(Ser8)-GLP-1 (7-36) amide (human, bovine, guinea pig, mouse, rat) Trifluoroacetate, H-His-Ser-Glu-Gly-Thr-Phe-Thr-Ser-Asp-Val-Ser-Ser-Tyr-Leu-Glu-Gly-Gln-Ala-Ala-Lys-Glu-Phe-Ile-Ala-Trp-Leu-Val-Lys-Gly-Arg-NH2, 215777-46-1, C149H226N40O46, Mr 3313.68, 1mg. (Ser79)-Proglucagon (78-107) amide (human, bovine, guinea pig, mouse, rat), (Ser8)-Glucagon-Like Peptide 1 (7-36) amide (human, bovine, guinea pig, mouse, rat), (Ser99)-Preproglucagon (98-127) amide (human, bovine, guinea pig, mouse, rat). The replacement of alanine by serine significantly improved the plasma stability of GLP-1 (7-36) amide against DPP IV without impairing its insulinotropic activity. This may indicate that this modification could improve the potential of GLP-1 in the treatment of type-II diabetes.