Seki H, Schnabel W
Z Naturforsch C Biosci. 1982 Jan-Feb;37(1-2):63-9. doi: 10.1515/znc-1982-1-212.
The aggregation of bovine ribonuclease (RNase) induced by either .OH or Br(2) radicals has been studied. These radicals, which were generated by pulse radiolysis of aqueous solution with 16 MeV electrons, readily attack the enzyme thus producing RNase-radicals which subsequently combine. At initial radical concentrations low enough (less than 0.1 radical per enzyme molecule) to prevent multimerizations other than dimerization, rate constants for the latter process were determined from the increase of the light scattering intensity after the pulse: 2k2 = (22 +/- 0.3) 106 l/mol s (Br(2) initiated dimerization) and (5.4 +/- 0.4) 106 l/mol s (.OH initiated dimerization). The G-values for dimerization are: 1.3 (Br(2) and 0.85 (.OH). Transient optical absorption measurements revealed the existence of phenoxyl radicals of tyrosine (TyrO.) that decayed with a rate constant of 2 K2 (total) = (5.5 +/- 0.7) 106 l/mol s (Br(2)-case). The difference between k2 and k2 (total) presumably indicates the occurrence of disproportionation.
研究了由·OH或Br₂自由基诱导的牛核糖核酸酶（RNase）的聚集。这些自由基通过用16 MeV电子对水溶液进行脉冲辐解产生，它们很容易攻击酶，从而产生核糖核酸酶自由基，随后这些自由基会结合。在初始自由基浓度足够低（每个酶分子少于0.1个自由基）以防止除二聚化之外的多聚化时，通过脉冲后光散射强度的增加来确定后者过程的速率常数：2k₂ = (22 ± 0.3)×10⁶ l/mol·s（Br₂引发的二聚化）和(5.4 ± 0.4)×10⁶ l/mol·s（·OH引发的二聚化）。二聚化的G值分别为：1.3（Br₂）和0.85（·OH）。瞬态光吸收测量揭示了酪氨酸的苯氧自由基（TyrO·）的存在，其衰减速率常数为2k₂（总） = (5.5 ± 0.7)×10⁶ l/mol·s（Br₂情况）。k₂和k₂（总）之间的差异可能表明发生了歧化反应。
