FAST-ATOM-BOMBARDMENT MASS-SPECTROMETRIC STUDY OF BENZYLOXYCARBONYL-PROTECTED TETRAPEPTIDES CONTAINING PROLINE

Fragmentations of N-benzyloxycarbonyl-protected tetrapeptide ethyl esters containing L-alanine and L-proline, in which changes in the numbers and positions of prolyl residues were observed, were studied by negative-ion fast atom bombardment mass spectrometry. A significant difference was found among the abundances of the molecule ions and the fragment ions formed by the cleavage of the benzyloxycarbonyl group, depending on the numbers and positions of prolyl residues in the derivatives. The results indicate that the conformational differences in the tetrapeptide derivatives due to the existence of proline affect fragmentations of molecules in the solution phase in negative-ion fast atom bombardment mass spectrometry.