The endogenous peptides of normal human serum extracted from the acetonitrile-insoluble precipitate using modified aqueous buffer with analysis by LC-ESI-Paul ion trap and Qq-TOF.

Many peptides of biological or medicinal importance may be derived from proteolytic actions and are found at low concentrations in human blood fluids. Endogenous polypeptides from human serum were precipitated in acetonitrile and the precipitate was then selectively extracted with water modified by organic solvents and collected over C18 resin. Extraction of serum with C18 alone, and the acetonitrile supernatant or ultrafiltration collected over C18, served as controls.