[Effect of temperature on the secondary structure of fish scale collagen]

Pepsin-soluble collagen (PSC) was extracted from fish scale of grass carp and was analyzed by SDS-PAGE, which confirmed that PSC are typical type I collagen and reach electrophoretic purity. Effect of temperature on the secondary structure of collagen was studied by FTIR, Raman and CD. FTIR indicated that the fish scale PSC had typically characteristic absorptions of collagen, and 1659, 1552 and 1238 cm(-1) were assigned to be amide I, II and III respectively. When the temperature increased, amide A and amide B shifted to low frequency, the absorption of 1658 cm(-1) split into several absorption peaks, the absorption at 1552 cm(-1) had a slight red-shift followed by a distinct blue-shift, and the frequency of 1238 cm(-1) declined. Raman spectra showed that the absorptions of amide I, amide II and amide III appeared at 1669, 1557 and 1245 cm(-1) respectively, which were higher than those in FTIR spectra. Furthermore, the characteristic absorptions of proline at 921 and 855 cm(-1) only appeared in Raman spectra. CD spectra demonstrated a rotatory maximum at 221.6 nm and a negative peak at 204.4 nm of PSC solution, which were typical spectral characteristics of the collagen triple helix structure. The structure changes of the lyophilized PSC appeared mainly between 35 and 60 degrees C in FTIR and Raman spectra, yet CD spectra demonstrated that the configurational changes of PSC in acidic solution appeared in the range of 20 to 35 degrees C, indicating that the lyophilized PSC was more stable than the acidic solution of PSC.