Zimm B H, Schumaker V N, Zimm C B
Biophys Chem. 1976 Jul;5(1-2):265-70. doi: 10.1016/0301-4622(76)80039-7.
The theory of a preceding paper [B.H. Zimm, Biophys, Chem. 1 (1974) 279] is used to calculate a numerical table for the change of sedimentation coefficient with centrifugal field for chain molecules. A simple formula is found to fit the results within 1.3% up to the centrifugal field at which S/So = 0.377; this formula is S/So=(1+0.1155y2)-1/4, where y is proportional to M2/So times the centripetal acceleration, M being the molecular weight and So the sedimentation coefficient at zero acceleration. Applying this formula to DNA, we conclude that at a given centrifuge speed the sedimentation coefficient must reach a maximum at a particular molecular weight and be smaller at higher molecular weights. The value of the maximum depends on the conditions, but can come at less than 150 S for DNA under typical conditions. When a maximum is present, the profile of a sedimenting non-homogeneous band is also severely distorted.
前文[B.H. 齐姆，《生物物理学与化学》1 (1974) 279]中的理论被用于计算链状分子沉降系数随离心场变化的数值表。发现一个简单公式在S/So = 0.377之前的离心场范围内，能以1.3%的精度拟合结果；该公式为S/So=(1 + 0.1155y²)^(-1/4)，其中y与M²/So乘以向心加速度成正比，M为分子量，So为零加速度时的沉降系数。将此公式应用于DNA，我们得出在给定离心机转速下，沉降系数在特定分子量时必定达到最大值，而在更高分子量时则较小。最大值的具体数值取决于条件，但在典型条件下，DNA的最大值可能小于150 S。当存在最大值时，沉降的非均匀条带的轮廓也会严重扭曲。
