Imaging disulfide dinitroxides at 250 MHz to monitor thiol redox status

Abstract

Measurement of thiol-disulfide redox status is crucial for characterization of tumor physiology. The electron paramagnetic resonance (EPR) spectra of disulfide-linked dinitroxides are readily distinguished from those of the corresponding monoradicals that are formed by cleavage of the disulfide linkage by free thiols. EPR spectra can thus be used to monitor the rate of cleavage and the thiol redox status. EPR spectra of 1H,14N- and 2H,15N-disulfide dinitroxides and the corresponding monoradicals resulting from cleavage by glutathione have been characterized at 250 MHz, 1.04 GHz, and 9 GHz and imaged by rapid-scan EPR at 250 MHz.

Imaging thiol redox status in murine tumors in vivo with rapid-scan electron paramagnetic resonance

“…In this report, the term “PxSSPx” designates the 2 H, 15 N-substituted disulfide-dinitroxide. The disulfide-dinitroxides and the corresponding monomeric forms (generated through cleavage by thiols) have been characterized by EPR spectroscopy at X-band, L-band, and at 250 MHz 4,17 . Importantly, the rate of disulfide cleavage in living cells is markedly decreased after treatment with L -buthionine sulfoximine (BSO, a specific inhibitor of GSH biosynthesis), which suggests that the disulfide-dinitroxides could be useful as probes of thiol redox status in vivo.…”

Resonators for In Vivo Imaging: Practical Experience

“…For relaxation time studies, it is convenient to use resonator Q-switching, as described in [36]. If the resonator filling factor is high, the animal usually lowers the Q to the extent that the ring-down time is not limiting for pulsed EPR imaging of trityl radicals, but nitroxide relaxation is so short (less than a μs) that pulsed imaging of nitroxide probes is a challenge [42], and rapid scan is the method of choice for imaging nitroxides [43, 44]. …”

“…A wide range of applications of EPR imaging use nitroxide radicals, for which pulsed EPR is less widely useful [42] than is rapid scan EPR. Rapid scan EPR [44] can use much higher incident power than can be used in CW EPR without saturating the spin system. The isolation of the detection system from the incident power achieved by the CLR makes the CLR advantageous over a reflection resonator for rapid scan imaging.…”

Rapid Scan Electron Paramagnetic Resonance Opens New Avenues for Imaging Physiologically Important Parameters <em>In Vivo</em>

“…Note: Specific instructions related to analysis of phantoms containing BMPO-OH 24 , pH sensitive TAM radicals 19,27 and redox sensitive dinitroxides 28 are provided in the literature.…”