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Sedimentation and viscosity of bacteriophage T7 DNA in presence of CH 3 HgOH
Author(s) -
Gruenwedel Dieter W.,
Brown Susan E.
Publication year - 1978
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.1978.360170306
Subject(s) - chemistry , dna , viscosity , sedimentation coefficient , salt (chemistry) , intrinsic viscosity , sodium hydroxide , solvent , sedimentation , sodium , chromatography , polymer , nuclear chemistry , analytical chemistry (journal) , biochemistry , organic chemistry , thermodynamics , paleontology , physics , sediment , biology , enzyme
The effects of increasing concentartions of methylmercuric hydroxide (CH 3 HgOH) on the rate of sedimentation, S 0 , and intrinsic viscosity, [η], of T7 DNA have been studied at 20°C in 0.005, 0.05, and 0.5 M Na 2 SO 4 , respectively, whereby each salt solvent conatined, in addition, 0.005 M sodium borate, pH 9.18, as a buffer. Both S 0 and [η] are independent of organomercurial concentration as long as DNA remains native. Denaturation, brought about by the complexing of CH 3 HgOH with the polymer, produces large changes in S 0 as wll as [η]. The sedimentation coefficient increases strongly with increasing oragnomercurial concentration once strand separation has occured. Experimental difficulties prevented measuring of [η] in the posttransition region. The data on S 0 have been used, in combination with available information on the so‐called density increment (∂ρ/∂ c 2 ) 0 μ , to obtain information on the frictional properties of single‐stranded and methylmercurated T7 DNA. The frictional coefficient, defined as f′ 2 = M 2 (∂ p /∂ c 2 ) 0 μ / S 0 η N A , where M 2 is the molecular wieght of T7 DNA, c 2 is the concentration of DNA in g/ml of solution, η r the realtive viscosity of the salt solvents, and N A is Avogadro's number, was evaluated for all three salt media as a function of organomercurial concentration. f′ 2 of native T7 DNA was found not to be sensitive to changes in ionic strngth; but f′ 2 of single‐stranded and methylmercurated T7 DNA varied strongly with salt concentration. Since f′ 2 of single‐stranded T7 DNA was barely affected by organomercurial concentration at a given ionic strength, it is concluded that the dramatic variations of S 0 with pM (pM ≡ ‐log[CH 3 HgOH]) observed in the posttransition zone reflect only changes in the thermodynamic interactions (“preferential interactions”) existing between DNA and the vatious other solution components, but not changes in the coil dimensions of the polymer.