Investigation of crudes of synthesis of neuropeptide Y by high-performance liquid chromatography-electrospray mass spectrometry

Neuropeptide Y (NPY) and its modified form, [Leu31, Pro34]NPY, are both thirty six amino acids long and they have relative molecular masses of 4250 and 4220. Solid-phase synthesis of both peptides resulted in complex crudes of reaction, which were investigated by means of combines high-performance liquid chromatography-electrospray mass spectrometry (HPLC-ES-MS). The combination of these two powerful analytical techniques allowed rapid and reliable identification of the target peptides and furnished comprehensive information on other reaction products, which were mainly peptidic chains containing a smaller number of amino acids compared to those present in the intact peptides. The possible origin of such side-products and the eventual purification and unambiguous identification of both peptides are discussed.