Sasiene Zachary J, Ropartz David, Rogniaux Hélène, Jackson Glen P
C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia, 26506-6121, USA.
UR BIA, INRAE, Nantes, F-44316, France.
J Mass Spectrom. 2021 Jul;56(7):e4774. doi: 10.1002/jms.4774.
Alkali and alkaline earth metal adducts of a branched glycan, XXXG, were analyzed with helium charge transfer dissociation (He-CTD) and low-energy collision-induced dissociation (LE-CID) to investigate if metalation would impact the type of fragments generated and the structural characterization of the analyte. The studied adducts included 1+ and 2+ precursors involving one or more of the cations: H , Na , K , Ca , and Mg . Regardless of the metal adduct, He-CTD generated abundant and numerous glycosidic and cross-ring cleavages that were structurally informative and able to identify the 1,4-linkage and 1,6-branching patterns. In contrast, the LE-CID spectra mainly contained glycosidic cleavages, consecutive fragments, and numerous neutral losses, which complicated spectral interpretation. LE-CID of [M + K + H] and [M + Na] precursors generated a few cross-ring cleavages, but they were not sufficient to identify the 1,4-linkage and 1,6-branching pattern of the XXXG xyloglucan. He-CTD predominantly generated 1+ fragments from 1+ precursors and 2+ product ions from 2+ precursors, although both LE-CID and He-CTD were able to generate 1+ product ions from 2+ adducts of magnesium and calcium. The singly charged fragments derive from the loss of H from the metalated product ions and the formation of a protonated complementary product ion; such observations are similar to previous reports for magnesium and calcium salts undergoing electron capture dissociation (ECD) activation. However, during He-CTD, the [M + Mg] precursor generated more singly charged product ions than [M + Ca] , either because Mg has a higher second ionization potential than Ca or because of conformational differences and the locations of the charging adducts during fragmentation. He-CTD of the [M + 2Na] and the [M + 2 K] precursors generated singly charged product ions from the loss of a sodium ion and potassium ion, respectively. In summary, although the metal ions influence the mass and charge state of the observed product ions, the metal ions had a negligible effect on the types of cross-ring cleavages observed.
对一种支链聚糖XXXG的碱金属和碱土金属加合物进行了氦电荷转移解离（He-CTD）和低能碰撞诱导解离（LE-CID）分析，以研究金属化是否会影响产生的碎片类型以及分析物的结构表征。所研究的加合物包括涉及一种或多种阳离子（H⁺、Na⁺、K⁺、Ca²⁺和Mg²⁺）的1+和2+前体。无论金属加合物如何，He-CTD都会产生丰富且众多的糖苷键和跨环裂解，这些裂解在结构上具有信息价值，能够识别1,4-连接和1,6-分支模式。相比之下，LE-CID光谱主要包含糖苷键裂解、连续碎片和大量中性损失，这使得光谱解释变得复杂。[M + K + H]和[M + Na]前体的LE-CID产生了一些跨环裂解，但不足以识别XXXG木葡聚糖的1,4-连接和1,6-分支模式。He-CTD主要从1+前体产生1+碎片，从2+前体产生2+产物离子，尽管LE-CID和He-CTD都能够从镁和钙的2+加合物产生1+产物离子。单电荷碎片源自金属化产物离子中H⁺的损失以及质子化互补产物离子的形成；这些观察结果与先前关于镁盐和钙盐经历电子捕获解离（ECD）活化的报道相似。然而，在He-CTD过程中，[M + Mg]前体产生的单电荷产物离子比[M + Ca]多，这要么是因为Mg的第二电离势高于Ca，要么是由于构象差异以及碎片化过程中电荷加合物的位置不同。[M + 2Na]和[M + 2K]前体的He-CTD分别通过损失钠离子和钾离子产生单电荷产物离子。总之，虽然金属离子会影响观察到的产物离子的质量和电荷状态，但金属离子对观察到的跨环裂解类型的影响可以忽略不计。
