Electrospray ionization mass spectrometry synthetic peptides

Because anurans, including L. splendida, often breed in water, the peptide components of the secretions of the paratoid and rostral glands were purified directly by HPLC. The active component was sequenced with the aid of electrospray ionization mass spectrometry (ESI-MS) and given the name splendipherin (17).76 The structure of this 25-amino acid peptide subsequently was confirmed by comparison with a synthetically prepared sample, which further established that all amino acids were of the L-configuration. 

Leu (DADLE), an analog of leucine-enkephalin, a naturally occurring linear pentapeptide (Tyr-Gly-Gly-Phe-Leu)that binds to opioid receptors (Fig. 15.40) (354). In rat brain tissue samples collected 15 min after i.v. CDS-ad-ministration, electrospray ionization mass spectrometry clearly showed the presence of the locked-in T-D form at an estimated concentration of 600 pmol/g of tissue. The same ion was absent from the sample collected from the control animals treated with the vehicle solution only. To optimize this delivery strategy, an effective synthetic route was established for peptide CDSs, and the role of the spacer and the lipophilic functions was investigated (355). Four different CDSs were synthesized by a segment-coupling method. Their... 

In the past decade, mass spectrometry (MS) has become the method of choice for quality control of synthetic peptides. Historically, plasma desorption (PD) and fast atom bombardment (FAB) were the first ionization methods used for the mass analysis of nonderivatized peptides. More recently, electrospray ionization (ESI) MS and matrix-assisted laser desorption ionization (MALDI) MS have found widespread utility for peptide analysis. Both of the latter methods yield protonated molecules and, thus, provide direct molecular weight information. As will be covered later, ESI can be employed with a variety of mass analyzers, including quadrupole, magnetic sector, ion trap, and time-of-flight (TOF) analyzers. On the other hand,... 

Electrospray ionization and MALDI represent major advances in the application of mass spectrometry to analysis of biomolecules. Although in many cases the two techniques are able to provide the same information, quite frequently they are complementary. For a variety of reasons, some samples are more successfully analyzed by MALDI and other by ESI. Thus, it is highly beneficial to have access to both types of instrument for characterization of synthetic peptides. In ESI-MS, the samples are introduced in solution at flow rates from less than 1 tL/min up to 1 mL/min, depending on the design of the ESI interface. Pure samples and simple mixtures are often analyzed by direct infusion more complex mixtures (such as proteolytic digests) generally require either on-line or off-line HPLC fractionation prior to MS analysis. 

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