Fermi Resonance of Infrared Vibrations in the —NH₂ Groups of Polynucleotides

Abstract

The —NH2 group causes an intensive band pair in the i.r. spectra of DNA, r.RNA, poly (A + U), and poly (G + C). One band occurs at 3330, another at 3180 cm−1. This band pair is due to the NH stretching vibration of the hydrogen-bonded NH group as well as to the harmonic vibration of the —NH2 bending vibration, whereby these vibrations are coupled via Fermi resonance. This follows on comparison with papers on amines. The weak shoulder in the 3500–3400 cm−1 range is to be assigned to the stretching vibrations of the non hydrogen-bonded NH groups. The doublet structure disappears to a large extent in the denaturated DNA, since the strength of the Fermi resonance depends on the strength of the hydrogen bonds and the hydrogen bonds are of differing strength, due to the bending and stretching. The relative intensities of the two bands are interchanged in the corresponding band pair of the —ND2 groups, for which an explanation can also be given.

Vibrational Predissociation Spectroscopy of Cold Protonated Tryptophan with Different Messenger Tags

“…This was also seen, although less strongly, by Pereverzev et al In the Innsbruck spectrum in Figure b, it is not evident. This feature may possibly be a Fermi resonance of an overtone of the amino umbrella with an NH stretch fundamental in analogy to the NH 2 groups in neutral DNA …”

“…This feature may possibly be a Fermi resonance of an overtone of the amino umbrella with an NH stretch fundamental in analogy to the NH 2 groups in neutral DNA. 51 4.B. Conformer-Resolved Hole Burning Spectra.…”

Programming a Gold Nanocrystal to Recognize and Selectively Bind a Molecular Substrate in Solution

“…The band at 3391 cm -1 is assigned to the imidic N−H stretch of the uracil moiety in II . ,,,, The band at 3423 cm -1 is assigned to the amidic N−H stretch of the diaminopyridine moiety in III . ,,,, As established above, II and III form a triply hydrogen bonded 1:1 complex in solution. Accordingly, upon complexation, the bands assigned to the imidic and amidic N−H stretching modes of II and III , respectively, are reduced in intensity, ,,,− while a series of bands newly observed at lower frequencies (3278 and 3212 cm -1 ) are assigned to the N−H stretches of the hydrogen bonded protons in ( II + III ). ,,,− …”

Experimental and theoretical evidence of dihydrogen bonds in lithium amidoborane

“…This corresponds to the broad shape of unassigned spectral feature detected in the region of N-H symmetric stretching. In case of hydrogen bonding the frequency might shift somewhat towards higher energy region 34 . The strength of the Fermi resonance depends on the strength of the hydrogen bonds 35 .…”