title: Oligonucleotides forming an i-motif: the pH-dependent assembly of individual strands and branched structures containing 2'-deoxy-5-propynylcytidine.
abstract: Non-branched and branched oligonucleotides incorporating consecutive runs of 2'-deoxy-5-propynylcytidine residues () instead of 2'-deoxycytidine () were synthesized. For this, phosphoramidite building blocks of 2'-deoxy-5-propynylcytidine () were prepared using acetyl, benzoyl or N,N-di-n-butylaminomethylidene protecting groups. The formation of the i-motif assemblies incorporating 2'-deoxy-5-propynylcytidine residues was confirmed by temperature-dependent CD- and UV-spectra as well as by ion-exchange chromatography. The low pK(a)-value of nucleoside (pK(a) = 3.3) compared to dC (pK(a) = 4.5) required strong acidic conditions for i-motif formation. Branched oligonucleotide residues with strands in a parallel orientation lead to a strong stabilization of the i-motif allowing aggregation even at non-optimal pH conditions (pH = 5). The immobilization of oligonucleotides incorporating multiple residues of on 15 nm gold nanoparticles generated DNA-gold nanoparticle conjugates which are able to aggregate into i-motif structures at pH 5.
authors.affiliation: Laboratory of Bioorganic Chemistry and Chemical Biology, Center for Nanotechnology, Münster, Germany. Frank.Seela@uni-osnabrueck.de
authors.forename: Frank
authors.initials: F
authors.lastname: Seela
authors.forename: Simone
authors.initials: S
authors.lastname: Budow
authors.forename: Peter
authors.initials: P
authors.lastname: Leonard
mesh_terms: D020816:Amino Acid Motifs; D004277:DNA, Single-Stranded / Q000737:chemistry*; D003841:Deoxycytidine / Q000031:analogs & derivatives* / Q000737:chemistry; D006046:Gold / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D053758:Nanoparticles / Q000737:chemistry*; D019906:Nuclear Magnetic Resonance, Biomolecular; D009690:Nucleic Acid Conformation; D009841:Oligonucleotides / Q000138:chemical synthesis* / Q000737:chemistry*
chemical_list: C518429:2'-deoxy-5-propynylcytidine; D004277:DNA, Single-Stranded; D009841:Oligonucleotides; D003841:Deoxycytidine; D006046:Gold