Probing telomeric-like G4 structures with full or partial 2'-deoxy-5-hydroxyuridine substitutions.

Guanine quadruplexes (G4s) are stable four-stranded secondary DNA structures held together by noncanonical G-G base tetrads. We synthesised the nucleoside analogue 2'-deoxy-5-hydroxyuridine (H) and inserted its phosphoramidite into telomeric repeat-type model oligonucleotides. Full and partial substitutions were made, replacing all guanines in all the three tetrads of a three-tier G4 structure, or only in the putative upper, central, or lower tetrads.

Improved Metal-Free Approach for the Synthesis of Protected Thiol Containing Thymidine Nucleoside Phosphoramidite and Its Application for the Synthesis of Ligatable Oligonucleotide Conjugates.

Oligonucleotide conjugates are versatile scaffolds that can be applied in DNA-based screening platforms and ligand display or as therapeutics. Several different chemical approaches are available for functionalizing oligonucleotides, which are often carried out on the 5' or 3' end. Modifying oligonucleotides in the middle of the sequence opens the possibility to ligate the conjugates and create DNA strands bearing multiple different ligands.

Analytical and Structural Studies for the Investigation of Oxidative Stress in Guanine Oligonucleotides.

DNA damage plays a decisive role in epigenetic effects. The detection and analysis of DNA damages, like the most common change of guanine (G) to 8-oxo-7,8-dihydroguanine (OG), is a key factor in cancer research. It is especially true for G quadruplex structure (GQ), which is one of the best-known examples of a non-canonical DNA arrangement.

Niosomes decorated with dual ligands targeting brain endothelial transporters increase cargo penetration across the blood-brain barrier.

Nanoparticles targeting transporters of the blood-brain barrier (BBB) are promising candidates to increase the brain penetration of biopharmacons. Solute carriers (SLC) are expressed at high levels in brain endothelial cells and show a specific pattern at the BBB. The aim of our study was to test glutathione and ligands of SLC transporters as single or dual BBB targeting molecules for nanovesicles.

Synthesis and in vitro investigation of potential antiproliferative monosaccharide-d-secoestrone bioconjugates.

The syntheses of monosaccharide-d-secoestrone conjugates are reported. They were prepared from 3-(prop-2-inyloxy)-d-secoestrone alcohol or oxime and monosaccharide azides via Cu(I)-catalyzed azide-alkyne cycloaddition reactions (CuAAC). The antiproliferative activities of the conjugates were investigated in vitro against a panel of human adherent cancer cell lines (HeLa, A2780 and MCF-7) by means of MTT assays.

The evaluation of 5-amino- and 5-hydroxyuracil derivatives as potential quadruplex-forming agents.

5-Substituted uracils (NH or OH groups in position 5) have been examined theoretically and experimentally as potential building blocks in quadruplex structures. Our high level Density Functional Theory (DFT) calculations showed that the tetramer formation and stacking energies for 5-substituted uracils are similar to the energies of purine-based xanthine (X) or guanine (G) structures. As tetrads of 5-substituted uracils cover almost exactly the same area as purine tetrads, mixed tetrads or quadruplex structures based on X or G and 5-substituted uracil motifs are possible.

Synthesis and Biological Evaluation of Triazolyl 13α-Estrone-Nucleoside Bioconjugates.

2'-Deoxynucleoside conjugates of 13α-estrone were synthesized by applying the copper-catalyzed alkyne-azide click reaction (CuAAC). For the introduction of the azido group the 5'-position of the nucleosides and a propargyl ether functional group on the 3-hydroxy group of 13α-estrone were chosen. The best yields were realized in our hands when the 3'-hydroxy groups of the nucleosides were protected by acetyl groups and the 5'-hydroxy groups were modified by the tosyl-azide exchange method.

A three-component reagent system for rapid and mild removal of O-, N- and S-trityl protecting groups.

