Modified oligonucleotides containing lithocholic acid in their backbones: their enhanced cellular uptake and their mimicking of hairpin structures

Their enhanced cell permeability and their ability to mimic DNA structures make modified oligodeoxyribonucleotides (ODNs) very important substances for increasing our understanding of cell biology and for therapeutic applications. Lithocholic acid is a hydrophobic secondary bile acid that is a substrate of nuclear Pregnane X receptor (PXR). We designed and synthesized novel lithocholic acid-based ODNs (L-ODNs) by using a new phosphoramidite derived from lithocholic acid. By comparing data obtained from circular-dichroism, melting-point, and theoretical studies, we believe that these L-ODNs adopt DNA hairpin structures. Furthermore, L-ODNs have enhanced cellular uptake properties with respect to regular ODNs. To demonstrate their enhanced cell permeabilities, we carried out cellular uptake experiments of L-ODNs in HeLa cells. By attaching fluorescein as a fluorescence label and using confocal microscopy, we observed that the permeability of L-ODNs is much higher than that of natural ODNs.     

Label-free detection of antibody-antigen interactions on (R)-lipo-diaza-18-crown-6 self-assembled monolayer modified gold electrodes

Novel (R)-diaza-18-crown-6 has been prepared by a simple two-step synthetic method and characterized for its ability to form a uniform self-assembled monolayer (SAM) on gold as well as to immobilize proteins using atomic force microscopy, quartz crystal microbalance, and electrochemical impedance spectroscopy (EIS) experiments. The (R)-lipo-diaza-18-crown-6 was shown to form a well-defined SAM on gold, which subsequently captures the antibody (Ab) molecules that in turn capture the antigen (Ag) molecules. The Ab molecules studied include antibody C-reactive protein (Ab-CRP) and antibody ferritin (Ab-ferritin) along with their Ag's, i.e., CRP and ferritin. Quantitative detection of the Ab-Ag interactions was accomplished by EIS experiments with a Fe(CN)6(3-/4-) redox probe present. The ratios of the charge-transfer resistances for the redox probe on the SAM-antibody-covered electrode to those with the antigen molecules attached show an excellent linearity for log[Ag] with lower detection limits than those of other SAMs for the electrochemical sensing of proteins.     

Nucleoside-based phospholipids and their liposomes formed in water

Phospholipids and liposomes have been the subjects of considerable attention because of their importance in biological systems. We have efficiently synthesized novel nucleoside-based phospholipids in six-step sequences starting from their corresponding nucleosides. These nucleoside-based phospholipids self-assemble into liposome-like structures in aqueous solutions. We have analyzed the structures of these liposomes by dynamic light scattering, transmission electron microscopy, and confocal microscopy.