Mass spectrometric decompositions of cationized beta-cyclodextrin

Area of Science:

• Analytical Chemistry
• Physical Chemistry
• Supramolecular Chemistry

Background:

• Beta-cyclodextrin (beta-CD) is a cyclic oligosaccharide with a unique toroidal structure.
• Metal-cyclodextrin complexes are relevant in various fields, including drug delivery and catalysis.
• Understanding the fragmentation of these complexes is crucial for structural elucidation.

Purpose of the Study:

• To investigate the mass spectrometric fragmentation pathways of beta-cyclodextrin complexed with divalent metal cations.
• To elucidate the mechanisms of fragmentation, including bond cleavage and hydrogen transfer.
• To utilize isotope labeling to gain deeper insights into ion formation.

Main Methods:

• Electrospray ionization mass spectrometry (ESI-MS) was employed.
• Complexes of beta-cyclodextrin with Mg2+, Ca2+, Cd2+, Cu2+, Co2+, and Pb2+ were analyzed.
• Deuterium isotope labeling (hydroxyl hydrogen exchange) was performed.

Main Results:

• The primary fragmentation pathway involved consecutive losses of sugar units from the [beta-CD+Cat]2+ ions.
• Rupture of C-C bonds within sugar units was observed, accompanied by hydrogen atom transfer.
• Isotope labeling confirmed that C-H hydrogen transfer is specific to C-C bond fragmentation.

Conclusions:

• The fragmentation of metal-beta-cyclodextrin complexes is characterized by sugar unit loss and C-C bond cleavage.
• Hydrogen atom transfer plays a significant role in specific fragmentation events.
• Mass spectrometry, aided by isotope labeling, provides valuable mechanistic insights into these complexes.