Circular dichroism spectra of isolated soybean and chickpea trypsin-chymotrypsin inhibitors.

Circular dichroism spectra of trypsin-chymotrypsin inhibitors from soybeans and chickpeas have been determined in acidic, neutral and highly alkaline solutions. Neither protein contains alpha-helix although a small amount of beta-structure cannot be excluded. Negative dichroism above 250 nm has been assigned largely to disulfide bonds in both molecules with neither showing evidence for tyrosine residues buried in hydrophobic regions. The spectra of these inhibitors between 230 and 250 nm have been compared with the spectra of a number of structurally related proteins suggesting that previous interpretations of this region may have been incomplete or incorrect.