UV-induced small structural changes in the T7 bacteriophage studied by melting methods.

UV optical absorption and circular dichroism (CD) properties (spectra and melting curves) of T7 bacteriophage were investigated to detect "in situ" structural damages which can be related to the biological inactivation due to UV irradiation. UV doses (0.2-1.2 kJ/m2 at 254 nm) near to the biologically effective minimal dose were applied where the initial genetic damage (approximately 10 events/phage) was observed. The decrease of the melting temperature of the helix-coil transition and the broadening of the transition range indicate the destabilization of the intraphage structure due to the presence of about 0.1-0.6% damaged base concentration.