Studies of the Fragmentation Mechanisms of Deprotonated Lignin Model Compounds in Tandem Mass Spectrometry

Abstract

Unlabeled and deuterium-labeled dimeric lignin model compounds with β-O-4 linkages were evaporated and ionized using negative ion mode electrospray ionization, transferred into a linear quadrupole ion trap, isolated, and subjected to collision-activated dissociation (CAD; MS2 experiments). The elemental compositions of the fragment ions were determined by using a high-resolution Orbitrap mass analyzer, and their structures were examined using further CAD experiments (MS n experiments wherein n = 2–5). Data analysis was facilitated by determining the fragmentation pathways for several deprotonated model compounds. The structures of the key fragment ions of several pathways were determined by comparison of the CAD mass spectra measured for undeuterated and deuterated analogues and for deprotonated authentic compounds. Some of the proposed reaction mechanisms were tested by examining additional deprotonated synthetic model compounds. Quantum chemical calculations were used to delineate the most likely reaction pathways and reaction mechanisms. This work provides basic information needed for the design of tandem mass spectrometry-based CAD sequencing strategies for mixtures of lignin degradation products.

Automatic MS/MS Data Mining Strategy for Discovering Target Natural Products: A Case of Lindenane Sesquiterpenoids

“…The RDA reaction was calculated to have an energy barrier of 46.78 kcal/mol and the hydrogen migration needed to cross the energy barrier of 71.28 kcal/mol (Figure S40). In other LS monomers, which enabled the generation of fragment ion with Δ 8 (9) , ion of either m/z 138 or 137 can be detected but in low abundance. The characteristic signals of m/z 91, 77, and 65 indicated a benzyl cation.…”

“…Furthermore, in-depth structural elucidation of characteristic ions is the prerequisite for their further utilization. Recently, density functional theory (DFT)-based chemical calculation combined with hydrogen–deuterium exchange has been successfully applied to study the CID mechanism of NPs . These techniques could provide a robust explanation of the fragmentation processes …”

“…Recently, density functional theory (DFT)-based chemical calculation combined with hydrogen− deuterium exchange has been successfully applied to study the CID mechanism of NPs. 9 These techniques could provide a robust explanation of the fragmentation processes. 10 Lindenane sesquiterpenoids (LSs), a kind of NP with diverse and complicated structure and significant antimalarial, 11 antiinflammatory, 12,13 and cytotoxic activities, 14 have attracted much attention in the past decade.…”

First Direct Evidence of Interpartner Hydride/Deuteride Exchanges for Stored Sodiated Arginine/Fructose-6-phosphate Complex Anions within Salt-Solvated Structures

“…This method has been primarily introduced to deduce the mobile proton number in small size molecules in solution or in the gas phase for the study of even-electron molecular species. [44][45][46][47][48] Such proton/deuteron exchanges (HDX) are also currently applied to study non-covalent system conformations in biomolecules, [49][50][51][52] and/or to highlight gas phase fragmentation patterns. [53][54][55] In the present work, HDX approach was applied to explore the HB and SSA forms of sodiated NCC anions formed between fructose-6-phosphate (F6P) and arginine (R).…”

“…Otherwise, in-solution hydrogen/deuterium exchange (HDX) represents a useful tool to investigate structure and fragmentation patterns of complex ions. This method has been primarily introduced to deduce the mobile proton number in small-size molecules in solution or in the gas phase for the study of even-electron molecular species. − Such proton/deuteron exchanges (HDX) are also currently applied to study noncovalent system conformations in biomolecules − and/or to highlight gas-phase fragmentation patterns. − In the present work, the HDX approach was applied to explore the HB and SSA forms of sodiated NCC anions formed between fructose-6-phosphate (F6P) and arginine (R). Fragmentation patterns of deuterium-labeled sodiated NCC anions after complete in-solution mobile proton exchanges were studied using the CID as well as and HCD modes (higher energy dissociation, a non-resonant excitation mode) under variable excitation energy conditions and excitation times.…”