Comparative study of spectral properties of the bovine serum albumin complexes with acridine orange and methylene blue under the effect of millimeter range electromagnetic waves

Effect of millimeter range electromagnetic waves (MM EMW) with the frequency 51.8 GHz on the interaction of DNA-specific ligands-intercalators acridine orange (AO) and methylene blue (MB) with bovine serum albumin (BSA) has been studied. The measurements were implemented by the spectroscopic methods that open new opportunities for such goals. The methods of absorption, differential and fluorescence spectroscopies were applied. The obtained data permit revealing several peculiarities of MM EMW effect on the interaction of these ligands with BSA, as well as possible sites and modes for the binding. AO and MB were found out to bind to BSA by two modes, moreover, under the effect of MM EMW, one of these modes for MB disappears. The values of the quenching constant - K_SV were determined for the types that compose 4.7⋅10⁴ and 9.2⋅10⁴ L/mole for non-irradiated and 4.6⋅10⁴ and 11.0⋅10⁴ L/mole for irradiated complexes AO-BSA, respectively. For the non-irradiated complexes MB-BSA the values of K_SV were equal to 4.0⋅10⁴ and 0.87⋅10⁴ L/mole, respectively. Because of the irradiation, the first type of the binding disappears, while for the second type the value 0.43⋅10⁴ L/mole was obtained. It was also revealed that MM EMW invokes structural transformations in BSA molecule that touch those sites to which AO and MB bind. Moreover, for AO it results in an increase of preferable binding to this site; though, for MB, vice versa, it leads to the disappearance of stronger (specific) binding mode, while the electrostatic interaction appears for both non-irradiated and irradiated protein.