The effect of solvent viscosity and temperature on DNA viscoelastic behavior

✍ Scribed by J. Y. Ostashevsky; C. S. Lange

• Publisher: Wiley (John Wiley & Sons)
• Year: 1986
• Tongue: English
• Weight: 807 KB
• Volume: 25
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.360250210

✦ Synopsis

The effect of solvent viscosity (q8) and temperature (2') on the shape of the concentration dependence of the principal and total recoils in creeprecovery viscoelastometry experiments has been studied for T4 DNA solutions. The range of DNA concentration ( c ) was 2 -40 pg/ml; glycerol, 70-80% v/v, sucrose, 60% v/v; NaCl, 5 mM -1M; and T, 275 -323 K. A linear proportionality between recoil and c was obtained at high q 8 / T. At low q8/r the cdependence was nonlinear, approaching saturation a t higher c.

At low c, the slope of both curves was the same. Transition between "linear" and "nonlinear" values occurred over a narrow range of q,/T (a width of 1-5 K if q 8 / T was changed by varying 2'). ( v # / T ) ~~, the midpoint of the transition, was independent of solvent properties other than viscosity. Also, (q8/T)tr increased with c. For a given c, v e / T values above this transitional value yield linear behavior; below this, nonlinear behavior. The ratio of linear to nonlinear recoil values is a linear function of c with K,, the slope of this dependence, independent of q, and T. A kinetic model for the observed nonlinearity of recoil with c is presented. It explains the independence of K, on q s and T. An attempt has been made to explain the linear-nonlinear transitions by comparison of T~ and TR, the lifetime of the contact points of the polymer network in the de Gennes theory. The nonlinear values are consistent with a pseudogel that exists when T~ < T R . At f l > T R , the DNA behavior is similar to that in dilute solutions (linear values). Thus, the condition for transition is r 1 = T R . However, some unsolved problems remain.