An NMR fingerprint matching approach for the identification and structural re-evaluation of Pseudomonas lipopeptides
Cyclic lipopeptides (CLiPs) are secondary metabolites secreted by a range of bacterial phyla. CLiPs display diverse structural variations in terms of the number of the amino acid residues, macrocycle size, amino acid identity and stereochemistry (e.g. D- vs. L-amino acids). Reports detailing the discovery of novel or already characterized CLiPs from new sources appear regularly in literature. However, in some cases, the lack of characterization detail threatens to cause considerable confusion,
... specially if configurational heterogeneity is present for one or more amino acids. The NMR fingerprint matching approach introduced in this work exploits the fact that the 1H and 13C NMR chemical shift fingerprint is sufficiently sensitive to differentiate the diastereomers of a particular CLiP even when they only differ in a single D/L configuration. This provides a means for a fast screening to determine whether an extracted CLiP has been reported before, by simply comparing the fingerprint of a novel CLiP with that of a reference CLiP. Even when the stereochemistry of a particular reference CLiP is unknown, the NMR fingerprint approach still allows to verify whether a CLiP from a novel source is identical to the reference. To facilitate this, we have made a publicly available knowledge base at https://www.rhizoclip.be, where we present an overview of published NMR fingerprint data of characterized CLiPs, together with literature data on the originally determined structures. The latter includes a description of the CLiPs original description, molecular mass, three dimensional structures (if available), and a summary of published antimicrobial activities. Moreover, a detailed protocol will be made available for researchers that wish to record NMR data of their newly extracted lipopeptides to compare them to the publicly available reference data.