Thermally induced permutations of antigenicity and conformation of arachin (peanut globular protein)*

The reactivity of arachin (principal storage protein of the peanut) with anti-arachin decreased after arachin was heated at certain temperatures. Infrared and circular dichroic spectra of heated and unheated samples of arachin were examined to determine whether conformational modes changed concomitantly with decreased antigenicity. Infrared absorbances of each sample at amide I, II and V bands were essentially identical; however, absorbances at amide IV and VI bands were altered in relative intensities proportionally to the temperatures of treatment. Conformational modes, determined by circular dichroism, gradually increased in content of unordered structure from x-helical and pleated sheet modes relative to the temperature of treatment. These observations are discussed in regard to relationships of the loss of antigenicity to conformatonal changes in heated arachin.