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Formation of Z‐DNA in negatively supercoiled plasmids is sensitive to small changes in salt concentration within the physiological range.
Author(s) -
Azorin F.,
Nordheim A.,
Rich A.
Publication year - 1983
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1983.tb01479.x
Subject(s) - biology , plasmid , dna , dna supercoil , range (aeronautics) , genetics , biophysics , dna replication , materials science , composite material
Negative supercoiling of the plasmid pBR322 with or without an insert of (dG‐dC)n induces the formation of Z‐DNA as measured by the binding of antibodies specific for Z‐DNA. Increasing the concentration of Na+ (or K+) is shown to inhibit the B to Z‐DNA conversion. This may be due to the effect of the cation on the B‐Z junction. Using the data for B to Z‐DNA conversion of the (dG‐dC)n inserts, we have estimated the free energy change per base pair as well as the energy of the B‐Z junction. In pBR322, a 14‐bp segment [CACGGGTGCGCATG] is believed to form Z‐DNA at bacterial negative superhelical densities under salt conditions which are similar to those found in vivo.