Ultraweak sugar-sugar interactions for transient cell adhesion

Carbohydrate-carbohydrate interactions are rarely considered in biologicall y relevant situations such as cell recognition:and adhesion. One Ca2+-media ted homotypic interaction between two Lewis(x) determinants (Lex) has been proposed to drive cell adhesion in murine embryogenesis. Here, we confirm t he existence of this specific interaction by reporting the first direct qua ntitative measurements in an environment akin to that provided by membranes . The adhesion between giant vesicles functionalized with Le(x) was obtaine d by micropipette aspiration and contact angle measurements. This interacti on is below the thermal energy, and cell-cell adhesion will require a large number of molecules, as illustrated by the Le(x) concentration peak observ ed at the cell membranes during the morula stage of the embryo. This adhesi on is ultralow and: therefore difficult to measure. Such small interactions explain why the concept of specific interactions between carbohydrates is often neglected.