Dinucleoside polyphosphates, or dinucleotides (Np_nN′; N, N′ = A, U, G, C; n = 2–7), are naturally occurring ubiquitous physiologically active compounds. Despite the interest in dinucleotides, and the relevance of their conformation to their biological function, the conformation of dinucleotides has been insufficiently studied. Therefore, here we performed conformational analysis of a series of Np_nN′ Na⁺ salts (N = A, G, U, C; N′ = A, G, U, C; n = 2–5) by various NMR techniques. All studied dinucleotides, except for Up_4/5U, formed intramolecular base stacking interactions in aqueous solutions as indicated by NMR. The conformation around the glycosidic angle in Np_nN′s was found to be anti/high anti and the preferred conformation around the C4′–C5′, C5′–O5′ bonds was found to be gauche–gauche (gg). The ribose moiety in Np_nN′s showed a small preference for the S conformation, but when attached to cytosine the ribose ring preferred the N conformation. However, no predominant conformation was observed for the ribose moiety in any of the dinucleotides. Molecular dynamics simulations of Ap₂A and Ap₄A Na⁺ salts supported the experimental results. In addition, three modes of base-stacking were found for Ap_2/4A: α–α, β–β and α–β, which exist in equilibrium, while none is dominant. We conclude that natural, free Np_nN′s (n = 2–5) at physiological pH exist mostly in a folded (stacked), rather than extended conformation, in several interconverting stacking modes. Intramolecular base stacking of Np_nN′s does not alter the conformation of each of the nucleotide moieties, which remains the same as that of the mononucleotides in solution.

Alzheimer’s disease (AD) is a complex and widespread condition, still not fully understood and with no cure yet. Amyloid beta (Aβ) peptide is suspected to be a major cause of AD, and therefore, simultaneously blocking its formation and aggregation by inhibition of the enzymes BACE-1 (β-secretase) and AChE (acetylcholinesterase) by a single inhibitor may be an effective therapeutic approach, as compared to blocking one of these targets or by combining two drugs, one for each of these targets. We used our ISE algorithm to model each of the AChE peripheral site inhibitors and BACE-1 inhibitors, on the basis of published data, and constructed classification models for each. Subsequently, we screened large molecular databases with both models. Top scored molecules were docked into AChE and BACE-1 crystal structures, and 36 Molecules with the best weighted scores (based on ISE indexes and docking results) were sent for inhibition studies on the two enzymes. Two of them inhibited both AChE (IC₅₀ between 4–7 μM) and BACE-1 (IC₅₀ between 50–65 μM). Two additional molecules inhibited only AChE, and another two molecules inhibited only BACE-1. Preliminary testing of inhibition by F681-0222 (molecule 2) on APPswe/PS1dE9 transgenic mice shows a reduction in brain tissue of soluble Aβ42.

Infectious diseases are still a major problem worldwide. This includes microbial infections, with a constant increase in resistance to the current anti-infectives employed. Toll-like receptors (TLRs) perform a fundamental role in pathogen recognition and activation of the innate immune response. Promising new approaches to combat infections and inflammatory diseases involve modulation of the host immune system via TLR4. TLR4 and its co-receptors MD2 and CD14 are required for immune response to fungal and bacterial infection by recognition of microbial cell wall components, making it a prime target for drug development. To evaluate the efficacy of anti-infective compounds early on, we have developed a series of human-based immune responsive infection models, including immune responsive 3D-skin infection models for modeling fungal infections. By using computational methods: pharmacophore modeling and molecular docking, we identified a set of 46 potential modulators of TLR4, which were screened in several tests systems of increasing complexity, including immune responsive 3D-skin infection models. We could show a strong suppression of cytokine and chemokine response induced by lipopolysacharide (LPS) and Candida albicans for individual compounds. The development of human-based immune responsive assays provides a more accurate and reliable basis for development of new anti-inflammatory or immune-modulating drugs.