CIRCULAR DICHROISM SPECTRA OF CLEAVAGE FRAGMENTS OF SOYBEAN TRYPSIN-CHYMOTRYPSIN INHIBITOR

Abstract
Circular dichroism spectra of biologically active fragments of Bowman-Birk soybean inhibitor have been determined in acidic, neutral, and alkaline conditions. Neither fragment showed evidence of α-helix or β-structure. Negative dichroism above 260 nm has been assigned in both fragments primarily to disulfide bonds, with a minor contribution from tyrosine in a hydrophilic environment. The individual spectra of these fragments, and their sum between 230 and 340 nm have been compared with the spectra of the intact inhibitor and several structurally related proteins. Possible interactions which may give rise to CD bands in this region are discussed.