Loehr J, Hanawalt P
Biophys J. 1979 Oct;28(1):65-79. doi: 10.1016/S0006-3495(79)85159-0.
A theoretical model for the kinetics of uptake of a putative precursor molecule into nucleotide pools and into replicating DNA has been developed. The relationship between the accumulation of radioactively labeled precursors in the pool and the appearance of radioactivity in DNA is then derived. Experiments have been carried out in bacteria to compare the uptake of radioactive thymine into deoxythymidine triphosphate, deoxythymidine diphosphate sugars, and DNA to test the suitability of either compound as the direct precursor of thymine in DNA. New one-dimensional, thin-layer chromatographic procedures were used to determine the specific activity of deoxythymidine triphosphate and deoxythymidine triphosphate and deoxythymidine diphosphate sugars in growing cultures of 32PO4-labeled Escherichia coli during pulse labeling with [3H]-thymine. A comparison of the experimental data with our theoretical model supports the hypothesis that deoxythymidine triphosphate, but not deoxythymidine sugar, is the direct precursor of thymine in normally replicating DNA in vivo.
已建立了一个理论模型，用于描述假定的前体分子摄取到核苷酸池及复制DNA中的动力学过程。接着推导了池中放射性标记前体的积累与DNA中放射性出现之间的关系。已在细菌中开展实验，比较放射性胸腺嘧啶摄取到三磷酸脱氧胸苷、二磷酸脱氧胸苷糖及DNA中的情况，以测试这两种化合物作为DNA中胸腺嘧啶直接前体的适用性。采用新的一维薄层色谱法，测定了用[3H] - 胸腺嘧啶脉冲标记期间，32PO4标记的大肠杆菌生长培养物中三磷酸脱氧胸苷、二磷酸脱氧胸苷糖的比活性。将实验数据与我们的理论模型进行比较，支持了以下假设：在体内正常复制的DNA中，三磷酸脱氧胸苷而非脱氧胸苷糖是胸腺嘧啶的直接前体。
