Effect of cyanide concentrations on the secondary structures of protein in the crude homogenates of the fish gill tissue.

The effect of cyanide concentrations on the secondary conformation of protein in the fish gill homogenate was determined using an attenuated total reflectance (ATR)/Fourier transform infrared (FT-IR) microspectroscopy. Gills from male Tilapia zillii were isolated and homogenized in pH 8.0 Tris buffer solution and subjected to FT-IR study. The results indicate that the amide I and III bands of protein in fish gill homogenate deformed markedly with the increase of cyanide concentration. The fish gill homogenate shows a maximum peak at 1650 cm(-1) in amide I band, suggesting the predominant proportion of alpha-helical conformation. Once the KCN was added into the gill homogenate, the maximum peak shifted gradually from 1650 to 1643 cm(-1) due to the random coil structure, with the increase of cyanide concentration used. Two additional shoulders at 1657 (alpha-helix) and 1627 (beta-sheet) cm(-1) also appeared gradually, implying that the cyanide can in part induce changes in protein conformation of fish gill homogenate from alpha-helix to random coil and beta-sheet conformations.