Explore a selection of Dr. Rosen’s publications below.
Use of Rapid-Scan EPR to Improve Detection Sensitivity for Spin-Trapped Radicals
Published July 2013
The short lifetime of superoxide and the low rates of formation expected in vivo make detection by standard continuous wave (CW) electron paramagnetic resonance (EPR) challenging. The new rapid-scan EPR method offers improved sensitivity for these types of samples. In rapid-scan EPR, the magnetic field is scanned through resonance in a time that is short relative to electron spin relaxation times, and data are processed to obtain the absorption spectrum. To validate the application of rapid-scan EPR to spin trapping, superoxide was generated by the reaction of xanthine oxidase and hypoxanthine with rates of 0.1–6.0 µM/min and trapped with 5-tert-butoxycarbonyl-5-methyl-1-pyrroline-N-oxide (BMPO). Spin trapping with BMPO to form the BMPO-OOH adduct converts the very short-lived superoxide radical into a more stable spin adduct. There is good agreement between the hyperfine splitting parameters obtained for BMPO-OOH by CW and rapid-scan EPR. For the same signal acquisition time, the signal/noise ratio is >40 times higher for rapid-scan than for CW EPR. Rapid-scan EPR can detect superoxide produced by Enterococcus faecalis at rates that are too low for detection by CW EPR.
Acta Crystallographica Section E: Structure Reports Online
Published June 2013
The title compound, C17H29NO4, contains a chiral center and crystallizes as a racemate. The asymmetric unit consists of two non-equivalent molecules, in which the carbethoxy groups have markedly different orientations [C(=O)CC(OEt)=O torsion angles = 59.3 (2) and 156.0 (2)°]. In the crystal, molecules form chains along  through N—H…O hydrogen bonds.
In Vivo Electron Paramagnetic Resonance Imaging of Differential Tumor Targeting Using cis-3,4-Di(Acetoxymethoxycarbonyl)-2,2,5,5-Tetramethyl-1-Pyrrolidinyloxyl
Magnetic Resonance in Medicine
Published June 2013
Electron paramagnetic resonance spectroscopy promises quantitative images of important physiologic markers of animal tumors and normal tissues, such as pO2, pH, and thiol redox status. These parameters of tissue function are conveniently reported by tailored nitroxides. For defining tumor physiology, it is vital that nitroxides are selectively localized in tumors relative to normal tissue. Furthermore, these paramag- netic species should be specifically taken up by cells of the tumor, thereby reporting on both the site of tumor formation and the physiological status of the tissue. This study investigates the tumor localization of the novel nitroxide, cis-3,4-di(acetoxymethoxycarbonyl)-2,2,5,5-tetramethyl-1-pyrrolidinyloxyl 3 relative to the corresponding di-acid 4.