ABSTRACT
N stretch combination bands. See Chapter 8 for a more complete description of amide bands.
Hermans and Scheraga
made measurements of the backbone peptide hydrogen bond system (NH group) using NIR measurements in the extended spectral region from 14,286 to 2,857 cm
(700-3500 nm). The authors describe the use of NIR to distinguish between hydrogen-bonded and non-hydrogen-bonded N
ˇ
H and O
ˇ
H groups. Molecules examined include methanol, aniline, and poly-
γ
-benzyl-
-glutamate. Elliott and Ambrose
identified absorption bands for polypeptides and proteins at approximately 3505 cm
(2853 nm) as N
ˇ
H-associated stretching bands and at 4825 cm
(2073 nm) in the overtone region. The main result of their work was to demonstrate that a band at 4840 cm
(2066 nm) is useful for distinguishing the presence of extended vs. folded configurations for polypeptides and proteins even in the presence of liquid-phase water. The band near 4824 cm
(2073 nm) was classified earlier by Glatt and Ellis
on work in nylon as a combination band of the N
ˇ
H deformation and stretching modes.
