Intrinsic viscosities of cyclic and linear λ DNA

✍ Scribed by Richard J. Douthart; Victor A. Bloomfield

• Publisher: Wiley (John Wiley & Sons)
• Year: 1968
• Tongue: English
• Weight: 682 KB
• Volume: 6
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.1968.360060906

✦ Synopsis

The ratio of the intrirlsic viscosities of the linear and circulitr forms of X DNA, [q]~/[q]c, has been measured aa a fnnc'ion of ionic strength in the range "a+] = 0.6.ll-0.03M. Correciions were made for the presence of uncyclizable linear contaminant in circular preparations. By combining data in the literature on the ionic strength dependence of linear DNA of various molecular weights with that obtained here, it was possible to determine the expansion parameter €1. as a function of "a+]. SL is defined by the relation ( L 2 ) = b2N1+eL, where ( L 2 ) is the mean-square end-to-end distance of a chain of N segments of length b. The empirical relation EL = 0.05 -0.11 log "a+] for native NaDNA a t 25°C is found. When €I, = 0, [q]~/[q]c extrapolates to 1.6, in good agreement with the theoretical prediction of 1.55. As e~ increases, [q]~/[q]c increases, in agreement with a theory of Bloomfield and Zimm.