FLEXIBILITY OF LOW-MOLECULAR WEIGHT DOUBLE-STRANDED DNA AS A FUNCTION OF LENGTH .2. LIGHT-SCATTERING MEASUREMENTS AND ESTIMATION OF PERSISTENCE LENGTHS FROM LIGHT-SCATTERING, SEDIMENTATION AND VISCOSITY
FLEXIBILITY OF LOW-MOLECULAR WEIGHT DOUBLE-STRANDED DNA AS A FUNCTION OF LENGTH .2. LIGHT-SCATTERING MEASUREMENTS AND ESTIMATION OF PERSISTENCE LENGTHS FROM LIGHT-SCATTERING, SEDIMENTATION AND VISCOSITY
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DOI：
10.1016/0301-4622(76)80042-7
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发表时间：
1976-01-01
影响因子：
3.8
通讯作者：
EISENBERG, H
中科院分区：
文献类型：
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作者：
GODFREY, JE;EISENBERG, H
作者先前描述了小牛胸腺DNA的7个窄分散级分的分离和物理表征，其分子量范围为0.3-1.3 × 10 - 6。106道尔顿。本研究确定了这些馏分的分子量和均方根半径的光散射在溶剂中，包括0.2 M NaCl，2 mM EDTA，2 mM Na-PO 4，pH 7。在改进的Wippler-Scheibling光度计中进行测量，直到20 °。通过所述程序使溶液几乎无尘的散射角下限。测量DNA组分的光学各向异性，允许将实验分子量和均方根半径校正到其真实值。由这些值，通过适当的多分散性校正，可以得到Kratky-Porod持续长度α，54.0 +-。5.6计算在所检查的分子量范围内不变的mm。根据沉淀系数和Yamakawa和Fujii的理论，计算出该值为66 nm，发现该值同样适用于几种不同来源的DNA样品，其沉降速率已知在约4 × 10 - 4的MW范围内。104到108道尔顿。根据特性粘度和Yamakawa和Fujii的理论，计算的粘度为59 nm，这同样适用于许多DNA样品，这些样品的粘度已由其他工作者在3 × 105 MW范围内测量。105到108道尔顿。Flory-Mandelkern参数β，发现随分子量以Yamakawa和Fujii理论预测的方式变化。α的平均值从3组测量中得到的值为60 ± 10。6 nm，这可以适用于双链DNA分子，与链长无关，在存在可靠数据的整个分子量范围内。
The authors previously described the isolation and physical characterization of 7 narrowly disperse fractions of calf thymus DNA in the MW range 0.3-1.3 .times. 106 daltons. The present study determined the molecular weights and root mean square radii of these fractions by light scattering in a solvent comprising 0.2 M NaCl, 2 mM EDTA, 2 mM Na-PO4, pH 7. Measurements were made in a modified Wippler-Scheibling photometer to a 20.degree. lower limit of scattering angle on solutions rendered virtually dust-free by procedures described. The optical anisotropies of the DNA fractions were measured permitting the experimental molecular weights and root mean square radii to be corrected to their true values. From these values, with appropriate polydispersity corrections, a Kratky-Porod persistence length, .alpha., of 54.0 .+-. 5.6 mm is calculated which is invariant over the molecular weight range examined. From the sedimentation coefficients and the theory of Yamakawa and Fujii, .alpha. is calculated to be 66 nm, a value found to apply equally well to several DNA samples of various origins whose sedimentation rates are known in the MW range from about 4 .times. 104 to 108 daltons. From the intrinsic viscosities and the theory of Yamakawa and Fujii, .alpha. is calculated to be 59 nm, which again adequately applies to a number of DNA samples whose viscosities have been measured by other workers in the MW range 3 .times. 105 to 108 daltons. The Flory-Mandelkern parameter, .beta., was found to vary with molecular weight in the manner predicted by the theory of Yamakawa and Fujii. The average value of .alpha. from the 3 sets of measurements is 60 .+-. 6 nm, which may apply to double-stranded DNA molecules, independent of chain length, over the whole range of molecular weights for which reliable data exist.