Accurate quantification of modified cyclic peptides without the need for authentic standards

Rosemary I. Adaba, Greg Mann, Andrea Raab, Wael E. Houssen, Andrew R. McEwan, Louise Thomas, Jioji Tabudravu, James H. Naismith, Marcel Jaspars*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)
8 Downloads (Pure)


There is a growing interest in the use of cyclic peptides as therapeutics, but their efficient production is often the bottleneck in taking them forward in the development pipeline. We have recently developed a method to synthesise azole-containing cyclic peptides using enzymes derived from different cyanobactin biosynthetic pathways. Accurate quantification is crucial for calculation of the reaction yield and for the downstream biological testing of the products. In this study, we demonstrate the development and validation of two methods to accurately quantify these compounds in the reaction mixture and after purification. The first method involves the use of a HPLC coupled in parallel to an ESMS and an ICP-MS, hence correlating the calculated sulfur content to the amount of cyclic peptide. The second method is an NMR ERETIC method for quantifying the solution concentration of cyclic peptides. These methods make the quantification of new compounds much easier as there is no need for the use of authentic standards when they are not available. (C) 2016 Elsevier Ltd. All rights reserved.

Original languageEnglish
Pages (from-to)8603-8609
Number of pages7
Issue number52
Early online date16 Nov 2016
Publication statusPublished - 29 Dec 2016

Bibliographical note


MJ, JHN, WEH, LT gratefully acknowledge support from the the Leverhulme Trust (RPG 2012-504). JT and AR were funded by EU-FP7 project ‘PharmaSea’ (contract 312184) and ARM and GM were funded by Scottish Enterprise High Growth Spinout ProgrammePS7305CA38.


  • cyclic peptides
  • LC-MS
  • ICP-MS
  • NMR
  • quantification without authentic standards
  • cyanobacteria
  • qNMR
  • solid-phase extraction
  • element mass-spectrometry
  • liquid-chromatography
  • isotope-dilution
  • affinity tag
  • quantitative proteomics
  • human plasma
  • absolute quantification
  • lissoclinum-patella
  • prochloron-didemni


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