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The vibrational spectra and structure of poly (rA‐rU). Poly (rA‐rU)
Author(s) -
Morikawa Kosuke,
Tsuboi Masamichi,
Takahashi Seizo,
Kyogoku Yoshimasa,
Mitsui Yukio,
Iitaka Yoichi,
Thomas George J.
Publication year - 1973
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1973.360120409
Subject(s) - raman spectroscopy , chemistry , infrared spectroscopy , crystallography , copolymer , infrared , titration , organic chemistry , polymer , physics , optics
Infrared and Raman spectra of aqueous poly(rA‐rU)·poly(rA‐rU), the double‐helical complex containing strands of alternating riboadenylate and ribouridylate residues, display significant differences from one another and from corresponding spectra of poly(rA)·poly(rU), the double‐helical complex of riboadenylate and ribouridylate homopolymers. Parallel studies on the copolymer and homopolymer complexes by cesium sulfate density gradient centrifugation, ultraviolet absorption spectroscopy, hydrogenion titration, 1‐N oxidation of adenine residues by monoperphthalic acid and X‐ray diffraction reveal, however, that the geometry of base pairing between adenine and uracil is closely similar in each complex and apparently of the Watson‐Crick type. Therefore the differences observed between vibrational spectra of poly (rA‐rU)·poly (rA‐rU) and poly(rA)·poly(rU) are not due to different base‐pairing schemes but may be attributed to differences in vibrational coupling between vertically stacked bases. Vibrational coupling may also account for the differences between infrared and Raman spectra of the same complex. Thus, the present results indicate that infrared and Raman frequencies of RNA in the region 1750–1550 cm −1 should be dependent on the base sequence.