The (R-X-R) motif-containing arginine-rich peptides are among the most effective cell-penetrating peptides. The replacement of amide linkages in the (R-X-R) motif by carbamate linkages as in (r-ahx-r)(4) or (r-ahx-r-r-apr-r)(2) increases the efficacy of such oligomers several-fold. Internalization of these oligomers in mammalian cell lines occurs by an energy-independent process. These oligomers show efficient delivery of biologically active plasmid DNA into CHO-K1 cells.

The regioisomeric 3'-deoxy-2'-5'-linked thrombin binding DNA aptamers (isoTBAs) were chemically synthesized and their ability to form unimolecular anti-parallel G-quadruplexes in the presence of K(+) ions was evaluated. These modified sequences retain the function of the native thrombin binding aptamer (TBA), exhibit better stability against exonuclease and are capable of slowing down the process of blood clotting.

The fluorescently labelled short octameric oligothymine sequences of DNA, PNA and PCNA were used in fluorescence quenching studies in conjunction with dispersed graphene oxide. The measurable restoration of their fluorescence by complementary oligodeoxyadenylate was compared. This is the first study aimed at replacing the natural DNA probes with synthetic DNA mimics that show excellent properties in terms of formation of very strong duplexes with cDNA in addition to their stability towards proteases and nucleases.

The synthesis of 4′-methoxymethyl threofuranosyl (4′-MOM-TNA) thymidine and derived oligomers of the G-rich thrombin-binding aptameric (TBA) sequence is reported. The G-quadruplex stability, anticoagulation activity, and the enzymatic stability of these oligomers bearing the 2′-3′-phosphodiester backbone as single substitutions in the loop regions are studied. Amongst all the oligomers, TBA-7T bearing the 4′-MOM-TNA unit at the T7 position formed a quadruplex with the highest thermal stability. It also resulted in enhanced anticlotting activity that allowed a one-third reduction in the dose, relative to TBA. Further, TBA-7T exhibited enhanced nuclease resistance properties to both endo- and exonucleases.