Nitroxides with two pK values -: Useful spin probes for pH monitoring within a broad range
Nitroxides with two pK values -: Useful spin probes for pH monitoring within a broad range
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DOI：
10.1039/b418707e
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发表时间：
2005-01-01
影响因子：
3.2
通讯作者：
Grigor'ev, IA
中科院分区：
文献类型：
--
作者：
Kirilyuk, IA;Bobko, AA;Grigor'ev, IA
利用RMgBr与相应的5-二烷氨基-4，4-二甲基-4H-咪唑-3-氧化物反应，合成了一系列咪唑环2位带有吡啶基、4-二甲氨基苯基或4-羟基苯基的4-二烷氨基-2，5-二氢咪唑氮氧化物。氮氧自由基的EPR谱显示出pH敏感性，这是由于咪唑环2位的脒基部分和碱性基团连续质子化所致。5，5-二甲基-4-（二甲氨基）-2-乙基-2-吡啶-4-基-2，5-二氢-1H-咪唑-1-氧基在pH 2至6.5的范围内显示出各向同性氮超精细（hfi）耦合常数a（N）为1.4 G的单调增加。如此广泛的pH敏感性可用于许多生物物理和生物医学应用，包括胃中的pH监测。
A series of 4-dialkylamino-2,5-dihydroimidazole nitroxides with pyridine-4-yl, 4-dimethylaminophenyl or 4-hydroxyphenyl groups in position 2 of the imidazole ring were prepared using the reaction of RMgBr with corresponding 5-dialkylamino-4,4-dimethyl-4H-imidazole3-oxides. The EPR spectra of the nitroxides were shown to be pH-sensitive due to consecutive protonation of the amidino moiety and the basic group(s) at position 2 of the imidazole ring. The 5,5-dimethyl-4-(dimethylamino)-2-ethyl-2-pyridine-4-yl-2,5-dihydro-1H-imidazol-1-oxyl showed a monotonic increase in the isotropic nitrogen hyperfine (hfi) coupling constant a(N) of 1.4 G over a pH range from 2 to 6.5. Such a broad range of pH-sensitivity could be useful for many biophysical and biomedical applications, including pH-monitoring in the stomach.