Table 3. The major peaks, functional group, and wavenumber (cm⁻¹) in the FT-IR spectra for collagen isolated from four species of mantis shrimp

Wavenumber (cm−1)	Functional group	Mantis shrimp species
3,400–3,440	N–H stretching vibrations (amide A)	3,406–3,421
2,840–3,000	C–H stretching (amide B-alkane)	2,916–2,940
2,349	O=C=O stretching (carbon dioxide)	2,334–2,361
1,600–1,660	Associate with stretching vibrations of carbonyl group in peptides (amide I)	1,639–1,640
~1,550	Associate with NH bonding and CN stretching (amide II)	1,539–1,570
1,330–1,420	O-H bending (alcohol)	1,396–1,460
1,220–1,320	CN stretching and NH and it is involved with the triple helical structure of collagen (amide III)	1,234–1,250
1,000–1,300	C-O stretching (ester and ether)	1,076–1,084
600–800	C-Cl (chloride compound)	609–625

FT-IR, Fourier transform-infrared.