abstract and metadata and may be incomplete or incorrect. This material is for informational purposes and is not medical advice.

Identifiers and source

DOI: 10.1021/jp0519722
PubMed: 16833913

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