[Study of complexes of poly-L-histidine with DNA using hyperchromic spectra].

Complexes of DNA with poly-L-histidine in acidic media were investigated by the method of hyperchromic spectra. Making use of the least squares hyperchromic spectra were partitioned into the components corresponding to the melting of AT and GC base pairs and protonation of cytosine. The protonation of cytosine was found to be proportional to the fraction of broken GC base pairs and was not influenced by the presence of poly-L-histidine. Selectivity of poly-L-histidine towards the base pairs was found to be very weak or absent.