ATR-FTIR spectra of both ASC and PSC from the skin of striped
catfish are depicted in the Fig. 3. FTIR spectra for both ASC and
PSC were similar to those of collagens from other fish species
(Muyonga et al., 2004). The amide A band of ASC and PSC was
found at a wavenumber of 3321 cm1. According to Doyle, Bendit,
and Blout (1975), a free N–H stretching vibration occurs in the
range of 3400–3440 cm1 and when the NH group of a peptide is
involved in a hydrogen bond, the position is shifted to lower frequencies,
usually around 3300 cm1.