Shigesada Higuchi

Self-complementary tetradeoxyribonucleoside triphosphates: convenient chemical preparation and spectroscopic studies in solution

Abstract Eight kinds of self-complementary tetradeoxyribonucleoside triphosphates were prepared by a simplified method which enabled us to omit purification of synthetic intermediates and provided the tetramers very rapidly and conveniently. The tetramers were characterized by enzyme assay and their conformations were studied by the use of UV and CD spectroscopic methods under various conditions. The detailed analysis of the CD spectra suggested that conformation of the tetramer duplexes was dependent on the sequence.

A New Synthesis of Hydrangenol1)

Abstract As a phenolic component in Hydrangea opulaides Stend var Otakusa Maxim, hydrangenol (I) was isolated2) and identified by Asahina and Asano.3)

Interactions of poly-N6-methyladenylic Acid and N6-substituted-9-methyladenines with poly-5-bromouridylic Acid: A Novel Base-pairing

The interaction of poly-N6-methyladenylic acid (poly(m6A) with poly-5-bromouridylic acid (poly(BU) was studied by the mixing curve method. A.1 m6A: 2 BU stoichiometry was clearly indicated over a wide range of ionic strengths at neutral pH, while the binding of poly(m6A) to poly(U) is known to occur with 1 m6A:1 U. Digestion by nuclease S1 confirmed this stoichiometry, indicating the absence of single strands in a 1:2 mixture. Heating profile analysis and hydroxyapatite column chromatography provided further confirmation of this finding. To determine whether 1:2 stoichiometry holds in a monomer-polymer system, the interaction of N6-methyl-9-methyladenine (m6m9A), a corresponding monomer of poly(m6A), with poly(BU) was investigated. Equilibrium dialysis experiments showed the stoichiometry of the interaction to be 1 m6A:2 BU. Thus, we would describe some structural studies of the above complexes using c.d. and i.r. spectroscopy. Poly (m6A).2poly(BU) and m6m9A.2poly(BU) are helical and analogous to each other in structure, and the bases in the complexes are all bound by hydrogen-bonding. N6-(delta 2-isopentenyl)- and N6-allyl-9-methyladenine were also found to form complexes with poly(BU), giving similar c.d. spectra with that of m6m9A.2poly(BU). The melting experiments indicated the Tms to be substantially decreased, compared to the parent unmodified complexes, even though the Tm dependence of the polymer complex on salt concentration conforms to the typical triple strand. In the following, the biological significance of this novel pairing will be discussed.