Structure-based design of a highly constrained nucleic acid analogue: improved duplex stabilization by restricting sugar pucker and torsion angle γ

Dual conformational restriction: a new, highly constrained modification of the α-L-locked nucleic acid (α-L-LNA) scaffold that locks the sugar furanose ring in an N-type configuration and also restricts rotation around torsion angle γ was synthesized. This new modification increases the thermostability of an oligonucleotide duplex compared to using a single mode of constraint alone.

Thermodynamic analysis of nylon nucleic acids

The stability and structure of nylon nucleic acid duplexes with complementary DNA and RNA strands was examined. Thermal denaturing studies of a series of oligonucleotides that contained nylon nucleic acids (1-5 amide linkages) revealed that the amide linkage significantly enhanced the binding affinity of nylon nucleic acids towards both complementary DNA (up to 26 degrees C increase in the thermal transition temperature (T(m)) for five linkages) and RNA (around 15 degrees C increase in T(m) for five linkages) compared with nonamide linked precursor strands. For both DNA and RNA complements, increasing derivatization decreased the melting temperatures of uncoupled molecules relative to unmodified strands; by contrast, increasing lengths of coupled copolymer raised T(m) from less to slightly greater than T(m) of unmodified strands. Thermodynamic data extracted from melting curves and CD spectra of nylon nucleic acid duplexes were consistent with loss of stability due to incorporation of pendent groups on the 2'-position of ribose and recovery of stability upon linkage of the side chains.