Abstract
Thermal decomposition of peroxidized coelenterazines with and without external perturbations has been studied theoretically using the hybrid density functional theory (B3LYP) and the Coulomb-attenuating method (CAM). Possible roles of a hydrogen-bonding interface constituted by amino acid residues in the coelenterazine-biding site of aequorin are addressed by using simple model clusters with a polarizable continuum model to grasp some important aspects that may affect the electronic mechanism operating within the photoprotein. Calculations have revealed that the electronic property and stability of the peroxide are greatly affected by its protonation state and/or environmental effects, such as a polarizing medium and specific (localized) short-range electrostatic interactions, which may be critical for the bioluminescence activity. Theory highlights two mechanisms by which the neutral species can be activated, which otherwise decomposes by a homolytic 0-0 dissociation with a high barrier. In the first mechanism, the Tyr82Hisl6-Trp86 triad motif facilitates the deprotonation process of the phenolic OH group at the CO position of the coelenterazine and thereby makes it a sufficiently good electron donor to activate the 0-0 bond. In the second mechanism, intramolecular charge transfer is accomplished within the neutral peroxide by a proton delivery mediated via another triad motif, Tyr l84-His l69-Trp l73, without the activation of the substrate itself. The combination of the first and second mechanisms leads to complete electron transfer for the formation of a radical pair as a local intermediate stabilized by the nearby triad motifs.
| Original language | English |
|---|---|
| Pages (from-to) | 15171-15187 |
| Number of pages | 17 |
| Journal | Journal of Physical Chemistry A |
| Volume | 113 |
| Issue number | 52 |
| DOIs | |
| Publication status | Published - Dec 31 2009 |
| Externally published | Yes |
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ASJC Scopus subject areas
- Physical and Theoretical Chemistry
Cite this
Theoretical investigation of thermal decomposition of peroxidized coelenterazines with and without external perturbations. / Isobe, Hiroshi; Yamanaka, Syusuke; Okumura, Mitsutaka; Yamaguchi, Kizashi.
In: Journal of Physical Chemistry A, Vol. 113, No. 52, 31.12.2009, p. 15171-15187.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Theoretical investigation of thermal decomposition of peroxidized coelenterazines with and without external perturbations
AU - Isobe, Hiroshi
AU - Yamanaka, Syusuke
AU - Okumura, Mitsutaka
AU - Yamaguchi, Kizashi
PY - 2009/12/31
Y1 - 2009/12/31
N2 - Thermal decomposition of peroxidized coelenterazines with and without external perturbations has been studied theoretically using the hybrid density functional theory (B3LYP) and the Coulomb-attenuating method (CAM). Possible roles of a hydrogen-bonding interface constituted by amino acid residues in the coelenterazine-biding site of aequorin are addressed by using simple model clusters with a polarizable continuum model to grasp some important aspects that may affect the electronic mechanism operating within the photoprotein. Calculations have revealed that the electronic property and stability of the peroxide are greatly affected by its protonation state and/or environmental effects, such as a polarizing medium and specific (localized) short-range electrostatic interactions, which may be critical for the bioluminescence activity. Theory highlights two mechanisms by which the neutral species can be activated, which otherwise decomposes by a homolytic 0-0 dissociation with a high barrier. In the first mechanism, the Tyr82Hisl6-Trp86 triad motif facilitates the deprotonation process of the phenolic OH group at the CO position of the coelenterazine and thereby makes it a sufficiently good electron donor to activate the 0-0 bond. In the second mechanism, intramolecular charge transfer is accomplished within the neutral peroxide by a proton delivery mediated via another triad motif, Tyr l84-His l69-Trp l73, without the activation of the substrate itself. The combination of the first and second mechanisms leads to complete electron transfer for the formation of a radical pair as a local intermediate stabilized by the nearby triad motifs.
AB - Thermal decomposition of peroxidized coelenterazines with and without external perturbations has been studied theoretically using the hybrid density functional theory (B3LYP) and the Coulomb-attenuating method (CAM). Possible roles of a hydrogen-bonding interface constituted by amino acid residues in the coelenterazine-biding site of aequorin are addressed by using simple model clusters with a polarizable continuum model to grasp some important aspects that may affect the electronic mechanism operating within the photoprotein. Calculations have revealed that the electronic property and stability of the peroxide are greatly affected by its protonation state and/or environmental effects, such as a polarizing medium and specific (localized) short-range electrostatic interactions, which may be critical for the bioluminescence activity. Theory highlights two mechanisms by which the neutral species can be activated, which otherwise decomposes by a homolytic 0-0 dissociation with a high barrier. In the first mechanism, the Tyr82Hisl6-Trp86 triad motif facilitates the deprotonation process of the phenolic OH group at the CO position of the coelenterazine and thereby makes it a sufficiently good electron donor to activate the 0-0 bond. In the second mechanism, intramolecular charge transfer is accomplished within the neutral peroxide by a proton delivery mediated via another triad motif, Tyr l84-His l69-Trp l73, without the activation of the substrate itself. The combination of the first and second mechanisms leads to complete electron transfer for the formation of a radical pair as a local intermediate stabilized by the nearby triad motifs.
UR - http://www.scopus.com/inward/record.url?scp=73949125685&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=73949125685&partnerID=8YFLogxK
U2 - 10.1021/jp905401b
DO - 10.1021/jp905401b
M3 - Article
C2 - 19877684
AN - SCOPUS:73949125685
VL - 113
SP - 15171
EP - 15187
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
SN - 1089-5639
IS - 52
ER -