Post-Extraction Disulfide Bond Cleavage for MS/MS Quantification of Collision-Induced Dissociation-Resistant Cystine-Cyclized Peptides and its Application to the Ultra-Sensitive UPLC-MS/MS Bioanalysis of Octreotide in Plasma
Posted by Adam Awdish on
Innovative Grade US Origin Canine Beagle Plasma from Innovative Research was used in the following study:
Max Sauter, Philipp Uhl, Jürgen Burhenne, Walter E. Haefeli
Analytica Chimica Acta
April 10, 2020
Peptides are gaining importance in therapeutics due to their biocompatibility and chemical diversity. However, linear peptides are prone to degradation. Cyclic peptides, in contrast, have significant advantages over linear peptides, especially if the peptides are small. Cyclic peptides are usually resistant to collision-induced dissociation (CID) at moderate collision energy (CE). Therefore, mainly single amino acid ions are abundant in CID of these peptides, especially at high CE.
Unfortunately, single amino acid ions often show high background in selected reaction monitoring (SRM), complicating analysis of cyclic peptides. A common technique for peptide cyclization is to use intramolecular disulfide bridges, which are naturally found in many peptides. Previously developed methods to facilitate analysis of cyclic peptides deal with the challenge of low intensity ions in CID by monitoring the intact precursor mass.
One approach is to avoid molecular fragmentation monitor the intact precursor directly or as pseudo-transition, called selected ion monitoring (SIM; also multiple ion monitoring [MIM). A related approach is the survivor SIM, in which the CID-resistant precursor is monitored after the removal of isobaric matrix interferences by CID. Another methodology is to utilize SIM after separating the precursor by ion mobility spectrometry (IMS). However, although desirable signal-to-noise ratios can be obtained with IMS, it is prone to loss of intensity. Additional hurdles in creating peptide therapeutics stem from their route of administration, which is limited to parenteral. Therefore, alternative formulations that enabling noninvasive administration are desirable to avoid long-term parental therapy.
This study introduced a simple workflow suitable for ultrasensitive peptide analysis applicable to standard mass spectrometers. By breaking the cyclic structure through disulfide bond reduction, the generation of larger, specific fragments in CID is enabled. This procedure can serve as a general methodology for the analysis of circular cystine-bearing peptides lacking specific fragments in CID. Assay applicability was demonstrated by the determination of plasma concentrations of octreotide after intravenous administration to canine beagles.
Related products available from Innovative Research also include:
Innovative Grade US Origin Canine Beagle Single Donor Plasma