Thrombin receptor activating peptides: importance of the N-terminal serine and its ionization state as judged by pH dependence, nuclear magnetic resonance spectroscopy, and cleavage by aminopeptidase M - Coller, B S; Ward, P; Ceruso, M; Scudder, L E; Springer, K; Kutok, J; Prestwich, G D (Biochemistry, 1992)