The biological activity of oligoribonucleotide (ORN) based drugs studied very actively at the same time. However, at the same time, it is of great importance to study their biophysical particularly spectral properties.As the samples, we worked with the "Nuclex", pharmaceutical drugs that are based on a combination of ORN and alcohol sugar D-mannitol (D-M), and the main components of these drugs (active substance -ORN and excipient -D-M). We have measured the UV-Vis absorption, fluorescence, and fluorescence excitation spectra of drugs and their components dissolved in the water under the room temperatures.In the course of our research, we found the autofluorescence centers of Nuklex and identified the possibility of forming complexes between ORN and D-M.

(1) Background: It is known that RNA in Na+ salt form has only immunomodulatory activity, and in acid form additionally acquires anti-inflammatory activity and in combination with D-mannitol acquires an even broader antiviral effect. The study aimed to study the ability of adenosinmonophosphat (AMP) and oligoribonucleotides (ORNs) in acid and salt form and in combination with D-mannitol to affect the conformation and fluorescence of interferon (INF) α-2b and to determine the energy parameters of these interactions. (2) Methods: spectroscopy (time pulsed and fluorescence), isothermal nanocalorimetry. (3) Results: AMP and ORNs in acid form and complex with D-mannitol bind more strongly to interferon α-2b than salt analogues. In the interaction of interferon α-2b and acid AMP and especially in complex with D-mannitol, the reaction occurs exothermically and change in conformational mobility INF by increasing the content of disordered regions. When INF α-2b interacts with salt AMP, the reaction occurs endothermically, and probably the salt form increases the conformational stiffness of INF α-2b. The greater efficiency of nonradiative energy transfer from INF α-2b to acid AMP has been shown, due to the closer distance between molecules. (4) Conclusions: AMP in acid form interacts more actively and increases the conformational mobility of INF, at a greater relative distance and with less Gibbs energy compared to the salt form, which probably causes the appearance of additional biological properties of acidic AMP.

Adenosine 5′-monophosphate monohydrate (AMP) Adenosine 5′-monophosphate disodium salt (AMPNa)

Oligonucleotides antiviral drugs have actively used in medicine, but the molecular mechanism of their action remains unclear. We studied the conformation changes of IFN with ligands, the quenching and lifetime of fluorescence, and isothermal titration calorimetry (ITC). The most active quenching and decrease lifetime of fluorescence INF, when titrated with NMPs and ORNs, was obtained using acid forms in combination with mannitol. And when titrated INF saline forms slightly different from control. Spectra of circular dichroism show the decrease in the structure of the number of secondary elements when interacting between INF and acidic forms nucleotides. An increase in the content of secondary structure in the interaction between INF and salt forms ligands. The ITC curves titration indicate that the reaction between protein and acidic ligands is exothermic. And between INF with saline ligands endothermically. Exothermic protein-ligand interaction increases the conformational mobility of the protein and endothermic decrease. The ORNs have the advantage of interacting with proteins, unlike salt ORNs and NMPs, because they have a stronger binding. Thus, we assume the same compound in various forms may act as an inhibitor and activator for the protein.