Sialic acid containing glycoprotein fragments were removed from the surface of the TA3 mammary adenocarcinoma ascites cell of the strain A mouse by short-term incubations with TPCK-trypsin at 4". The material eluted in the void volume of a Bio-Gel P-100 column, after fractionation on Bio-Gels P-4 and P-30, represented 9 % of the carbohydrate and protein material removed from the cells but 31 % of the total surface sialic acid. It was composed of approximately 70 x carbohydrate and 30 % protein and contained four carbo-I t was recently suggested (Sanford and Codington, 1971) that the reduced transplantability of neuraminidase-treated TA3 mammary adenocarcinoma ascites cells of the strain A mouse in the foreign strain C3H mouse (Sanford, 1967) may be due to a serum factor which was demonstrated to be toxic in r;itro to the cells after neuraminidase treatment. In a previous investigation of the sialic acid containing glycoproteins at the surface of this cell, Codington et al. (1970) demonstrated that peptide and carbohydrate material removed from the cells by chelating agents or proteolytic enzymes had widely different compositions, and all samples exhibited marked heterogeneity .The mixture of glycoprotein fragments initially cleaved from the cells by mild treatment with TPCK-trypsin at 15-22" contained the highest proportion of sialic acid, suggesting that the glycoprotein structures richest in sialic acid were probably located at the periphery of the TA3 cell. This paper describes the fractionation by gel filtration of material obtained by short-term successive incubations with TPCKt From the laboratory for Carbohydrate Research,

Recrystallization from 1700 ml. of diethyl ether gave 0.39 g. of white solid, m.p. 97-111°, [«]S6d +35°( 0.25% in water), "®,1 268 m¡u (£ 8840), 268 µ (« 4900), X°l,e 268(e 7260).The material traveled as one component in solvent A with R"d 1.81. In solvent C, it travelled as an elongated spot with fim 1.29-1.37.

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