THE USE OF POLARIZED FT-IR MICROSCOPIC SPECTROMETRY TO DETECT AN ORIENTATED ARRANGEMENT OF CALCIUM-CARBONATE CRYSTALS IN THE HINGE-LIGAMENT OF THE SURF CLAM

The authors have applied polarized FT-IR microscopic spectrometry in order to detect the oriented arrangement of calcium carbonate crystals in the protein matrix of the bivalve hinge-ligament of the surf clam. It is shown that the absorption of the in-plane stretching mode of carbonate anions (ν3) in aragonite crystals appears as a broad band centered at 1480 cm-1. In the IR spectrum of the resilium measured by the conventional KBr-disk method, the amide II band of the resilium protein was overlapped by the ν3 band of the carbonate. When the resilium was decalcified with 10% acetic acid, the protein remained insoluble and gave a typical amide II band at 1540 cm-1.