Isolation of the 12 S globulin from Rapeseed (Brassica napus L.) and characterization as a “neutral” protein On seed proteins. Part 13

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Abstract
An isolation procedure for the 12 S rapeseed globulin is described which includes precipitation by dialysis, purification using gel chromatography on Sephadex G-200 and ion-exchange chromatography on DEAE Sephadex A-50. The isolated globulin represents a neutral protein with an isoelectric point at pH 7.25, determined by isoelectric focusing, and a relation of the acidic to basic amino acid residues (.SIGMA. Glu, Asp-Amide ammonia: .SIGMA. Arg, Lys, His) of 1.0. As in other storage globulins high contents of glutamic (19%) and aspartic (10%) acid and a low content of S- containing amino acids are characteristic for the amino acid composition. Among the basic amino acids arginine has the highest percentage (7%). Contary to results of other authors the sugar content of the globulin is low (0.5%). From the amino acid composition an average hydrophobicity according to Bigelow was calculated which amounts to 1041 cal/res (residues) (4.36 kJ/res).