The metalloprotein, Concanavalin A, requires the presence of transition metal and calcium ions before the protein adopts the active conformation which recognizes monosaccharides and polysaccharides having free hydroxyl groups at C3, C4, and C6 in the D-arabino-pyranoside configuration. The agglutination of tumorous and chemically transformed cells by Con A is thought to result from intercellular crosslinking of cell surface glycoprotein receptors. Yet recent evidence suggests Con A may possess heterogeneous cell recognition sites which display allosteric behavior. Chemical methods for introducing carbon-13 enriched nuclei into the native Con A molecule will be investigated and cell binding and/or agglutination tests will be directed toward delineating competitive versus allosteric non-cooperative inhibition by alpha-methylmannopyranoside. The spectral and magnetic properties of the lanthanides will be utilized to determine solution distances from fluorescence data and assign individual carbon resonances in magnetic resonance experiments, respectively. The assigned single carbon resonances will be monitored to differentiate between simple sugar versus whole cell binding to Con A. These data will establish a general mechanism for lectin-whole cell interactions.