Study of the nettle (Urtica diоica) lignin by orbitrap mass spectrometry with atmospheric pressure photoionization
T16N1
I.I. Pikovskoi, D.S. Kosyakov, I.S. Shavrina, N.V. Ul’yanovskii
The orbital ion trap high-resolution mass spectrometry method with atmospheric pressure acetone-doped photoionization was first used to characterize the structure of lignins of herbaceous plants using the example of nettle (Urtíca dióica) dioxane lignin. The obtained mass spectrum contains about 3,000 peaks of deprotonated molecules of lignin oligomers in the molecular mass range up to 1.6 kDa. The study of tandem mass spectra and the composition of monomers formed during the collision-induced dissociation of lignin macromolecules showed the special role of p-hydroxycinnamic acids in the formation of nettle lignin. Based on the results of tandem mass spectrometry, possible structures of nettle lignin oligomers, which are formed by the addition of guaiacyl- and syringylpropane units with their subsequent etherification with p-coumaric, ferulic and dihydroferulic acids, are proposed.
Optimization of sample preparation conditions in the study of lignin by MALDI mass spectrometry method
T11N2
D.S. Kosyakov, N.V. Ul’yanovskii, E.A. Sorokina, N.S. Gorbova
In the present study the comparison of efficacy of six crystalline matrices, as well as their mixtures for MALDI of lignin is done, the effect of sample application technique and matrix/analyte ratio on the quality of the mass spectra is studied. It is established that the best results can be obtained when α-cyano-4-hydroxycinnamic and 2,5-dihydroxybenzoic acids, a well as 2,4,6-trihydroxyacetophenone are used as matrices, taken in 10–100-fold excess with respect to lignin and sequentially applied to the target in order «analyte–matrix– analyte». It is proposed for the first time to use ionic liquids as martices for obtaining of lignin MALDI mass spectra. It is shown that the ionic liquid N-tert-butyl-N-isopropyl-N-methylammonium α-cyano-4-hydroxycinnamate, forming a homogeneous solution with lignin gives substantially better results when compared with crystalline matrices in terms of intensity of the obtained mass spectra, and reproducibility. The structure of the MALDI mass spectra of dioxane lignin of fir caused by the predominance in the macromolecule units derived from α-guaiacylpropanone is analyzed.
