The major goal of our research is an understanding of the structures of the complex carbohydrates found on cell surfaces and of how these structures are involved in recognition between cells. Our current efforts toward this goal are divided into two different approaches. The first involves the purification and structural characterization of a unique glycoprotein from the surface of chick embryo cells. This glycoprotein has a number of properties which make it desirable for detailed study, including the observation that this glycoprotein is missing in virally transformed cells. We have devised a simple procedure for extraction of this glycoprotein from the cell surface, leaving the cells intact and viable. We now intend to develop a purification scheme to obtain this protein in pure form. This will be followed by structural characterization and attempts to understand the role of this glycoprotein in cell surface functions. The second approach involves the use of a small glycoprotein-containing virus (Sindbis) as a probe of the ability of a host cell to make various oligosaccharide structures. This approach is based on the hypothesis that the carbohydrates of the Sindbis glycoproteins are added by host glycosyl transferases. We are comparing the structure of the carbohydrates added to Sindbis when it is grown either in virally transformed cells or their untransformed parent cells. In this way we hope to detect transformation-specific changes in the ability of a cell to make various complex carbohydrates.