A new reagent system consisting of a Lewis acid such as BF3·Et2O or Cu(OTf)2, the mild protic acid hexafluoroisopropanol and the reducing quenching agent triethylsilane was elaborated for O-, N- and S-detritylation of nucleoside, carbohydrate and amino acid derivatives. The method is compatible with acetyl, silyl, acetal and Fmoc groups.

Supramolecular H-bonded porous networks at surfaces: exploiting primary and secondary interactions in a bi-component melamine-xanthine system.

The control over the formation of a bi-component porous network was attained by the self-assembly at a solid-liquid interface by exploiting both primary and secondary non-covalent interactions between melamine and N(3)-alkylated xanthine modules.

Supramolecular ring structures of 7-methylguanine: a computational study of its self-assembly and anion binding.

The density functional theory calculations of 7-methylguanine clusters revealed that stable ring assemblies can be formed with or without anions in the center position and hexameric clusters are the most stable and most planar ones. The coordination of anions (Cl⁻, Br⁻, NO₃⁻) stabilizes and thus favors the formation of planar aggregates. We believe that the predicted planar structures stabilized by anions are good models for self-assembly structures formed at solid-liquid or solid-gas interfaces.

Electrospray ionization mass spectrometric analysis of highly reactive glycosyl halides.

Highly reactive glycosyl chlorides and bromides have been analysed by a routine mass spectrometric method using electrospray ionization and lithium salt adduct-forming agents in anhydrous acetonitrile solution, providing salient lithiated molecular ions [M+Li]⁺, [2M+Li]⁺ etc. The role of other adduct-forming salts has also been evaluated. The lithium salt method is useful for accurate mass determination of these highly sensitive compounds.

Streamlined process for the chemical synthesis of RNA using 2'-O-thionocarbamate-protected nucleoside phosphoramidites in the solid phase.

An improved method for the chemical synthesis of RNA was developed utilizing a streamlined method for the preparation of phosphoramidite monomers and a single-step deprotection of the resulting oligoribonucleotide product using 1,2-diamines under anhydrous conditions. The process is compatible with most standard heterobase protection and employs a 2'-O-(1,1-dioxo-1λ(6)-thiomorpholine-4-carbothioate) as a unique 2'-hydroxyl protective group. Using this approach, it was demonstrated that the chemical synthesis of RNA can be as simple and robust as the chemical synthesis of DNA.

Enrichment of O-GlcNAc modified proteins by the periodate oxidation-hydrazide resin capture approach.

A chemical derivatization approach has been developed for the enrichment of O-GlcNAc modified proteins. The procedure is based on the isolation technique used for N-glycoproteins with appropriate modifications because of the differences in the two types of glycosylation: a prolonged periodate oxidation is followed by hydrazide resin capture, on-resin proteolytic digestion, and release of the modified peptides by hydroxylamine. This enrichment strategy offers a fringe benefit in mass spectrometry analysis.

An electrospray mass spectrometric method for accurate mass determination of highly acid-sensitive phosphoramidites.

An accurate mass determination method utilizing electrospray ionization mass spectrometry is described for analysis of several different types of phosphoramidites that are extremely acid-sensitive compounds. An earlier method, which applied a LiCl/acetonitrile system, was extended for this special application by using polymeric standards including poly(ethylene glycol) (PEG), poly(ethylene glycol) dimethyl ether (PDE) and poly(propylene glycol) (PPG). Concentrations of standards, samples and LiCl were optimized and potential impurities that affect the analyses were also investigated.

Cleavage of the human thyrotropin receptor by ADAM10 is regulated by thyrotropin.

The thyrotropin receptor (TSHR) has a unique 50 residue (317-366) ectodomain insertion that sets it apart from other glycoprotein hormone receptors (GPHRs). Other ancient members of the leucine-rich repeat G protein-coupled receptor (GPCR) (LGR) family do exhibit ectodomain insertions of variable lengths and sequences. The TSHR-specific insert is digested, apparently spontaneously, to release the ectodomain (A-subunit) leaving the balance of the ectodomain attached to the serpentine (B-subunit).