Bellelli A, Blackmore R S, Gibson Q H
Centro di Biologie Molecolare del Consiglio Nationale delle Ricerche, Universitá La Sapienza, Roma, Italy.
J Biol Chem. 1990 Aug 15;265(23):13595-600.
The time course of ligand recombination to the myoglobin from Aplysia limacina, which has Val(E7), was measured following photolysis by flashes of 35 ps to 300 ns with a time resolution of 10 ps or 1 ns. CO shows only biomolecular recombination. O2 has a small geminate reaction with a half-time of tens of picoseconds, but no nanosecond geminate reaction. NO has two picosecond relaxations with half-times of 70 ps (15%) and 1 ns (80%) and one nanosecond relaxation with a half-time of 4.6 ns. The biomolecular rates for O2 and NO are the same: 2 x 10(7) M-1 s-1. Methyl and ethyl isonitriles have a geminate reaction with a half-time of 35 ps. Ethyl isonitrile has, in addition, a nanosecond relaxation (25%) with a half-time of 100 ns. t-Butyl isonitrile has four geminate relaxations (10 ps, 35 ps, 1 ns, and 1 microseconds). Analysis of the results suggests much easier movement of ligand between the heme pocket and the exterior than in sperm whale myoglobin (His(E7]. The reactivity of the heme is little different, placing the effect of the differences from sperm whale myoglobin on the distal side of the heme.
对来自加利福尼亚海兔（含有缬氨酸（E7））的肌红蛋白进行配体重组的时间进程进行了测量，在35皮秒至300纳秒的闪光光解后，时间分辨率为10皮秒或1纳秒。一氧化碳仅显示双分子重组。氧气有一个半衰期为几十皮秒的小双分子反应，但没有纳秒级双分子反应。一氧化氮有两个皮秒级弛豫，半衰期分别为70皮秒（15%）和1纳秒（80%），以及一个半衰期为4.6纳秒的纳秒级弛豫。氧气和一氧化氮的双分子反应速率相同：2×10⁷ M⁻¹ s⁻¹。甲基和乙基异腈有一个半衰期为35皮秒的双分子反应。此外，乙基异腈还有一个半衰期为100纳秒的纳秒级弛豫（25%）。叔丁基异腈有四个双分子弛豫（10皮秒、35皮秒、1纳秒和1微秒）。结果分析表明，与抹香鲸肌红蛋白（组氨酸（E7））相比，配体在血红素口袋和外部之间的移动要容易得多。血红素的反应性差异不大，这表明与抹香鲸肌红蛋白的差异作用于血红素的远端。
