Vizard D L, Ansevin A T
Biochemistry. 1976 Feb 24;15(4):741-50. doi: 10.1021/bi00649a004.
High resolution thermal denaturation profiles are presented for the DNAs of bacteriophages lambda and T7. It is concluded that the temperature increment in data gathering and the method of calculating results meet the requirements for quantitative recording of the large amount of information found in the thermal transitions of both DNAs. The high resolution derivative denaturation profiles of these bacteriophage DNAs demonstrate that individual subtransitions (thermalites) of natural DNA are Gaussian in form and have narrow transition widths. Curve resolution performed on these profiles indicates that the mean thermalite width (2 sigma) is 0.33 degrees C and that this breadth is relatively invariant. Transition widths are not influenced by the position of thermalites in the profile or by cation concentration in the range from 5 to 30 mM Na+. However, the relative position of thermalites within a denaturation profile is a function of the solution ionic strength. The distribution of lengths of the DNA sequences which these thermalites represent is broad, with a number average length of 900 base pairs. Although we find an approximate similarity between the number of thermalites in the denaturation profile of T7 DNA and the number of looping regions in the electron microscopic partial denaturation map of Gomez and Lang ((1972), J. Mol. Biol. 70, 239-251) we conclude that free solution thermal denaturation experiments can be compared only superficially to the mapping results.
本文给出了噬菌体λ和T7 DNA的高分辨率热变性图谱。得出的数据采集温度增量和结果计算方法符合对这两种DNA热转变中大量信息进行定量记录的要求。这些噬菌体DNA的高分辨率导数变性图谱表明，天然DNA的各个亚转变（热解链单元）呈高斯形式，且转变宽度较窄。对这些图谱进行的曲线解析表明，平均热解链单元宽度（2σ）为0.33℃，且该宽度相对恒定。转变宽度不受热解链单元在图谱中的位置或5至30 mM Na+范围内阳离子浓度的影响。然而，热解链单元在变性图谱中的相对位置是溶液离子强度的函数。这些热解链单元所代表的DNA序列长度分布很广，数均长度为900个碱基对。尽管我们发现T7 DNA变性图谱中的热解链单元数量与Gomez和Lang（（1972年），《分子生物学杂志》70卷，239 - 251页）电子显微镜部分变性图谱中的环化区域数量大致相似，但我们得出结论，自由溶液热变性实验只能与图谱结果进行表面上的比较。
