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Electron spin polarization transfer induced by triplet-radical interactions in the weakly coupled regime.
Dal Farra, Maria Giulia; Martin, Caterina; Bergantino, Elisabetta; Kandrashkin, Yuri E; van der Est, Art; Di Valentin, Marilena.
Affiliation
  • Dal Farra MG; Dipartimento di Scienze Chimiche, Università degli studi di Padova, Via Marzolo 1, 35131 Padova, Italy. marilena.divalentin@unipd.it.
  • Martin C; Dipartimento di Biologia, Università degli Studi di Padova, via U. Bassi 58B/viale G. Colombo 3, I-35131 Padova, Italy.
  • Bergantino E; Dipartimento di Biologia, Università degli Studi di Padova, via U. Bassi 58B/viale G. Colombo 3, I-35131 Padova, Italy.
  • Kandrashkin YE; Zavoisky Physical-Technical Institute, FRC Kazan Scientific Center of RAS, Sibirsky Tract 10/7, Kazan 420029, Russian Federation.
  • van der Est A; Department of Chemistry, Brock University, 1812 Sir Isaac Brock Way, St. Catharines, Ontario L2S 3A1, Canada. avanderest@brocku.ca.
  • Di Valentin M; Dipartimento di Scienze Chimiche, Università degli studi di Padova, Via Marzolo 1, 35131 Padova, Italy. marilena.divalentin@unipd.it.
Phys Chem Chem Phys ; 22(35): 19982-19991, 2020 Sep 16.
Article in En | MEDLINE | ID: mdl-32869045
We report the observation of electron spin polarization transfer from the triplet state of a porphyrin to a weakly coupled nitroxide radical in a mutant of human neuroglobin (NGB). The native iron-containing heme substrate of NGB has been substituted with Zn(ii) protoporphyrin IX and the nitroxide has been attached via site-directed spin labeling to the Cys120 residue. A reference synthetic polypeptide with free base tetraphenylporphyrin and a nitroxide bound to it is also studied. In both systems the nitroxide and the porphyrin are held at a fixed distance of approximately 2.4 nm. The transient EPR data of the NGB sample show that the triplet state of Zn(ii) protoporphyrin acquires significant net polarization, which is attributed to the dynamic Jahn-Teller effect. As the spin polarization of the protoporphyrin triplet state decays, a polarized EPR signal of the nitroxide arises. In contrast, the free base porphyrin in the reference polypeptide does not acquire net polarization and no polarization of the nitroxide label is observed. This is likely a result of the fact that the porphyrin is not Jahn-Teller active because of its lower symmetry. A perturbation theory treatment suggests that in the NGB sample, the polarization of the radical occurs by the transfer of net polarization from the triplet state. This process is also enhanced by the spectral broadening caused by the back and forth transitions associated with the dynamic Jahn-Teller effect. We propose that the novel transfer of polarization to the radical could be exploited to enhance the sensitivity of light-induced dipolar spectroscopy experiments.
Subject(s)

Full text: 1 Collection: 01-internacional Database: MEDLINE Main subject: Free Radicals / Neuroglobin Limits: Humans Language: En Journal: Phys Chem Chem Phys Journal subject: BIOFISICA / QUIMICA Year: 2020 Document type: Article Affiliation country: Italy Country of publication: United kingdom

Full text: 1 Collection: 01-internacional Database: MEDLINE Main subject: Free Radicals / Neuroglobin Limits: Humans Language: En Journal: Phys Chem Chem Phys Journal subject: BIOFISICA / QUIMICA Year: 2020 Document type: Article Affiliation country: Italy Country of publication: United kingdom