I propose to chemically synthesize the hydrophobic intramembraneous peptide of glycophorin A, the major sialoglycoprotein of the human erythrocyte membrane and to investigate the secondary structure, aggregation properties, and lipid binding properties of this peptide and its fragments. The specific objectives of this proposal are: 1. Synthesis of three fragments of the intramembraneous peptide (residues 73-94). 2. Synthesis of the entire hydrophobic sequence 73-84 by condensation of the three fragments. 3. To determine if any of the fragments or the 73-94 segment have an alpha-helical structure in solution. (Such a structure has been proposed for the naturally isolated intramembraneous peptide, residues 62-97). 4. To determine if any of the fragments in the 73-94 segment aggregate with each other or with native glycophorin. (The native 62-97 peptide does bind to native glycophorin.) 5. To determine if lipids are specifically bound by any of the fragments or by the 73-94 peptide. 6. To determine the role of methionine-81 in the secondary structure and aggregation properties of these peptides. (Carboxymethylation of met-81 has been shown to break a glycophorin aggregate to lower molecular weight by SDS gel electrophoresis.) Methods to be employed are: 1. Classical solution phase peptide synthesis. 2. Nuclear magnetic resonance and circular dichroism. 3. Sodium dodecyl sulfate gel electrophoresis.