Effect of temporarily increased ionic strength and of urea on stability of DNA complexes with native and acetylated BPTI.

Hyperchromism of DNA-BPTI and DNA-acetylated BPTI complexes following dialysis/re-dialysis against solutions of increasing/decreasing concentrations of NaCl, urea or urea and NaCl, amounted to ca 50% of hyperchromism values obtained with free DNA or non-dialyzed complexes Stability of DNA-BPTI and DNA-acetylated BPTI complexes subjected to a temporary effect of NaCl, urea or urea and NaCl resembled stability of the complexes in the presence of Nacl or urea. The presence of all three geometrical DNA forms was detected in re-dialyzed DNA-BPTI and DNA-acetylated BPTI complexes. Possible mechanisms of interaction between BPTI and DNA are discussed.