M.S. Narasinga Rao

Studies on groundnut proteins. III. Physicochemical properties of arachin prepared by different methods

Abstract The homogeneity of arachin prepared by different methods was determined by the techniques of polyacrylamide gel electrophoresis, DEAE-cellulose chromatography, and ultracentrifugation. Arachin obtained by the method of Tombs ( Biochem. J. 96 , 119, 1965) or Dawson ( Anal. Biochem. 41 , 305, 1971) appeared to be homogeneous by these techniques. Total groundnut proteins, extracted in 1 m NaBr solution and subjected to double precipitation with 23% (NH 4 ) 2 SO 4 , also gave a homogeneous arachin preparation. These three homogeneous arachin preparations differed in their rate of hydrolysis by alpha-chymotrypsin, heat coagulation, and dissociation into subunits. However, SDS 1 and GuHCl denatured them to the same extent, as could be judged by the difference spectra. The phosphorus and carbohydrate content of the three preparations did not differ significantly.

Interaction of allylisothiocyanate with bovine serum albumin

The interaction of allylisothiocyanate with bovine serum albumin was monitored by fluorescence titration. The interaction was weak with an apparent association constant of 2 × 10 2 . The interaction was unaffected in the pH range of 5·0 to 8·3 and by NaCl. However, the addition of dioxane upto 4% increased the value of the association constant. N-Methyl bovine serum albumin and bovine serum albumin with sulphydryl groups blocked had the same affinity for allyl- isothiocyanate suggesting that amino and sulphydryl groups may not be involved in the interaction. Polyacrylamide gel electrophoresis and estimation of available lysine suggested that there were perhaps two types of groups involved in the inter- action of allylisothiocyanate with bovine serum albumin.