NET HYDRATION OF T-4 BACTERIOPHAGE DEOXYRIBONUCLEIC ACID AND EFFECT OF HYDRATION ON BUOYANT BEHAVIOR IN A DENSITY GRADIENT AT EQUILIBRIUM IN ULTRACENTRIFUGE
NET HYDRATION OF T-4 BACTERIOPHAGE DEOXYRIBONUCLEIC ACID AND EFFECT OF HYDRATION ON BUOYANT BEHAVIOR IN A DENSITY GRADIENT AT EQUILIBRIUM IN ULTRACENTRIFUGE
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DOI：
10.1073/pnas.47.7.1005
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发表时间：
1961-01-01
影响因子：
11.1
通讯作者：
VINOGRAD, J
中科院分区：
文献类型：
--
作者：
HEARST, JE;VINOGRAD, J
Po=Pe.2+d(roe，-Re，2)dp\Pe，2-P5j(dr(ro-rh)-(ro，2-r，2))，其中ro是带状位置，Re是等浓度点，P0和P6是相应点处的密度。下标1和2表示不同的解，Dp/DR是密度梯度。位置Re被认为在每个单元的液柱的中心。用校准的0.3毫升微吸管测量密度P，测量精度为±0.001克/毫升。这种处理忽略了压力的影响，并假设密度梯度是恒定的。对单元格中心的修正通常很小，所以误差也很小。密度估计精度为±0.3%。T-4噬菌体DNA是用氯化胍从噬菌体中释放出来的。‘DNA没有用酒精沉淀来进行溶剂化研究。DNA的原液在pH为9的缓冲液中，除硅钨酸锂溶液外，所有的原盐溶液都用相同的缓冲液稀释到合适的浓度。用于密度梯度运行的DNA浓度为2至20×10-gm/cc。除了醋酸铯，所有的谱带位置都是用纹影光学系统测定的。在醋酸铯中，谱带太宽，用纹影系统看不到，所以使用了紫外光。表2列出了几种盐溶液的折射率与密度的关系式。这些方程式是在列出的密度范围内通过实验确定的。它们应该被认为是近似值，因为盐溶液用pH 9的缓冲液稀释，因此
Po= Pe. 2+ d(roe,-re, 2)() dp\ Pe, 2-P5J (dr(ro-rh)-(ro, 2-r, 2) where ro is the banding position, re is the isoconcentration point, and po and p6 are the densities at the respective points. The subscripts 1 and 2 refer to the different solutions, and dp/dr is the density gradient. The position re was taken to be at the center ofthe liquid column of each cell. The density P, was measured with a calibrated 0.3 milliliter micropipette to an accuracy of±0.001 gm/cc. This treatment neglects the effects of pressure and assumes thatthe densitygradient is constant. Corrections to the center of the cell were generally small, so errors were small. Densities are estimated to be accurate to±0.3%. The T-4 bacteriophage DNA was liberated from a phage stock with guanidinium chloride as described.'The DNA was not precipitated with alcohol for the solvation studies. The stock solutions of DNA were in thepH 9 buffer,'and all stock salt solutions with the exception of the lithium silicotungstate solution were diluted with the same buffer to the appropriate density. The DNA concentrations employed for the density gradient runs were 2 to 20 X 10-gm/cc. Except in cesium acetate, all band positions were determined using the schlieren optical system. In cesium acetate, the band was too broad to be seen with the schlieren system, so the ultraviolet optics were used. Equations for refractive index versus density of several of the salt solutions are listed in Table 2. These were experimentally determinedfor the density ranges listed. They should be considered approximate because the salt solutions were diluted with pH 9 buffer and therefore