Characterization of betidamino acid-containing somatostatin and gonadotropin-releasing hormone analogs with electrospray mass spectrometry and tandemmass spectrometry

We report the electrospray mass spectra and tandem mass (MS/MS) spectra of a series of chemically-stable somatostatin (SRIF) and gonadotropin-releasin g hormone (GnRH) analogs which incorporate acylated or alkylated/acylated a minoglycine residues (betidamino acids) into their structure. In the case o f SRIF, we compare the betidamino acid-containing analogs with the equivale nt peptide without the betide-type linkage. We observe significant differen ces in the fragmentation patterns of each class of compound. We extend this study by comparing a variety of different betidamino acid-containing GnRH analogs to investigate the effects of different acyl groups, chirality and methylation of the side-chain nitrogen of amino glycine on the gas-phase st ability of these protonated peptide molecules.