Adinarayana M, Bothe E, Schulte-Frohlinde D
Max-Planck-Institut für Strahlenchemie, Mulheim a.d. Ruhr, F.R. Germany.
Int J Radiat Biol. 1988 Nov;54(5):723-37. doi: 10.1080/09553008814552171.
Combining conductivity measurements and molecular weight determination by means of low-angle laser light scattering, we have found for the polyribonucleotides (polyuridylic acid (poly(U], polyadenylic acid (poly(A], polycytidylic acid (poly(C] and polyguanylic acid (poly(G] and for single-stranded DNA (ssDNA) that, on average, 8.5 counterions per single-strand break (ssb) are liberated under salt-free conditions. This relationship allows us to estimate, from conductivity measurements alone, G-values of single-strand break formation (G(ssb] for the polydeoxyribonucleotides (polydeoxyriboadenylic acid (poly(dA], polydeoxyribocytidylic acid (poly(dC], polydeoxyribothymidylic acid (poly(dT], polydeoxyribouridylic acid (poly(dU] and polydeoxyriboguanylic acid (poly(dG]. The following G(ssb) values (units of mumol J-1) have been obtained for anoxic conditions: poly(dA), 0.23; poly(dC), 0.14; poly(dT), 0.06; poly(dU), 0.046 and poly(dG), 0.009. Time-resolved conductivity measurements in pulse radiolysis enable us to measure the rate of strand break formation. The rate has been found to be similar for poly(dA) and ssDNA over a range of pH values. Poly(dC) and poly(dU) exhibit conductivity increase components with half-lives similar to those of poly(dA) and ssDNA at corresponding pH values. The implications of these results are discussed.
通过结合电导率测量和利用低角度激光光散射测定分子量，我们发现对于多聚核糖核苷酸（聚尿苷酸（聚（U））、聚腺苷酸（聚（A））、聚胞苷酸（聚（C））和聚鸟苷酸（聚（G））以及单链DNA（ssDNA），在无盐条件下，平均每个单链断裂（ssb）会释放8.5个抗衡离子。这种关系使我们能够仅通过电导率测量来估算多聚脱氧核糖核苷酸（聚脱氧核糖腺苷酸（聚（dA））、聚脱氧核糖胞苷酸（聚（dC））、聚脱氧核糖胸苷酸（聚（dT））、聚脱氧核糖尿苷酸（聚（dU））和聚脱氧核糖鸟苷酸（聚（dG））的单链断裂形成的G值（G（ssb））。在缺氧条件下获得了以下G（ssb）值（单位：μmol J⁻¹）：聚（dA），0.23；聚（dC），0.14；聚（dT），0.06；聚（dU），0.046；聚（dG），0.009。脉冲辐解中的时间分辨电导率测量使我们能够测量链断裂形成的速率。已发现聚（dA）和ssDNA在一系列pH值范围内的速率相似。聚（dC）和聚（dU）在相应pH值下表现出电导率增加成分，其半衰期与聚（dA）和ssDNA的半衰期相似。讨论了这些结果的意义。
