Comparison of 2,2'-azobis(2-amidinopropane) hydrochloride (AAPH) and 2,2'azobis(2,4-dimethylvaleronitrile) (AMVN) as free radical initiators: A spin-trapping study
Comparison of 2,2'-azobis(2-amidinopropane) hydrochloride (AAPH) and 2,2'azobis(2,4-dimethylvaleronitrile) (AMVN) as free radical initiators: A spin-trapping study
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DOI：
10.1039/p29960000747
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发表时间：
1996-04-01
期刊：
影响因子：
--
通讯作者：
Bigelow, DJ
中科院分区：
文献类型：
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作者：
Krainev, AG;Bigelow, DJ
使用 5,5-二甲基-1-吡咯啉 1-氧化物 (DMPO) 及其疏水类似物 2,2-二甲基-4-苯基-2H-咪唑 1-氧化物 (DMPIO) 进行自旋捕获，用于识别和监测由以下化合物引发的氧化反应中参与自由基物质的浓度：水溶性 2,2'-偶氮二(2-脒基丙烷) 盐酸盐 (AAPH) 和亲脂性2,2'-偶氮二(2,4-二甲基戊腈) (AMVN)，在水性介质中将 AAPH 与自旋陷阱一起孵育，产生烷氧基自由基自旋加合物，其超精细分裂常数为 a(N) = 14.62 G、(beta)a(H) = 15.29 G、(gamma)a(H) = 0.72 G 和 a(N) = 13.46 G， DMPO 和 DMPIO 的 (beta)a(H) = 12.53 G。相比之下，通过直接EPR和DMSO（二甲基亚砜）溶液中的自旋捕获均检测到AMVN衍生的过氧自由基的形成。在预载有AMVN的兔骨骼肌浆网（SR）膜（10 g dm(-3) SR蛋白）或卵磷脂酰胆碱脂质体（10 g dm(-3)脂质）存在的情况下，没有自旋加合物形成。观察到，对于 DMPO 和 DMPIO 自旋陷阱，表明 AMVN 衍生的自由基物质不会逃离脂质环境。在 SR 膜存在的情况下，只有一小部分 AAPH 衍生的烷氧基自由基被 DMPIO 捕获，DMPIO 自旋加合物的光谱特征表明其位于脂水界面。同时，SR 对水相中形成的 DMPO-自旋加合物的形成速率和稳态水平几乎没有影响。根据这些数据，我们表明 SR Ca2+-ATP 酶的庞大胞质结构域可保护膜表面免受大量（水）溶剂中产生的自由基的影响。其他证据还表明 AAPH 和 AMVN 偶氮引发剂形成自由基的不同机制。
Spin trapping with 5,5-dimethyl-1-pyrroline 1-oxide (DMPO) and its hydrophobic analogue 2,2-dimethyl-4-phenyl-2H-imidazole 1-oxide (DMPIO) was used to identify and to monitor the concentration of participating radical species in oxidation reactions initiated by ate compounds: water-soluble 2,2'-azobis(2-amidinopropane) hydrochloride (AAPH) and lipophilic 2,2'-azobis(2,4-dimethylvaleronitrile) (AMVN), Incubation of AAPH with spin traps in aqueous media produced alkoxyl radical spin adducts with hyperfine splitting constants being a(N) = 14.62 G, (beta)a(H) = 15.29 G, (gamma)a(H) = 0.72 G and a(N) = 13.46 G, (beta)a(H) = 12.53 G, for DMPO and DMPIO, respectively. In contrast, formation of AMVN-derived peroxyl radicals was detected by both direct EPR and spin trapping in DMSO (dimethylsulfoxide) solutions, In the presence of either rabbit skeletal sarcoplasmic reticulum (SR) membranes (10 g dm(-3) of SR protein) or egg phosphatidylcholine liposomes (10 g dm(-3) of lipid) preloaded with AMVN no spin adduct formation was observed, for both DMPO and DMPIO spin traps, indicating that AMVN-derived radical species do not escape the lipid environment. Only a small portion of AAPH-derived alkoxyl radicals was trapped by DMPIO in the presence of SR membranes, Spectral characteristics of the DMPIO spin adduct indicate its location at the lipid-water interface. At the same time, there was virtually no effect of SR on the rate of formation and steady-state level of the DMPO-spin adduct formed in the aqueous phase. From these data we suggest that the bulky cytosolic domains of the SR Ca2+-ATPase protect the membrane surface from radicals generated in the bulk (aqueous) solvent, Other evidence also demonstrates different mechanisms for free radical formation by AAPH and AMVN azo-initiators.