一氧化氮介导的自由基聚合
电子顺磁共振
化学
亲脂性
核磁共振
生物物理学
光化学
聚合
生物化学
有机化学
自由基聚合
生物
聚合物
物理
作者
Minoru Miyake,Scott R. Burks,John Weaver,Pei Tsai,Wenlan Liu,David I. Bigio,Kenneth S. Bauer,Ke Jian Liu,Gerald M. Rosen,Joseph P. Y. Kao
摘要
In vivo quantitation of O2 in brain has been hindered by a lack of suitable imaging modalities. Development of low-frequency electron paramagnetic resonance (EPR) spectrometers that can detect free radicals in animals in real time makes it feasible to image paramagnetic oximetry probes such as nitroxides in brain tissue. We have shown that masking the carboxyl group of 3-carboxy-2,2,5,5-tetramethyl-1-pyrrolidinyloxyl (nitroxide 1) as an esterase-labile acetoxymethyl ester yields 3-acetoxymethoxycarbonyl-2,2,5,5-tetramethyl-1-pyrrolidinyloxyl (nitroxide 2). Nitroxide 2 can cross the blood-brain barrier and is then hydrolyzed in situ by esterases to regenerate nitroxide 1, which becomes entrapped in brain tissue. Seeking to improve the loading of nitroxides into brain, we synthesized the more lipophilic pentanoyloxymethyl ester, 3-pentanoyloxymethoxycarbonyl-2,2,5,5-tetramethyl-1- pyrrolidinyloxyl (nitroxide 3). We report that the higher lipophilicity of nitroxide 3 does not significantly increase its ability to generate EPR signals in the mouse brain. Therefore, irrespective of whether nitroxide 2 or 3 was injected, similar levels of nitroxide were entrapped in brain tissue. These findings suggest that nitroxides 2 and 3 perform comparably well as proimaging agents for measuring O2 distribution in brain.
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