Base pairing, in nucleic acids

The point arose as to the actual site of action of moniliformin in plants. Earlier, it had been stated that the geometrical criteria of hydrogen bond formation suggested that MH could be regarded as either a purine or pyrimidine analogue and, therefore, could substitute as one of the base pairs in nucleic acid.11 And the fact that it had shown plant growth regulatory activity had led an industrial company to become interested in the product as a potential herbicide. 

FIGURE 12.42. Base pairs in nucleic acids, (a) Numbering of nucleic-acid bases. 

FIGURE 12.42 (cont d). (b) Arrangement of atoms in base pairs in nucleic acids. 

Displacement A conformational description of base pairs in nucleic acids. An axis of reference is taken as the line joining C6 of a pyrimidine and C8 of a purine. The displacement is the perpendicular deviation of this axis from the helix axis of the nucleic acid. 

Imino IH NMR. Imino NMR spectroscopy is a powerful direct probe for the presence and nature of the base pairing in nucleic acids. As shown in Figure 6, the imino spectra for the control and the four stable a-containing duplexes exhibit resonances for the five chemically distinct imino protons in each self-complementary decamer, indicative of stable base pair formation. In addition, temperature dependent experiments showed no evidence for pre-melting of the base pairs comprising the a-nucleotides. Virtually identical NMR spectra have been obtained for the a-duplexes at optical concentrations (3 to 6 pM duplex), demonstrating that the duplex form exists under the conditions used in the thermodynamic studies. 

An understanding of the kinetics of formation of molecular complexes held together by hydrogen bonds gives insight into the formation of base pairs in nucleic acids. Use the data provided below... 

B. Base Pairing in Nucleic Acids Double Helical Structure of DNA... 

Metal-Mediated Base Pairs in Nucleic Acids with Purine-and Pyrimidine-Derived Nucleosides... 

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