EPR and Quantum Chemical Studies of the pH-sensitive Imidazoline and Imidazolidine Nitroxides with Bulky Substituents.
EPR and Quantum Chemical Studies of the pH-sensitive Imidazoline and Imidazolidine Nitroxides with Bulky Substituents.
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DOI：
10.1007/s00723-010-0179-z
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发表时间：
2010-12-01
影响因子：
1
通讯作者：
Bagryanskaya, E. G.
中科院分区：
文献类型：
--
作者：
Bobko, A. A.;Kirilyuk, I. A.;Gritsan, N. P.;Polovyanenko, D. N.;Grigor'ev, I. A.;Khramtsov, V. V.;Bagryanskaya, E. G.
利用X-和W-波段电子顺磁共振（EPR）谱研究了一系列在杂环2位和5位上具有不同数目乙基和甲基取代基的咪唑烷氮氧自由基在液态和冷冻溶液中的行为。实验研究了取代基对谱线形状和宽度的影响，并利用量子化学计算进行了分析。发现咪唑烷环的位置2或5中的每对偕乙基在氮氧化合物的EPR谱中产生约0.2 mT的额外超精细分裂（hfs）。这种效应归因于两个偕乙基取代基的四个亚甲基氢原子中只有一个的hfs常数没有被乙基旋转和环起皱完全平均。根据这一假设，在2，2，5，5-四乙基取代的咪唑烷氮氧自由基中CH 2基团的氢原子被氘取代导致EPR谱线的实质性变窄，这可用于许多生物化学和生物医学应用，包括pH监测。2，2，5，5-四乙基取代咪唑烷氮氧自由基及其氘代衍生物的W带EPR谱表明，它们的g因子对pH值具有很高的敏感性，表明它们可作为自旋标记物，具有很高的稳定性。
The X- and W-band electron paramagnetic resonance (EPR) spectroscopies were employed to investigate a series of imidazolidine nitroxide radicals with different number of ethyl and methyl substituents at positions 2 and 5 of a heterocycle in liquid and frozen solutions. The influence of the substituents on the line shape and width was studied experimentally and analyzed using quantum chemical calculations. Each pair of the geminal ethyl groups in the positions 2 or 5 of the imidazolidine ring was found to produce an additional hyperfine splitting (hfs) of about 0.2 mT in the EPR spectra of the nitroxides. The effect was attributed to the hfs constant of only one of four methylene hydrogen atoms of two geminal ethyl substituents not fully averaged by ethyl group rotation and ring puckering. In accordance with this assumption, the substitution of hydrogen atoms of CH2 groups in 2,2,5,5-tetraethyl-substituted imidazolidine nitroxides by deuterium leads to the substantial narrowing of EPR lines which could be useful for many biochemical and biomedical applications, including pH-monitoring. W-band EPR spectra of 2,2,5,5-tetraethyl-substituted imidazolidine nitroxide and its 2,2,5,5-tetraethyl–d8 deuterium-substituted analog measured at low temperatures demonstrated high sensitivity of their g-factors to pH, which indicates their applicability as spin labels possessing high stability.
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影响因子：
2.8
作者：
KHRAMTSOV, VV;WEINER, LM;VOLODARSKY, LB
通讯作者：
VOLODARSKY, LB
影响因子：
3.3
作者：
Foster, MA;Grigor'ev, IA;Nicholson, I
通讯作者：
Nicholson, I
影响因子：
2.2
作者：
Potapenko, Dmitrii I.;Foster, Margaret A.;Khramtsov, Valery V.
通讯作者：
Khramtsov, Valery V.
影响因子：
2.8
作者：
Improta, R;Scalmani, G;Barone, V
通讯作者：
Barone, V
影响因子：
2
作者：
KHRAMTSOV, VV;WEINER, LM;VOLODARSKY, LB
通讯作者：
VOLODARSKY, LB