Comparison of theories for the translational and rotational diffusion coefficients of rodhyphen;like macromolecules. Application to short DNA fragments

摘要

Two theories relating the translational and rotational diffusion coefficientsDtandDrof a rodhyphen;like macromolecule to its length and diameter, proposed by Broersma lsqb;J. Chem. Phys. 74, 6989 (1981)rsqb;, and Tirado and Garciacute;a de la Torre lsqb;J. Chem. Phys.71, 2581 (1979);73, 1986 (1980)rsqb; are shown to predict different values of the coefficients for a particle of given dimensions. Next, we use the two theories to analyze existing experimental data of sedimentation coefficientssand translational and rotational diffusion coefficients of short DNA fragments, and obtain values of the hydrated diameter of DNAdwhich is treated as an adjustable parameter. The results are compared with the expected value,dbartil;26Aring;. This comparison favors clearly the Tiradondash;Garcia de la Torre theory in the case ofDtands. ForDr, and using a rise per base pairr=3.4 Aring;, this theory gives best agreement for all the data examined, while whenr=3.3 Aring;, the agreement depends on the source of data.