Fast atom bombardment mass spectra of peptides. Dimer ion studies. Part VI

Positive ion fast atom bombardment mass spectra of the opioid pentapeptides leucine enkephalin (1) (H‐Tyr‐Gly‐Gly‐Phe‐Leu‐OH or YGGFL), methionine enkephalin (2) (H‐Tyr‐Gly‐Gly‐Phe‐Met‐OH or YGGFM) and leucine enkephalin‐ 2 H 2 (3) (H‐Tyr‐ 2 Gly‐ 2 H 2 ‐Gly‐Phe‐Leu‐OH or YGGFL‐ 2 H 2 ) have been recorded in glycerol. The following experiments have been carried out: (i) dimer studies [2M + 1] + ; (ii) decompositions of dimers: daughter ions from (YGGFL) 2 , (YGGFL‐YGGFL‐ 2 H 2 ) and (YGGFL‐ 2 H 2 ) 2 as well as (YGGFM–YGGFL) and (YGGFM) 2 dimers; (iii) solvation site and pyridine collision‐activated dissociation studies for dimer ions; (iv) mechanism of formation of [(2M + 1) – Gly 4 ] + ions.