Backbone inclination is a parameter which can be used for the classification of the structure type of oligonucleotide duplexes. Its significance for the interpretation of the sequence dependence of duplex stability is illustrated based on examples of the p-RNA and homo-DNA series.

[formula: see text] The L-alpha-lyxopyranosyl (4'-->3') oligonucleotide system shows cooperative base-pairing in spite of containing only five instead of the usual six covalent bonds per repetitive backbone unit. In contrast, corresponding D-beta-ribofuranosyl (4'-->3') oligonucleotides do not show adenine-thymine pairing under comparable conditions. The difference in pairing behavior relates to the conformation of the two systems' vicinal 3',4'-phosphodiester substituents, which is diaxial in the lyxopyranosyl system and 3'-axial-4'-equatorial in the ribopyranosyl system.

Edgar Heilbronner zum 80. Geburtstag gewidmet, in Erinnerung an die guten alten ZeitenTo determine whether the remarkable chemical properties of the pyranosyl isomer of RNA as an informational Watson-Crick base-pairing system are unique to the pentopyranosyl-(4' 3 2')-oligonucleotide isomer derived from the RNA-building block d-ribose, studies on the entire family of diastereoisomeric pyranosyl-(4' 3 2')-oligonucleotide systems deriving from d-ribose, l-lyxose, d-xylose, and l-arabinose were carried out. The result of these extended studies is unambiguous: not only pyranosyl-RNA, but all members of the pentopyranosyl-(4' 3 2')-oligonucleotide family are highly efficient Watson-Crick base-pairing systems. Their synthesis and pairing properties will be described in a series of publications in this journal. The present paper describes the a-l-lyxopyranosyl-(4' 3 2')-system.

Die Rückgratneigung ist ein Parameter, der zur Klassifizierung des Strukturtyps von Oligonucleotid‐Duplexen dienen kann. Anhand von Beispielen der p‐RNA‐ und der Homo‐DNA‐Reihe wird seine Bedeutung für die Interpretation der Sequenzabhängigkeit von Duplexstabilitäten illustriert.

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