Abstract
Highly water-soluble ubiquinone-0 (CoQ0) reacts with ascorbate monoanion (Asc) to mediate the production of ascorbyl free radicals (AFR). Using aqueous reaction mixture of CoQ0 and Asc, we obtained positively enhanced dynamic nuclear polarization (DNP)-magnetic resonance (MR) images of the AFR at low frequency (ranging from 515 to 530 MHz) of electron spin resonance (ESR) irradiation. The shape of the determined DNP spectrum was similar to ESR absorption spectra with doublet spectral peaks. The relative locational relationship of spectral peaks in the DNP spectra between the AFR (520 and 525 MHz), 14N-labeled carbamoyl-PROXYL (14N-CmP) (526.5 MHz), and Oxo63 (522 MHz) was different from that in the X-band ESR spectra, but were similar to that in the 300-MHz ESR spectra. The ratio of DNP enhancement to radical concentration for the AFR was higher than those for 14N-CmP, Oxo63, and flavin semiquinone radicals. The spectroscopic DNP properties observed for the AFR were essentially the same as those for AFR mediated by pyrroloquinoline quinone. Moreover, we made a success of in vivo DNP-MR imaging of the CoQ0-mediated AFR which was administered by the subcutaneous and oral injections as an imaging probe.
Highlights
Dinucleotide, α -tocopherol, vitamin K1, and ubiquinone-10 [oxidized coenzyme Q10 (CoQ10)]29
We found that an aqueous mixture of 1250 mM ascorbate monoanion (Asc) and 12.5 mM coenzyme Q0 (CoQ0) gave the ascorbyl free radicals (AFR) with enough amount and chemical stability (Figure S-2) to allow for the successful in vitro DNP-MR imaging using our system at low electron spin resonance (ESR) irradiation frequency (515–530 MHz)
We report the basic spectroscopy on DNP properties of the CoQ0-mediated AFR, and discuss it comparing with those of AFR produced in the similar typed reaction of Asc and pyrroloquinoline quinone (PQQ) and in the different typed reaction of Asc and Trolox radicals
Summary
Dinucleotide, α -tocopherol, vitamin K1, and ubiquinone-10 [oxidized coenzyme Q10 (CoQ10)]29. DNP-MR imaging at the low ESR irradiation frequency has the potential for noninvasive and real-time in vivo imaging of AFR for preclinical and clinical applications, such as the evaluations of oxidative stress-induced diseases and injuries[30]. We found that an aqueous mixture of 1250 mM Asc and 12.5 mM CoQ0 gave the AFR with enough amount and chemical stability (Figure S-2) to allow for the successful in vitro DNP-MR imaging using our system at low ESR irradiation frequency (515–530 MHz). We report the basic spectroscopy on DNP properties of the CoQ0-mediated AFR, and discuss it comparing with those of AFR produced in the similar typed reaction of Asc and pyrroloquinoline quinone (PQQ) and in the different typed reaction of Asc and Trolox radicals. We demonstrate in vivo DNP-MR imaging of the CoQ0-mediated AFR administered subcutaneously or orally into mice
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