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Intrinsic viscosity of native and single‐stranded T7 DNA and its relationship to sedimentation coefficient
Author(s) -
Rosenberg Alan H.,
Studier F. William
Publication year - 1969
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1969.360070511
Subject(s) - ionic strength , chemistry , viscosity , intrinsic viscosity , sedimentation coefficient , ionic bonding , thermodynamics , denaturation (fissile materials) , ionic liquid , chemical physics , crystallography , aqueous solution , ion , organic chemistry , physics , polymer , nuclear chemistry , enzyme , catalysis
The intrinsic viscosity and sedimentation coefficient, of native and single‐stranded T7 DNA have been determined at 25°C as a function of ionic strength in neutral and alkaline NaCl. The relationship between [η] and S 0 20,w is well represented by the Mandelkern‐Flory equation over the entire range of conditions between 0.0013 and 1 M Na + . An apparent discrepancy between the two methods at moderate to high ionic strengths is probably due to a change in V with ionic strength. It appears that [η] is a more sensitive and reliable measure of molecular expansion for native DNA, S 0 20,w but is a better index of conformational change in single strands, since [η] becomes too small to measure conveniently at high ionic strengths. At moderate to high ionic strengths, denaturation leads to a decrease in [η], although unfolded single strands retain considerable viscosity. At sufficiently low ionic strength, the intrinsic viscosity of the single strands becomes higher than that of native DNA, and the effective volume of a single strand approaches that of the native molecule.