Burke R L, Bauer W
J Biol Chem. 1977 Jan 10;252(1):291-2.
The dye-induced separation between closed and open duplex DNAs in buoyant CsCl is determined primarily by the superhelix density of the closed DNA, provided that all other experimental variables (such as the solution density and dye concentration) are held constant. The extent of the buoyant separation may be used to estimate the superhelix density of an uncharacterized closed DNA, by comparison with the corresponding separation with native SV40 DNAs under identical conditions. We present here an extension of these quantitative relationships to permit the use of an arbitrarily selected closed duplex DNA of known superhelix density, with the accompanying open form, as a reference. The general result is that the ratio of buoyant separations for any two closed/open DNA pairs remains a linear function of the difference in superhelix densities between the closed DNAs. The value of the proportionality constant depends, however, upon the magnitude of the superhelix density of the closed DNA selected as reference.
在浮力氯化铯中，染料诱导的封闭双链DNA和开放双链DNA之间的分离主要由封闭DNA的超螺旋密度决定，前提是所有其他实验变量（如溶液密度和染料浓度）保持恒定。通过在相同条件下与天然SV40 DNA的相应分离进行比较，浮力分离的程度可用于估计未表征的封闭DNA的超螺旋密度。我们在此展示了这些定量关系的扩展，以允许使用任意选择的已知超螺旋密度的封闭双链DNA及其相应的开放形式作为参考。总体结果是，任何两个封闭/开放DNA对的浮力分离比仍然是封闭DNA之间超螺旋密度差异的线性函数。然而，比例常数的值取决于所选作为参考的封闭DNA的超螺旋密度大小。
