The hypertrehalosemic neuropeptides of cicadas are structural isomers—evidence by ion mobility mass spectrometry

• Published in: Analytical and bioanalytical chemistry Vol. 409; no. 27; pp. 6415 - 6420
• Main Authors: König, Simone, Marco, Heather, Gäde, Gerd
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.11.2017; Springer; Springer Nature B.V
• Subjects: Amino Acid Sequence; Amino acids; Analytical Chemistry; Animals; Biochemistry; Characterization and Evaluation of Materials; Chemical properties; Chemistry; Chemistry and Materials Science; Chromatography, Reverse-Phase; Cicadas; Cicadidae; Conformation; Corpora cardiaca; Food Science; Glands; Hemiptera - chemistry; Hydrophobicity; Ionic mobility; Ions; Isomerism; Isomers; Isomers (Chemistry); Laboratory Medicine; Liquid chromatography; Mass spectrometry; Mass spectroscopy; Mobility; Monitoring/Environmental Analysis; Neuropeptides; Neuropeptides - chemistry; Peptides; Physiological aspects; Racemization; Research Paper; Retention time; Scientific imaging; Spectra; Spectroscopy; Studies; Tandem Mass Spectrometry; Ion mobility mass spectrometry; AKH; Conformation; Isomer
• ISSN: 1618-2642; 1618-2650
• DOI: 10.1007/s00216-017-0583-4

It has been known for more than 20 years that the neurosecretory glands of the cicadas, the corpora cardiaca, synthesize two isobaric peptides with hypertrehalosemic activity. Both decapeptides have exactly the same amino acid sequence (pGlu-Val-Asn-Phe-Ser-Pro-Ser-Trp-Gly-Asn-NH 2 ) and mass but differ in their retention time in reversed-phase liquid chromatography. A synthetic peptide with the same sequence elutes together with the second more hydrophobic peptide peak of the natural cicada extract. It is not clear what modification is causing the described observations. Therefore, in the current study, ion mobility separation in conjunction with high-resolution mass spectrometry was used to investigate this phenomenon as it was sensitive to changes in conformation. It detected different drift times in buffer gas for both the intact peptides and some of their fragment ions. Based on the ion mobility and fragment ion intensity of the corresponding ions, it is concluded that the region Pro 6 -Ser 7 -Trp 8 contains a structural feature differing from the L-amino acids present in the known peptide. Whether the conformer is the result of racemization or other biochemical processes needs to be further investigated.