Analysis of Insect Cuticular Hydrocarbons Using Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry

Abstract

Insect cuticular hydrocarbons (CHCs) were probed by matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) mass spectrometry with a lithium 2,5-dihydroxybenzoate matrix. CHC profiles were obtained for 12 species of diverse insect taxa (termites, ants, a cockroach, and a flesh fly). MALDI spectra revealed the presence of high molecular weight CHCs on the insect cuticle. Hydrocarbons with more than 70 carbon atoms, both saturated and unsaturated, were detected. When compared with gas chromatography/mass spectrometry (GC/MS), MALDI-TOF covered a wider range of CHCs and enabled CHCs of considerably higher molecular weight to be detected. Good congruity between GC/MS and MALDI-TOF was observed in the overlapping region of molecular weights. Moreover, a number of previously undiscovered hydrocarbons were detected in the high mass range beyond the analytical capabilities of current GC/MS instruments. MALDI was shown to hold potential to become an alternative analytical method for insect CHC analyses. The ability of MALDI to discriminate among species varying in the degree of their relatedness was found to be similar to GC/MS. However, neither MALDI-MS nor GC/MS data were able to describe the phylogenetic relationships.

MALDI imaging of neutral cuticular lipids in insects and plants

“…Our data agree with previously published results [47]. HCs of N. bullata have been studied since the 1970s [22,47,48]. As our previous findings led us to expect [22], the MALDI spectra provided evidence of saturated and unsaturated HCs with odd and even numbers of carbons (Supplementary Figure S1b) 7 Li adduct ions, fully collaborating with data from GC/MS and ESI/MS (Supplemental Table 2, entries 11 and 13, respectively).…”

“…However, the surface of living organisms is more complex and subject to various signal suppression/enhancement effects from other compounds. From our previous studies [21,22] it is apparent that spots must be irradiated by UV laser for a longer time than used usually, and more that 100 lasers shots are necessary to obtain clean spectra of lithiated HC. As the cuticle of plants and insects contains diverse classes of lipids with different polarity and, hence, high or low affinity to lithium cationization, the imaging on real sample is a challenging task.…”

Direct Laser Desorption Ionization of Endogenous and Exogenous Compounds from Insect Cuticles: Practical and Methodologic Aspects

“…MALDI MS analysis of cuticular HCs from extract has previously been demonstrated with lithiated dihydroxybenzoate matrix using a standard "axial"-MALDI-TOF mass spectrometer operated with high vacuum in the ion source [20]. Notably, this approach allowed the analysis of saturated HCs, detected in form of lithium adducts, albeit with sensitivity limits that appear to fall into the low μg-range [21].…”

Deciphering the signature of cuticular lipids with contact sex pheromone function in a parasitic wasp

“…they conclude behavioural activity of CHCs from their apparently exclusive presence in bioactive insect extracts (Millar, 2010). It is often neglected, however, that those extracts may contain further compounds that might contribute to the behavioural activity of cuticular lipids without being detectable by standard GC-MS methods (Cvacka et al, 2006;Millar, 2010). Such a compound class is represented by triacylglycerides (TAGs).…”