Helical polynucleotides

The above potential energy approach of building double helical polynucleotides is illustrated below for some hypothetical B-family poly(dA) poly(dT) chains. For simplicity, the helices are generated as a function of the phosphodiester angles < and u> only. 

Usually the asymmetric unit of a helical polynucleotide chain is effectively one nucleotide residue. To date, over two dozen nucleic acid structures of this kind—both native and synthetic and of varying base composition and sequence have been defined accurately and in most cases refined extensively. 

The existence of base stacking interaction for poly-VUr was also suggested from UV spectra25). At pH 12, the value of hypochromicity for poly-VUr was 29 to 51 % as compared to 1-ethyluradl. For poly-U solution, the value is only a few percent at room temperature while at lower temperature, about 30% of hypochromicity is observed which is attributed to the formation of a stacked helical polynucleotide structure. It seems therefore likely that the high value of hypochromicity observed for poly-VUr solution may be due to base stacking interactions. 

Two helical polynucleotide chains are coiled around a common axis. The chains run in opposite directions. 

Procedures for preparation of the immunizing antigen, injection schedules, and assays for antibody formation are similar to those used for helical polynucleotide-MBSA antigens and are discussed in detail in the following section and in Vol. 12B [174] of this series. 

Antibodies specific for triple-helical polynucleotides clearly distin-... 

The strong interactions between certain bivalent cations and the highly ordered polynucleotides such as DNA, certain synthetic duplex homo- and heteropolymers, and s-RNA have been the subject of much current interest. With this idea in mind, it is interesting to note that the steroidal diamine cyclobuxine-D (242) was shown to exert a profound effect on the stability of helical polynucleotides (DNA, s-RNA, and dAT dAT). The effect is biphasic in the sense that at low concentrations of the agent there is stabilisation of the native conformation, while at higher concentrations there is stabilisation of the denatured conformation. 

Structure and Thermodynamic Properties of Single-Strand Helical Polynucleotides... 

A few helical polynucleotide structures containing interstrand metal cross-links in place of hydrogen bonds between natural bases have been described. The... 

A Double Helical Polynucleotide Stabilized by three interbase Hydrogen Bonds... 

When two nucleic acid strands have complementary nucleic acid sequence, they can undergo hybridization to form double-stranded duplex structures. DNA forms a double-stranded helix composed of two complementary helical polynucleotide chains, aligned antiparallel, which are coiled around a common axis. In helix form, the anionic backbone lies on the outside of the structure with the nucleobases in the core, perpendicular to the axis and separated by a distance of 3.4 A. This B-form helix (Figure 2a) has a right-handed coil that repeats itself every 34 A with a turn every... 

B. D. Stollar Double-helical polynucleotides immunochemical recognition... 

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