Background. Complexes of oligoribonucleotides with D-mannitol are highly effective, non-toxic and possess a wide range of biological effects. In particular, such complexes can increase immune reactivity and have antiviral and anti-inflammatory activity. Oligonucleotides without D-mannitol do not have such biological effects.
Methods. Spectroscopy of circular dichroism, absorption spectroscopy, fluorescence spectroscopy.
Results. During the research, we have observed the decrease of fluorescence intensity of the dye water solution with polyribonucleosides. An additional decrease of intensity was observed in complexes with D – mannitol. The maximum effect was obtained for fluorescent sensor solution with polyadenylate and polycytosine. In the cases of polyguanilate and polyuridine minimum changes were observed. The spectral effect may indicate a more intense interaction between polyadenylate and polycytosine with D-mannitol.
Linear absorption was carried out in the temperature range from 25°C to 60°C. We recorded an increase of the magnitude of absorption of the polynucleotides when increasing the temperature in the cases of polyadenylate and polycytosine. The value of the hyperchromic effect is 10% for polyadenylate, and 5% for polycytosine. Additional increase of the amount of hyperchromic effect was recorded in complexes with D¬-mannitol. Circular dichroism spectroscopy has shown spectra with a large difference in the structure of polyadenylate and polycytosine when compared with their complexes with D-mannitol. In the cases of polyguanilate and polyuridine and their complexes with D-mannitol, we observed no change in structure. Based on quantum-chemical calculations, it was established that hydrogen bonds between D-mannitol and polynucleotides can be generated. Also, calculations indicated appreciable changes in charge distribution especially at atoms that can generate hydrogen bonds.
Conclusion. The obtained data allow us to assume the presence of an additional D-mannitol helix in the complexes of polynucleotides with D-mannitol. This assumption is also confirmed by the simulation of this complexes with the help of the program package Gaussian 09. That can explained the wide spectrum of antiviral action of the complexes of polynucleotides and D-mannitol against both single and two-spiral viruses.