Isotopic labelling of CLPs for the study of their self-assembling properties
The enrichment of CLPs with 13C and 15N isotopes greatly improves the sensitivity of NMR measurements involving carbon and nitrogen nuclei. This is may not only cut back the experimental time, but allows us to explore interactions mediated by (a series of) weak heteronuclear couplings (e.g. intra- and intermolecular H-bonds). CLPs form self-assemblies in apolar solvents, which feature is typically linked to the ability for ion pore creation in cellular membranes. Employing 13C and 15N labelling, intermolecular peptide-peptide interactions in such supramolecular aggregates can be directly identified. Thus, this technique - complemented with diffusion and relaxation NMR studies on - serves essential information about the structure of monomeric CLPs and self-assemblies and bring us closer towards understanding the mechanism behind the biological activity of cyclic lipopeptides.