Reactive desorption electrospray ionization mass spectrometry (DESI-MS) of natural products of a marine alga |
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| Authors: | Leonard Nyadong Edward G Hohenstein Asiri Galhena Amy L Lane Julia Kubanek C David Sherrill and Facundo M Fernández |
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| Institution: | (1) School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332, USA;(2) School of Biology, Georgia Institute of Technology, Atlanta, GA 30332, USA |
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| Abstract: | Presented here is the optimization and development of a desorption electrospray ionization mass spectrometry (DESI-MS) method
for detecting natural products on tissue surfaces. Bromophycolides are algal diterpene-benzoate macrolide natural products
that have been shown to inhibit growth of the marine fungal pathogen Lindra thalassiae. As such, they have been implicated in antimicrobial chemical defense. However, the defense mechanisms are not yet completely
understood. Precise detection of these compounds on algal tissue surfaces under ambient conditions without any disruptive
sample processing could shed more light onto the processes involved in chemical defense of marine organisms. Conventional
DESI-MS directly on algal tissue showed relatively low sensitivity for bromophycolide detection. Sensitivity was greatly improved
by the addition of various anions including Cl−, Br−, and CF3COO− into the DESI spray solvent. Chloride adduction gave the highest sensitivity for all assayed anions. Density functional optimization
of the bromophycolide anionic complexes produced during DESI supported this observation by showing that the chloride complex
has the most favorable binding energy. Optimized DESI protocols allowed the direct and unambiguous detection of bromophycolides,
including A, B, and E, from the surface of untreated algal tissue.
Figure Desorption Electrospray Ionization, a novel technique for mass spectrometric analysis under open air conditions reveals the
presence of naturally-occurring antibiotics on the surface of marine algae. Ab-initio calculations and experimental results
indicate that sensitiviity could be greatly enhanced by means of dynamic complexation of these antibiotics with various small
anions during the dynamic desorption process.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
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| Keywords: | Desorption electrospray ionization Mass spectrometry Direct analysis Natural products |
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