Murthy C P, Deeble D J, von Sonntag C
Max-Planck-Institut für Strahlenchemie, Bundesrepublik Deutschland.
Z Naturforsch C J Biosci. 1988 Jul-Aug;43(7-8):572-6. doi: 10.1515/znc-1988-7-814.
The polynucleotides poly(U), poly(C), poly(A) and poly(G) have been gamma-irradiated in N2O- and N2O/O2 (4:1)-saturated aqueous solutions. Hydroxyl radicals from the radiolysis of water react with the polynucleotides thereby producing among other lesions strand breaks. Strand breakage is connected with the formation of phosphomonoester end groups. Such end groups have been determined by measuring inorganic phosphate after a three hour incubation at 37 degrees C with acid or alkaline phosphatase. In the absence of oxygen G(phosphomonoester end groups) (in units of mumol J-1) are 0.47 (poly(U)), 0.17 (poly(C)) and less than or equal to 0.04 (poly(A) and poly(G)). In the case of poly(U) and poly(C) on heating the sample for one hour at 95 degrees C prior to incubation with phosphatases the above values increased by 0.14 and 0.07 mumol J-1, resp., whereas such treatment of the purine polynucleotides still did not produce a measurable yield of phosphomonoester end groups. Comparing these values with G values for strand breakage taken from the literature, about two phosphomonoester end groups are formed per strand break in poly(U) while for poly(C) this ratio is about unity. The purine polynucleotides show very low yields of strand breakage in agreement with the negligible phosphomonoester yields. In the presence of oxygen G(phosphomonoester end groups) are 0.46 (poly(U)), 0.21 (poly(C)), and less than or equal to 0.04 (poly(A) and poly(G)). On heating, these values increase, most markedly for poly(U) and poly(C). This is possibly linked to the decomposition of unstable hydroperoxides which are formed in high yields in poly(U) and poly(C) (G = 0.7 and 0.19 mumol J-1, resp.).(ABSTRACT TRUNCATED AT 250 WORDS)
多聚核苷酸聚（U）、聚（C）、聚（A）和聚（G）在N₂O饱和水溶液以及N₂O/O₂（4:1）饱和水溶液中进行了γ辐照。水辐解产生的羟基自由基与多聚核苷酸发生反应，除其他损伤外还会导致链断裂。链断裂与磷酸单酯端基的形成有关。通过在37℃下用酸性或碱性磷酸酶孵育三小时后测量无机磷酸盐来确定此类端基。在无氧条件下，G（磷酸单酯端基）（以μmol J⁻¹为单位）分别为：聚（U）0.47、聚（C）0.17、聚（A）和聚（G）≤0.04。对于聚（U）和聚（C），在与磷酸酶孵育之前将样品在95℃加热一小时，上述值分别增加了0.14和0.07 μmol J⁻¹，而对嘌呤多聚核苷酸进行此类处理仍未产生可测量的磷酸单酯端基产量。将这些值与文献中链断裂的G值进行比较，聚（U）中每条链断裂大约形成两个磷酸单酯端基，而聚（C）的该比例约为1。嘌呤多聚核苷酸的链断裂产量非常低，这与可忽略不计的磷酸单酯产量一致。在有氧条件下，G（磷酸单酯端基）分别为：聚（U）0.46、聚（C）0.21、聚（A）和聚（G）≤0.04。加热后，这些值会增加，聚（U）和聚（C）增加最为明显。这可能与不稳定氢过氧化物的分解有关，在聚（U）和聚（C）中大量形成了不稳定氢过氧化物（G分别为0.7和0.19 μmol J⁻¹）。（摘要截选至250字）
