Affinity of the duplex was calculated to be 54?nM in phosphate buffered saline (PBS) supplemented with 4% human serum at 37C. using RNA analogs are being used, which take advantage of natural self-assembly of oligonucleotide for crosslinking (Bos et al., 1994). Exploiting naturally occurring RNACRNA hybridization to design a pretargeting system is attractive, but poor nuclease stability in plasma and a requirement for long TPOP146 oligomers (18C20 in length) limits its application in a clinical setting. However, recent advances in the design and the synthesis of unnatural RNA/DNA analogues with superior biochemical properties have allowed the TPOP146 application of oligonucleotides such as phosphothioate DNA (PS) oligomers (Villa et al., 2008), peptide nucleic acid (PNA) oligomers (Rusckowski et al., 1997) and morpholino (MORFs) oligomers (Liu et al., 2002b) as pretargeting molecules. Nevertheless, PS oligomers show substantial nonspecific interactions with serum proteins, and PNA oligomers are also known to have poor aqueous solubility. MORFs show greater aqueous solubility; however, affinity is not substantially improved compared to their natural analogues. Thus, the design of MORFs is restricted to 22-mers or more. Longer oligomer strands show higher degree of inter- or intra-annealing. Alternatively, oligomers based on locked nucleic acid (LNA) have been shown to be effective in shorter lengths compared to other counterparts. These oligomers are widely being used in antisense technology, DNAzymes, and decoy oligonucleotides and show a great potential to be used in pretargeting systems (Kaur et al., 2007; Moschos et al., 2011). LNA inherently shows excellent thermal stability, affinity, nuclease stability, and mismatch discrimination when hybridized with RNA or DNA. Similarly, 2OMe RNA based oligonucleotides exhibit improved properties such as efficient hybridization, specificity and resistance to nuclease degradation, chemical stability, convenient synthesis, and minimal nonspecific interactions with nucleic acid binding proteins (Beijer et al., 1990; Iribarren et al., 1990; Lamond et al., 1990). Most of the new altered oligos used in this study were designed with modifications of 2-oxygen moieties of the sugar backbone; these modifications improved the biochemical compatibility without compromising solubility and unique features of self-assembly. Taking advantage of these unique properties, here we introduce a novel pretargetable cross-linking oligonucleotide system comprised of LNA and 2OMe-RNA. Due to excellent thermodynamic properties exhibited by LNA, this novel duplex contains only 7 bases compared to 20 bases for morpholinos. The duplex shows fast hybridization, high melting temperatures, excellent affinity, and high nuclease stability in human plasma. Rapid whole body clearance was observed detection assays, (2) an internal amine moiety for the conjugation of chelating brokers/drugs, (3) TPOP146 an LNA base platform, (4) a PEG unit for further nuclease stabilization, and (5) a disulfide moiety for conjugation of multifunctional groups. (B) Schematic representation of oligo-F1. The oligo is usually comprised of (1) an aldehyde group to conjugated to an TPOP146 antibody, (2) PEG units as a flexible linker between c-oligo and antibody, (3) a 2O-Methyloligoribonucleotide (2OMe) RNA base platform, and (4) a fluorescein for detection assays. R-oligo design is the same as the oligo-F1, except the platform sequence is comprised of c-oligo LNA bases. Cy5, cyanine 5; F1, fluorescein; LNA, TPOP146 locked nucleic CEACAM6 acids; PEG, polyethylene glycol. Controlled-pore glass columns with fluorescein were used for 3 fluorescein (fluorophore) modifications. For 5 modifications in dabsyl (quencher)-made up of sequences, dabsyl-dT, 5-dimethoxytrityloxy-5-[(N-4-carboxy-4-(dimethylamino)-azobenzene)-aminohexyl-3-acrylimido]-2-deoxyuridine-3-[(2-cyanoethyl)-(N,N-diisopropyl)]-phosphoramidite, was used. Oligo-fluorescein (F1)-CHO, c-oligo-Cy5-NH2, and r-oligo-Cy5-CHO were designed for both and experiments involving rituximab oligonucleotide conjugates. An aldehyde moiety was incorporated using 2-[4-(5,5-diethyl-1,3-dioxan-2-yl)phenoxy]ethan-1-yl-[(2-cyanoethyl)-(N,N-diisopropyl)]-phosphoramidite in olgio-F1-CHO to conjugate to the rituximab using hydrazine-aldehyde chemistry. For c-oligo-Cy5-NH2, a 5-dimethoxytrityl-5-[N-(trifluoroacetylaminohexyl)-3-acrylimido]-2-deoxyuridine-3-[(2-cyanoethyl)-(N,N-diisopropyl)]-phosphoramidite was introduced as an internal amine-dT to conjugate chelating brokers, and 1-O-dimethoxytrityl-propyl-disulfide,-1-succinyl-lcaa-CpG was.