Norcarane (1) and spiro[2.5]octane (2) yield different product distributions depending on whether they are oxidized via concerted, radical, or cationic mechanisms. For this reason, these two probes were used to investigate the mechanisms of hydrocarbon hydroxylation by two mammalian and two bacterial cytochrome P450 enzymes. Products indicative of a radical intermediate with a lifetime ranging from 16 to 52 ps were detected during the oxidation of norcarane by P450(cam) (CYP101), P450(BM3) (CYP102), CYP2B1, and CYP2E1. Trace amounts of the cation rearrangement product were observed with norcarane for all but CYP2E1, while no cation or radical rearrangement products were observed for spiro[2.5]octane. The results for the oxidation of norcarane with a radical rearrangement rate of 2 x 10(8) s(-1) are consistent with the involvement of a two-state radical rebound mechanism, while for the slower (5 x 10(7) s(-1)) spiro[2,5]oct-4-yl radical rearrangement products were beyond detection. Taken together with earlier data for the hydroxylation of bicyclo[2.1.0]pentane, which also suggested a 50 ps radical lifetime, these three structurally similar and functionally simple substrates show a consistent pattern of rearrangement that supports a radical rebound mechanism for this set of cytochrome P450 enzymes.

中文翻译：

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用自由基钟正戊烷和螺[2,5]辛烷重新研究P450酶的机制。

正二十烷（1）和螺[2.5]辛烷（2）产生不同的产物分布，具体取决于它们是通过协同，自由基还是阳离子机理被氧化。因此，使用这两种探针来研究两种哺乳动物和两种细菌细胞色素P450酶引起的烃羟基化机理。在正戊烷被P450（cam）（CYP101），P450（BM3）（CYP102），CYP2B1和CYP2E1氧化的过程中，检测到指示自由基中间体的产品，该中间体的寿命为16到52 ps。对于除CYP2E1以外的其他化合物，均用正烷发现了痕量的阳离子重排产物，而对螺[2.5]辛烷没有观察到阳离子或自由基重排产物。自由基重排率为2 x 10（8）s（-1）的正烷的氧化结果与两态自由基反弹机制的参与一致，而较慢的（5 x 10（7）s （-1））螺[2,5]辛-4-基自由基重排产物无法检测。连同较早的双环[2.1.0]戊烷羟基化数据（也表明自由基寿命为50 ps）一起，这三种结构相似且功能简单的底物均显示出一致的重排模式，从而支持该组自由基的反弹机制。细胞色素P450酶。